Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Mar. 05, 2019	Jun. 30, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	Arbutus Biopharma Corp
Document Type	10-K
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		56,120,868
Entity Public Float			$ 269,738,700
Amendment Flag	false
Entity Central Index Key	0001447028
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Well-known Seasoned Issuer	No
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 36,942	$ 54,292
Short-term investments	87,675	72,060
Accounts receivable	1,431	402
Accrued revenue	0	128
Investment tax credits receivable	389	340
Prepaid expenses and other assets	2,792	2,144
Total current assets	129,229	129,366
Restricted investment	0	12,601
Investment in Genevant	22,224	0
Property and equipment	17,041	24,854
Less accumulated depreciation	(6,896)	(12,671)
Property and equipment, net of accumulated depreciation	10,145	12,183
Intangible assets	43,836	58,647
Goodwill	22,471	24,364
Total assets	227,905	237,161
Current liabilities:
Accounts payable and accrued liabilities	9,429	10,646
Deferred revenue	0	2,742
Site consolidation accrual	1,331	0
Liability-classified options	479	1,239
Total current liabilities	11,239	14,627
Deferred rent and inducements, long term	645	693
Loan payable	0	12,001
Contingent consideration	3,126	10,424
Deferred tax liability	12,661	16,943
Total liabilities	27,671	54,688
Stockholders’ equity:
Preferred shares, Authorized - 1,164,000 with no par value, Issued and outstanding: 1,164,000 (December 31, 2017 - 500,000)	126,136	49,780
Common shares, Authorized - unlimited number with no par value, Issued and outstanding: 55,518,800 (December 31, 2017 - 55,060,650)	879,405	876,108
Additional paid-in capital	48,084	42,840
Deficit	(805,221)	(738,070)
Accumulated other comprehensive loss	(48,170)	(48,185)
Total stockholders' equity	200,234	182,473
Total liabilities and stockholders' equity	$ 227,905	$ 237,161

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, no par value (in USD per share)
Preferred stock, shares authorized (in shares)	1,164,000	1,164,000,000
Preferred stock, shares issued (in shares)	1,164,000	500,000,000
Preferred stock, shares outstanding (in shares)	1,164,000	500,000,000
Common shares, no par value (in USD per share)
Common shares, shares issued (in shares)	55,518,800	55,060,650
Common shares, shares outstanding (in shares)	55,518,800	55,060,650

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Revenue
Revenue	$ 5,945	$ 10,700
Expenses
Research and development	57,934	62,676
General and administrative	16,002	16,129
Depreciation of property and equipment	2,181	2,027
Site consolidation	4,797	0
Impairment of intangible assets	14,811	40,798
Total expenses	95,725	121,630
Loss from operations	(89,780)	(110,930)
Other income (loss)
Interest income	3,047	1,538
Interest expense	(226)	(261)
Gain on investments	24,884	0
Equity investment (loss)	(5,562)	0
Foreign exchange gains/(loss)	(1,003)	2,301
Decrease (increase) in fair value of warrant liability	0	(22)
Increase in fair value of contingent consideration	7,298	(1,359)
Total other income	28,438	2,197
Loss before income taxes	(61,342)	(108,733)
Deferred income tax recovery	4,282	24,320
Net loss	(57,060)	(84,413)
Items applicable to preferred shares
Accrual of coupon on convertible preferred shares	(10,091)	(911)
Net loss attributable to common shares	$ (67,151)	$ (85,324)
Net loss attributable to common shareholders, per share
Basic net loss per common share (in USD per share)	$ (1.21)	$ (1.56)
Diluted net loss per common share (in USD per share)	$ (1.21)	$ (1.56)
Weighted average number of common shares
Basic weighted average number of common shares (in shares)	55,304,083	54,723,272
Diluted weighted average number of common shares (in shares)	55,304,083	54,723,272
Other Comprehensive loss
Cumulative translation adjustment	$ 15	$ 0
Comprehensive loss	$ (57,045)	$ (84,413)

Consolidated Statement of Stockholders’ Equity - USD ($) $ in Thousands	Total	Convertible Preferred Shares	Common Shares	Additional paid-in capital	Deficit	Accumulated other comprehensive loss
Beginning balance (in shares) at Dec. 31, 2016		0	54,841,494
Beginning balance at Dec. 31, 2016	$ 203,005	$ 0	$ 867,393	$ 36,543	$ (652,746)	$ (48,185)
Issuance of Preferred Shares, net of issuance cost (in shares)		500,000
Issuance of Preferred Shares, net of issuance cost	48,869	$ 48,869
Accrual of coupon on Preferred Shares	0	$ 911			(911)
Stock-based compensation	14,858		$ 7,972	6,886
Certain fair value adjustments to liability stock option awards	(540)			(540)
Issuance of common shares pursuant to exercise of options (in shares)			40,156
Issuance of common shares pursuant to exercise of options	213		$ 262	(49)
Issuance of common shares pursuant to exercise of warrants (in shares)			179,000
Issuance of common shares pursuant to exercise of warrants	481		$ 481
Net loss	(84,413)				(84,413)
Ending balance (in shares) at Dec. 31, 2017		500,000	55,060,650
Ending balance at Dec. 31, 2017	182,473	$ 49,780	$ 876,108	42,840	(738,070)	(48,185)
Issuance of Preferred Shares, net of issuance cost (in shares)		664,000
Issuance of Preferred Shares, net of issuance cost	66,265	$ 66,265
Accrual of coupon on Preferred Shares	0	$ 10,091			(10,091)
Stock-based compensation	6,687			6,687
Certain fair value adjustments to liability stock option awards	472			472
Issuance of common shares pursuant to exercise of options (in shares)			458,150
Issuance of common shares pursuant to exercise of options	1,382		$ 3,297	(1,915)
Currency translation adjustment	15					15
Net loss	(57,060)				(57,060)
Ending balance (in shares) at Dec. 31, 2018		1,164,000	55,518,800
Ending balance at Dec. 31, 2018	$ 200,234	$ 126,136	$ 879,405	$ 48,084	$ (805,221)	$ (48,170)

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
Consolidated Statements of Cash Flows - USD ($)	Dec. 31, 2018	Dec. 31, 2017
OPERATING ACTIVITIES
Net loss for the period	$ (57,060,000)	$ (84,413,000)
Items not involving cash:
Deferred income taxes	(4,282,000)	(24,320,000)
Depreciation of property and equipment	2,181,000	2,027,000
Gain on sale of property and equipment	(26,000)	(3,000)
Stock-based compensation	6,241,000	15,117,000
Unrealized foreign exchange gains (losses)	1,003,000	(2,374,000)
Change in fair value of warrant liability	0	22,000
Change in fair value of contingent consideration	(7,298,000)	1,359,000
Impairment of intangible assets	14,811,000	40,798,000
Site consolidation non-cash portion	396,000	0
Gain on equity investment	(24,884,000)	0
Equity investment loss	5,327,000	0
Net change in non-cash operating items:
Accounts receivable	(1,029,000)	(129,000)
Accrued revenue	128,000	0
Investment tax credits receivable	(49,000)	(47,000)
Prepaid expenses and other assets	(648,000)	(833,000)
Accounts payable and accrued liabilities	(1,266,000)	736,000
Deferred revenue	(2,742,000)	2,727,000
Deferred rent and inducements	0	693,000
Site consolidation accrual	1,331,000	0
Net cash used in operating activities	(67,866,000)	(48,640,000)
INVESTING ACTIVITIES
Disposition (acquisition) of investments	(3,014,000)	35,086,000
Proceeds from sale of property and equipment	25,000	3,000
Acquisition of property and equipment	(1,138,000)	(7,264,000)
Net cash provided by (used in) investing activities	(4,127,000)	27,825,000
FINANCING ACTIVITIES
Promissory note repayment	(12,001,000)	0
Proceeds from sale of Preferred Shares, net of issuance costs	66,265,000	48,869,000
Issuance of common shares pursuant to exercise of options	1,382,000	100,000
Issuance of common shares pursuant to exercise of warrants	0	353,000
Net cash provided by financing activities	55,646,000	49,322,000
Effect of foreign currency rate changes on cash and cash equivalents	(1,003,000)	2,372,000
Increase in cash and cash equivalents	(17,350,000)	30,879,000
Cash and cash equivalents, beginning of period	54,292,000	23,413,000
Cash and cash equivalents, end of period	36,942,000	54,292,000
Supplemental cash flow information
Preferred shares dividends accrued	10,091,000	0
Investment in Genevant (note 4)	27,377,000	0
Investment tax credits received	$ 0	$ 108,000

Nature of Business and Future Operations	12 Months Ended
Nature of Business and Future Operations	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of business and future operations	Nature of business and future operations Arbutus Biopharma Corporation (the “Company” or “Arbutus”) is a biopharmaceutical business dedicated to discovering, developing, and commercializing a cure for patients suffering from chronic hepatitis B infection, a disease of the liver caused by the hepatitis B virus (“HBV”). To pursue our strategy of developing a curative combination regimen, the Company has assembled a pipeline of multiple drug candidates with differing and complementary mechanisms of action targeting HBV. The success of the Company is dependent on obtaining the necessary regulatory approvals to bring its products to market and achieve profitable operations. The Company's research and development activities and commercialization of its products are dependent on its ability to successfully complete these activities and to obtain adequate financing through a combination of financing activities and operations. It is not possible to predict either the outcome of the Company's existing or future research and development programs or the Company’s ability to continue to fund these programs in the future.

Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Significant accounting policies

Basis of presentation and principles of consolidation

Tekmira Pharmaceuticals Corporation ("Tekmira") was incorporated in Canada on October 6, 2005 as an inactive wholly-owned subsidiary of Inex Pharmaceuticals Corporation ("Inex"). Pursuant to a “Plan of Arrangement” effective April 30, 2007, the business and substantially all of the assets and liabilities of Inex were transferred to Tekmira.

On March 4, 2015, Tekmira completed a business combination pursuant to which OnCore Biopharma, Inc. ("OnCore"), became a wholly-owned subsidiary of Tekmira.

On July 31, 2015, Tekmira changed its corporate name to Arbutus Biopharma Corporation and OnCore changed its corporate name to Arbutus Biopharma, Inc. (“Arbutus Inc.”).

The Company has two wholly-owned subsidiaries as of December 31, 2018: Arbutus, Inc. and Arbutus Biopharma US Holdings, Inc., which was formed in 2018.

Protiva Biotherapeutics Inc. ("Protiva") was acquired by the Company on May 30, 2008. On January 1, 2018, Protiva was amalgamated with Arbutus Biopharma Corporation. The Company's former wholly-owned subsidiary, Protiva Agricultural Development Company Inc ("PADCo") was previously recorded by the Company using the equity method. On March 4, 2016, Monsanto Company exercised its option to acquire 100% of the outstanding shares of PADCo.

These consolidated financial statements include the accounts of the Company and its two wholly-owned subsidiaries, in accordance with U.S. generally accepted accounting principles ("GAAP"). All intercompany balances and transactions have been eliminated. Certain prior year amounts have been reclassified to conform to the current year presentation.

Foreign currency translation and functional currency conversion

Prior to January 1, 2016, the Company's functional currency was the Canadian dollar. Translation gains and losses from the application of the U.S. dollar as the reporting currency during the period that the Canadian dollar was the functional currency are included as part of cumulative currency translation adjustment, which is reported as a component of shareholders' equity under accumulated other comprehensive loss.

The Company re-assessed its functional currency and determined as of January 1, 2016, its functional currency was changed from the Canadian dollar to the U.S. dollar based on management's analysis of changes in the primary economic environment in which the Company operates. The change in functional currency is accounted for prospectively from January 1, 2016.

For periods commencing January 1, 2016, monetary assets and liabilities denominated in foreign currencies are translated into U.S. dollars using exchange rates in effect at the balance sheet date. Opening balances related to non-monetary assets and liabilities are based on prior period translated amounts, and non-monetary assets and non-monetary liabilities are translated at the approximate exchange rate prevailing at the date of the transaction. Revenue and expense transactions are translated at the approximate exchange rate in effect at the time of the transaction. Foreign exchange gains and losses are included in the statement of operations and comprehensive loss as foreign exchange gains.

Use of estimates

The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions about future events that affect the reported amounts of assets, liabilities, revenue, expenses, contingent assets and contingent liabilities as at the end or during the reporting period. Actual results could significantly differ from those estimates. Significant areas requiring the use of management estimates relate valuation of intangible assets and goodwill, recognition of revenue, stock-based compensation, and the amounts recorded as accrued liabilities, contingent consideration, and income tax recovery.

Cash and cash equivalents

Cash and cash equivalents are all highly liquid instruments with an original maturity of three months or less when purchased. Cash equivalents are recorded at cost plus accrued interest. The carrying value of these cash equivalents approximates their fair value.

Short-term investments

Short-term investments have original maturities exceeding three months and have remaining maturities less than one year. Short-term investments accrue interest daily based on a fixed interest rate for the term. The carrying value of these investments are recorded at cost plus accrued interest, which approximates their fair value. All investments are governed by the Company's Investment Policy approved by the Company's board of directors.

Equity method investment

The Company accounts for its investment in associated companies in accordance with the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") 323, Investments - Equity Method and Joint Ventures ("ASC 323"). In accordance with ASC 323, associated companies are accounted for as equity method investments. Results of associated companies are presented on a one-line basis. Investments in, and advances to, associated companies are presented on a one-line basis in the caption “Investment in Genevant” in the Company's consolidated balance sheets, net of allowance for losses, which represents the Company's best estimate of probable losses inherent in such assets. The Company's proportionate share of any associated companies' net income or loss is presented on a one-line basis in the caption "Equity investment (loss)" in the Company's consolidated statement of operations. Transactions between the Company and any associated companies are eliminated on a basis proportional to the Company's ownership interest. Financial results of Genevant Sciences Ltd. ("Genevant") are recorded on a one-quarter lag basis.

Property and equipment

Property and equipment is recorded at cost less impairment losses, accumulated depreciation, related government grants and investment tax credits. The Company records depreciation using the straight-line method over the estimated useful lives of the capital assets as follows:



	Useful life (years)
Laboratory equipment		5
Computer and office equipment	2	to	5
Furniture and fixtures		5

Leasehold improvements are depreciated over their estimated useful lives but in no case longer than the lease term, except where lease renewal is reasonably assured.

If there is a major event indicating that the carrying value of property and equipment may be impaired then management will perform an impairment test and if the carrying value exceeds the recoverable value, based on undiscounted future cash flows, then such assets are written down to their fair values.

Goodwill and intangible assets

The costs incurred in establishing and maintaining patents for intellectual property developed internally are expensed in the period incurred.

Intangible assets consist of in-process research and development arising from the Company’s acquisition of Arbutus Inc. in 2015 (see note 6). In-process research and development ("IPR&D") intangible assets are classified as indefinite-lived and are not amortized. IPR&D becomes definite-lived upon the completion or abandonment of the associated research and development efforts. Intangible assets with finite useful lives are amortized on a straight-line basis over their estimated useful lives, which are the respective patent terms. Amortization begins when intangible assets with finite lives are put into use. If there is a major event indicating that the carrying value of intangible assets may be impaired, then management will perform an impairment test in an interim period and if the carrying value exceeds the recoverable value, based on discounted future cash flows, then such assets are written down to their fair values.

The Company reviews the recoverable amount of intangible assets and goodwill on an annual basis, and the annual evaluation is performed as of December 31 each year. In addition, the Company evaluates for events or changes in the business that could indicate impairment and earlier testing. Such indicators include, but are not limited to, on an ongoing basis: (a) industry and market considerations such as increased competitive environment or adverse change in legal factors including an adverse assessment by regulators; (b) an accumulation of costs significantly in excess of the amount originally expected for the development of the asset; (c) current period operating or cash flow loss combined with a history of operating or cash flow losses or a projection or forecast that demonstrates continuing losses associated with the use of the asset; (d) adverse research and development program results; and (e) if applicable, a sustained decrease in share price.

Goodwill represents the excess of purchase price over the value assigned to the net tangible and identifiable intangible assets of Arbutus Inc. Goodwill has an indefinite accounting life and is therefore not amortized. Instead, goodwill is assessed for impairment on an annual basis, unless the Company identifies impairment indicators that would require earlier testing. For the period ended December 31, 2017, the Company elected to early adopt Accounting Standards Update (“ASU”) 2017-04 – Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment, which simplifies the subsequent measurement of goodwill by eliminating Step 2 from the goodwill impairment test, which required a hypothetical purchase price allocation. A goodwill impairment will now be the amount by which a reporting unit's carrying value exceeds its fair value, not to exceed the carrying amount of goodwill. All other goodwill impairment guidance remains substantially unchanged, and management continues to have the ability to perform a qualitative assessment to determine if a quantitative impairment test is necessary. The Company performs its qualitative analysis using factors including but not limited to: (a) macroeconomic conditions; (b) industry and market considerations; (c) cost factors; (d) overall financial performance; (e) other relevant entity-specific events; (f) events affecting a reporting unit; and (g) if applicable, a sustained decrease in share price in absolute terms and relative to peers.

In the twelve months ended December 31, 2018, the Company disposed of a portion of its single reporting unit to Genevant. At that time, the Company allocated a portion of goodwill to its investment in Genevant based upon the relative fair value of Genevant to the Company as of April 11, 2018 (see note 4), as a result of which the carrying value of goodwill decreased by this same amount.

Revenue recognition

ASC 606, Revenue From Contracts with Customers ("ASC 606") became effective for the Company on January 1, 2018, and was adopted using the modified retrospective method under which previously presented financial statements are not restated and the cumulative effect of adopting ASC 606 on contracts in process is recognized by an adjustment to retained earnings at the effective date. The adoption of ASC 606 did not change recognized revenue under the Company's ongoing significant collaboration and license agreements and no cumulative effect adjustment was required.

ASC 606 requires an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers under a five-step model: (i) identify contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when or as a performance obligation is satisfied.

The Company generates revenue primarily through collaboration agreements and license agreements. Such agreements may require the Company to deliver various rights and/or services, including intellectual property rights or licenses and research and development services. Under such agreements, the Company is generally eligible to receive non-refundable upfront payments, funding for research and development services, milestone payments, and royalties.

In contracts where the Company has more than one performance obligation to provide its customer with goods or services, each performance obligation is evaluated to determine whether it is distinct based on whether (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available and (ii) the good or service is separately identifiable from other promises in the contract. The consideration under the contract is then allocated between the distinct performance obligations based on their respective relative stand-alone selling prices. The estimated stand-alone selling price of each deliverable reflects the Company's best estimate of what the selling price would be if the deliverable was regularly sold on a stand-alone basis and is determined by reference to market rates for the good or service when sold to others or by using an adjusted market assessment approach if the selling price on a stand-alone basis is not available.

The consideration allocated to each distinct performance obligation is recognized as revenue when control is transferred to the customer for the related goods or services. Consideration associated with at-risk substantive performance milestones, including sales-based milestones, is recognized as revenue when it is probable that a significant reversal of the cumulative revenue recognized will not occur. Sales-based royalties received in connection with licenses of intellectual property are subject to a specific exception in the revenue standards, whereby the consideration is not included in the transaction price and recognized in revenue until the customer’s subsequent sales or usages occur.

Leases and lease inducements

Leases are classified as either capital or operating leases. Leases which substantially transfer all benefits and risks of ownership of property to the Company are accounted for as capital leases. At the time a capital lease is entered into, an asset is recorded together with its related long-term obligation to reflect the purchase and financing. All other leases are accounted for as operating leases wherein rental payments are expensed as incurred. Lease inducements represent leasehold improvement allowances and reduced or free rent periods and are amortized on a straight-line basis over the term of the lease and are recorded as a reduction of rent expense. Sublease income resulting from the site consolidation is netted with lease expense for the facility after its cease-use date and the net amount is presented within site consolidation expense.

Research and development costs

Research and development costs, including acquired in-process research and development expenses for which there is no alternative future use, are charged as an expense in the period in which they are incurred.

Net loss attributable to common shareholders per share

The Company follows the two-class method when computing net loss attributable to common shareholders per share as the Company has issued Preferred Shares (note 10) that meet the definition of participating securities. The Company's Series A participating convertible preferred shares ("Preferred Shares") entitle the holders to participate in dividends but do not require the holders to participate in losses of the Company. Accordingly, if the Company reports a net loss attributable to holders of the Company's common shares, net losses are not allocated to holders of the Preferred Shares.

Net loss attributable to common shareholders per share is calculated based on the weighted average number of common shares outstanding. Diluted net loss attributable to common shareholders per share does not differ from basic net loss attributable to common shareholders per share for the years ended December 31, 2018 and 2017, since the effect of the Company’s stock options and warrants is anti-dilutive.

The following table sets out the computation of basic and diluted net loss attributable to common shareholders per share:



	For the year ended December 31
	2018					2017
Numerator:	Common Shares			Preferred Shares		Common Shares			Preferred Shares
Allocation of distributable earnings	$	—		$	10,091	$	—		$	911
Allocation of undistributed earnings (loss)	(67,151		)	—		(85,324		)	—
Allocation of earnings (loss) attributed to shareholders	$	(67,151	)	$	10,091	$	(85,324	)	$	911
Denominator:
Weighted average number of shares - basic and diluted	55,304,083			1,142,170		54,723,272			104,110
Basic and diluted net loss attributable to shareholders per share	$	(1.21	)	$	8.83	$	(1.56	)	$	8.75

For the year ended December 31, 2018, potential common shares of 6,849,000 pertaining to stock options outstanding and 17,868,000 pertaining to if-converted preferred shares for a total of 24,717,000 were excluded from the calculation of income per common share because their inclusion would be anti-dilutive (December 31, 2017 total – 12,521,550).

Government grants and refundable investment tax credits

Government grants and tax credits provided for current expenses are included in the determination of income or loss for the year, as a reduction of the expenses to which they relate.

Deferred income taxes

Income taxes are accounted for using the asset and liability method of accounting. Deferred income taxes are recognized for the future income tax consequences attributable to differences between the carrying values of assets and liabilities and their respective income tax bases and for loss carry-forwards. Deferred income tax assets and liabilities are measured using enacted income tax rates expected to apply to taxable income in the periods in which temporary differences are expected to be recovered or settled. The effect on deferred income tax assets and liabilities of a change in tax laws or rates is included in earnings in the period that includes the enactment date. When realization of deferred income tax assets does not meet the more-likely-than-not criterion for recognition, a valuation allowance is provided.

Equity classified stock option awards

The Company grants stock options to employees, directors and consultants pursuant to share incentive plans described in note 12. Compensation expense is recorded for issued stock options using the fair value method with a corresponding increase in additional paid-in capital. Any consideration received on the exercise of stock options is credited to share capital.

The fair value of equity classified stock options is measured at the grant date and amortized on a straight-line basis over the vesting period.

Liability-classified stock option awards

The Company accounts for liability-classified stock option awards ("liability options") under ASC 718 - Compensation - Stock Compensation ("ASC 718"), under which awards of options that provide for an exercise price that is not denominated in: (a) the currency of a market in which a substantial portion of the Company's equity securities trades, (b) the currency in which the employee's pay is denominated, or (c) the Company's functional currency, are required to be classified as liabilities. Due to the change in functional currency as of January 1, 2016, certain stock option awards with exercise prices denominated in Canadian dollars changed from equity classification to liability classification. As such, the historic equity classification of these stock option awards changed to liability classification effective January 1, 2016. The change in classification resulted in reclassification of these awards from additional paid-in capital to liability-classified options.

Liability options are re-measured to their fair values at each reporting date with changes in the fair value recognized in share-based compensation expense or additional paid-in capital until settlement or cancellation. Under ASC 718, when an award is reclassified from equity to liability, if at the reclassification date the original vesting conditions are expected to be satisfied, then the minimum amount of compensation cost to be recognized is based on the grant date fair value of the original award. Fair value changes below this minimum amount are recorded in additional paid-in capital.

Replacement awards

Replacement awards are share-based payment awards exchanged for awards held by employees of Arbutus Inc. As part of the Company’s acquisition of Arbutus Inc., the Company's common shares were exchanged for Arbutus Inc.’s shares subject to repurchase rights held by Arbutus Inc.’s employees.

As at the date of acquisition of Arbutus Inc., the Company determined the total fair value of replacement awards and attributed a portion of the replacement awards to pre-combination service as part of the total acquisition consideration, and a portion to post-combination service, which is recognized as compensation expense over the expiry period of repurchase provision rights subsequent to the acquisition date.

The replacement awards consist of common shares that were issued upon the closing of the acquisition. Accordingly, as stock compensation expense related to these awards is recognized, share capital is increased by a corresponding amount. Replacement awards are excluded in the calculation of basic net income (loss) per common share until the repurchase rights have expired.

Warrants

The Company accounts for the warrants under the authoritative guidance on accounting for derivative financial instruments indexed to, and potentially settled in, a company’s own stock, on the understanding that in compliance with applicable securities laws, the registered warrants require the issuance of registered securities upon exercise and do not sufficiently preclude an implied right to net cash settlement. The Company classifies warrants in its consolidated balance sheet as a liability which is revalued at each balance sheet date subsequent to the initial issuance. The Company uses the Black-Scholes pricing model to value the warrants. Determining the appropriate fair-value model and calculating the fair value of registered warrants requires considerable judgment. A small change in the estimates used may cause a relatively large change in the estimated valuation. The estimated volatility of the Company’s common shares at the date of issuance, and at each subsequent reporting period, is based on historic fluctuations in the Company’s stock price. The risk-free interest rate is based on the Government of Canada rate for bonds with a maturity similar to the expected remaining life of the warrants at the valuation date. The expected life of the warrants is based on the historical pattern of exercises of warrants.

Preferred Shares

The Company accounts for Preferred Shares under ASC 480 – Distinguishing Liabilities from Equity (“ASC 480”), which provides guidance for equity instruments with conversion features. The Company classifies Preferred Shares in its consolidated balance sheet wholly as equity, with no bifurcation of conversion feature from the host contract, given that the Preferred Shares cannot be cash settled and the redemption features, which include a fixed conversion ratio with predetermined timing and proceeds, are within the Company's control. The Company accrues for the 8.75% per annum compounding accrual at each reporting period end date as an increase to share capital, and an increase to deficit.

Segment information

The Company operates in a single reporting segment. Substantially all of the Company’s revenues to date were earned from customers or collaborators based in the United States. Substantially all of the Company’s premises, property and equipment are located in Canada and the United States.

Recent accounting pronouncements

ASC 606, Revenue From Contracts with Customers ("ASC 606") became effective for the Company on January 1, 2018, and was adopted using the modified retrospective method under which previously presented financial statements are not restated and the cumulative effect of adopting ASC 606 on contracts in process is recognized by an adjustment to retained earnings at the effective date. The adoption of ASC 606 did not change the Company’s recognized revenue under its ongoing significant collaboration and license agreements and no cumulative effect adjustment was required.

In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments ("ASU 2016-15"). ASU 2016-15 clarifies certain aspects of the statement of cash flows, and aims to reduce diversity in practice regarding how certain transactions are classified in the statement of cash flows. ASU 2016-15 was effective as of January 1, 2018 and was adopted by the Company in the first quarter of 2018. The adoption of ASU 2016-15 did not have a material impact on the Company's condensed consolidated balance sheets or condensed consolidated statements of operations and comprehensive income (loss).

In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash ("ASU 2016-18") that clarifies how entities should present restricted cash in the statement of cash flows. Under ASU 2015-18, changes in total cash, inclusive of restricted cash, should be reflected in the statement of cash flows. As a result, transfers between cash and restricted cash are no longer reflected as activity within the statement of cash flows. The Company adopted ASU 2016-18 on January 1, 2018. The adoption of ASU 2018-18 did not have a material impact on the Company's condensed consolidated statements of cash flows.

In October 2016, the FASB issued ASU No. 2016-16, Income Taxes (Topic 740): Intra-Entity Transfer of Assets Other Than Inventory ("ASU 2016-16"). ASU 2016-16 eliminates the deferral of the tax effects of intra-entity asset transfers other than inventory. As a result, the income tax consequences from the intra-entity transfer of an asset other than inventory and associated changes to deferred taxes will be recognized when the transfer occurs. The Company adopted ASU 2016-16 in the first quarter of 2018. The adoption of ASU 2016-16 did not have a material impact on the Company's condensed consolidated balance sheets or condensed consolidated statements of operations and comprehensive income (loss).

In June 2018, the FASB issued ASU No. 2018-07, Compensation-Stock Compensation (Topic 718), Improvements to Nonemployee Share-Based Payment Accounting ("ASU 2018-07"). ASU 2018-07 provides guidance about aligning nonemployee and employee share-based payment accounting. ASU 2018-07 is effective for all entities for annual periods, and interim periods within those annual periods, beginning after December 15, 2018. The Company early adopted the new standard as of January 1, 2018. The adoption of ASU 2018-07 did not have a material impact on the Company's condensed consolidated balance sheets or condensed consolidated statements of operations and comprehensive income (loss).

Accounting pronouncements not yet adopted

In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842), which generally requires the recognition of operating and financing lease liabilities with corresponding right-of-use assets on the balance sheet. The Company adopted the new standard on January 1, 2019 using the modified retrospective basis applied at the effective date of the new standard and elected to utilize a package of practical expedients. The new lease standard only impacts the Company's three property leases. The Company continues to evaluate and finalize the effect of adopting this guidance on our consolidated financial statements and related disclosures.

In November 2018, the FASB issued targeted amendments to Topic 808, Collaborative Arrangements, and Topic 606, Revenue from Contracts with Customers, to clarify that certain transactions between parties to collaborative arrangements should be accounted for in accordance with FASB revenue guidance when the counterparty is a customer. This guidance also prohibits the presentation of collaborative arrangements as revenues from contracts with customers if the counterparty is not a customer. This guidance, which is required to be applied retrospectively and is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted, is not expected to have an impact on the Company’s consolidated financial statements.

Fair Value Measurements

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Fair value measurements

The Company measures certain financial instruments and other items at fair value.

To determine the fair value, the Company uses the fair value hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs market participants would use to value an asset or liability and are developed based on market data obtained from independent sources. Unobservable inputs are inputs based on assumptions about the factors market participants would use to value an asset or liability. The three levels of inputs that may be used to measure fair value are as follows:


•	Level 1 inputs are quoted market prices for identical instruments available in active markets.


•	Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability either directly or indirectly. If the asset or liability has a contractual term, the input must be observable for substantially the full term. An example includes quoted market prices for similar assets or liabilities in active markets.


•	Level 3 inputs are unobservable inputs for the asset or liability and will reflect management’s assumptions about market assumptions that would be used to price the asset or liability.

Assets and liabilities are classified based on the lowest level of input that is significant to the fair value measurements. Changes in the observability of valuation inputs may result in a reclassification of levels for certain securities within the fair value hierarchy.

The carrying values of cash and cash equivalents, short-term investments, accounts receivable and accounts payable and accrued liabilities approximate their fair values due to the immediate or short-term maturity of these financial instruments.

As quoted prices for the warrants are not readily available, the Company has used a Black-Scholes pricing model to estimate fair value. These are level 3 inputs as defined above.

To determine the fair value of the contingent consideration (note 15), the Company uses a probability weighted assessment of the likelihood the milestones would be met and the estimated timing of such payments, and then the potential contingent payments were discounted to their present value using a probability adjusted discount rate that reflects the early stage nature of the development program, time to complete the program development, and overall biotech indices. The Company determined the fair value of the contingent consideration was $3,126,000 and the decrease of $7,298,000 has been recorded in other losses in the statement of operations and comprehensive loss for the year ended December 31, 2018. The assumptions used in the discounted cash flow model are level 3 inputs as defined above.

The following tables present information about the Company’s assets and liabilities that are measured at fair value on a recurring basis, and indicates the fair value hierarchy of the valuation techniques used to determine such fair value:



	Level 1		Level 2	Level 3	December 31, 2018
Assets
Cash and cash equivalents	$	36,942	—	—	$	36,942
Short-term investments	87,675		—	—	87,675
Restricted investment	—		—	—	—
Total	$	124,617	—	—	$	124,617
Liabilities
Liability-classified stock option awards	—		—	479	479
Contingent consideration	—		—	3,126	3,126
Total	—		—	3,605	$	3,605



	Level 1		Level 2	Level 3		December 31, 2017
Assets
Cash and cash equivalents	$	54,292	—	—		$	54,292
Guaranteed investment certificates	72,060		—	—		72,060
Restricted investment	12,601		—	—		12,601
Total	$	138,953	—	—		$	138,953
Liabilities

Liability-classified stock option awards	—		—	1,239		1,239
Contingent consideration	—		—	10,424		10,424
Total	—		—	$	11,663	$	11,663

The following table presents the changes in fair value of the Company’s warrants:



	Liability at beginning of the period		Fair value of warrants exercised in the period			Increase (decrease) in fair value of warrants		Foreign exchange loss		Liability at end of the period
Year ended December 31, 2017	$	107	$	(129	)	$	22	$	—	$	—
Year ended December 31, 2018	$	—	$	—		$	—	$	—	$	—

The following table presents the changes in fair value of the Company’s liability-classified stock option awards:



	Liability at beginning of the period		Fair value of liability-classified stock option awards exercised in the period			Increase (decrease) in fair value of liability			Liability at end of the period
Year ended December 31, 2017	$	553	$	(103	)	$	789		$	1,239
Year ended December 31, 2018	$	1,239	$	(93	)	$	(667	)	$	479

The following table presents the changes in fair value of the Company’s contingent consideration:



	Contingent consideration at beginning of the period		Increase in fair value of contingent consideration			Contingent consideration at end of the period
Year ended December 31, 2017	$	9,065	$	1,359		$	10,424
Year ended December 31, 2018	$	10,424	$	(7,298	)	$	3,126

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Equity method investment

12 Months Ended

Dec. 31, 2018

Equity Method Investments and Joint Ventures [Abstract]

Equity method investment

On April 11, 2018, the Company entered into an agreement (the "Genevant Agreement") with Roivant Sciences Ltd.("Roivant") to launch Genevant Sciences Ltd. ("Genevant"), a company focused on the discovery, development, and commercialization of a broad range of RNA-based therapeutics enabled by the Company's proprietary lipid nanoparticle ("LNP") and ligand conjugate delivery technologies.

Under the terms of the Genevant Agreement, the Company contributed a license for the delivery technologies and fixed assets. The fixed assets had a carrying value of $600,000. The contributed license provides Genevant with exclusive rights to the LNP and ligand conjugate delivery platforms for RNA-based applications outside of HBV. Roivant contributed $37,500,000 in transaction-related seed capital to Genevant, consisting of an initial capital contribution of $22,500,000 and a subsequent investment of $15,000,000 at a pre-determined, stepped-up valuation. The Company retains all rights to the LNP and ligand conjugate delivery platforms for HBV, and is entitled to a tiered low single-digit royalty from Genevant on future sales of products enabled by those delivery platforms. The Company also retains the entirety of its royalty entitlement on the commercialization of Alnylam Pharmaceutical, Inc.'s ("Alnylam") Onpattro.

The Company determined that, since the Genevant Agreement stipulates that significant decisions relating to the management of Genevant must be shared between the Company and Roivant, the Company does not control Genevant but does exercise significant influence over it and, will therefore, account for its investment in Genevant using the equity method. On April 11, 2018, the Company and Roivant each received a 50% ownership interest in Genevant. As a result of a pre-determined, subsequent investment in Genevant by Roivant and other parties, as contemplated in the initial agreement, as of December 31, 2018, the Company owned approximately 40% of the common equity of Genevant.

The Company's contribution of licenses related to the delivery technologies and fixed assets in exchange for an equity interest in Genevant resulted in a gain of $24,884,000 during the second quarter of 2018. The gain reflected the fair value of the equity in Genevant received by the Company less the $600,000 carrying value of the fixed assets contributed by the Company and $1,893,000 of goodwill allocated to Genevant based upon the relative fair value of Genevant to the Company as of April 11, 2018. The fair value of equity in Genevant received by the Company was based on a valuation performed by external valuation specialists.

The following table provides a summary of the Company's investment in Genevant for the year ended December 31, 2018, in thousands:



	Year ended December 31, 2018
Beginning balance	$	—
Initial investment in Genevant	27,377
Share of stock based compensation for Genevant employees who continue to vest in Arbutus stock options	159
Share of net loss (on a one-quarter lag basis)	(5,206		)
Dilution loss	(122		)
Share of comprehensive loss - currency translation adjustment	16
Ending balance	$	22,224

The basis difference between the Company’s carrying value in Genevant and the Company’s share of Genevant's net assets is attributed primarily to indefinite-lived IPR&D (the delivery technology transferred to Genevant).

The following table summarizes unaudited financial information for our equity method investee and is reported on a one quarter lag.



	2018
Balance Sheet:
Current assets	$	32,027
Non-current assets	1,644
Total assets	33,671

Current liabilities	4,911
Non-current liabilities	253
Shareholders' equity	28,507
Total liabilities and shareholders' equity	$	33,671



	2018
Results of Operations:
Revenue	$	—
Gross profit	—
Operating Loss	(12,421		)
Net Loss	$	(12,770	)

Property and Equipment

12 Months Ended

Dec. 31, 2018

Property, Plant and Equipment [Abstract]

Property and equipment



December 31, 2018	Cost		Accumulated depreciation			Net book value
Lab equipment	$	5,420	$	(2,455	)	$	2,965
Leasehold improvements	9,308		(2,401		)	6,907
Computer hardware and software	2,313		(2,040		)	273
Furniture and fixtures	—		—			—
	$	17,041	$	(6,896	)	$	10,145



December 31, 2017	Cost		Accumulated depreciation			Net book value
Lab equipment	$	9,567	$	(5,325	)	$	4,242
Leasehold improvements	12,578		(5,139		)	7,439
Computer hardware and software	2,318		(1,878		)	440
Furniture and fixtures	391		(329		)	62
	$	24,854	$	(12,671	)	$	12,183

During 2018, the Company disposed of certain fixed assets in connection with the closure of the Burnaby facility. The fixed assets had a net book value of $0.3 million ($6.2 million at cost, net of $5.9 million of accumulated depreciation) related to the closure of the Burnaby facility. The Company also transferred certain assets to Genevant in 2018 with a net book value of $0.6 million ($1.1 million at cost, net of $0.5 million of accumulated depreciation).

Intangible Assets and Goodwill

12 Months Ended

Dec. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible assets and goodwill

All IPR&D acquired is currently classified as indefinite-lived and is not currently being amortized. IPR&D becomes definite-lived upon the completion or abandonment of the associated research and development efforts, and will be amortized from that time over an estimated useful life based on respective patent terms. The Company evaluates the recoverable amount of intangible assets on an annual basis and performs an annual evaluation of goodwill as of December 31 each year, unless there is an event or change in the business that could indicate a requirement to test at an interim period, in which case earlier testing is performed.

Intangible assets impairment evaluation

During the year-ended December 31, 2018, the Company recorded an intangible assets impairment charge of $14,811,000 and a corresponding income tax benefit of $4,282,000 related to the decrease in deferred tax liability for the indefinite delay of further development of its AB-423 program in the capsid inhibitor drug class as a result of the Company's decision to advance its second generation capsid agent into the HBV patient portion of its phase 1 clinical trial.

During the year-ended December 31, 2017, the Company recorded a total impairment charge of $40,798,000 for the discontinuance of the stimulator of interferon genes (“STING”) agonists. This charge represents the remaining value of the acquired Immune Modulator drug class. In addition, the Company recorded an income tax benefit of $16,926,000 corresponding to the impairment charge - see note 13.

The following table summarizes the carrying values, net of impairment of the intangible assets as at December 31, 2018:



Year ended December 31,	2018		2017
IPR&D – Immune Modulators	$	—	$	—
IPR&D – Antigen Inhibitors	—		14,811
IPR&D – cccDNA Sterilizers	43,836		43,836
Total IPR&D	$	43,836	$	58,647

Annual impairment evaluation of goodwill

The Company has one reporting unit for goodwill purposes given that resource allocation and performance is largely driven by consolidated metrics. In addition, there is limited discrete financial information available and reviewed below the consolidated level.

Goodwill represents the excess of purchase price over the value assigned to the net tangible and identifiable intangible assets of Arbutus Inc.

In April 2018, the Company allocated $1,893,000 of goodwill to its investment in Genevant based upon the relative fair value of Genevant to the Company (see note 4), as a result of which the carrying value of goodwill decreased by this same amount. As of December 31, 2018, the Company performed a qualitative assessment and did not identify any indicators of impairment of goodwill, and therefore no impairment charge on goodwill was recorded during the twelve months then ended December 31, 2018 (twelve months ended December 31, 2017 - $0). The intangible impairment charge of $14,811,000 described above represents a discrete, program specific event and was not considered to be an indicator of impairment of goodwill.

The Company determines the fair value of the reporting unit using accepted valuation methods, including the use of discounted cash flows supplemented by market-based assessments of fair value. The income approach is used for the quantitative assessment to estimate the fair value of the reporting unit, which requires estimating future cash flows and risk-adjusted discount rates in the Company's discounted cash flow model. The overall market outlook and cash flow projections of the reporting unit involves the use of key assumptions, including cash flows, discount rates and probability of success. Due to uncertainties in the estimates that are inherent to the Company's industry, actual results could differ significantly from the estimates made. Many key assumptions in the cash flow projections are interdependent on each other. A change in any one or combination of these assumptions could impact the estimated fair value of the reporting unit. See note 2 for additional discussion of the Company's policy for accounting for goodwill.

Site Consolidation

12 Months Ended

Dec. 31, 2018

Restructuring and Related Activities [Abstract]

Site consolidation

On February 8, 2018, the Company announced a site consolidation and organizational restructuring to align its HBV business in Warminster, PA, by reducing its global workforce by approximately 35% and by closing its Burnaby facility. In March 2018, the Company began executing its site consolidation plan and began to incur related costs.

The Company estimates that the total expenses to complete the site consolidation will be approximately $5,600,000. Included in the site consolidation plan is the payment of one-time employee termination benefits, employee relocation costs, and site closure costs, which were primarily paid in cash in the second quarter of 2018. In addition, as of June 30, 2018 the Company ceased to use its Burnaby facility. The Company has entered into subleases with various tenants, including Genevant, for a portion of the Burnaby facility. The Company does not, however, expect the subleasing income to completely cover the costs under the lease to which the Company remains the primary obligor. Therefore, the Company has recognized the remaining committed cost, less sublease income currently under contract, in site consolidation expenses.

The Company accounts for site consolidation expense in accordance with ASC 420, Exit or Disposal Cost Obligations ("ASC 420"). ASC 420 specifies that a liability for a cost associated with an exit or disposal activity be recognized when the liability is incurred, except for a liability where employees are required to render service until they are terminated in order to receive termination benefits and will be retained to render service beyond the minimum retention period. A liability for such one-time termination benefits shall be measured initially at the communication date based on the fair value of the liability as of the termination date and recognized ratably over the future service period.

The following table shows expenses for the twelve months ended December 31, 2018 and the liability as of December 31, 2018, in thousands:



Description of expense	Twelve months ended December 31, 2018
Employee severance	$	2,851
Employee relocation	823
Lease and facility	1,123
Total site consolidation expense	4,797
Amounts paid and adjustments	(3,466		)
Accrued balance	$	1,331

Loan Payable	12 Months Ended
Loan Payable	Dec. 31, 2018
Debt Disclosure [Abstract]
Loan payable	Loan payable The Company had a bank loan of $12,001,000 in the form of a promissory note for the purpose of financing its operations and expanding its laboratory facilities in the U.S. The loan accrued interest daily at a rate of one-month London Interbank Offered Rate (LIBOR) plus 1.25% per annum. The maturity date of the loan was December 27, 2019. The loan was secured by the Company's cash of $12,601,000 and was restricted from use until the loan was settled in full. The Company invested the restricted cash in a two-year fixed certificate of deposit with a bank and was presented as restricted investment in the Company's balance sheet for the period ended December 31, 2017. In March 2018, the Company repaid the loan and accrued interest in full, resulting in the release of $12,601,000 from restricted cash to short-term investments on the Company's condensed consolidated balance sheet.

Shareholders' Equity	12 Months Ended
Shareholders' Equity	Dec. 31, 2018
Equity [Abstract]
Shareholders' equity	Shareholders' equity Authorized share capital The Company’s authorized share capital consists of an unlimited number of common shares and 1,164,000 preferred shares without par value. Open Market Sale Agreement In December 2018, we entered into an Open Market Sale Agreement (“Sale Agreement”) with Jefferies LLC, under which we may issue and sell common shares, from time to time, for an aggregate sales price of up to $50.0 million. We have not sold any shares under the Sale Agreement during the year ended December 31, 2018. Series A Preferred Shares On October 2, 2017, the Company announced that it entered into a subscription agreement with Roivant for the sale of Preferred Shares to Roivant for gross proceeds of $116,400,000. The Preferred Shares are non-voting and are convertible into common shares at a conversion price of $7.13 per share (which represents a 15% premium to the closing price of $6.20 per share). The purchase price for the Preferred Shares plus an amount equal to 8.75% per annum, compounded annually, will be subject to mandatory conversion into common shares on October 18, 2021 (subject to limited exceptions in the event of certain fundamental corporate transactions relating to Arbutus’ capital structure or assets, which would permit earlier conversion at Roivant’s option). Assuming conversion of the Preferred Shares into common shares, based on the number of common shares outstanding on December 31, 2018, Roivant would hold 49.6% of the Company's common shares. Roivant has agreed to a four year lock-up period for this investment and its existing holdings in Arbutus. Roivant has also agreed to a four year standstill whereby Roivant will not acquire greater than 49.99% of the Company's common shares or securities convertible into common shares. The initial investment of $50,000,000 closed on October 16, 2017, and the remaining amount of $66,400,000 closed on January 12, 2018 following regulatory and shareholder approvals. The Company records the Preferred Shares wholly as equity under ASC 480, with no bifurcation of conversion feature from the host contract, given that the Preferred Shares cannot be cash settled and the redemption features are within the Company's control, which include a fixed conversion ratio with predetermined timing and proceeds. The Company accrues for the 8.75% per annum compounding coupon at each reporting period end date as an increase to share capital, and an increase to deficit (see statement of stockholder's equity). Warrants to purchase common shares The Company has no outstanding warrants as of December 31, 2018 and December 31, 2017. During the year ended December 31, 2017, there were 179,000 warrants exercised for $353,000 in cash. In March 2017, the remaining balance of 22,000 of the Company's warrants expired. The decrease in fair value from the previous balance sheet date relating to the expired warrants was included in the total decrease in fair value of warrant liability in the Company's statement of net loss and comprehensive loss for the year ended December 31, 2017.

Collaborations, Contracts and Licensing Agreements

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Collaborations, contracts and licensing agreements

The following tables set forth revenue recognized under collaborations, contracts and licensing agreements:



	Year ended December 31
	2018		2017
Alexion (a)	$	—	$	7,956
Gritstone (b)	4,318		2,499
Other milestone and royalty payments (c)	1,627		245
Total revenue	$	5,945	$	10,700

The following table sets forth deferred collaborations and contracts revenue:



	Year ended December 31
	2018		2017
Gritstone (b)	$	—	$	2,727
Other	—		15
Total deferred revenue	$	—	$	2,742

(a) License Agreement with Alexion Pharmaceuticals, Inc.

On March 16, 2017, the Company signed a license agreement with Alexion Pharmaceuticals, Inc. ("Alexion") that entitles Alexion to research, develop, manufacture, and commercialize products with the Company's LNP technology in their single orphan disease target. In consideration for the rights granted under the agreement, the Company received a $7,500,000 non-refundable upfront cash payment, as well as payments for services provided. This upfront payment was amortized over the period of expected benefit.

On July 27, 2017, the Company received notice of termination from Alexion for the Company's LNP license agreement. The termination was driven by a strategic review of Alexion's business and research and development portfolio, which included a decision to discontinue development of mRNA therapeutics. The $7,500,000 upfront payment received in March 2017 is non-refundable, and the Company has recorded the upfront payment as well as any revenue and costs related to closeout procedures in the statement of operations and comprehensive loss for the period ended December 31, 2017.

(b) License agreement with Gritstone Oncology, Inc.

On October 16, 2017, the Company entered into a license agreement with Gritstone Oncology, Inc. ("Gritstone") that entitles Gritstone to research, develop, manufacture and commercialize products with the Company’s LNP technology. The Company received an upfront payment in November 2017, and is eligible to receive future potential payments including research services, development and commercial milestone payments and royalty payments on future product sales. As a result of the Company's agreement with Genevant (see note 3 for details), from April 11, 2018 going forward Genevant is entitled to 50% of the revenues earned by the Company from Gritstone and the Company will record revenues on a net basis.

The Company determined the deliverables under the Agreements included the rights and license granted, involvement in the joint steering committee, and other services provided, as determined under the research plan. The license and involvement in the joint steering committee have been determined by the Company to not have standalone value. Therefore, these deliverables are treated as one unit of accounting and recognized as revenue over the performance period as the Company transfers the technical "know-how" for the customized formulations.

The Company has determined that other materials and services provided have standalone value. The relative fair values are estimated upon the execution of each activity and charged at rates comparable to market with embedded margins on each service activity.

Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received.

As a result of the Company's agreement with Genevant (see note 4 for details), from April 11, 2018 going forward, Genevant is entitled to 50% of the revenues earned by the Company from Gritstone. The Company is the agent in this arrangement and records revenue on a net basis. In 2018, Gritstone paid a development milestone payment of $2,500,000 pursuant to the license agreement. The Company recorded revenue of $1,250,000, net of the portion paid to Genevant.

Alnylam Pharmaceuticals, Inc.

In 2012, the Company entered into a license agreement with Alnylam that entitles Alnylam to develop and commercialize products with the Company’s LNP technology. During the third quarter of 2018, Alnylam's Onpattro^TM, which utilizes the Company's LNP technology, was approved by the Food and Drug Administration ("FDA") in the United States and the European Medicines Agency. See Item 1 - Business for additional information. In 2018, the Company recorded revenue of $750,000 for development milestones related to FDA approval and the first commercial sale of Onpattro^TM. Additionally, the Company retains full rights to low to mid single-digit royalties on global sales of Onpattro^TM. The Company received the first royalty payment for sales of Onpattro^TM from Alnylam in the fourth quarter of 2018.

Acuitas Therapeutics Inc.

Consistent with the terms of the settlement agreement signed in November 2012, the Company finalized and entered a cross-license agreement with Acuitas Therapeutics, Inc. ("Acuitas") in December 2013. The terms of the cross-license agreement provide Acuitas with access to certain of the Company's earlier IP generated prior to mid-April 2010 in the fields of gene replacement therapy and antisense. Acuitas may only grant access to the Company's LNP technology to its partners if it is part of a product sublicense. At the same time, the terms provide the Company with certain access to Acuitas’ technology and licenses in the RNAi field, along with a percentage of each milestone and royalty payment with respect to certain products. Acuitas has agreed that it would not compete in the RNAi field for a period of five years, ending in November 2017. The Company considered Acuitas to be in material breach of their cross-license agreement and in February 2018, the Company and Acuitas reached a settlement terminating Acuitas’ right to further use or sublicense Arbutus' LNP technology. Please refer to "Item 3. Legal Proceedings" for additional information.

Spectrum Pharmaceuticals, Inc.

In May 2006, the Company signed a number of agreements with Talon Therapeutics, Inc. (“Talon”, formerly Hana Biosciences, Inc.) including the grant of worldwide licenses (the “Talon License Agreement”) for three of the Company’s chemotherapy products, Marqibo®, Alocrest ™ (Optisomal Vinorelbine) and Brakiva ™ (Optisomal Topotecan).

In 2012, Talon had received approval for Marqibo from the FDA for the treatment of adult patients with Philadelphia chromosome negative acute lymphoblastic leukemia in second or greater relapse or whose disease has progressed following two or more anti-leukemia therapies. Marqibo is a liposomal formulation of the chemotherapy drug, vincristine. In 2012, the Company received a milestone of $1,000,000 based on the FDA’s approval of Marqibo and receives royalty payments based on Marqibo’s commercial sales. There are no further milestones related to Marqibo but the Company is eligible to receive total milestone payments of up to $18,000,000 on Alocrest and Brakiva. Talon was acquired by Spectrum Pharmaceuticals, Inc. in July 2013. The acquisition did not affect the terms of the license between Talon and the Company.

United States Government’s Department of Defense to develop TKM-Ebola

On July 14, 2010, the Company signed a contract with the Department of Defense ("DoD") to advance TKM-Ebola, an RNAi therapeutic utilizing the Company’s LNP technology to treat Ebola virus infection.

Under the contract, the Company was reimbursed for costs incurred, including an allocation of overhead costs, and was paid an incentive fee. At the beginning of the fiscal year, the Company estimated its labor and overhead rates for the year ahead. At the end of the year the actual labor and overhead rates are calculated and revenue is adjusted accordingly. The Company’s actual labor and overhead rates differed from its estimated rates based on actual costs incurred and the proportion of the Company’s efforts on contracts and internal products versus indirect activities. Within minimum and maximum collars, the amount of incentive fee the Company earned under the contract was variable based on costs incurred versus budgeted costs. During the contractual period, incentive fee revenue and total costs were impacted by management’s estimate and judgments which were continuously reviewed and adjusted as necessary using the cumulative catch-up method. From the year ended December 31, 2015 onwards, the Company believed it could reliably estimate the final contract costs so recognized the portion of expected incentive fee which had been earned to date.

On October 1, 2015, the Company received formal notification from the DoD that, due to the unclear development path for TKM-Ebola and TKM-Ebola-Guinea, the Ebola-Guinea Manufacturing and the Ebola-Guinea IND submission statements of work had been terminated, subject to the completion of certain post-termination obligations. The TKM-Ebola portion of the contract was completed in November 2015. In 2018 the Company concluded contract close out procedures with the DoD.

Stock-based Compensation

12 Months Ended

Dec. 31, 2018

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-based compensation

Awards outstanding and available for issuance

Combining all of the Company’s share-based compensation plans, at December 31, 2018, the Company has 6,848,861 options outstanding and a further 3,158,353 Awards available for issuance.

At the Company’s annual general and special meeting of shareholders on May 19, 2016, the shareholders of the Company approved the adoption of the Company's 2016 Omnibus Share and Incentive Plan (the "2016 Plan") and the reserve of 5,000,000 common shares of the Company issuable pursuant to awards under the 2016 Plan.

In June 2011, the shareholders of the Company approved the 2011 Omnibus Share Compensation Plan, as amended in May 2016 (the "2011 Plan"), which still remains in effect. The 2011 Plan replaced the 2007 Omnibus Compensation Plan (the "2007 Plan"). The 2007 Plan continued to govern the options granted thereunder. No further options were granted under the Company’s 2007 Plan.

Under the 2016 and 2011 Plans, the Company's board of directors may grant options, and other types of Awards, to employees, directors and consultants of the Company. The exercise price of the options is determined by the Company’s Board of Directors but will be at least equal to the closing market price of the common shares the date of grant and the term may not exceed 10 years. Options granted generally vest over three years for employees and for directors' initial grants, and immediately for directors' annual grants.

Additionally, the Company granted a total of 200,000 options in 2013 to two executive officers in conjunction with their new appointments as executive officers. These options were granted in accordance with the policies of the Toronto Stock Exchange and pursuant to newly designated share compensation plans (the “Designated Plans”). During 2016, one of the two executive officers departed from the Company, and the unexercised options under his Designated Plan expired. No new options can be granted under the Designated Plans. The Designated Plan is governed by substantially the same terms as the 2011 Plan. 150,000 options were outstanding for one of the Company's former executive officers as of December 31, 2018, all of which expired unexercised in February 2019.

Hereafter, information on options governed by the 2016 Plan, the 2011 Plan, the 2007 Plan and the Designated Plans (the "Arbutus Plans") is presented on a consolidated basis as the terms of the plans are similar. Information on the Protiva Option Plan and the OnCore Option Plan are presented separately.

Stock option activity for the Arbutus Plans

Equity-classified stock option activity:



	Number of optioned common shares		Weighted average exercise price		Aggregate intrinsic value
Balance, December 31, 2016	2,911,204		8.53		56
Options granted	2,026,500		3.20
Options exercised	(11,105	)	3.45		13
Options forfeited, canceled or expired	(208,272	)	11.41
Balance, December 31, 2017	4,718,327		$	6.06	$	5,842
Options granted	2,557,669		$	5.87
Options exercised	(357,072	)	$	3.60	$	1,142
Options forfeited, canceled or expired	(587,836	)	$	6.71
Balance, December 31, 2018	6,331,088		$	6.05	$	1,170

Options under the Arbutus Plans expire at various dates from March 15, 2019 to December 10, 2028.

The following table summarizes information pertaining to stock options outstanding at December 31, 2018 under the Arbutus Plans:



			Options outstanding December 31, 2018				Options exercisable December 31, 2018
Range of Exercise prices (US$)			Number of options outstanding	Weighted average remaining contractual life (years)	Weighted average exercise price (US$)		Number of options exercisable	Weighted average exercise price (US$)
$1.54	to	$3.22	1,541,466	8.1	3.13		545,966	3.09
$3.23	to	$3.92	340,252	6.4	3.57		248,750	3.57
$3.93	to	$3.96	1,084,991	7.2	3.94		729,085	3.94
$3.97	to	$4.96	369,850	9.1	4.41		51,833	3.99
$4.97	to	$5.34	1,464,204	9.3	5.20		61,450	5.20
$5.35	to	$12.55	769,075	8.4	8.09		222,208	7.95
$12.56	to	$17.57	761,250	6.1	16.44		761,250	16.44
$1.54	to	$17.57	6,331,088	8.0	$	6.05	2,620,542	$	7.73

At December 31, 2018, there were 2,620,542 options exercisable (December 31, 2017 - 1,520,131). The weighted average remaining contractual life of exercisable options as of December 31, 2018 was 6.77 years. The aggregate intrinsic value of in-the-money options exercisable at December 31, 2018 was $469,111 (December 31, 2017 -$1,098,000.)

A summary of the Company’s non-vested stock option activity and related information for the year ended December 31, 2018 is as follows:



	Number of optioned common shares		Weighted average fair value
Non-vested at December 31, 2017	3,198,196		$	3.23
Options granted	2,557,669		4.08
Options vested	(1,584,733	)	4.36
Non-vested options forfeited	(460,586	)	2.82
Non-vested at December 31, 2018	3,710,546		$	3.39

The weighted average remaining contractual life for options expected to vest at December 31, 2018 was 8.0 years and the weighted average exercise price for these options was $6.05 per share.

The aggregate intrinsic value of options expected to vest as of December 31, 2018 was $1,169,784 (December 31, 2017 - $5,842,000).

The total fair value of options that vested during the year ended December 31, 2018 was $6,913,360 (December 31, 2017 - $5,657,000).

Valuation assumptions for the Arbutus Plans

On March 3, 2015, the Company voluntarily de-listed from the Toronto Stock Exchange. All stock options granted after March 3, 2015 were denominated in US dollars based on the Company's stock price on the Nasdaq Global Select Market. The methodology and assumptions used to estimate the fair value of stock options at date of grant under the Black-Scholes option-pricing model remain unchanged. Assumptions on the dividend yield are based on the fact that the Company has never paid cash dividends and has no present intention to pay cash dividends. Assumptions about the Company’s expected stock-price volatility are based on the historical volatility of the Company’s publicly traded stock. The risk-free interest rate used for each grant is equal to the zero coupon rate for instruments with a similar expected life. Expected life assumptions are based on the Company’s historical data. The Company recognizes forfeitures as they occur, and the effects of forfeitures are reflected in stock-based compensation expense recorded in the statement of operations and comprehensive loss for the years ended December 31, 2018 and 2017, respectively. The weighted average option pricing assumptions for options granted during the year are as follows:



	Year ended December 31
	2018		2017
Dividend yield	—	%	—	%
Expected volatility	75.26	%	73.05	%
Risk-free interest rate	2.81	%	1.28	%
Expected average option term	6.7 years		6.9 years

Liability-classified stock option activity:

Due to the change in the Company's functional currency as of January 1, 2016, certain stock option awards with exercise prices denominated in Canadian dollars changed from equity classification to liability classification - see note 2.

Valuation assumptions

Liability options are re-measured to their fair values at each reporting date, using the Black-Scholes valuation model. The methodology and assumptions prevailing at the re-measurement date used to estimate the fair values of liability options remain unchanged from the date of grant of equity classified stock option awards. Assumptions about the Company’s expected stock-price volatility are based on the historical volatility of the Company’s publicly traded stock. The risk-free interest rate used for each grant is equal to the zero coupon rate for instruments with a similar expected life. Expected life assumptions are based on the Company’s historical data. The weighted average Black-Scholes option-pricing assumptions and the resultant fair values as of December 31, 2018 and December 31, 2017, are presented in the following table:



	December 31,			December 31,
	2018			2017
Stock price	$	3.83		$	5.05
Dividend yield	—		%	—		%
Expected volatility	75.20		%	70.31		%
Risk-free interest rate	2.48		%	2.10		%
Expected average term (years)	2.2			4.3
Weighted average fair value per share of options outstanding	$	1.27		$	2.75
Fair value of vested liability-classified options (in thousands)	$	479		$	1,239

Stock option activity for liability options



	Number of optioned common shares		Weighted average exercise price		Aggregate intrinsic value (in thousands)
Balance, December 31, 2017	451,500		$	5.78	$	525
Options exercised	(30,000	)	1.73		71
Options forfeited, canceled, or expired	(44,000	)	3.63		—
Balance, December 31, 2018	377,500		$	5.81	$	224

Liability options expire at various dates from January 27, 2020 to February 4, 2024.

The following table summarizes information pertaining to liability options outstanding at December 31, 2018:



			Options outstanding December 31, 2018				Options exercisable December 31, 2018
Range of Exercise prices (US$)			Number of options outstanding	Weighted average remaining contractual life (years)	Weighted average exercise price		Number of options exercisable	Weighted average exercise price
$1.25	to	$2.29	80,000	2.8	$	1.50	80,000	$	1.50
$2.60	to	$3.30	35,000	1.9	2.82		35,000	2.82
$3.31	to	$5.23	40,000	3.8	3.78		40,000	3.78
$5.24	to	$7.93	150,000	4.8	6.69		150,000	6.69
$7.94	to	$10.60	17,500	2.6	9.18		17,500	9.18
$10.61	to	$12.03	55,000	5.1	12.03		55,000	12.03
$1.25	to	$12.03	377,500	3.9	$	5.82	377,500	$	5.82

As of December 31, 2018, all liability options were fully vested.

Protiva Option Plan

In May 2008, as a condition of the acquisition of Protiva, a total of 350,457 common shares of the Company were reserved for the exercise of 519,073 Protiva share options (“Protiva Options”). Upon exercise, each option was converted into approximately 0.6752 shares of the Company (the same ratio at which Protiva common shares were exchanged for Company common shares at completion of the acquisition of Protiva). The Protiva Options had an exercise price of C$0.30 and were fully vested and exercisable as of May 30, 2008. The Protiva Plan expired on March 1, 2018 when the last outstanding options were exercised.

The following table sets forth outstanding options under the Protiva Option Plan:



	Number of Protiva Options		Equivalent number of Company common shares		Weighted average exercise price (C$)		Weighted average exercise price (US$)
Balance, December 31, 2016	46,000		31,058		0.30		0.22
Options exercised	(6,000	)	(4,051	)	0.30		0.23
Options forfeited, canceled or expired	—		—		—		N/A
Balance, December 31, 2017	40,000		27,007		0.30		0.24
Options exercised	(40,000	)	(27,007	)	0.30		0.24
Options forfeited, canceled or expired	—		—		—		N/A
Balance, December 31, 2018	—		—		$	—	$	—

The intrinsic value of Protiva Options exercised in the year ended December 31, 2018 was $132,000 (2017 - $10,000).

OnCore Option Plan

As of the acquisition date in March 2015, the Company reserved 184,332 shares for the future exercise of OnCore stock options. The total fair value of OnCore stock options at the date of acquisition has been determined to be $3,287,000, using the Black-Scholes pricing model with an assumed risk-free interest rate of 0.97%, volatility of 78%, a zero dividend yield and an expected life of 8 years, which are consistent with the assumption inputs used by the Company to determine the fair value of its options. Of the total fair value, $1,127,000 has been attributed as pre-combination service and included as part of the total acquisition consideration. The post-combination attribution of $2,160,000 was recognized as compensation expense over the vesting period of the stock options through to December 2018.

Following the merger, the Company is not permitted to grant any further options under the OnCore Option Plan. The Company has included $524,872 of compensation expense related to the vesting of OnCore stock options for the year ended December 31, 2018.

The following table sets forth outstanding options under the OnCore Option Plan:



	Number of OnCore Options		Equivalent number of Company common shares		Weighted average exercise price (US$)
Balance, December 31, 2017	183,040		184,332		$	0.57
Options exercised	(43,750	)	(44,059	)	0.58
Options forfeited, canceled or expired	—		—		N/A
Balance, December 31, 2018	139,290		140,273		$	0.56

At December 31, 2018, there were 139,290 OnCore options (140,273 Arbutus equivalent) exercisable with a weighted average exercise price of $0.56. The weighted average remaining contractual life of exercisable options as at December 31, 2018 was 5.9 years. The aggregate intrinsic value of in-the-money options exercisable at December 31, 2018 was $458,319.

A summary of the OnCore Option Plan's non-vested stock option activity and related information for the year ended December 31, 2018 is as follows:



	Number of OnCore Options		Equivalent number of Company common shares		Weighted average fair value (US$)
Non-vested at December 31, 2017	32,128		32,354		$	17.83
Options vested	(32,128	)	(32,354	)	17.83
Non-vested options forfeited	—		—		N/A
Non-vested at December 31, 2018	—		—		$	17.83

The total fair value of options that vested during the year ended December 31, 2018 was $576,942.

Stock-based compensation expense

Total stock-based compensation expense is comprised of: (1) the vesting options awarded to employees under the Arbutus and OnCore option plans calculated in accordance with the fair value method as described above; and (2) the expiration of repurchase rights related to the post-combination service portion of the total fair value of shares issued to Arbutus Inc.'s employees.

The total stock-based compensation has been recorded in the consolidated statement of operations and comprehensive income (loss) as follows:



	Year ended December 31
	2018		2017
Research, development, collaborations and contracts expenses	$	2,670	$	9,236
General and administrative expenses	3,337		5,881
Total	$	6,007	$	15,117

At December 31, 2018, there remains $9,126,000 of unearned compensation expense related to unvested equity employee stock options to be recognized as expense over a weighted-average period of approximately 18 months.

Replacement awards

Included in the total consideration paid in the Company's acquisition of Arbutus Inc. were common shares issued as replacement awards, which were subject to repurchase provisions. The total fair value of these common shares attributed to the post acquisition period was approximately $56,934,000 and was recognized as compensation expense over the expiry period of repurchase provision rights subsequent to the acquisition date.

During 2017, all remaining repurchase provision rights expired and the Company recorded compensation expense of $7,972,000.

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income taxes

Income tax (recovery) expense varies from the amounts that would be computed by applying the combined Canadian federal and provincial income tax rate of 27% (2017 - 26%) to the loss before income taxes as shown in the following tables:



	Year ended December 31,
	2018			2017
Computed taxes (recoveries) at Canadian federal and provincial tax rates	$	(19,287	)	$	(28,270	)
Difference due to change in tax rate on opening deferred taxes	—			(6,633		)
Permanent and other differences	396			1,476
Change in valuation allowance - other	13,062			6,945
Difference due to income taxed at foreign rates	(138		)	(966		)
Stock-based compensation	1,685			3,128
Impairment of goodwill	—			—
Deferred income tax recovery	$	(4,282	)	$	(24,320	)

On December 22, 2017, the Tax Cuts and Jobs Act (the “2017 Tax Act”) was signed into law making significant changes to the Internal Revenue Code. Changes include, but are not limited to, a federal corporate tax rate decrease from 35% to 21% for tax years beginning after December 31, 2017. Certain income tax effects of the 2017 Tax Act, principally due to the write-down of our net deferred tax assets, are reflected in our financial results. We have remeasured certain deferred tax assets and liabilities based on the rates at which they are expected to reverse in the future, which is generally 21%. The STET amount recorded related to the re-measurement of our deferred tax assets was a reduction of $8.3 million to deferred tax liabilities and a reduction of $3.6 million to our deferred tax assets, which have a full valuation allowance provided against them. However, we are still analyzing certain aspects of the Act and refining our calculations, which could potentially affect the measurement of these balances or potentially give rise to new deferred tax amounts.

As at December 31, 2018, the Company has investment tax credits available to reduce Canadian federal income taxes of $8,784,000 (December 31, 2017 - $9,546,000) and provincial income taxes of $4,002,000 (December 31, 2017 - $4,866,000), expiring between 2026 and 2036. In addition, the Company has research and development credits of $4,265,000 (December 31, 2017 - $3,639,000) available for indefinite carry-forward, which can be used to reduce future taxable income in the U.S.

At December 31, 2018, the Company has scientific research and experimental development expenditures of $61,493,000 (December 31, 2017 - $61,493,000) available for indefinite carry-forward and $182,256,000 (December 31, 2017 - $124,451,000) of net operating losses due to expire between 2027 and 2037 and which can be used to offset future taxable income in Canada.

As of December 31, 2018, the Company has $11,040,000 (December 31, 2017 - $13,723,000) of net operating losses due to expire in 2035 and which can be used to offset future taxable income in the U.S. Future use of a portion of the U.S. loss carry-forwards is subject to limitations under the Internal Revenue Code Section 382.

As a result of ownership changes occurring on October 1, 2014 and March 4, 2015, the Company's ability to use these losses may be limited. Losses incurred to date may be further limited if a subsequent change in control occurs.

Significant components of the Company’s deferred tax assets and liabilities are shown below:



	As at December 31,
	2018			2017
Deferred tax assets (liabilities):
Non-capital loss carryforwards	$	51,575		$	36,652
Research and development deductions	15,803			16,603
Book amortization in excess of tax	(608		)	(650		)
Share issue costs	307			456
Revenue recognized for tax purposes in excess of revenue recognized for accounting purposes	—			1,162
Tax value in excess of accounting value in lease inducements	147			173
Federal investment tax credits	9,686			9,079
Provincial investment tax credits	3,955			4,819
In-process research and development	(12,664		)	(16,943		)
Upfront license fees	283			311
Equity accounted for investment	37			—
Other	2,503			2,017
Total deferred tax assets (liabilities)	71,024			53,679
Valuation allowance	(83,685		)	(70,622		)
Net deferred tax assets (liabilities)	$	(12,661	)	$	(16,943	)

Contingencies and Commitments

12 Months Ended

Dec. 31, 2018

Commitments and Contingencies Disclosure [Abstract]

Contingencies and commitments

Property lease

The total minimum rent and estimated operating cost commitment, net of lease inducements, for our head office and leased facilities in Warminster, Pennsylvania is as follows, in thousands:



Year ended December 31, 2019	$	746
Year ended December 31, 2020	766
Year ended December 31, 2021	787
Year ended December 31, 2022 and after	3,813
	$	6,112

The Company’s lease expense for the year ended December 31, 2018 was $1,789,000 has been recorded in the consolidated statements of operations and comprehensive loss (2017 of $1,653,000 )

Product development partnership with the Canadian Government

The Company entered into a Technology Partnerships Canada ("TPC") agreement with the Canadian Federal Government on November 12, 1999. Under this agreement, TPC agreed to fund 27% of the costs incurred by the Company, prior to March 31, 2004, in the development of certain oligonucleotide product candidates up to a maximum contribution from TPC of $7,179,000 (C$9,330,000). As at December 31, 2018, a cumulative contribution of $2,714,000 (C$3,702,000) had been received and the Company does not expect any further funding under this agreement. In return for the funding provided by TPC, the Company agreed to pay royalties on the share of future licensing and product revenue, if any, that is received by the Company on certain non-siRNA oligonucleotide product candidates covered by the funding under the agreement. These royalties are payable until a certain cumulative payment amount is achieved or until a pre-specified date. In addition, until a cumulative amount equal to the funding actually received under the agreement has been paid to TPC, the Company agreed to pay 2.5% royalties on any royalties the Company receives for Marqibo. For the year ended December 31, 2018, the Company earned royalties on Marqibo sales in the amount of $154,000 ((2017- 191,000 (see note 11(d)), resulting in $4,000 recorded by the Company as royalty payable to TPC (2017 - $5,000). The cumulative amount paid or accrued up to December 31, 2018 was $26,000, resulting in the contingent amount due to TPC being $2,690,000 (C$3,669,000).

Arbitration with the University of British Columbia

Certain early work on lipid nanoparticle delivery systems and related inventions was undertaken at the University of British Columbia (“UBC”). These inventions are licensed to the Company by UBC under a license agreement, initially entered in 1998 as amended in 2001, 2006 and 2007. The Company has granted sublicenses under the UBC license to Alnylam. Alnylam has in turn sublicensed back to the Company the licensed UBC patents for discovery, development and commercialization of siRNA products. Certain sublicenses were also granted to other parties.

On November 10, 2014, UBC filed a demand for arbitration against the Company and on January 16, 2015, filed a Statement of Claim, which alleges entitlement to $3,500,000 in allegedly unpaid royalties based on publicly available information, and an unspecified amount based on non-public information. UBC also seeks interest and costs, including legal fees. The Company filed its Statement of Defense to UBC's Statement of Claims, as well as filed a Counterclaim involving a patent application that the Company alleges UBC wrongly licensed to a third party rather than to the Company. The Company seeks license payments for said application, and an exclusive worldwide license to said application. The proceeding has been divided into three phases, with the first hearing taking place in June 2017. The arbitrator determined in the first phase which agreements are sublicense agreements within UBC's claim, and which are not. In the first phase, UBC updated its alleged entitlement from $3,500,000 originally claimed to seek $10,900,000 in alleged unpaid royalties, plus interest arising from payments as early as 2008. No finding was made as to whether any licensing fees are due to UBC under these agreements; this will be the subject of the second phase of arbitration which is scheduled during the second quarter of 2019. The arbitrator also held that the patent application that is the subject of the Counterclaim was not required to be licensed to Arbutus. A schedule for the third phase of the arbitration has not yet been set. Arbitration and related matters are costly and may divert the attention of the Company's management and other resources that would otherwise be engaged in other activities. However, the Company notes that arbitration is subject to inherent uncertainty and an arbitrator could rule against the Company. The Company has not recorded an estimate of the possible loss associated with this arbitration, due to the uncertainties related to both the likelihood and amount of any possible loss or range of loss. Costs related to the arbitration have been recorded in the statement of operations and comprehensive loss by the Company as incurred.

Litigation with Acuitas

In August 2017, the Company provided Acuitas with notice that it considered Acuitas to be in material breach of the cross-license agreement. The cross-license agreement provides that it may be terminated upon any material breach by the other party 60 days after receipt of written notice of termination describing the material breach in reasonable detail. In October 2016, Acuitas filed a Notice of Civil Claim in the Supreme Court of British Columbia seeking an order that the Company perform its obligations under the Cross License Agreement, for damages ancillary to specific performance, injunctive relief, interest and costs. The Company disputed Acuitas’ position, and filed a Counterclaim seeking a declaration that Acuitas is in breach of the cross-license agreement, and claiming injunctive relief, damages, interest and costs.

In January 2017, the Company filed an application seeking an order to enjoin Acuitas from, among other things, entering into any further agreements purporting to sublicense Arbutus’ technology from the date of the order to the date of trial or further order from the Court. In February 2017, the Company announced that the Supreme Court of British Columbia granted its request for a pre-trial injunction against Acuitas, preventing Acuitas from further sublicensing of the Company's LNP technology until the end of October, or further order of the Court. Under the terms of the pre-trial injunction, Acuitas is prevented from entering into any new agreements which include sublicensing of the Company's LNP. In March 2017, Acuitas sought leave to appeal from the injunction decision and in April 2017, the appeal was denied. In September 2017, the injunction order was extended by consent to March 2, 2018. In February 2018, the contractual issues concerning the cross-license agreement (excluding the claims for damages) were settled out of court, resulting in the termination of Acuitas’ rights to further use or sublicense our LNP technology, making permanent the effect of the Court’s prior injunction.

Arbitration and related matters are costly and may divert the attention of the Company’s management and other resources that would otherwise be engaged in other activities. Costs related to the arbitration are recorded by the Company as incurred.

Contingent consideration from Arbutus Inc. acquisition of Enantigen Therapeutics, inc. and License Agreements between Enantigen Therapeutics, Inc. and Baruch S. Blumberg Institute and Drexel University

In October 2014, Arbutus Inc. acquired all of the outstanding shares of Enantigen Therapeutics, Inc. (“Enantigen”) pursuant to a stock purchase agreement. Through this transaction, Arbutus Inc. acquired a HBV surface antigen secretion inhibitor program and a capsid assembly inhibitor program, each of which are now assets of Arbutus, following it’s merger with Arbutus Inc.

Under the stock purchase agreement, Arbutus Inc. agreed to pay up to a total of $21,000,000 to Enantigen’s selling stockholders upon the achievement of certain triggering events related to HBV therapies. The first triggering event is enrollment of the first patient in a Phase 1b clinical trial utilizing the acquired assets in HBV patients. Due to the indefinite deferral of further development of AB-423, the Company believes this triggering event is not likely to occur in the next twelve-month period.

The regulatory, development and sales milestone payments had an estimated fair value of approximately $6,727,000 as at the date of acquisition of Arbutus Inc., and were treated as contingent consideration payable in the purchase price allocation. The contingent consideration was calculated based on information available at the date of acquisition, using a probability weighted assessment of the likelihood the milestones would be met and the estimated timing of such payments, and then the potential contingent payments were discounted to their present value using a probability adjusted discount rate that reflects the early stage nature of the development program, time to complete the program development, and market comparatives.

Contingent consideration is a financial liability and measured at its fair value at each reporting period, with any changes in fair value from the previous reporting period recorded in the statement of operations and comprehensive loss (see note 2).

Drexel University and The Baruch S. Blumberg Institute

In February 2014, Arbutus Inc. entered into a license agreement with The Baruch S. Blumberg Institute ("Blumberg") and Drexel University ("Drexel") that granted an exclusive, worldwide, sub-licensable license to three different compound series: cccDNA inhibitors, capsid assembly inhibitors and HCC inhibitors.

In partial consideration for this license, Arbutus Inc. paid a license initiation fee of $150,000 and issued warrants to Blumberg and Drexel. The warrants were subsequently exercised in 2014. Under this license agreement, Arbutus Inc. also agreed to pay up to $3,500,000 in development and regulatory milestones per licensed compound series, up to $92,500,000 in sales performance milestones per licensed product, and royalties in the mid-single digits based upon the proportionate net sales of licensed products in any commercialized combination. The Company is obligated to pay Blumberg and Drexel a double-digit percentage of all amounts received from the sub-licensees, subject to customary exclusions.

In November 2014, Arbutus Inc. entered into an additional license agreement with Blumberg and Drexel pursuant to which it received an exclusive, worldwide, sub-licensable license under specified patents and know-how controlled by Blumberg and Drexel covering epigenetic modifiers of cccDNA and STING agonists. In consideration for these exclusive licenses, Arbutus Inc. made an upfront payment of $50,000. Under this agreement, the Company will be required to pay up to $1,000,000 for each licensed product upon the achievement of a specified regulatory milestone and a low single-digit royalty, based upon the proportionate net sales of compounds covered by this intellectual property in any commercialized combination. The Company is also obligated to pay Blumberg and Drexel a double digit percentage of all amounts received from its sub-licensees, subject to exclusions.

Research Collaboration and Funding Agreement with Blumberg

In October 2014, Arbutus Inc. entered into a research collaboration and funding agreement with Blumberg under which the Company will provide $1,000,000 per year of research funding for three years, renewable at the Company’s option for an additional three years, for Blumberg to conduct research projects in HBV and liver cancer pursuant to a research plan to be agreed upon by the parties. Blumberg has exclusivity obligations to the Company with respect to HBV research funded under the agreement. In addition, the Company has the right to match any third party offer to fund HBV research that falls outside the scope of the research being funded under the agreement. Blumberg has granted the Company the right to obtain an exclusive, royalty-bearing, worldwide license to any intellectual property generated by any funded research project. If the Company elects to exercise its right to obtain such a license, the Company will have a specified period of time to negotiate and enter into a mutually agreeable license agreement with Blumberg. This license agreement will include the following pre negotiated upfront, milestone and royalty payments: an upfront payment in the amount of $100,000; up to $8,100,000 upon the achievement of specified development and regulatory milestones; up to $92,500,000 upon the achievement of specified commercialization milestones; and royalties at a low single to mid-single digit rates based upon the proportionate net sales of licensed products from any commercialized combination.

In June 2016, the Company and Blumberg entered into an amended and restated research collaboration and funding agreement, primarily to: (i) increase the annual funding amount to Blumberg from $1,000,000 to $1,100,000; (ii) extend the initial term through to October 29, 2018; (iii) provide an option for the Company to extend the term past October 2018 for two additional one year terms; and (iv) expand the Company's exclusive license under the Agreement to include the sole and exclusive right to obtain an exclusive, royalty-bearing, worldwide and all-fields license under Blumberg's rights in certain other inventions described in the agreement. The amended agreement expired in October 2018, at the end of its initial term.

In November 2018, we entered into a new two-year master services agreement with Blumberg that expires in November 2020. The new agreement replaces all rights and obligations of the prior research collaboration and funding agreements, as amended. Under the new agreement, Blumberg will perform specific research activities based upon statements of work and we will no longer provide a fixed amount of funding to Blumberg. In November and December 2018, we executed statements of work with Blumberg for an aggregate cost of $750,000.

Related Party Transactions	12 Months Ended
Related Party Transactions	Dec. 31, 2018
Related Party Transactions [Abstract]
Related party transactions	Related Party Transactions During 2018, the Company purchased certain research and development services from Roivant, which are billed at agreed hourly rates and reflective of market rates for such services. The total cost of these services was $644,000 during 2018 and is included in the income statement under research, development, collaborations and contracts expenses. During 2018, the Company purchased certain research and development services from its equity method investee, Genevant. These services are billed at agreed hourly rates and reflective of market rates for such services. The total cost of these services was $398,000 during 2018 and are included in the income statement under research, development, collaborations and contracts expenses. Conversely, Genevant purchased certain administrative and transitional services from the Company totaling $226,000 during 2018 and was netted against research, development, collaborations and contracts expenses in the income statement. In addition, Genevant has a sublease for 17,900 square feet in the Company's Burnaby facility. Estimated sublease income from Genevant to the completion of the Burnaby lease of $466,000 was netted against site consolidation costs in 2018 (see note 8).

Concentrations of Business Risk

12 Months Ended

Dec. 31, 2018

Risks and Uncertainties [Abstract]

Concentrations of business risk

Credit risk

Credit risk is defined by the Company as an unexpected loss in cash and earnings if a collaborative partner is unable to pay its obligations in due time. The Company’s main source of credit risk is related to its accounts receivable balance which principally represents temporary financing provided to collaborative partners in the normal course of operations.

The Company does not currently maintain a provision for bad debts as the majority of accounts receivable are from collaborative partners or government agencies and are considered low risk.

The carrying amount of financial assets represents the maximum credit exposure. The maximum exposure to credit risk at December 31, 2018 was the accounts receivable balance of $1,431,000 (2017 - $402,000).

All accounts receivable balances were current as at December 31, 2018 and December 31, 2017.

Significant collaborators and customers risk

We depend on a small number of collaborators and customers for a significant portion of our revenues (see note 11).

Liquidity Risk

Liquidity risk results from the Company’s potential inability to meet its financial liabilities, for example payments to suppliers. The Company ensures sufficient liquidity through the management of net working capital and cash balances.

The Company’s liquidity risk is primarily attributable to its cash and cash equivalents, and short-term investments. The Company limits exposure to liquidity risk on its liquid assets through maintaining its cash and cash equivalent, and short-term investments with high-credit quality financial institutions. Due to the nature of these investments, the funds are available on demand to provide optimal financial flexibility.

The Company believes that its current sources of liquidity are sufficient to cover its likely applicable short term cash obligations. The Company’s financial obligations include accounts payable and accrued liabilities which generally fall due within 45 days. The net liquidity of the Company is considered to be the cash and cash equivalents and short-term investments less accounts payable and accrued liabilities.



	December 31, 2018			December 31, 2017
Cash, cash equivalents and short-term investments	$	124,617		$	126,352
Less: Accounts payable and accrued liabilities	(9,429		)	(10,646		)
	$	115,188		$	115,706

Foreign currency risk

The results of the Company’s operations are subject to foreign currency transaction and translation risk as the Company’s revenues and expenses are denominated in both Canadian and US dollars. The fluctuation of the Canadian dollar in relation to the US dollar will consequently have an impact upon the Company’s reported income or loss and may also affect the value of the Company’s assets, liabilities, and the amount of shareholders’ equity both as recorded in the Company’s financial statements, in the US functional currency, and as reported, for presentation purposes, in the US dollar.

The Company manages its foreign currency risk by using cash received in a currency to pay for expenses in that same currency, whenever possible. The Company’s policy to maintain US and Canadian dollar cash and investment and short-term investment balances based on long term forecasts of currency needs thereby creating a natural currency hedge.

The Company has not entered into any agreements or purchased any instruments to hedge possible currency risks. The Company’s exposure to Canadian dollar currency expressed in US dollars was as follows:



	December 31, 2018		December 31, 2017
Cash and cash equivalents and short-term investments	$	1,427	$	25,921
Accounts receivable	293		375
Accrued revenue	—		—
Accounts payable and accrued liabilities	—		(1,273		)
	$	1,720	$	25,023

An analysis of the Company’s sensitivity to foreign currency exchange rate movements is not provided in these financial statements as the Company’s Canadian dollar cash holdings and expected Canadian dollar revenues are sufficient to cover Canadian dollar expenses for the foreseeable future.

Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Basis of presentation

Basis of presentation and principles of consolidation

Consolidation

Foreign currency translation and functional currency conversion

Use of estimates

Cash and cash equivalents

Short-term investments

Equity method investment

Property and equipment



	Useful life (years)
Laboratory equipment		5
Computer and office equipment	2	to	5
Furniture and fixtures		5

Leasehold improvements are depreciated over their estimated useful lives but in no case longer than the lease term, except where lease renewal is reasonably assured.

Impairment of property and equipment

Goodwill and intangible assets

The costs incurred in establishing and maintaining patents for intellectual property developed internally are expensed in the period incurred.

Revenue recognition

Leases and lease inducements

Research and development costs

Net loss attributable to common shareholders per share

Government grants and refundable investment tax credits

Government grants and tax credits provided for current expenses are included in the determination of income or loss for the year, as a reduction of the expenses to which they relate.

Deferred income taxes

Equity and liability classified stock option awards

Equity classified stock option awards

The fair value of equity classified stock options is measured at the grant date and amortized on a straight-line basis over the vesting period.

Liability-classified stock option awards

Recent accounting pronouncements

ASC 606, Revenue From Contracts with Customers ("ASC 606") became effective for the Company on January 1, 2018, and was adopted using the modified retrospective method under which previously presented financial statements are not restated and the cumulative effect of adopting ASC 606 on contracts in process is recognized by an adjustment to retained earnings at the effective date. The adoption of ASC 606 did not change the Company’s recognized revenue under its ongoing significant collaboration and license agreements and no cumulative effect adjustment was required.

Accounting pronouncements not yet adopted

Fair value of financial instruments

Fair value measurements

The Company measures certain financial instruments and other items at fair value.


•	Level 1 inputs are quoted market prices for identical instruments available in active markets.


•	Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability either directly or indirectly. If the asset or liability has a contractual term, the input must be observable for substantially the full term. An example includes quoted market prices for similar assets or liabilities in active markets.


•	Level 3 inputs are unobservable inputs for the asset or liability and will reflect management’s assumptions about market assumptions that would be used to price the asset or liability.

As quoted prices for the warrants are not readily available, the Company has used a Black-Scholes pricing model to estimate fair value. These are level 3 inputs as defined above.

Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

Accounting Policies [Abstract]

Schedule of estimated useful lives of property and equipment

The Company records depreciation using the straight-line method over the estimated useful lives of the capital assets as follows:



	Useful life (years)
Laboratory equipment		5
Computer and office equipment	2	to	5
Furniture and fixtures		5

Schedule of computation of basic and diluted net loss per common share

The following table sets out the computation of basic and diluted net loss attributable to common shareholders per share:



	For the year ended December 31
	2018					2017
Numerator:	Common Shares			Preferred Shares		Common Shares			Preferred Shares
Allocation of distributable earnings	$	—		$	10,091	$	—		$	911
Allocation of undistributed earnings (loss)	(67,151		)	—		(85,324		)	—
Allocation of earnings (loss) attributed to shareholders	$	(67,151	)	$	10,091	$	(85,324	)	$	911
Denominator:
Weighted average number of shares - basic and diluted	55,304,083			1,142,170		54,723,272			104,110
Basic and diluted net loss attributable to shareholders per share	$	(1.21	)	$	8.83	$	(1.56	)	$	8.75

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

Fair Value Disclosures [Abstract]

Schedule of assets and liabilities measured at fair value on a recurring basis



	Level 1		Level 2	Level 3	December 31, 2018
Assets
Cash and cash equivalents	$	36,942	—	—	$	36,942
Short-term investments	87,675		—	—	87,675
Restricted investment	—		—	—	—
Total	$	124,617	—	—	$	124,617
Liabilities
Liability-classified stock option awards	—		—	479	479
Contingent consideration	—		—	3,126	3,126
Total	—		—	3,605	$	3,605



	Level 1		Level 2	Level 3		December 31, 2017
Assets
Cash and cash equivalents	$	54,292	—	—		$	54,292
Guaranteed investment certificates	72,060		—	—		72,060
Restricted investment	12,601		—	—		12,601
Total	$	138,953	—	—		$	138,953
Liabilities

Liability-classified stock option awards	—		—	1,239		1,239
Contingent consideration	—		—	10,424		10,424
Total	—		—	$	11,663	$	11,663

Schedule of changes in fair value of warrants

The following table presents the changes in fair value of the Company’s warrants:



	Liability at beginning of the period		Fair value of warrants exercised in the period			Increase (decrease) in fair value of warrants		Foreign exchange loss		Liability at end of the period
Year ended December 31, 2017	$	107	$	(129	)	$	22	$	—	$	—
Year ended December 31, 2018	$	—	$	—		$	—	$	—	$	—

Schedule of changes in fair value of liability-classified stock options

The following table presents the changes in fair value of the Company’s liability-classified stock option awards:



	Liability at beginning of the period		Fair value of liability-classified stock option awards exercised in the period			Increase (decrease) in fair value of liability			Liability at end of the period
Year ended December 31, 2017	$	553	$	(103	)	$	789		$	1,239
Year ended December 31, 2018	$	1,239	$	(93	)	$	(667	)	$	479

Schedule of changes in fair value of contingent consideration

following table presents the changes in fair value of the Company’s contingent consideration:



	Contingent consideration at beginning of the period		Increase in fair value of contingent consideration			Contingent consideration at end of the period
Year ended December 31, 2017	$	9,065	$	1,359		$	10,424
Year ended December 31, 2018	$	10,424	$	(7,298	)	$	3,126

Equity method investment (Tables)

12 Months Ended

Dec. 31, 2018

Equity Method Investments and Joint Ventures [Abstract]

Schedule of equity method balance

The following table summarizes unaudited financial information for our equity method investee and is reported on a one quarter lag.



	2018
Balance Sheet:
Current assets	$	32,027
Non-current assets	1,644
Total assets	33,671

Current liabilities	4,911
Non-current liabilities	253
Shareholders' equity	28,507
Total liabilities and shareholders' equity	$	33,671



	2018
Results of Operations:
Revenue	$	—
Gross profit	—
Operating Loss	(12,421		)
Net Loss	$	(12,770	)

The following table provides a summary of the Company's investment in Genevant for the year ended December 31, 2018, in thousands:



	Year ended December 31, 2018
Beginning balance	$	—
Initial investment in Genevant	27,377
Share of stock based compensation for Genevant employees who continue to vest in Arbutus stock options	159
Share of net loss (on a one-quarter lag basis)	(5,206		)
Dilution loss	(122		)
Share of comprehensive loss - currency translation adjustment	16
Ending balance	$	22,224

Collaborations, Contracts and Licensing Agreements (Tables)

12 Months Ended

Dec. 31, 2018

Revenue from Contract with Customer [Abstract]

Schedule of revenue recognized under collaborations, contracts and licensing agreements

(a) License Agreement with Alexion Pharmaceuticals, Inc.

(b) License agreement with Gritstone Oncology, Inc.

Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received.

Alnylam Pharmaceuticals, Inc.

Acuitas Therapeutics Inc.

Spectrum Pharmaceuticals, Inc.

United States Government’s Department of Defense to develop TKM-Ebola

The following tables set forth revenue recognized under collaborations, contracts and licensing agreements:



	Year ended December 31
	2018		2017
Alexion (a)	$	—	$	7,956
Gritstone (b)	4,318		2,499
Other milestone and royalty payments (c)	1,627		245
Total revenue	$	5,945	$	10,700

Schedule of deferred collaborations and contracts revenue

(a) License Agreement with Alexion Pharmaceuticals, Inc.

(b) License agreement with Gritstone Oncology, Inc.

Milestone payments that are not within the control of the Company or the licensee, such as regulatory approvals, are not considered probable of being achieved until those approvals are received.

Alnylam Pharmaceuticals, Inc.

Acuitas Therapeutics Inc.

Spectrum Pharmaceuticals, Inc.

United States Government’s Department of Defense to develop TKM-Ebola

The following table sets forth deferred collaborations and contracts revenue:



	Year ended December 31
	2018		2017
Gritstone (b)	$	—	$	2,727
Other	—		15
Total deferred revenue	$	—	$	2,742

Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of stock option activity for the Arbutus Plans

Equity-classified stock option activity:



	Number of optioned common shares		Weighted average exercise price		Aggregate intrinsic value
Balance, December 31, 2016	2,911,204		8.53		56
Options granted	2,026,500		3.20
Options exercised	(11,105	)	3.45		13
Options forfeited, canceled or expired	(208,272	)	11.41
Balance, December 31, 2017	4,718,327		$	6.06	$	5,842
Options granted	2,557,669		$	5.87
Options exercised	(357,072	)	$	3.60	$	1,142
Options forfeited, canceled or expired	(587,836	)	$	6.71
Balance, December 31, 2018	6,331,088		$	6.05	$	1,170

Summary of stock options outstanding by exercise price range

The following table summarizes information pertaining to stock options outstanding at December 31, 2018 under the Arbutus Plans:



			Options outstanding December 31, 2018				Options exercisable December 31, 2018
Range of Exercise prices (US$)			Number of options outstanding	Weighted average remaining contractual life (years)	Weighted average exercise price (US$)		Number of options exercisable	Weighted average exercise price (US$)
$1.54	to	$3.22	1,541,466	8.1	3.13		545,966	3.09
$3.23	to	$3.92	340,252	6.4	3.57		248,750	3.57
$3.93	to	$3.96	1,084,991	7.2	3.94		729,085	3.94
$3.97	to	$4.96	369,850	9.1	4.41		51,833	3.99
$4.97	to	$5.34	1,464,204	9.3	5.20		61,450	5.20
$5.35	to	$12.55	769,075	8.4	8.09		222,208	7.95
$12.56	to	$17.57	761,250	6.1	16.44		761,250	16.44
$1.54	to	$17.57	6,331,088	8.0	$	6.05	2,620,542	$	7.73

Schedule of non-vested stock option activity

A summary of the Company’s non-vested stock option activity and related information for the year ended December 31, 2018 is as follows:



	Number of optioned common shares		Weighted average fair value
Non-vested at December 31, 2017	3,198,196		$	3.23
Options granted	2,557,669		4.08
Options vested	(1,584,733	)	4.36
Non-vested options forfeited	(460,586	)	2.82
Non-vested at December 31, 2018	3,710,546		$	3.39

Schedule of weighted average option pricing assumptions and the resultant fair values

The weighted average option pricing assumptions for options granted during the year are as follows:



	Year ended December 31
	2018		2017
Dividend yield	—	%	—	%
Expected volatility	75.26	%	73.05	%
Risk-free interest rate	2.81	%	1.28	%
Expected average option term	6.7 years		6.9 years

Schedule of allocation of stock-based compensation

The total stock-based compensation has been recorded in the consolidated statement of operations and comprehensive income (loss) as follows:



	Year ended December 31
	2018		2017
Research, development, collaborations and contracts expenses	$	2,670	$	9,236
General and administrative expenses	3,337		5,881
Total	$	6,007	$	15,117

Protiva Option Plan

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of option activity

The following table sets forth outstanding options under the Protiva Option Plan:



	Number of Protiva Options		Equivalent number of Company common shares		Weighted average exercise price (C$)		Weighted average exercise price (US$)
Balance, December 31, 2016	46,000		31,058		0.30		0.22
Options exercised	(6,000	)	(4,051	)	0.30		0.23
Options forfeited, canceled or expired	—		—		—		N/A
Balance, December 31, 2017	40,000		27,007		0.30		0.24
Options exercised	(40,000	)	(27,007	)	0.30		0.24
Options forfeited, canceled or expired	—		—		—		N/A
Balance, December 31, 2018	—		—		$	—	$	—

OnCore Option Plan

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of non-vested stock option activity

A summary of the OnCore Option Plan's non-vested stock option activity and related information for the year ended December 31, 2018 is as follows:



	Number of OnCore Options		Equivalent number of Company common shares		Weighted average fair value (US$)
Non-vested at December 31, 2017	32,128		32,354		$	17.83
Options vested	(32,128	)	(32,354	)	17.83
Non-vested options forfeited	—		—		N/A
Non-vested at December 31, 2018	—		—		$	17.83

Schedule of option activity

The following table sets forth outstanding options under the OnCore Option Plan:



	Number of OnCore Options		Equivalent number of Company common shares		Weighted average exercise price (US$)
Balance, December 31, 2017	183,040		184,332		$	0.57
Options exercised	(43,750	)	(44,059	)	0.58
Options forfeited, canceled or expired	—		—		N/A
Balance, December 31, 2018	139,290		140,273		$	0.56

Liability classified stock options

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Schedule of stock option activity for the Arbutus Plans

Stock option activity for liability options



	Number of optioned common shares		Weighted average exercise price		Aggregate intrinsic value (in thousands)
Balance, December 31, 2017	451,500		$	5.78	$	525
Options exercised	(30,000	)	1.73		71
Options forfeited, canceled, or expired	(44,000	)	3.63		—
Balance, December 31, 2018	377,500		$	5.81	$	224

Summary of stock options outstanding by exercise price range

The following table summarizes information pertaining to liability options outstanding at December 31, 2018:



			Options outstanding December 31, 2018				Options exercisable December 31, 2018
Range of Exercise prices (US$)			Number of options outstanding	Weighted average remaining contractual life (years)	Weighted average exercise price		Number of options exercisable	Weighted average exercise price
$1.25	to	$2.29	80,000	2.8	$	1.50	80,000	$	1.50
$2.60	to	$3.30	35,000	1.9	2.82		35,000	2.82
$3.31	to	$5.23	40,000	3.8	3.78		40,000	3.78
$5.24	to	$7.93	150,000	4.8	6.69		150,000	6.69
$7.94	to	$10.60	17,500	2.6	9.18		17,500	9.18
$10.61	to	$12.03	55,000	5.1	12.03		55,000	12.03
$1.25	to	$12.03	377,500	3.9	$	5.82	377,500	$	5.82

Schedule of weighted average Black-Scholes option-pricing assumptions and resultant fair values

The weighted average Black-Scholes option-pricing assumptions and the resultant fair values as of December 31, 2018 and December 31, 2017, are presented in the following table:



	December 31,			December 31,
	2018			2017
Stock price	$	3.83		$	5.05
Dividend yield	—		%	—		%
Expected volatility	75.20		%	70.31		%
Risk-free interest rate	2.48		%	2.10		%
Expected average term (years)	2.2			4.3
Weighted average fair value per share of options outstanding	$	1.27		$	2.75
Fair value of vested liability-classified options (in thousands)	$	479		$	1,239

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Schedule of effective income tax rate reconciliation



	Year ended December 31,
	2018			2017
Computed taxes (recoveries) at Canadian federal and provincial tax rates	$	(19,287	)	$	(28,270	)
Difference due to change in tax rate on opening deferred taxes	—			(6,633		)
Permanent and other differences	396			1,476
Change in valuation allowance - other	13,062			6,945
Difference due to income taxed at foreign rates	(138		)	(966		)
Stock-based compensation	1,685			3,128
Impairment of goodwill	—			—
Deferred income tax recovery	$	(4,282	)	$	(24,320	)

Schedule of components of deferred tax assets

Significant components of the Company’s deferred tax assets and liabilities are shown below:



	As at December 31,
	2018			2017
Deferred tax assets (liabilities):
Non-capital loss carryforwards	$	51,575		$	36,652
Research and development deductions	15,803			16,603
Book amortization in excess of tax	(608		)	(650		)
Share issue costs	307			456
Revenue recognized for tax purposes in excess of revenue recognized for accounting purposes	—			1,162
Tax value in excess of accounting value in lease inducements	147			173
Federal investment tax credits	9,686			9,079
Provincial investment tax credits	3,955			4,819
In-process research and development	(12,664		)	(16,943		)
Upfront license fees	283			311
Equity accounted for investment	37			—
Other	2,503			2,017
Total deferred tax assets (liabilities)	71,024			53,679
Valuation allowance	(83,685		)	(70,622		)
Net deferred tax assets (liabilities)	$	(12,661	)	$	(16,943	)

Concentrations of Business Risk (Tables)

12 Months Ended

Dec. 31, 2018

Risks and Uncertainties [Abstract]

Schedule of net liquidity

The net liquidity of the Company is considered to be the cash and cash equivalents and short-term investments less accounts payable and accrued liabilities.



	December 31, 2018			December 31, 2017
Cash, cash equivalents and short-term investments	$	124,617		$	126,352
Less: Accounts payable and accrued liabilities	(9,429		)	(10,646		)
	$	115,188		$	115,706

Schedule of exposure to US dollar currency expressed in Canadian dollars

The Company’s exposure to Canadian dollar currency expressed in US dollars was as follows:



	December 31, 2018		December 31, 2017
Cash and cash equivalents and short-term investments	$	1,427	$	25,921
Accounts receivable	293		375
Accrued revenue	—		—
Accounts payable and accrued liabilities	—		(1,273		)
	$	1,720	$	25,023

Significant Accounting Policies - Narrative (Details)	12 Months Ended
Significant Accounting Policies - Narrative (Details)	Dec. 31, 2018 subsidiary lease shares	Dec. 31, 2017 shares	May 30, 2008
Business Acquisition [Line Items]
Wholly-owned subsidiaries \| subsidiary	2
Anti-dilutive common shares excluded from calculation of income per common share (in shares)	24,717,000	12,521,550
Interest rate on restricted investment	8.75%
Number of property leases \| lease	3
Convertible Preferred Shares
Business Acquisition [Line Items]
Issuance of Preferred Shares, net of issuance cost (in shares)	664,000	500,000
Stock Option
Business Acquisition [Line Items]
Anti-dilutive common shares excluded from calculation of income per common share (in shares)	6,849,000
Convertible Preferred Shares
Business Acquisition [Line Items]
Anti-dilutive common shares excluded from calculation of income per common share (in shares)	17,868,000
PADCo. \| Monsanto
Business Acquisition [Line Items]
Business acquisition, percentage of outstanding shares acquired			100.00%

Significant Accounting Policies - Estimated Useful Lives of Property and Equipment (Details)	12 Months Ended
	Dec. 31, 2018
Laboratory equipment
Property, Plant and Equipment [Line Items]
Useful life (years)	5 years
Computer and office equipment \| Minimum
Property, Plant and Equipment [Line Items]
Useful life (years)	2 years
Computer and office equipment \| Maximum
Property, Plant and Equipment [Line Items]
Useful life (years)	5 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Useful life (years)	5 years

Significant Accounting Policies - Computation of Basic and Diluted Net Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Allocation of distributable earnings									$ 10,091	$ 911
Allocation of earnings (loss) attributed to shareholders	$ (20,896)	$ (27,040)	$ 550	$ (19,765)	$ (36,842)	$ (11,600)	$ (18,255)	$ (18,627)	(67,151)	$ (85,324)
Basic and diluted net loss attributable to shareholders per share (USD per share)					$ (0.67)	$ (0.21)	$ (0.33)	$ (0.34)		$ (1.56)
Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Allocation of undistributed earnings (loss)									(67,151)	$ (85,324)
Allocation of earnings (loss) attributed to shareholders									$ (67,151)	$ (85,324)
Weighted average number of shares - basic diluted (in shares)									55,304,083	54,723,272
Basic and diluted net loss attributable to shareholders per share (USD per share)									$ (1.21)	$ (1.56)
Preferred Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Allocation of distributable earnings									$ 10,091	$ 911
Allocation of earnings (loss) attributed to shareholders									$ 10,091	$ 911
Weighted average number of shares - basic diluted (in shares)									1,142,170	104,110
Basic and diluted net loss attributable to shareholders per share (USD per share)									$ 8.83	$ 8.75

Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair value of contingent consideration	$ 3,126	$ 10,424	$ 9,065
Decrease in fair value of contingent consideration	$ 7,298	$ (1,359)

Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Liabilities
Contingent consideration	$ 3,126	$ 10,424	$ 9,065
Fair Value, Measurements, Recurring
Assets
Cash and cash equivalents	36,942	54,292
Short-term investments	87,675	72,060
Restricted investment	0	12,601
Total	124,617	138,953
Liabilities
Liability-classified stock option awards	479	1,239
Contingent consideration	3,126	10,424
Total	3,605	11,663
Fair Value, Measurements, Recurring \| Level 1
Assets
Cash and cash equivalents	36,942	54,292
Short-term investments	87,675	72,060
Restricted investment	0	12,601
Total	124,617	138,953
Liabilities
Liability-classified stock option awards	0	0
Contingent consideration	0	0
Total	0	0
Fair Value, Measurements, Recurring \| Level 2
Assets
Cash and cash equivalents	0	0
Short-term investments	0	0
Restricted investment	0	0
Total	0	0
Liabilities
Liability-classified stock option awards	0	0
Contingent consideration	0	0
Total	0	0
Fair Value, Measurements, Recurring \| Level 3
Assets
Cash and cash equivalents	0	0
Short-term investments	0	0
Restricted investment	0	0
Total	0	0
Liabilities
Liability-classified stock option awards	479	1,239
Contingent consideration	3,126	10,424
Total	$ 3,605	$ 11,663

Fair Value Measurements - Changes in Fair Value of Warrants (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Liability at beginning of the period	$ 0	$ 107
Fair value of warrants exercised in the period	0	(129)
Increase (decrease) in fair value of warrants	0	22
Foreign exchange loss	0	0
Liability at end of the period	$ 0	$ 0

Fair Value Measurements - Changes in Fair Value of Liabilities-Classified as Stock Option (Details) - Liability classified stock options - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Liability at beginning of the period	$ 1,239	$ 553
Fair value of liability-classified stock option awards exercised in the period	(93)	(103)
Increase (decrease) in fair value of liability	(667)	789
Liability at end of the period	$ 479	$ 1,239

Fair Value Measurements - Changes in Fair Value of Contingent Consideration (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Contingent consideration at beginning of the period	$ 10,424	$ 9,065
Increase (decrease) in fair value of contingent consideration	(7,298)	1,359
Contingent consideration at end of the period	$ 3,126	$ 10,424

Equity method investment - Narrative (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Apr. 11, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Gain on investments			$ 24,884	$ 0
Genevant
Schedule of Equity Method Investments [Line Items]
Initial investment in Genevant	$ 600		$ 27,377
Ownership interest in equity method investment	50.00%		40.00%
Gain on investments		$ 24,884
Goodwill transfer to equity method investment	$ 1,893
Genevant \| Roivant Sciences Ltd
Schedule of Equity Method Investments [Line Items]
Initial investment in Genevant	37,500
Initial capital contribution	22,500
Commitment to contribute to equity method investment	$ 15,000

Equity method investment - Schedule of Equity Investment Balance (Details) - USD ($) $ in Thousands		12 Months Ended
	Apr. 11, 2018	Dec. 31, 2018	Dec. 31, 2017
Year ended December 31, 2018
Beginning balance		$ 0
Dilution loss		(5,562)	$ 0
Ending balance		22,224	0
Genevant
Year ended December 31, 2018
Beginning balance		0
Initial investment in Genevant	$ 600	27,377
Share of stock based compensation for Genevant employees who continue to vest in Arbutus stock options		159
Share of net loss (on a one-quarter lag basis)		(5,206)
Dilution loss		(122)
Share of comprehensive loss - currency translation adjustment		16
Ending balance		$ 22,224	$ 0

- Definition

This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

+ References + Details

Equity method investment - Balance Sheet of Equity Method Investment (Details) - Genevant $ in Thousands	Dec. 31, 2018 USD ($)
Balance Sheet:
Current assets	$ 32,027
Non-current assets	1,644
Total assets	33,671
Current liabilities	4,911
Non-current liabilities	253
Shareholders' equity	28,507
Total liabilities and shareholders' equity	$ 33,671

Equity method investment - Results of Operations of Equity Method Investment (Details) - Genevant $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Results of Operations:
Revenue	$ 0
Gross profit	0
Operating Loss	(12,421)
Net Loss	$ (12,770)

Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Cost	$ 17,041	$ 24,854
Accumulated depreciation	(6,896)	(12,671)
Property and equipment, net of accumulated depreciation	10,145	12,183
Lab equipment
Property, Plant and Equipment [Line Items]
Cost	5,420	9,567
Accumulated depreciation	(2,455)	(5,325)
Property and equipment, net of accumulated depreciation	2,965	4,242
Leasehold improvements
Property, Plant and Equipment [Line Items]
Cost	9,308	12,578
Accumulated depreciation	(2,401)	(5,139)
Property and equipment, net of accumulated depreciation	6,907	7,439
Computer hardware and software
Property, Plant and Equipment [Line Items]
Cost	2,313	2,318
Accumulated depreciation	(2,040)	(1,878)
Property and equipment, net of accumulated depreciation	273	440
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Cost	0	391
Accumulated depreciation	0	(329)
Property and equipment, net of accumulated depreciation	$ 0	$ 62

Property and Equipment - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Net book value	$ 10,145	$ 12,183
Cost	17,041	24,854
Accumulated depreciation	$ 6,896	12,671
Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations \| Genevant
Property, Plant and Equipment [Line Items]
Net book value		600
Cost		1,100
Accumulated depreciation		500
Burnaby Facility \| Facility closing \| Disposal Group, Disposed of by Means Other than Sale, Not Discontinued Operations
Property, Plant and Equipment [Line Items]
Net book value		300
Cost		6,200
Accumulated depreciation		$ 5,900

Intangible Assets and Goodwill - Narrative (Details)		12 Months Ended
Intangible Assets and Goodwill - Narrative (Details)	Apr. 11, 2018 USD ($)	Dec. 31, 2018 USD ($) reporting_unit	Dec. 31, 2017 USD ($)
Indefinite-lived Intangible Assets [Line Items]
Impairment of intangible assets		$ 14,811,000	$ 40,798,000
Tax benefit related to decrease in deferred tax liability for indefinite delay of further development		4,282,000
Income tax benefit corresponding to impairment charge		$ 4,282,000	24,320,000
Number of reporting units for goodwill purposes \| reporting_unit		1
Goodwill impairment charge		$ 0	$ 0
STING
Indefinite-lived Intangible Assets [Line Items]
Impairment of intangible assets		40,798,000
Income tax benefit corresponding to impairment charge		$ 16,926,000
Genevant
Indefinite-lived Intangible Assets [Line Items]
Goodwill allocated to equity method investment	$ 1,893,000

Intangible Assets and Goodwill - Summary of Carrying Value of Intangible Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	$ 43,836	$ 58,647
IPR&D – Immune Modulators
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	0	0
IPR&D – Antigen Inhibitors
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	0	14,811
IPR&D – cccDNA Sterilizers
Indefinite-lived Intangible Assets [Line Items]
Intangible assets	$ 43,836	$ 43,836

Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Trade accounts payable	$ 3,192	$ 1,987
Payroll accruals	2,341	2,893
Research and development accruals	2,716	4,937
Professional fee accruals	871	429
Deferred lease inducements	0	42
Other accrued liabilities	309	358
Accounts payable and accrued liabilities	$ 9,429	$ 10,646

Site Consolidation (Details) - USD ($) $ in Thousands	12 Months Ended
Site Consolidation (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2018	Feb. 08, 2018
Description of expense
Total site consolidation expense	$ 4,797	$ 0
Amounts paid and adjustments	(3,466)
Accrued balance	1,331
Facility closing
Restructuring Cost and Reserve [Line Items]
Percentage of workforce reduction				35.00%
Expected total cost of site consolidation			$ 5,600
Employee severance
Description of expense
Total site consolidation expense	2,851
Employee relocation
Description of expense
Total site consolidation expense	823
Lease and facility
Description of expense
Total site consolidation expense	$ 1,123

Loan Payable (Details) - USD ($)	Dec. 27, 2016	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Restricted investment	$ 12,601,000	$ 0		$ 12,601,000
Restricted investment, term	2 years
Short-term investments		$ 87,675,000		$ 72,060,000
Wells Fargo
Debt Instrument [Line Items]
Short-term investments			$ 12,601,000
Loans payable \| Promissory note with Wells Fargo \| Wells Fargo
Debt Instrument [Line Items]
Loan payable	$ 12,001,000
Loans payable \| Promissory note with Wells Fargo \| LIBOR
Debt Instrument [Line Items]
Fixed component of interest rate	1.25%

Shareholders' Equity (Details)					12 Months Ended
Shareholders' Equity (Details)	Jan. 12, 2018 USD ($)	Oct. 16, 2017 USD ($)	Oct. 02, 2017 USD ($) $ / shares	Mar. 01, 2017 shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares
Class of Stock [Line Items]
Preferred stock, shares authorized (in shares) \| shares					1,164,000	1,164,000,000
Issuance of common shares in conjunction with the private offering, net of issuance costs					$ 66,265,000	$ 48,869,000
Proceeds from sale of preferred shares, net of issuance costs					$ 66,265,000	$ 48,869,000
Warrants outstanding (in shares) \| shares					0
Warrants exercised (in shares) \| shares						179,000
Issuance of common shares pursuant to exercise of warrants					$ 0	$ 353,000
Warrants expired (in shares) \| shares				22,000
Roivant
Class of Stock [Line Items]
Noncontrolling interest, ownership percentage by owners after conversion			49.60%
Noncontrolling interest, maximum ownership percentage by noncontrolling owners			49.99%
Proceeds from sale of preferred shares, net of issuance costs	$ 66,400,000	$ 50,000,000
Common Shares \| Sale Agreement \| Jefferies LLC
Class of Stock [Line Items]
Aggregate share sales price					$ 50,000,000.0
Number of shares issued under agreement (in shares) \| shares					0
Convertible Preferred Stock \| Roivant
Class of Stock [Line Items]
Issuance of common shares in conjunction with the private offering, net of issuance costs			$ 116,400,000
Preferred stock, par value (USD per share) \| $ / shares			$ 7.13
Premium percentage on closing stock price			15.00%
Shares price (in USD per share) \| $ / shares			$ 6.20
Preferred dividend percentage			8.75%			8.75%
Noncontrolling interest, investment commitment period			4 years
Liability classified stock options
Class of Stock [Line Items]
Fair Value, Stock Options, Measurement Input					0
Shares price (in USD per share) \| $ / shares					$ 3.83	$ 5.05

Collaborations, Contracts and Licensing Agreements - Revenue Recognized Under Collaborations, Contracts and Licensing Agreements (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue	$ 1,678	$ 1,587	$ 1,244	$ 1,436	$ 2,534	$ 6,892	$ 1,039	$ 235	$ 5,945	$ 10,700
Alexion
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue									0	7,956
Gritstone
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue									4,318	2,499
Other milestone and royalty payments
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue									$ 1,627	$ 245

Collaborations, Contracts and Licensing Agreements - Deferred Collaborations and Contracts Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Contract with Customer, Liability [Line Items]
Total deferred revenue	$ 0	$ 2,742
Gritstone
Contract with Customer, Liability [Line Items]
Total deferred revenue	0	2,727
Other
Contract with Customer, Liability [Line Items]
Total deferred revenue	$ 0	$ 15

Collaborations, Contracts and Licensing Agreements - Narrative (Details)	1 Months Ended	3 Months Ended								12 Months Ended
	Nov. 30, 2012	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2012 USD ($)	Apr. 11, 2018	Mar. 16, 2017 USD ($)	May 06, 2006 chemotherapy_products
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue		$ 1,678,000	$ 1,587,000	$ 1,244,000	$ 1,436,000	$ 2,534,000	$ 6,892,000	$ 1,039,000	$ 235,000	$ 5,945,000	$ 10,700,000
Number of chemotherapy products with worldwide licenses \| chemotherapy_products															3
Alexion
Research and Development Arrangement, Contract to Perform for Others [Line Items]
License upfront payment														$ 7,500,000
Revenue										0	7,956,000
Talon Therapeutics
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Potential contract funding amount												$ 18,000,000
Gritstone
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue										4,318,000	$ 2,499,000
Marqibo Commercial Sales
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contracts revenue												$ 1,000,000
License \| Gritstone
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Development milestone payment										2,500,000
License \| Gritstone, Milestone
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue										$ 1,250,000
License \| Alnylam Pharmaceuticals, Inc
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue				$ 750,000
License \| Acuitas Therapeutics Inc.
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Term of agreement	5 years
Genevant \| License \| Gritstone
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Equity method investment, percentage or revenue entitled													50.00%

Stock-based Compensation - Narrative (Details)			1 Months Ended			12 Months Ended
Stock-based Compensation - Narrative (Details)	Mar. 04, 2015 USD ($) shares	May 30, 2008 $ / shares shares	Feb. 28, 2019 executive_officers shares	Jun. 30, 2011 shares	May 30, 2008 shares	Dec. 31, 2018 USD ($) executive_officers $ / shares shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2013 executive_officers shares	Dec. 31, 2016 shares	May 19, 2016 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock-based compensation awards approved to be issued (in shares)						6,848,861
Number of additional shares authorized (in shares)						3,158,353
Options granted (in shares)						2,557,669
Number of executive officers granted options with new appointments \| executive_officers								2
Options exercisable (in shares)						2,620,542	1,520,131
Weighted average remaining contractual life of exercisable options						6 years 9 months 7 days
Options exercisable, intrinsic value \| $						$ 469,000	$ 1,098,000
Weighted average remaining contractual life for options expected to vest						8 years
Average exercise price for options expected to vest (in CAD and USD per share) \| $ / shares						$ 6.05
Aggregate intrinsic value of option expected to vest \| $						$ 1,169,784	5,842,000
Total fair value of options that vested during period \| $						6,913,360	5,657,000
Business acquisition, post-combination attribution recognized as compensation expense \| $	$ 56,934,000
Stock-based compensation expense \| $						6,007,000	$ 15,117,000
Unearned compensation expense \| $						$ 9,126,000
Unearned compensation expense, recognition period						18 months
Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected average term (years)						2 years 2 months 12 days	4 years 3 months 30 days
Number of options outstanding (in shares)						377,500	451,500
Risk-free interest rate						0
Options exercised, aggregate intrinsic value \| $						$ 71,000
Expired repurchase rights on shares issued to Arbutus Inc.
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense \| $						$ 7,972,000
2016 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock-based compensation awards approved to be issued (in shares)										5,000,000
2011 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)				0
Expected average term (years)						10 years
Option vesting period						3 years
Designated Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)						0		200,000
Number of options outstanding (in shares)						150,000
Number of executive officers granted options with new appointments \| executive_officers						1
Arbutus Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)						2,557,669	2,026,500
Expected average term (years)						6 years 8 months 12 days	6 years 10 months 28 days
Number of options outstanding (in shares)						6,331,088	4,718,327		2,911,204
Options exercised, aggregate intrinsic value \| $						$ 1,142,000	$ 13,000
Arbutus Plans \| Measurement Input, Risk Free Interest Rate [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate						0
Protiva Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future exercise (in shares)		350,457			350,457
Option exercise price (in CAD per share) \| $ / shares		$ 0.30
Protiva Option Plan \| Revised new common shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future exercise (in shares)		519,073			519,073
Conversion of stock, shares converted (in shares)					0.6752
Protiva Option Plan \| Protiva Share Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options exercised, aggregate intrinsic value \| $						$ 132,000	$ 10,000
OnCore Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock-based compensation awards approved to be issued (in shares)	184,332
Number of options outstanding (in shares)						139,290	183,040
Options exercisable (in shares)						139,290
Weighted average remaining contractual life of exercisable options						5 years 10 months 24 days
Options exercisable, intrinsic value \| $						$ 458,000
Total fair value of options that vested during period \| $						577,000
Fair value of consideration issued \| $	$ 3,287,000
Business acquisition, fair value amount attributed as pre-combination service and included as part of acquisition consideration \| $	1,127,000
Business acquisition, post-combination attribution recognized as compensation expense \| $	$ 2,160,000
Stock-based compensation expense \| $						$ 525,000
Options exercisable weighted average exercise price (in USD per share) \| $ / shares						$ 0.56
OnCore Option Plan \| Measurement Input, Risk Free Interest Rate [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.0097
OnCore Option Plan \| Measurement Input, Option Volatility [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0.78
OnCore Option Plan \| Measurement Input, Expected Dividend Rate [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	0
OnCore Option Plan \| Measurement Input, Expected Term [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value stock options, term	8 years
OnCore Option Plan \| Equivalent number of Company common shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options outstanding (in shares)						140,273	184,332
Options exercisable (in shares)						140,273
Subsequent event \| Designated Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of executive officers granted options with new appointments \| executive_officers			1
Options expired (in shares)			150,000

Stock-based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Number of optioned common shares
Options granted (in shares)	2,557,669
Arbutus Plans
Number of optioned common shares
Balance - Number of optioned common shares (in shares)	4,718,327	2,911,204
Options granted (in shares)	2,557,669	2,026,500
Options exercised (in shares)	(357,072)	(11,105)
Options forfeited, canceled or expired (in shares)	(587,836)	(208,272)
Balance - Number of optioned common shares (in shares)	6,331,088	4,718,327
Weighted average exercise price
Balance - Weighted average exercise price (in CAD and USD per share)	$ 6.06	$ 8.53
Options granted - Weighted average exercise price (in CAD and USD per share)	5.87	3.20
Options exercised - Weighted average exercise price (in CAD and USD per share)	3.60	3.45
Options forfeited, canceled or expired - Weighted average exercise price (in CAD and USD per share)	6.71	11.41
Balance - Weighted average exercise price (in CAD and USD per share)	$ 6.05	$ 6.06
Aggregate intrinsic value
Balance - Aggregate intrinsic value	$ 5,842	$ 56
Options exercised, aggregate intrinsic value	1,142	13
Balance - Aggregate intrinsic value	$ 1,170	$ 5,842

Stock-based Compensation - Stock Options Outstanding (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Range 1
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	$ 1.54
Range of Exercise prices - High (in USD per share)	$ 3.22
Number of options outstanding (in shares) \| shares	1,541,466
Weighted average remaining contractual life (years)	8 years 1 month 6 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.13
Number of options exercisable (in shares) \| shares	545,966
Weighted average exercise price (in USD per share)	$ 3.09
Range 2
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	3.23
Range of Exercise prices - High (in USD per share)	$ 3.92
Number of options outstanding (in shares) \| shares	340,252
Weighted average remaining contractual life (years)	6 years 4 months 24 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.57
Number of options exercisable (in shares) \| shares	248,750
Weighted average exercise price (in USD per share)	$ 3.57
Range 3
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	3.93
Range of Exercise prices - High (in USD per share)	$ 3.96
Number of options outstanding (in shares) \| shares	1,084,991
Weighted average remaining contractual life (years)	7 years 2 months 12 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.94
Number of options exercisable (in shares) \| shares	729,085
Weighted average exercise price (in USD per share)	$ 3.94
Range 4
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	3.97
Range of Exercise prices - High (in USD per share)	$ 4.96
Number of options outstanding (in shares) \| shares	369,850
Weighted average remaining contractual life (years)	9 years 1 month 6 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 4.41
Number of options exercisable (in shares) \| shares	51,833
Weighted average exercise price (in USD per share)	$ 3.99
Range 5
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	4.97
Range of Exercise prices - High (in USD per share)	$ 5.34
Number of options outstanding (in shares) \| shares	1,464,204
Weighted average remaining contractual life (years)	9 years 3 months 18 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 5.20
Number of options exercisable (in shares) \| shares	61,450
Weighted average exercise price (in USD per share)	$ 5.20
Range 6
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	5.35
Range of Exercise prices - High (in USD per share)	$ 12.55
Number of options outstanding (in shares) \| shares	769,075
Weighted average remaining contractual life (years)	8 years 4 months 24 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 8.09
Number of options exercisable (in shares) \| shares	222,208
Weighted average exercise price (in USD per share)	$ 7.95
Range 7
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	12.56
Range of Exercise prices - High (in USD per share)	$ 17.57
Number of options outstanding (in shares) \| shares	761,250
Weighted average remaining contractual life (years)	6 years 1 month 6 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 16.44
Number of options exercisable (in shares) \| shares	761,250
Weighted average exercise price (in USD per share)	$ 16.44
Total Range
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Exercise prices - Low (in USD per share)	1.54
Range of Exercise prices - High (in USD per share)	$ 17.57
Number of options outstanding (in shares) \| shares	6,331,088
Weighted average remaining contractual life (years)	8 years
Options outstanding, Weighted average exercise price (in USD per share)	$ 6.05
Number of options exercisable (in shares) \| shares	2,620,542
Weighted average exercise price (in USD per share)	$ 7.73

Stock-based Compensation - Non-vested Stock Option Activity (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Number of optioned common shares
Non-vested, beginning balance (in shares) \| shares	3,198,196
Options granted (in shares) \| shares	2,557,669
Options vested (in shares) \| shares	(1,584,733)
Non-vested options forfeited (in shares) \| shares	(460,586)
Non-vested, ending balance (in shares) \| shares	3,710,546
Weighted average fair value
Non-vested, beginning balance, weighted average fair value (USD per share) \| $ / shares	$ 3.23
Options granted (USD per share) \| $ / shares	4.08
Options vested (USD per share) \| $ / shares	4.36
Non-vested options forfeited (USD per share) \| $ / shares	2.82
Non-vested, ending balance, weighted average fair value (USD per share) \| $ / shares	$ 3.39

Stock-based Compensation - Valuation Assumptions for Stock Options (Details) - Arbutus Plans	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividend yield	0.00%	0.00%
Expected volatility	75.26%	73.05%
Risk-free interest rate	2.81%	1.28%
Expected average option term	6 years 8 months 12 days	6 years 10 months 28 days

Stock-based Compensation - Valuation Assumptions for Liability-Classified Options (Details) - Liability classified stock options - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares price (in USD per share)	$ 3.83	$ 5.05
Dividend yield	0.00%	0.00%
Expected volatility	75.20%	70.31%
Risk-free interest rate	2.48%	2.10%
Expected average term (years)	2 years 2 months 12 days	4 years 3 months 30 days
Weighted average fair value per share of options outstanding (in USD per share)	$ 1.27	$ 2.75
Fair value of vested liability-classified options (in thousands)	$ 479	$ 1,239	$ 553

Stock-based Compensation - Stock Option Activity for Liability-Classified Options (Details) - Liability classified stock options $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) $ / shares shares
Number of optioned common shares
Balance - Number of optioned common shares (in shares) \| shares	451,500
Options exercised (in shares) \| shares	(30,000)
Options forfeited, canceled or expired (in shares) \| shares	(44,000)
Balance - Number of optioned common shares (in shares) \| shares	377,500
Weighted average exercise price
Balance - Weighted average exercise price (in CAD and USD per share) \| $ / shares	$ 5.78
Options exercised - Weighted average exercise price (in CAD and USD per share) \| $ / shares	1.73
Options forfeited, canceled or expired - Weighted average exercise price (in CAD and USD per share) \| $ / shares	3.63
Balance - Weighted average exercise price (in CAD and USD per share) \| $ / shares	$ 5.81
Aggregate intrinsic value
Balance - Aggregate intrinsic value \| $	$ 525
Options exercised, aggregate intrinsic value \| $	71
Balance - Aggregate intrinsic value \| $	$ 224

Stock-based Compensation - Liability-Classified Options Outstanding (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Range 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	$ 1.54
Range of Exercise prices - High (in USD per share)	$ 3.22
Number of options outstanding (in shares)	1,541,466
Weighted average remaining contractual life (years)	8 years 1 month 6 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.13
Number of options exercisable (in shares)	545,966
Weighted average exercise price (in USD per share)	$ 3.09
Range 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	3.23
Range of Exercise prices - High (in USD per share)	$ 3.92
Number of options outstanding (in shares)	340,252
Weighted average remaining contractual life (years)	6 years 4 months 24 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.57
Number of options exercisable (in shares)	248,750
Weighted average exercise price (in USD per share)	$ 3.57
Range 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	3.93
Range of Exercise prices - High (in USD per share)	$ 3.96
Number of options outstanding (in shares)	1,084,991
Weighted average remaining contractual life (years)	7 years 2 months 12 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.94
Number of options exercisable (in shares)	729,085
Weighted average exercise price (in USD per share)	$ 3.94
Range 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	3.97
Range of Exercise prices - High (in USD per share)	$ 4.96
Number of options outstanding (in shares)	369,850
Weighted average remaining contractual life (years)	9 years 1 month 6 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 4.41
Number of options exercisable (in shares)	51,833
Weighted average exercise price (in USD per share)	$ 3.99
Range 5
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	4.97
Range of Exercise prices - High (in USD per share)	$ 5.34
Number of options outstanding (in shares)	1,464,204
Weighted average remaining contractual life (years)	9 years 3 months 18 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 5.20
Number of options exercisable (in shares)	61,450
Weighted average exercise price (in USD per share)	$ 5.20
Range 6
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	5.35
Range of Exercise prices - High (in USD per share)	$ 12.55
Number of options outstanding (in shares)	769,075
Weighted average remaining contractual life (years)	8 years 4 months 24 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 8.09
Number of options exercisable (in shares)	222,208
Weighted average exercise price (in USD per share)	$ 7.95
Total Range
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	1.54
Range of Exercise prices - High (in USD per share)	$ 17.57
Number of options outstanding (in shares)	6,331,088
Weighted average remaining contractual life (years)	8 years
Options outstanding, Weighted average exercise price (in USD per share)	$ 6.05
Number of options exercisable (in shares)	2,620,542
Weighted average exercise price (in USD per share)	$ 7.73
Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding, Weighted average exercise price (in USD per share)	$ 5.81	$ 5.78
Number of options exercisable (in shares)	377,500
Weighted average exercise price (in USD per share)	$ 5.82
Liability classified stock options \| Range 1
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	1.25
Range of Exercise prices - High (in USD per share)	$ 2.29
Number of options outstanding (in shares)	80,000
Weighted average remaining contractual life (years)	2 years 9 months 18 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 1.50
Number of options exercisable (in shares)	80,000
Weighted average exercise price (in USD per share)	$ 1.50
Liability classified stock options \| Range 2
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	2.60
Range of Exercise prices - High (in USD per share)	$ 3.30
Number of options outstanding (in shares)	35,000
Weighted average remaining contractual life (years)	1 year 10 months 24 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 2.82
Number of options exercisable (in shares)	35,000
Weighted average exercise price (in USD per share)	$ 2.82
Liability classified stock options \| Range 3
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	3.31
Range of Exercise prices - High (in USD per share)	$ 5.23
Number of options outstanding (in shares)	40,000
Weighted average remaining contractual life (years)	3 years 9 months 18 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 3.78
Number of options exercisable (in shares)	40,000
Weighted average exercise price (in USD per share)	$ 3.78
Liability classified stock options \| Range 4
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	5.24
Range of Exercise prices - High (in USD per share)	$ 7.93
Number of options outstanding (in shares)	150,000
Weighted average remaining contractual life (years)	4 years 9 months 18 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 6.69
Number of options exercisable (in shares)	150,000
Weighted average exercise price (in USD per share)	$ 6.69
Liability classified stock options \| Range 5
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	7.94
Range of Exercise prices - High (in USD per share)	$ 10.60
Number of options outstanding (in shares)	17,500
Weighted average remaining contractual life (years)	2 years 7 months 6 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 9.18
Number of options exercisable (in shares)	17,500
Weighted average exercise price (in USD per share)	$ 9.18
Liability classified stock options \| Range 6
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	10.61
Range of Exercise prices - High (in USD per share)	$ 12.03
Number of options outstanding (in shares)	55,000
Weighted average remaining contractual life (years)	5 years 1 month 6 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 12.03
Number of options exercisable (in shares)	55,000
Weighted average exercise price (in USD per share)	$ 12.03
Liability classified stock options \| Total Range
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Range of Exercise prices - Low (in USD per share)	1.25
Range of Exercise prices - High (in USD per share)	$ 12.03
Number of options outstanding (in shares)	377,500
Weighted average remaining contractual life (years)	3 years 10 months 24 days
Options outstanding, Weighted average exercise price (in USD per share)	$ 5.82

Stock-based Compensation - Outstanding Options Under the Protiva Option Plan (Details) - Protiva Share Options	12 Months Ended
	Dec. 31, 2018 $ / shares shares	Dec. 31, 2018 $ / shares shares	Dec. 31, 2017 $ / shares shares	Dec. 31, 2017 $ / shares shares
Number of optioned common shares
Balance - Number of optioned common shares (in shares)	40,000	40,000	46,000	46,000
Options exercised (in shares)	(40,000)	(40,000)	(6,000)	(6,000)
Options forfeited, canceled or expired (in shares)	0	0	0	0
Balance - Number of optioned common shares (in shares)	0	0	40,000	40,000
Weighted average exercise price
Balance - Weighted average exercise price (in CAD and USD per share) \| (per share)	$ 0.30	$ 0.24	$ 0.30	$ 0.22
Options exercised - Weighted average exercise price (in CAD and USD per share) \| (per share)	0.30	0.24	0.30	0.23
Options forfeited, canceled or expired - Weighted average exercise price (in CAD and USD per share) \| $ / shares	0.00		0.00
Balance - Weighted average exercise price (in CAD and USD per share) \| (per share)	$ 0.00	$ 0.00	$ 0.30	$ 0.24
Equivalent number of Company common shares
Number of optioned common shares
Balance - Number of optioned common shares (in shares)	27,007	27,007	31,058	31,058
Options exercised (in shares)	(27,007)	(27,007)	(4,051)	(4,051)
Options forfeited, canceled or expired (in shares)	0	0	0	0
Balance - Number of optioned common shares (in shares)	0	0	27,007	27,007

Stock-based Compensation - Outstanding Options Under the OnCore Option Plan (Details) - OnCore Option Plan	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Number of optioned common shares
Balance - Number of optioned common shares (in shares)	183,040
Options exercised (in shares)	(43,750)
Options forfeited, canceled or expired (in shares)	0
Balance - Number of optioned common shares (in shares)	139,290
Weighted average exercise price
Balance - Weighted average exercise price (in CAD and USD per share) \| $ / shares	$ 0.57
Options exercised - Weighted average exercise price (in CAD and USD per share) \| $ / shares	0.58
Balance - Weighted average exercise price (in CAD and USD per share) \| $ / shares	$ 0.56
Equivalent number of Company common shares
Number of optioned common shares
Balance - Number of optioned common shares (in shares)	184,332
Options exercised (in shares)	(44,059)
Options forfeited, canceled or expired (in shares)	0
Balance - Number of optioned common shares (in shares)	140,273

Stock-based Compensation - Non-vested Stock Option Activity OnCore Option Plan (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares shares
Number of optioned common shares
Non-vested, beginning balance (in shares)	3,198,196
Options vested (in shares)	(1,584,733)
Non-vested options forfeited (in shares)	(460,586)
Non-vested, ending balance (in shares)	3,710,546
Weighted average fair value
Non-vested, beginning balance, weighted average fair value (USD per share) \| $ / shares	$ 3.23
Options vested (USD per share) \| $ / shares	4.36
Non-vested, ending balance, weighted average fair value (USD per share) \| $ / shares	$ 3.39
OnCore Option Plan
Number of optioned common shares
Non-vested, beginning balance (in shares)	32,128
Options vested (in shares)	(32,128)
Non-vested options forfeited (in shares)	0
Non-vested, ending balance (in shares)	0
Weighted average fair value
Non-vested, beginning balance, weighted average fair value (USD per share) \| $ / shares	$ 17.83
Options vested (USD per share) \| $ / shares	17.83
Non-vested, ending balance, weighted average fair value (USD per share) \| $ / shares	$ 17.83
Equivalent number of Company common shares \| OnCore Option Plan
Number of optioned common shares
Non-vested, beginning balance (in shares)	32,354
Options vested (in shares)	(32,354)
Non-vested options forfeited (in shares)	0
Non-vested, ending balance (in shares)	0

Stock-based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 6,007	$ 15,117
Research, development, collaborations and contracts expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2,670	9,236
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3,337	$ 5,881

Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
Canadian federal and provincial income tax rate	27.00%	26.00%
Provisional tax benefit as a reduction of deferred tax liabilities due to 2017 Tax Act		$ 8,300
Provisional tax expense as a reduction in tax deferred assets due to 2017 Tax Act		3,600
Research and development credits	$ 4,265	3,639
Scientific research and experimental development expenditures available for indefinite carry-forward	51,575	36,652
Deferred tax assets, operating loss carryforwards, subject to expiration	11,040	13,723
Investment tax credit carryforward
Income Taxes [Line Items]
Investment tax credits available to reduce Canadian federal income taxes	8,784	9,546
Investment tax credits available to reduce provincial income taxes	4,002	4,866
Research tax credit carryforward
Income Taxes [Line Items]
Scientific research and experimental development expenditures available for indefinite carry-forward	61,493	61,493
Deferred tax assets, operating loss carryforwards, subject to expiration	$ 182,256	$ 124,451

Income Taxes - Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Computed taxes (recoveries) at Canadian federal and provincial tax rates	$ (19,287)	$ (28,270)
Difference due to change in tax rate on opening deferred taxes	0	(6,633)
Permanent and other differences	396	1,476
Change in valuation allowance - other	13,062	6,945
Difference due to income taxed at foreign rates	(138)	(966)
Stock-based compensation	1,685	3,128
Impairment of goodwill	0	0
Deferred income tax recovery	$ (4,282)	$ (24,320)

Income Taxes - Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Components of Deferred Tax Assets [Line Items]
Non-capital loss carryforwards	$ 51,575	$ 36,652
Research and development deductions	15,803	16,603
Book amortization in excess of tax	(608)	(650)
Share issue costs	307	456
Revenue recognized for tax purposes in excess of revenue recognized for accounting purposes	0	1,162
Tax value in excess of accounting value in lease inducements	147	173
In-process research and development	(12,664)	(16,943)
Upfront license fees	283	311
Equity accounted for investment	37	0
Other	2,503	2,017
Total deferred tax assets (liabilities)	71,024	53,679
Valuation allowance	(83,685)	(70,622)
Net deferred tax assets (liabilities)	(12,661)	(16,943)
Federal
Components of Deferred Tax Assets [Line Items]
Investment tax credits	9,686	9,079
Provincial
Components of Deferred Tax Assets [Line Items]
Investment tax credits	$ 3,955	$ 4,819

Contingencies and Commitments - Minimum Rent and Estimated Operating Cost Commitment, Net of Lease Inducements (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Year ended December 31, 2019	$ 746
Year ended December 31, 2020	766
Year ended December 31, 2021	787
Year ended December 31, 2022 and after	3,813
Future minimum rent and estimated operating cost commitment, net of lease inducements	$ 6,112

Contingencies and Commitments - Narrative (Details) $ in Thousands			1 Months Ended				12 Months Ended			53 Months Ended
	Jun. 05, 2016 USD ($) research_funding_period_extensions	Jan. 16, 2015 USD ($)	Nov. 30, 2018 USD ($)	Nov. 30, 2014 USD ($)	Oct. 31, 2014 USD ($)	Feb. 28, 2014 USD ($) compound_series	Dec. 31, 2018 USD ($)	Dec. 31, 2018 CAD ($)	Dec. 31, 2017 USD ($)	Mar. 31, 2004 USD ($)	Mar. 31, 2004 CAD ($)	Dec. 31, 2018 CAD ($)
Contingencies and Commitments [Line Items]
Lease expense							$ 1,789,000		$ 1,653,000
Percent of costs funded by TPC										27.00%	27.00%
Maximum contribution for product										$ 7,179,000	$ 9,330
Cumulative contribution for product							$ 2,714,000	$ 3,702
Royalty guarantees commitments percentage							2.50%	2.50%
Arbutus Inc. \| Enantigen
Contingencies and Commitments [Line Items]
Business combination, high end of payment upon achievement of certain triggering events					$ 21,000,000
Business combination, regulatory, development and sales milestone payments estimated fair value					6,727,000
Arbitration with the University of British Columbia
Contingencies and Commitments [Line Items]
Loss contingency, damages sought for allegedly unpaid royalties		$ 3,500,000					$ 10,900,000
Blumberg and Drexel \| Arbutus Inc.
Contingencies and Commitments [Line Items]
Number of series of compounds \| compound_series						3
Development and regulatory milestones payment per licensed compound series, maximum				$ 1,000,000		$ 3,500,000
Sales performance milestones payment per licensed product, maximum						92,500,000
Blumberg \| Arbutus Inc.
Contingencies and Commitments [Line Items]
Research funding per year under research collaboration and funding agreement	$ 1,100,000		$ 750,000		$ 1,000,000
Research funding period			2 years		3 years
Research funding period, renewable option	1 year				3 years
Research funding agreement exclusive license upfront payment					$ 100,000
Research funding agreement exclusive license maximum development and regulatory milestone payments					8,100,000
Research funding agreement license maximum commercialization milestone payments					$ 92,500,000
Research funding period, number of renewable options \| research_funding_period_extensions	2
Royalty
Contingencies and Commitments [Line Items]
Collaborations and contracts							154,000		191,000
Royalty payable							4,000		$ 5,000
Royalties paid or accrued							26,000
Contractual obligation							$ 2,690,000					$ 3,669
License \| Blumberg and Drexel \| Arbutus Inc.
Contingencies and Commitments [Line Items]
License fee				$ 50,000		$ 150,000

Related Party Transactions (Details) $ in Thousands	12 Months Ended
Related Party Transactions (Details) $ in Thousands	Dec. 31, 2018 USD ($) ft²
Roivant Sciences Ltd \| Co-venturer \| Research and development services
Related Party Transaction [Line Items]
Expenses from transactions with related party	$ 644
Genevant \| Equity Method Investee \| Research and development services
Related Party Transaction [Line Items]
Expenses from transactions with related party	398
Genevant \| Equity Method Investee \| Administrative and transitional services
Related Party Transaction [Line Items]
Income from related party	$ 226
Genevant \| Equity Method Investee \| Sublease Burnaby facility
Related Party Transaction [Line Items]
Area of sublease facility \| ft²	17,900
Income from related party	$ 466

Concentrations of Business Risk - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Risks and Uncertainties [Abstract]
Accounts receivable	$ 1,431	$ 402
Financial obligations, period to pay	45 days

Concentrations of Business Risk - Net Liquidity (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Risks and Uncertainties [Abstract]
Cash, cash equivalents and short-term investments	$ 124,617	$ 126,352
Less: Accounts payable and accrued liabilities	(9,429)	(10,646)
Net liquidity	$ 115,188	$ 115,706

Concentrations of Business Risk - Foreign Currency Exposure (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Intercompany Foreign Currency Balance [Line Items]
Cash and cash equivalents and short-term investments	$ 124,617	$ 126,352
Accounts receivable	1,431	402
Accrued revenue	0	128
Accounts payable and accrued liabilities	(9,429)	(10,646)
Foreign currency exposure
Intercompany Foreign Currency Balance [Line Items]
Cash and cash equivalents and short-term investments	1,427	25,921
Accounts receivable	293	375
Accrued revenue	0	0
Accounts payable and accrued liabilities	0	(1,273)
Exposure to Canadian dollar	$ 1,720	$ 25,023

Interim Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 1,678	$ 1,587	$ 1,244	$ 1,436	$ 2,534	$ 6,892	$ 1,039	$ 235	$ 5,945	$ 10,700
Loss from operations	(16,903)	(32,426)	(22,046)	(18,405)	(60,249)	(12,897)	(19,485)	(18,299)	(89,780)	(110,930)
Net loss	(18,249)	(24,473)	3,091	(17,429)	(35,931)	(11,600)	(18,255)	(18,627)	(57,060)	(84,413)
Net loss attributable to common shares	$ (20,896)	$ (27,040)	$ 550	$ (19,765)	$ (36,842)	$ (11,600)	$ (18,255)	$ (18,627)	$ (67,151)	$ (85,324)
Basic net income/(loss) per common share (in USD per share)	$ (0.38)	$ (0.49)	$ 0.01	$ (0.36)					$ (1.21)	$ (1.56)
Diluted net income/(loss) per common share (in USD per share)	$ (0.38)	$ (0.49)	$ 0.01	$ (0.36)					$ (1.21)	(1.56)
Basic and diluted net loss attributable to shareholders per share (USD per share)					$ (0.67)	$ (0.21)	$ (0.33)	$ (0.34)		$ (1.56)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

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- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

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+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Consolidated Statement of Stockholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Statement of Stockholders' Equity [Abstract]
Issuance costs on preferred stock issued	$ 1,131

Refundable Investment Tax Credits	12 Months Ended
Refundable Investment Tax Credits	Dec. 31, 2018
Government Grants And Refundable Investment Tax Credits [Abstract]
Refundable investment tax credits	Refundable investment tax credits Refundable investment tax credits have been recorded as a reduction in research and development expenses. The Company’s estimated claim for refundable Scientific Research and Experimental Development investment tax credits for the year ended December 31, 2018 is $18,000 (2017 - $183,000).