<?xml version="1.0" encoding="US-ASCII"?>
<!-- Generated by CompSci Transform (tm) - http://www.compsciresources.com -->
<!-- Created: Tue Apr 14 21:02:04 UTC 2026 -->
<linkbase xmlns="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:xbrldt="http://xbrl.org/2005/xbrldt">
  <roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#IndividualsOnly" roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member"/>
  <arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" arcroleURI="http://xbrl.org/int/dim/arcrole/all"/>
  <definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <loc xlink:type="locator" xlink:label="ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllIndividualsMember"/>
    <loc xlink:type="locator" xlink:label="abus_MrMcElhaughMember" xlink:href="abus-20260526.xsd#abus_MrMcElhaughMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ecd_AllIndividualsMember" xlink:to="abus_MrMcElhaughMember" order="2" xbrldt:closed="true"/>
    <loc xlink:type="locator" xlink:label="abus_MsAndroskiMember" xlink:href="abus-20260526.xsd#abus_MsAndroskiMember"/>
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ecd_AllIndividualsMember" xlink:to="abus_MsAndroskiMember" order="4" xbrldt:closed="true"/>
    <loc xlink:type="locator" xlink:label="abus_WilliamCollierMember" xlink:href="abus-20260526.xsd#abus_WilliamCollierMember"/>
<!-- [WMV6][5EcZwweQ69Q9kqNiMlT4AcwXfkG5XbfZp8ceDXuo1ItSix2gS7fN36TtYTD3lhO80Gbmn1FSSZ+k4yfeG7LLoCtTs8Btw+tRhiwM+vdbe+TA++OeJbajkuZsJg1B/u/AHprUK/3pcIl4sPWuX5i8K6D+pdI3LudGcKMatBmvABp/T9KnkH7qctq5a2OvNiPpQgPkp7OUNhtVmYB2tf3Bqc54+KkTLYj9N8bn/kKW0YkZ9LORD0vEByUGhTBK0TjygG4O1h4PP1hORsHwbecNYgg8cwWme1H2MoOXRyR+WKeAlchS97u7iFwB01eOu0BHtCC/njF3fpKEpRuKI5AewmGpBY6vGT36mnxfT9X1vKRV24P5bNZoWgP/og==] CSR-->
    <definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="ecd_AllIndividualsMember" xlink:to="abus_WilliamCollierMember" order="6" xbrldt:closed="true"/>
  </definitionLink>
</linkbase>
