Arbutus Biopharma (ABUS) 10-K 4 Mar 21 2020 FY Annual report Financial data

Cover

Cover - USD ($)	12 Months Ended
	Dec. 31, 2020	Mar. 03, 2021	Jun. 30, 2020
Cover [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2020
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-34949
Entity Registrant Name	Arbutus Biopharma Corp
Amendment Flag	false
Entity Central Index Key	0001447028
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	FY
Entity Incorporation, State or Country Code	A1
Entity Tax Identification Number	98-0597776
Entity Address, Address Line One	701 Veterans Circle
Entity Address, City or Town	Warminster
Entity Address, State or Province	PA
Entity Address, Postal Zip Code	18974
City Area Code	267
Local Phone Number	469-0914
Title of 12(b) Security	Common shares, without par value
Trading Symbol	ABUS
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Entity Public Float			$ 129,686,974
Entity Common Stock, Shares Outstanding		95,583,915
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Portions of the registrant’s definitive proxy statement for its 2021 Annual Meeting of Shareholders, which the registrant intends to file pursuant to Regulation 14A with the Securities and Exchange Commission no later than 120 days after the registrant’s fiscal year ended December 31, 2020, are incorporated by reference into Part III of this Form 10-K.
Shares price (in USD per share)			$ 1.82

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 52,251	$ 31,799
Investments in marketable securities, current	71,017	59,035
Accounts receivable	1,312	1,204
Prepaid expenses and other current assets	3,124	1,790
Total current assets	127,704	93,828
Property and equipment, net of accumulated depreciation	6,927	8,676
Right of use asset	2,405	2,738
Other non-current assets	44	293
Total assets	137,080	105,535
Current liabilities:
Accounts payable and accrued liabilities	8,901	7,235
Liability-classified options	250	253
Lease liability, current	390	340
Total current liabilities	9,541	7,828
Liability related to sale of future royalties	19,554	18,992
Contingent consideration	3,426	2,953
Lease liability, non-current	2,593	3,018
Total liabilities	35,114	32,791
Stockholders' equity
Issued and outstanding: 1,164,000	149,408	137,285
Issued and outstanding: 89,678,722 (December 31, 2019: 64,780,314)	985,939	898,535
Additional paid-in capital	60,751	55,246
Deficit	(1,045,961)	(970,093)
Accumulated other comprehensive loss	(48,171)	(48,229)
Total stockholders' equity	101,966	72,744
Total liabilities and stockholders' equity	$ 137,080	$ 105,535

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - shares	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock, shares issued (in shares)	1,164,000	1,164,000
Preferred stock, shares outstanding (in shares)	1,164,000	1,164,000
Common shares, shares issued (in shares)	89,678,722	64,780,314
Common shares, shares outstanding (in shares)	89,678,722	64,780,314

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Revenue
Revenues	$ 6,914	$ 6,011
Operating expenses
Research and development	47,481	57,601
General and administrative	14,724	17,727
Depreciation	1,978	2,028
Change in fair value of contingent consideration	473	(173)
Site consolidation	64	156
Impairment of intangible assets	0	43,836
Impairment of goodwill	0	22,471
Arbitration	0	6,266
Total operating expenses	64,720	149,912
Loss from operations	(57,806)	(143,901)
Other income (loss)
Interest income	741	2,111
Interest expense	(4,011)	(2,108)
Equity investment loss	(2,545)	(22,522)
Foreign exchange gain (loss)	(124)	41
Total other loss	(5,939)	(22,478)
Loss before income taxes	(63,745)	(166,379)
Income tax benefit	0	12,656
Net loss	(63,745)	(153,723)
Items applicable to preferred shares
Dividend accretion of convertible preferred shares	(12,123)	(11,149)
Net loss attributable to common shares	$ (75,868)	$ (164,872)
Loss per share
Basic and diluted (in USD per share)	$ (1)	$ (2.89)
Weighted average number of common shares
Basic and diluted (in shares)	75,835,378	57,093,454
Comprehensive income (loss)
Unrealized gain on available-for-sale securities	$ 14	$ 0
Currency translation adjustments	44	(59)
Comprehensive loss	(63,687)	(153,782)
Collaborations and licenses
Revenue
Revenues	3,519	4,355
Non-cash royalty revenue
Revenue
Revenues	$ 3,395	$ 1,656

Consolidated Statement of Stock

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, 2018		1,164,000	55,518,800
Beginning balance at Dec. 31, 2018	$ 200,234	$ 126,136	$ 879,405	$ 48,084	$ (805,221)	$ (48,170)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accretion of accumulated dividends on Preferred Shares	0	$ 11,149			(11,149)
Stock-based compensation	7,204			7,204
Certain fair value adjustments to liability stock option awards	180			180
Issuance of common shares pursuant to the Open Market Sales Agreement (in shares)			9,138,232
Issuance of common shares pursuant to the Open Market Sales Agreement	18,601		$ 18,601
Issuance of common shares pursuant to exercise of options (in shares)			123,282
Issuance of common shares pursuant to exercise of options	307		$ 529	(222)
Currency translation adjustment	(59)					(59)
Net loss	(153,723)				(153,723)
Ending balance (in shares) at Dec. 31, 2019		1,164,000	64,780,314
Ending balance at Dec. 31, 2019	72,744	$ 137,285	$ 898,535	55,246	(970,093)	(48,229)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accretion of accumulated dividends on Preferred Shares	0	$ 12,123			(12,123)
Stock-based compensation	6,145			6,145
Certain fair value adjustments to liability stock option awards	18			18
Issuance of common shares pursuant to the Open Market Sales Agreement (in shares)			24,728,368
Issuance of common shares pursuant to the Open Market Sales Agreement	86,297		$ 86,297
Issuance of common shares pursuant to exercise of options (in shares)			170,040
Issuance of common shares pursuant to exercise of options	449		$ 1,107	(658)
Unrealized gain on available-for-sale securities	14					14
Currency translation adjustment	44					44
Net loss	(63,745)				(63,745)
Ending balance (in shares) at Dec. 31, 2020		1,164,000	89,678,722
Ending balance at Dec. 31, 2020	$ 101,966	$ 149,408	$ 985,939	$ 60,751	$ (1,045,961)	$ (48,171)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
OPERATING ACTIVITIES
Net loss	$ (63,745)	$ (153,723)
Non-cash items:
Deferred income tax benefit	0	(12,661)
Depreciation	1,978	2,028
Loss on sale of property and equipment	0	20
Stock-based compensation expense	6,161	6,799
Unrealized foreign exchange gains	(56)	(68)
Change in fair value of contingent consideration	473	(173)
Impairment of intangible assets	0	43,836
Impairment of goodwill	0	22,471
Net equity investment gain or loss	2,545	22,522
Non-cash royalty revenue	(3,395)	(1,656)
Non-cash interest expense	3,957	2,099
Net accretion and amortization of investments in marketable securities	210	(275)
Net change in operating items:
Accounts receivable	(108)	227
Prepaid expenses and other assets	(752)	1,606
Accounts payable and accrued liabilities	1,666	(3,314)
Lease liabilities	(375)	(744)
Net cash used in operating activities	(51,441)	(71,006)
INVESTING ACTIVITIES
Purchase of investments in marketable securities	(85,578)	(58,759)
Disposition of investments in marketable securities	73,398	87,675
Investment in Genevant	(2,500)	0
Proceeds from sale of property and equipment	0	11
Acquisition of property and equipment	(229)	(589)
Net cash provided by (used in) investing activities	(14,909)	28,338
FINANCING ACTIVITIES
Proceeds from sale of future royalties, net	0	18,549
Issuance of common shares pursuant to exercise of options	449	307
Issuance of common shares pursuant to the Open Market Sales Agreement	86,297	18,601
Net cash provided by financing activities	86,746	37,457
Effect of foreign exchange rate changes on cash and cash equivalents	56	68
Increase (decrease) in cash and cash equivalents	20,452	(5,143)
Cash and cash equivalents, beginning of period	31,799	36,942
Cash and cash equivalents, end of period	52,251	31,799
Supplemental cash flow information
Preferred shares dividends accrued	$ (12,123)	$ (11,149)

Organization

Organization	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Description of the Business Arbutus Biopharma Corporation (the “Company” or “Arbutus”) is a clinical-stage, biopharmaceutical company primarily focused on developing a cure for people with chronic hepatitis B virus (“HBV”) infection. The Company is advancing multiple product candidates with distinct mechanisms of action that it believes have the potential to provide a new curative regimen for chronic HBV infection. The Company has also initiated a drug discovery and development effort for treating coronaviruses, including COVID-19. The Company’s two lead product candidates are AB-729, the Company’s proprietary subcutaneously-delivered RNA interference (“RNAi”) product candidate that suppresses HBsAg expression, and AB-836, the Company’s proprietary next-generation oral capsid inhibitor that suppresses HBV DNA replication. AB-729 is currently in an ongoing Phase 1a/1b clinical trial and the Company expects AB-836 to progress into a Phase 1a/1b clinical trial in the first half of 2021. Liquidity At December 31, 2020, the Company had an aggregate of $123.3 million in cash, cash equivalents and investments in marketable securities. From January 1, 2021 through March 3, 2021, the Company received an additional $24.3 million of net proceeds from the issuance of common shares under the ATM program. The Company believes that its cash resources will be sufficient to fund its operations through the third quarter of 2022. 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. COVID-19 Impact In December 2019, an outbreak of a novel strain of coronavirus (COVID-19) was identified in Wuhan, China. This virus continues to spread globally, has been declared a pandemic by the World Health Organization and has spread to nearly every country in the world. The impact of this pandemic has been, and will likely continue to be, extensive in many aspects of society. The pandemic has resulted in and will likely continue to result in significant disruptions to businesses. A number of countries and other jurisdictions around the world have implemented extreme measures to try and slow the spread of the virus. These measures include the closing of businesses and requiring people to stay in their homes, the latter of which raises uncertainty regarding the ability to travel to hospitals in order to participate in clinical trials. Additional measures that have had, and will likely continue to have, a major impact on clinical development, at least in the near-term, include shortages and delays in the supply chain, and prohibitions in certain countries on enrolling subjects in new clinical trials. Future disruptions related to the COVID-19 pandemic could negatively impact the Company’s plans and timelines in 2021 and beyond, including enrolling and monitoring subjects in its clinical trials.

Significant accounting policies

Significant accounting policies	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Significant accounting policies	Significant accounting policies Basis of presentation and principles of consolidation These consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and include the accounts of Arbutus Biopharma Corporation and its two wholly-owned subsidiaries, Arbutus Biopharma, Inc. and Arbutus Biopharma U.S. Holdings, Inc. All intercompany balances and transactions have been eliminated. Certain prior year amounts have been reclassified to conform to the current year presentation. In February 2021, Arbutus Biopharma US Holdings, Inc merged into Arbutus Biopharma, Inc. with Arbutus Biopharma, Inc. continuing its legal existence and Arbutus Biopharma US Holdings, Inc ceasing to exist. 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 and contingent liabilities as of the end or during the reporting period. Actual results could significantly differ from those estimates. Significant estimates in the accompanying consolidated financial statements impact contingent consideration, income tax recoveries, stock-based compensation, clinical trial accruals and the sale of future royalties liability. 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. Investments in marketable securities The Company’s short-term investments consist of marketable securities that have original maturities exceeding three months and remaining maturities of less than one year. The Company classifies investments with remaining maturities of one year or longer as non-current. These investments are accounted for as available-for-sale securities and are reported at fair value, with unrealized gains and losses reported in other comprehensive loss, until their disposition. Realized gains and losses from the sale of marketable securities, if any, are calculated using the specific-identification method, and are recorded as a component of other income or loss. The Company reviews its available-for-sale securities at each period end to determine if they remain available-for-sale based on the Company’s current intent and ability to sell the security if it is required to do so. Declines in value judged to be other-than-temporary are included in interest income or expense in the Company’s statements of operations and comprehensive loss. As of December 31, 2020, the recorded value of the Company’s investments in marketable securities was deemed to be recoverable in all respects. All investments are governed by the Company’s Investment Policy approved by the Company’s board of directors. Foreign currency translation and functional currency conversion The Company’s functional currency is the United States dollar. M onetary assets and liabilities denominated in foreign currencies are translated into United States 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. Investment in Genevant As the result of a recapitalization of Genevant Sciences Ltd. (“Genevant”) in July 2020, Arbutus’ ownership interest in Genevant decreased to approximately 16%. Due to Arbutus’ loss of significant influence with respect to Genevant as a result of the recapitalization, Arbutus discontinued the use of the equity method of accounting for its interest in Genevant. Ownership interests that do not confer the ability to exercise significant influence are accounted for at fair value, except when the investment does not have a readily-determinable fair value. In that case, the investment is carried at cost, less any impairment. The carrying value is subsequently adjusted to fair value based on any observable price changes. Following the recapitalization, Arbutus accounts for its interest in Genevant as equity securities without readily determinable fair values. Accordingly, an estimate of the fair value of the securities is based on the original cost less previously recognized equity method losses, less impairments, plus or minus changes resulting from observable price changes in orderly transactions for identical or a similar Genevant securities. As of December 31, 2020, the carrying value of Arbutus’ investment in Genevant was zero and Arbutus owned approximately 16% of the common equity of Genevant. See note 5 for more information. Property and equipment Property and equipment is recorded at cost less impairment losses and accumulated depreciation. 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. Property and equipment is reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. If such a review should indicate that the carrying amount of long-lived assets is not recoverable, then such assets are written down to their fair values. Revenue recognition ASC 606, Revenue From Contracts with Customers (“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 As of January 1, 2019, the Company adopted FASB’s Accounting Standards Update 2016-02, Leases (ASC 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 using the modified retrospective basis applied at the effective date of the new standard and elected to utilize a package of practical expedients. See note 6 for more information. Research and development costs Research and development costs include compensation and benefits for research and development employees, an allocation of overhead expenses and costs associated with materials and supplies used in clinical trials and research and development, outside contracted services including clinical and pre-clinical study costs, legal, regulatory compliance and fees paid to consultants or outside parties for research and development activities performed on the Company’s behalf. Such costs are charged to expense in the period in which they are incurred. Research and development costs that are paid in advance of performance or receipt are recorded as prepaid expense and are amortized over the period that the services are performed. 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 Series A participating convertible preferred shares (“Preferred Shares”), as further described in note 13, that meet the definition of participating securities. The Company’s 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, 2020 and 2019, since the effect of the Company’s stock options and convertible preferred stock is anti-dilutive. For the year ended December 31, 2020, potential common shares of 10.7 million pertaining to stock options outstanding and approximately 21.1 million pertaining to if-converted preferred shares for a total of approximately 31.8 million shares were excluded from the calculation of net loss attributable to common shareholders, per share because their inclusion would be anti-dilutive. A total of approximately 28.4 million potential common shares and if-converted preferred shares were excluded from the calculation for the year ended December 31, 2019. 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, 2020 2019 (in thousands, except share and per share amounts) Numerator: Allocation of distributable earnings $ — $ — Allocation of undistributable loss (75,868) (164,872) Allocation of net loss attributed to common shareholders $ (75,868) $ (164,872) Denominator: Weighted average number of common shares - basic and diluted 75,835,378 57,093,454 Basic and diluted net loss attributable to common shareholders per share $ (1.00) $ (2.89) See note 13 and note 14 for more information about the Company’s common shares. 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. Stock-based compensation We measure and recognize compensation expense for all share-based compensation arrangements based on estimated fair values. We use the Black-Scholes option valuation model to estimate the fair value of stock options at the date of grant. The Black-Scholes option valuation model requires the input of subjective assumptions to calculate the value of stock options. For those assumptions, we use historical data and other information to estimate the expected price volatility and risk free interest rate for all awards. The expected life of stock options granted are estimated to be five years for employees and seven years for directors and executives, based on our historical experience. 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. Expense is recognized over the vesting period for all awards and commences at the grant date for time-based awards and upon the Company’s determination that the achievement of such performance conditions is probable for performance-based awards. Forfeitures are recognized as they occur. For the Company’s Employee Stock Purchase Plan, the fair value of the right to acquire stock at a discounted price under the plan is calculated using the Black-Scholes valuation model. Expense is recognized over the period the employee contributes to the plan through payroll deductions. 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. As of January 1, 2016, the Company changed its functional currency to US dollars, which resulted in certain stock option awards with exercise prices denominated in Canadian dollars having an exercise price that is not denominated in the Company’s functional currency. 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 a liability. 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. 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 the United States. Comprehensive loss Comprehensive loss is comprised of net loss, the impact of foreign currency translation adjustments and adjustments for the change in unrealized gains and losses on investments in available-for-sale marketable securities. The Company displays comprehensive loss and its components in the consolidated statements of operations and comprehensive loss, net of tax effects if any. Concentrations of Credit Risk Financial instruments which potentially subject the Company to credit risk consist primarily of cash, cash equivalents and marketable securities. The Company holds these investments in highly rated financial institutions, and, by policy, limits the amounts of credit exposure to any one financial institution. These amounts at times may exceed federally insured limits. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. The Company has no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements. Recent accounting pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments (ASC 326). The guidance is effective for the Company beginning January 1, 2023 and it changes how entities account for credit losses on financial assets and other instruments that are not measured at fair value through net income, including available-for-sale debt securities. The Company is currently evaluating the impact of the new standard on its consolidated financial statements.

Fair value measurements

Fair value measurements	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair value measurements	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, accounts receivable, accounts payable and accrued liabilities approximate their fair values due to the immediate or short-term maturity of these financial instruments. To determine the fair value of the contingent consideration (note 11), 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 $3.4 million as of December 31, 2020 and the increase of $0.5 million has been recorded within operating expenses in the statement of operations and comprehensive loss for the year ended December 31, 2020. The assumptions used in the discounted cash flow model are level 3 inputs as defined above. The Company assessed the sensitivity of the fair value measurement to changes in these unobservable inputs, and determined that changes within a reasonable range would not result in a materially different assessment of fair value. 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 Total As of December 31, 2020 (in thousands) Assets Cash and cash equivalents $ 52,251 $ — $ — $ 52,251 Investments in marketable securities 71,017 — — 71,017 Total $ 123,268 $ — $ — $ 123,268 Liabilities Liability-classified options $ — $ — $ 250 $ 250 Contingent consideration — — 3,426 3,426 Total $ — $ — $ 3,676 $ 3,676 Level 1 Level 2 Level 3 Total As of December 31, 2019 (in thousands) Assets Cash and cash equivalents $ 31,799 $ — $ — $ 31,799 Investments in marketable securities 59,035 — — 59,035 Total $ 90,834 $ — $ — $ 90,834 Liabilities Liability-classified options $ — $ — $ 253 $ 253 Contingent consideration — — 2,953 2,953 Total $ — $ — $ 3,206 $ 3,206 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 options exercised in the period Increase (decrease) in fair value of liability Liability at end of the period (in thousands) Year ended December 31, 2020 $ 253 $ — $ (3) $ 250 Year ended December 31, 2019 $ 479 $ — $ (226) $ 253 The following table presents the changes in fair value of the Company’s contingent consideration: Liability at beginning of the period Increase (decrease) in fair value of liability Liability at end of the period (in thousands) Year ended December 31, 2020 $ 2,953 $ 473 $ 3,426 Year ended December 31, 2019 $ 3,126 $ (173) $ 2,953

Investments in marketable secur

Investments in marketable securities	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Investments in marketable securities	Investments in marketable securities Investments in marketable securities consisted of the following: Amortized Cost Gross Unrealized Gain (1) Gross Unrealized Loss (1) Fair Value As of December 31, 2020 (in thousands) Cash equivalents Money market fund $ 13,703 $ — $ — $ 13,703 US government agency bonds — — — — US treasury bills 2,000 — — 2,000 Total $ 15,703 $ — $ — $ 15,703 Investments in marketable securities US government agency bonds $ 11,550 $ 7 $ — $ 11,557 US treasury bills 21,990 2 — 21,992 US government bonds 37,463 6 (1) 37,468 Total $ 71,003 $ 15 $ (1) $ 71,017 (1) Gross unrealized gain (loss) is pre-tax. Amortized Cost Gross Unrealized Gain (1) Gross Unrealized Loss (1) Fair Value As of December 31, 2019 (in thousands) Cash equivalents Money market fund $ 4,106 $ — $ — $ 4,106 US government agency bonds 1,511 — — 1,511 US treasury bills 1,499 — — 1,499 Total $ 7,116 $ — $ — $ 7,116 Investments in marketable securities Us government agency bonds $ 19,863 $ 2 $ (1) $ 19,864 US treasury bills 15,926 2 (1) 15,927 US government bonds 23,246 — (2) 23,244 Total $ 59,035 $ 4 $ (4) $ 59,035 (1) Gross unrealized gain (loss) is pre-tax.

Investment in Genevant

Investment in Genevant	12 Months Ended
	Dec. 31, 2020
Equity Method Investments and Joint Ventures [Abstract]
Investment in Genevant	Investment in GenevantIn April 2018, the Company entered into an agreement with Roivant Sciences Ltd. (“Roivant”), its largest shareholder, 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 lipid nanoparticle (“LNP”) and ligand conjugate delivery technologies. The Company licensed exclusive rights to its LNP and ligand conjugate delivery platforms to Genevant for RNA-based applications outside of HBV, except to the extent certain rights had already been licensed to other third parties (the “Genevant License”). The Company retained all rights to its LNP and conjugate delivery platforms for HBV. Under the Genevant License, the Company is entitled to receive tiered low single-digit royalties on future sales of Genevant products covered by the licensed patents. If Genevant sub-licenses the intellectual property licensed by the Company to Genevant, the Company is entitled to receive under the Genevant License, upon the commercialization of a product developed by such sub-licensee, the lesser of (i) twenty percent of the revenue received by Genevant for such sublicensing and (ii) tiered low single-digit royalties on product sales by the sublicensee. On July 23, 2020, the United States Patent and Trademark Office before the Patent Trial and Appeal Board ("PTAB") announced its decision in Moderna Therapeutics, Inc.'s (“Moderna”) challenge of the validity of U.S. Patent 8,058,069 ("the ‘069 Patent"). In this decision, the PTAB determined no challenged claims were unpatentable. On September 23, 2020, Moderna appealed the ‘069 Patent decision to the Federal Circuit Court of Appeals. Moderna filed its opening brief in that appeal on February 23, 2021, and the Company’s responsive brief is due on May 4, 2021. While the Company is the patent holder, this patent has been licensed to Genevant. The ‘069 Patent was included in the exclusive rights licensed by the Company to Genevant under the Genevant License. On July 31, 2020, Roivant recapitalized Genevant through an equity investment and conversion of previously issued convertible debt securities held by Roivant. The Company participated in the recapitalization of Genevant with an investment of $2.5 million. The Company determined that this $2.5 million additional investment in Genevant represented the funding of prior losses and accordingly, the Company recorded the amount as an equity investment loss on the Condensed Consolidated Statements of Operations and Comprehensive Loss in 2020. Following the recapitalization, the Company owned approximately 16% of the common equity of Genevant. In connection with the recapitalization, Genevant, the Company and Roivant entered into an Amended and Restated Shareholders Agreement that provides Roivant with substantial control of Genevant. The Company has a non-voting observer seat on Genevant’s Board of Directors. Due to the Company’s loss of significant influence with respect to Genevant as a result of the recapitalization, the Company discontinued the use of the equity method of accounting for its interest in Genevant. Following the recapitalization, the Company accounts for its interest in Genevant as equity securities without readily determinable fair values. Accordingly, an estimate of the fair value of the securities is based on the original cost less previously recognized equity method losses, less impairments, plus or minus changes resulting from observable price changes in orderly transactions for identical or a similar Genevant securities. The Company’s entitlement to receive future royalties or sublicensing revenue under the Genevant License was not impacted by the recapitalization.

Leases

Leases	12 Months Ended
	Dec. 31, 2019
Leases [Abstract]
Leases	Leases The Company has two operating leases for office and laboratory space. The Company’s corporate headquarters is located at 701 Veterans Circle, Warminster, Pennsylvania. The lease expires on April 30, 2027, and the Company has the option of extending the lease for two further five-year terms. The Company also leases office space located at 626 Jacksonville Rd, Warminster, Pennsylvania under a lease that expires on December 31, 2021, and the Company has an option to extend the lease term to April 30, 2027. In connection with the Company’s site consolidation in 2018, the Company ceased using its office and laboratory space located in Burnaby, British Columbia, Canada on June 30, 2018. The Company subleased a portion of the Burnaby facility to various tenants, including Genevant, until the lease expired on July 31, 2019. The Company recognized the remaining lease payments for the Burnaby facility, less sublease income under contract, in site consolidation expenses in 2018. The Company adopted ASU No. 2016-02, Leases (Topic 842) 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. Leases with an initial term of 12 months or less are not recorded on the balance sheet. The Company determines if an arrangement is a lease at inception. Right-of-use assets represent the Company’s right to use an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. Operating lease right-of-use assets and lease liabilities are recognized based on the present value of lease payments over the lease term. The leases do not provide an implicit rate so in determining the present value of lease payments, the Company utilized its incremental borrowing rate for the applicable lease, which was 9.0% for the 701 Veterans Circle lease, 7.6% for the 626 Jacksonville Rd. lease and 5.0% for the Burnaby lease. The Company recognizes lease expense on a straight-line basis over the remaining lease term. During the year ended December 31, 2020, the Company incurred total operating lease expenses of $0.7 million, which included lease expenses associated with fixed lease payments of $0.6 million, and variable payments associated with common area maintenance and similar expenses of $0.1 million. For the twelve months ended December 31, 2019, the Company incurred total operating lease expense of $1.2 million, which included fixed lease payments of $0.9 million, and variable payments of $0.3 million. Sublease income for the Company’s Burnaby site, which closed during that year, was $0.2 million for the twelve months ended December 31, 2019. Weighted average remaining lease term and discount rate were as follows: As of December 31, 2020 Weighted-average remaining lease term (years) 6.1 Weighted average discount rate 9.0% The Company did not include options to extend its lease terms as part of its ROU asset and lease liabilities. Supplemental cash flow information related to the Company’s operating leases was as follows: 2020 2019 (in thousands) Cash paid for amounts included in the measurement of lease liabilities $ 657 $ 1,116 Future minimum lease payments under operating leases that have remaining terms as of December 31, 2020 are as follows: As of December 31, 2020 (in thousands) 2021 $ 677 2022 581 2023 598 2024 616 2025 635 Thereafter 787 Total lease payments $ 3,894 Less: interest (911) Present value of lease payments $ 2,983

Property and equipment

Property and equipment	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property and equipment	Property and equipment The Company’s property and equipment balances as of the years ended December 31, 2020 and 2019 are as follows: Cost Accumulated depreciation Net book value December 31, 2020 (in thousands) Lab equipment $ 5,669 $ (4,369) $ 1,300 Leasehold improvements 8,555 (3,017) 5,538 Computer hardware and software 324 (235) 89 $ 14,548 $ (7,621) $ 6,927 Cost Accumulated depreciation Net book value December 31, 2019 (in thousands) Lab equipment $ 5,511 $ (3,316) $ 2,195 Leasehold improvements 8,521 (2,152) 6,369 Computer hardware and software 286 (174) 112 $ 14,318 $ (5,642) $ 8,676

Intangible assets and goodwill

Intangible assets and goodwill	12 Months Ended
	Dec. 31, 2020
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible assets and goodwill	Intangible assets and goodwillAll IPR&D intangible asset balance related to the Company’s cccDNA program. During 2019, the Company recorded a $43.8 million non-cash impairment expense to reduce the carrying value of its IPR&D intangible assets to zero. The Company also recognized a corresponding income tax benefit of $12.7 million related to the decrease in its deferred tax liability related to the IPR&D intangible assets. The impairment was due to a decision to delay indefinitely the further development of the Company’s cccDNA program while the Company focuses on its other development programs. The Company’s goodwill balance represented the excess of purchase price over the value assigned to the net tangible and identifiable intangible assets in connection with the business combination that formed Arbutus. During 2019, the Company assessed its changes in circumstances to determine if it was more likely than not that the fair value of its single reporting unit was below its carrying amount. Due to a sustained decrease in the Company’s share price during that time frame, the Company’s market capitalization was reduced below the book value of its net assets and the Company concluded that the fair value of its single reporting unit was below its carrying amount in excess of the carrying value of goodwill. As a result, the Company recorded a $22.5 million non-cash impairment expense to reduce the carrying value of its goodwill asset to zero in 2019.

Accounts payable and accrued li

Accounts payable and accrued liabilities	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
Accounts payable and accrued liabilities	Accounts payable and accrued liabilities Accounts payable and accrued liabilities are comprised of the following: December 31, 2020 December 31, 2019 (in thousands) Trade accounts payable $ 2,994 $ 2,398 Payroll accruals 3,566 2,314 Research and development accruals 1,653 1,433 Professional fee accruals 679 809 Site consolidation accrual — 137 Other accrued liabilities 9 144 Total $ 8,901 $ 7,235

Sale of future royalties

Sale of future royalties	12 Months Ended
	Dec. 31, 2020
Other Liabilities Disclosure [Abstract]
Sale of future royalties	Sale of future royalties On July 2, 2019, the Company entered into a Purchase and Sale Agreement (the “Agreement”) with the Ontario Municipal Employees Retirement System (“OMERS”), pursuant to which the Company sold to OMERS part of its royalty interest on future global net sales of ONPATTRO, an RNA interference therapeutic currently being sold by Alnylam. ONPATTRO utilizes Arbutus’s LNP technology, which was licensed to Alnylam pursuant to the Cross-License Agreement, dated November 12, 2012, by and between the Company and Alnylam (the “LNP License Agreement”). Under the terms of the LNP License Agreement, the Company is entitled to tiered royalty payments on global net sales of ONPATTRO ranging from 1.00% to 2.33% after offsets, with the highest tier applicable to annual net sales above $500 million. This royalty interest was sold to OMERS, effective as of January 1, 2019, for $20 million in gross proceeds before advisory fees. OMERS will retain this entitlement until it has received $30 million in royalties, at which point 100% of such royalty interest on future global net sales of ONPATTRO will revert to the Company. OMERS has assumed the risk of collecting up to $30 million of future royalty payments from Alnylam and Arbutus is not obligated to reimburse OMERS if they fail to collect any such future royalties. The $30 million in royalties to be paid to OMERS is accounted for as a liability, with the difference between the liability and the gross proceeds received accounted for as a discount. The discount, as well as $1.5 million of transaction costs, will be amortized as interest expense based on the projected balance of the liability as of the beginning of each period. Management estimated an effective annual interest rate of approximately 16%. Over the course of the Agreement, the actual interest rate will be affected by the amount and timing of royalty revenue recognized and changes in the timing of forecasted royalty revenue. On a quarterly basis, the Company will reassess the expected timing of the royalty revenue, recalculate the amortization and effective interest rate and adjust the accounting prospectively as needed. The Company recognizes non-cash royalty revenue related to the sales of ONPATTRO during the term of the Agreement. As royalties are remitted to OMERS from Alnylam, the balance of the recognized liability is effectively repaid over the life of the Agreement. From the inception of the royalty sale through December 31, 2020, the Company has recorded an aggregate of $5.1 million of non-cash royalty revenue for royalties earned by OMERS. There are a number of factors that could materially affect the amount and timing of royalty payments from Alnylam, none of which are within the Company’s control. During the year ended December 31, 2020, the Company recognized non-cash royalty revenue of $3.4 million and $4.0 million of related non-cash interest expense. During the year ended December 31, 2019, the Company recognized non-cash royalty revenue of $1.7 million and related non-cash interest expense of $2.1 million. The table below shows the activity related to the net liability for the years ended December 31, 2020 and December 31, 2019: Twelve Months Ended December 31, 2020 2019 (in thousands) Net liability related to sale of future royalties - beginning balance $ 18,992 $ — Initial recognition of liability — 30,000 Debt discount and issuance costs — (11,451) Non-cash royalty revenue (3,395) (1,656) Non-cash interest expense 3,957 2,099 Net liability related to sale of future royalties - ending balance $ 19,554 $ 18,992 In addition to the royalty from the Alnylam LNP License Agreement, the Company is also receiving a second, lower royalty interest on global net sales of ONPATTRO originating from a settlement agreement and subsequent license agreement with Acuitas Therapeutics, Inc. (“Acuitas”). The royalty from Acuitas has been retained by the Company and was not part of the royalty sale to OMERS.

Contingencies and commitments

Contingencies and commitments	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Contingencies and commitments	Contingencies and commitments 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 $7.2 million (C$9.3 million). The Company received a cumulative contribution of $2.7 million (C$3.7 million). 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-RNAi 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, a chemotherapy product sold by Acrotech Biopharma LLC (“Acrotech”). For the years ended December 31, 2020 and 2019, the Company earned royalties on Marqibo sales in the amount of $0.3 million in each period. The resulting royalties payable by the Company to TPC were not material in either period. The cumulative amount paid or accrued up to December 31, 2020 was less than $0.1 million, resulting in the contingent amount due to TPC being $2.7 million (C$3.7 million). 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”), as well as by Arbutus that was subsequently assigned to UBC. These inventions are licensed to the Company by UBC under a license agreement, initially entered into in 1998 and as amended in 2001, 2006 and 2007. The Company has granted sublicenses under the UBC license to certain third parties, including Alnylam. In November 2014, UBC filed a demand for arbitration against the Company which alleged entitlement to unpaid royalties. In August 2019, the arbitrator issued his decision for the second phase of the arbitration, awarding UBC $5.9 million, which includes interest of approximately $2.6 million. The Company paid the $5.9 million award to UBC in September 2019 and recorded a charge of $6.3 million, consisting of $5.9 million for the award (including interest) and $0.4 million for an estimate of a potential award for costs and attorneys’ fees. An award for costs and attorneys’ fees is still to be determined. On December 18, 2020, UBC delivered to the Company a notice of arbitration alleging that under the cross license between UBC and Arbutus, it is due royalties of $2.0 million plus interest arising from the Company’s sale to OMERS of part of its royalty interest on future global net sales of ONPATTRO, currently being sold by Alnylam. The Company does not believe that any royalties are due to UBC and the Company intends to vigorously contest UBC’s allegation. Stock Purchase Agreement with Enantigen In October 2014, Arbutus Inc., our wholly-owned subsidiary, acquired all of the outstanding shares of Enantigen Therapeutics, Inc. (“Enantigen”) pursuant to a stock purchase agreement. The amount paid to Enantigen’s selling shareholders could be up to an additional $102.5 million in sales performance milestones in connection with the sale of the first commercialized product by Arbutus for the treatment of HBV, regardless of whether such product is based upon assets acquired under this agreement, and a low single-digit royalty on net sales of such first commercialized HBV product, up to a maximum royalty payment of $1.0 million that, if paid, would be offset against Arbutus’ milestone payment obligations. Certain other development milestones related to the acquisition were tied to programs which are no longer under development by Arbutus, and therefore the contingency related to those development milestones is zero. The contingent consideration is a financial liability and is 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 (note 3).

Collaborations, contracts and l

Collaborations, contracts and licensing agreements	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Collaborations, contracts and licensing agreements	Collaborations, contracts and licensing agreements Assembly Biosciences, Inc. In August 2020, the Company entered into a clinical collaboration agreement with Assembly Biosciences, Inc. (“Assembly”) to evaluate AB-729 in combination with Assembly’s lead HBV core inhibitor (capsid inhibitor) candidate vebicorvir (“VBR”) and standard-of-care NA therapy for the treatment of subjects with chronic HBV infection. The Company and Assembly will share in the costs of the collaboration. The Company incurred $0.2 million of costs related to the collaboration during the year ended December 31, 2020 and reflected those costs in research and development in the statements of operations and comprehensive loss. Except to the extent necessary to carry out Assembly’s responsibilities with respect to the collaboration trial, the Company has not provided any license grant to Assembly for use of its AB-729 compound. Alnylam Pharmaceuticals, Inc. and Acuitas Therapeutics, Inc. The Company has two royalty entitlements to Alnylam’s global net sales of ONPATTRO. 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. Alnylam’s ONPATTRO, which represents the first approved application of the Company’s LNP technology, was approved by the United States Food and Drug Administration (“FDA”) and the European Medicines Agency (“EMA”) during the third quarter of 2018 and was launched by Alnylam immediately upon approval in the United States. Under the terms of this license agreement, the Company is entitled to tiered royalty payments on global net sales of ONPATTRO ranging from 1.00% - 2.33% after offsets, with the highest tier applicable to annual net sales above $500 million. This royalty interest was sold to OMERS, effective as of January 1, 2019, for $20 million in gross proceeds before advisory fees. OMERS will retain this entitlement until it has received $30 million in royalties, at which point 100% of this royalty entitlement on future global net sales of ONPATTRO will revert back to the Company. OMERS has assumed the risk of collecting up to $30.0 million of future royalty payments from Alnylam and the Company is not obligated to reimburse OMERS if they fail to collect any such future royalties. If this royalty entitlement reverts to the Company, it has the potential to provide an active royalty stream or to be otherwise monetized again in full or in part. See note 10 for further details. The Company also has rights to a second, lower royalty interest on global net sales of ONPATTRO originating from a settlement agreement and subsequent license agreement with Acuitas. This royalty entitlement from Acuitas has been retained by the Company and was not part of the royalty entitlement sale to OMERS. Gritstone Oncology, Inc. On October 16, 2017, the Company entered into a license agreement with Gritstone Oncology, Inc. (“Gritstone”) that granted them worldwide access to its portfolio of proprietary and clinically validated LNP technology and associated intellectual property to deliver Gritstone’s self-replicating, non-mRNA, RNA-based neoantigen immunotherapy products. Gritstone paid the Company an upfront payment, and will make payments for achievement of development, regulatory, and commercial milestones and royalties. As a result of the Company’s agreement with Genevant (see note 5 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. Milestone payments that are not within the control of the Company or the licensee, such as those that require regulatory approvals, are not considered probable of being achieved until those approvals are received. Acrotech Biopharma LLC and Spectrum Pharmaceuticals, Inc. In May 2006, the Company signed a number of agreements with Talon Therapeutics, Inc. (“Talon,” formerly Hana Biosciences, Inc.) that granted Talon worldwide licenses to certain of its LNP technology (the “Talon License Agreement”) for three of Talon’s chemotherapy products, Marqibo®, Alocrest ™ (Optisomal Vinorelbine) and Brakiva ™ (Optisomal Topotecan). In 2012, Talon 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 payment of $1.0 million 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 $18.0 million on Alocrest and Brakiva. Talon was acquired by Spectrum Pharmaceuticals, Inc. in July 2013, who subsequently sold the license of Marqibo to Acrotech in January 2019. The acquisitions and license sale did not affect the terms of the license between Talon and the Company. Revenues are summarized in the following table: Year ended December 31, 2020 2019 (in thousands) Revenue from collaborations and licenses Acuitas Therapeutics, Inc. $ 3,259 $ 1,931 Gritstone Oncology, Inc. — 1,819 Acrotech Biopharma, LLC 269 605 Non-cash royalty revenue Alnylam Pharmaceuticals, Inc. 3,386 1,656 Total revenue $ 6,914 $ 6,011

Shareholders_ equity

Shareholders’ equity	12 Months Ended
	Dec. 31, 2020
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, the Company entered into an Open Market Sale Agreement (“the Sale Agreement”) with Jefferies LLC (“Jefferies”), under which it could issue and sell common shares, from time to time, for an aggregate sales price of up to $50 million. In December 2019, the Company entered into an amendment to the Sale Agreement with Jefferies (the “2019 Amendment”) in connection with the filing of a shelf registration statement on Form S-3 (File No. 333-235674), filed with the SEC on December 23, 2019 (the “Shelf Registration Statement”). The 2019 Amendment revised the original Sale Agreement to reflect that the Company could sell its common shares, without par value, from time to time, for an aggregate sales price of up to $50 million, under the Shelf Registration Statement. In July 2020, the Company fully utilized the remaining availability under the Sale Agreement, as amended by the 2019 Amendment. In August 2020, the Company entered into a new amendment to the Sale Agreement (the “2020 Amendment”) with Jefferies. Pursuant to the 2020 Amendment, the Company can issue and sell common shares, from time to time, for an aggregate sales price of up to $75 million under the Sale Agreement, as amended. For the year ended December 31, 2020, the Company issued 24,728,368 common shares pursuant to the Sale Agreement, resulting in net proceeds of approximately $86.3 million. From January 1, 2021 through March 3, 2021, the Company received an additional $24.3 million of net proceeds from the issuance of 5.8 million common shares under the ATM program. For the year ended December 31, 2019, the Company issued 9,138,232 common shares pursuant to the Sale Agreement, resulting in net proceeds of approximately $19.5 million. 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 $116.4 million. 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 approximately 23 million 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, 2020 Roivant would hold 33% of the Company’s common shares. Roivant has agreed to a four year four year The Company records the Preferred Shares 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 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).

Stock-based compensation

Stock-based compensation	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-based compensation	Stock-based compensation Awards outstanding and available for issuance During the year ended December 31, 2020, the Company had stock options outstanding under the following plans (collectively, the “Plans”): the 2016 Omnibus Share and Incentive Plan (the “2016 Plan”), the 2011 Omnibus Share Compensation Plan (the “2011 Plan”), the 2019 inducement grant and the OnCore Option Plan. As of December 31, 2020, the aggregate number of shares authorized for awards under all Plans was 15,790,202. As of December 31, 2020, the Company had 10,669,776 options outstanding and 3,161,471 awards available for issuance under the Plans. The Company issues new common shares of stock to settle options exercised. 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 on the date of grant or the prior day and the term may not exceed 10 years. Options granted generally vest over three In June 2019, the Company provided an inducement grant of 1,112,000 options to its newly hired Chief Executive Officer. These options were awarded in a separate plan as non-qualified awards and are governed by the substantially the same terms as the 2016 Plan. Hereafter, information on options governed by the 2016 Plan, the 2011 Plan and inducement grant (the “Arbutus Plans”) is presented on a consolidated basis as the terms of the plans are similar. Information on the OnCore Option Plan is presented separately. Stock options under the Arbutus Plans Equity-classified stock options under the Arbutus Plans The following table summarizes activity related to the Company’s equity-classified stock options, including its performance options, for the year ended December 31, 2020: Stock Options Outstanding Vested Stock Options Non-Vested Stock Options Number Weighted-Average Exercise Price Number Number Weighted-Average Grant-Date Fair Value Balance as of December 31, 2019 8,249,093 $ 5.00 4,294,649 3,954,444 $ 2.86 Options granted 2,865,350 $ 3.21 — 2,865,350 $ 2.20 Options exercised (125,649) $ 3.04 (125,649) — $ — Options forfeit, canceled or expired (597,118) $ 5.10 (313,861) (283,257) $ 2.53 Options vested — $ — 2,529,247 (2,529,247) $ 2.69 Balance as of December 31, 2020 10,391,676 $ 4.53 6,384,386 4,007,290 $ 2.51 The intrinsic value of options exercised under the Arbutus Plans during 2020 and 2019 are $0.3 million and less than $0.1 million, respectively. The following table summarizes additional information related to the Company’s equity-classified stock options, including its performance options, as of December 31, 2020: As of December 31, 2020 Options outstanding and expected to vest Number of stock options outstanding 10,391,676 Weighted-average exercise price $ 4.53 Intrinsic value (in $000s) $ 3,532 Weighted-average term remaining 6.7 years Vested stock options Number of vested stock options 6,384,386 Weighted-average exercise price $ 5.11 Intrinsic value (in $000s) $ 1,758 Weighted-average term remaining 5.5 years The assumptions used in the Black-Scholes option-pricing for grants made during the years ended December 31, 2020 and 2019 are as follows: December 31, 2020 December 31, 2019 Expected average option term 6.2 years 7.3 years Expected volatility 80.2 % 75.9 % Expected dividends — % — % Risk-free interest rate 1.2 % 2.27 % Liability-classified stock options under the Arbutus Plans 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). The following table summarizes activity related to the Company’s liability-classified stock options for the year ended December 31, 2020: Stock Options Vested and Outstanding Number Weighted-Average Exercise Price Balance as of December 31, 2019 227,500 $ 5.49 Options exercised (25,000) $ 3.02 Options forfeit, canceled or expired (5,000) $ 3.02 Balance as of December 31, 2020 197,500 $ 6.00 The intrinsic value of liability-classified options exercised during 2020 was less than $0.1 million. The following table summarizes additional information related to the Company’s liability-classified stock options as of December 31, 2020: As of December 31, 2020 Options outstanding and expected to vest Intrinsic value (in $000s) $ 158 Weighted-average term remaining 0.9 years Liability options are re-measured to their fair values at each reporting date, using the Black-Scholes valuation model. The weighted average Black-Scholes option-pricing assumptions and the resultant fair values as of December 31, 2020 and December 31, 2019, are presented in the following table: December 31, 2020 December 31, 2019 Stock price $ 3.55 $ 2.78 Expected average option term 0.9 years 1.6 years Expected volatility 105.66 % 113.1 % Expected dividends — % — % Risk-free interest rate 0.11 % 1.59 % Weighted-average fair value per share $ 1.30 $ 1.11 Total fair value of vested liability-classified options (in $000s) $ 250 $ 253 OnCore Option Plan The Company has reserved shares for the future exercises of OnCore stock options that were granted prior to the merger in 2015. The Company is not permitted to grant any further options under the OnCore Option Plan. The following table summarizes activity related to the OnCore stock options for the year ended December 31, 2020: Stock Options Vested and Outstanding Number of OnCore Options Number of Equivalent Company Common Shares Weighted-Average Exercise Price Balance as of December 31, 2019 99,290 99,991 $ 0.56 Options exercised (19,255) (19,391) $ 0.56 Options forfeit, canceled or expired — — $ — Balance as of December 31, 2020 80,035 80,600 $ 0.56 The intrinsic value of options exercised under the OnCore plan during each of 2020 and 2019 was $0.1 million. The following table summarizes additional information related to the OnCore stock options as of December 31, 2020: As of December 31, 2020 Vested stock options Intrinsic value (in $000s) $ 241 Weighted-average term remaining 3.8 years Employee Stock Purchase Plan In May 2020, the Company’s stockholders approved the 2020 Employee Stock Purchase Plan (ESPP) which became effective on May 28, 2020. A total of 1,500,000 common shares were reserved for issuance under the ESPP. Company employees contribute funds via payroll deductions, which are used to buy Company common shares at a discount of up to 15% based on the lower of the price at the start of the offering period and at the end of the relevant purchase period within such offering period. The initial offering period under the ESPP is September 1, 2020 through August 31, 2021 with purchase dates set on February 26, 2021 and August 31, 2021. All 1,500,000 common shares remained available for future issuance under the ESPP at December 31, 2020. For the year ended December 31, 2020, the Company recognized $0.2 million of stock-based compensation expense related to the ESPP. The fair value of the right to acquire stock at a discounted price under the ESPP is calculated using the Black-Scholes valuation model and recorded as stock-based compensation. Expense is recognized over the period the employee contributes to the plan through payroll deductions. Stock-based compensation expense Total stock-based compensation expense was comprised of: (1) vesting of options awarded to employees under the Arbutus and OnCore Plans calculated in accordance with the fair value method as described above; (2) fair value adjustments for the Company’s liability-classified stock options; and (3) amortization of compensation cost related to the ESPP. The Company recognizes forfeitures as they occur, and the effects of forfeitures are reflected in stock-based compensation expense. Stock-based compensation has been recorded in the consolidated statement of operations and comprehensive income (loss) as follows: Year Ended December 31 2020 2019 (in thousands) Research and development $ 3,090 $ 2,971 General and administrative 3,071 3,828 Total $ 6,161 $ 6,799 During the year ended December 31, 2019, the Company recognized $1.1 million of non-cash stock-based compensation expense for the accelerated vesting stock options, related to the departure of the Company’s former President and Chief Executive Officer in June of 2019. At December 31, 2020, there remains $7.8 million of unearned compensation expense related to unvested equity employee stock options to be recognized as expense over a weighted-average period of approximately 2.3 years .

Income taxes

Income taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income taxes	Income taxes The Company is subject to taxation and files income tax returns in Canadian federal and provincial, United States federal and several state jurisdictions. The United States Internal Revenue service is currently examining the Company’s federal tax return for 2018. The outcome of tax audits cannot be predicted with certainty, however the Company believes that an adequate provision has been made for any adjustments that may result from the examination. If any issues addressed in the Company’s tax audits are resolved in a manner not consistent with management’s expectations, the Company could be required to adjust its provision for income tax in the period such resolution occurs. Income tax (benefit) expense varies from the amounts that would be computed by applying the combined Canadian federal and provincial income tax rate of 27% (2019 - 27%) to the loss before income taxes as shown in the following tables: Year ended December 31, 2020 2019 (in thousands) Computed taxes (benefits) at Canadian federal and provincial tax rates $ (17,211) $ (44,922) Difference due to change in tax rate on opening deferred taxes — 8,356 Adjustment to prior year 390 (525) Permanent and other differences 622 3,458 Change in valuation allowance - other 12,033 19,078 Difference due to income taxed at foreign rates 3,716 (3,343) Stock-based compensation 450 523 Impairment of goodwill — 4,719 Income tax expense (recovery) $ — $ (12,656) As of December 31, 2020, the Company has investment tax credits available to reduce Canadian federal income taxes of $8.0 million, versus $10.0 million as of December 31, 2019, which expire between 2030 and 2037, and provincial income taxes of $2.6 million, versus $4.5 million as of December 31, 2019, which expire between 2024 and 2027. In addition, the Company has research and development credits of $3.9 million as of December 31, 2020, and $3.9 million as of December 31, 2019, which expire between 2031 and 2038 and which can be used to reduce future taxable income in the United States. As of December 31, 2020, the Company had scientific research and experimental development expenditures of $58.6 million available for indefinite carry-forward, versus the $60.6 million it had as of December 31, 2019. The Company also had net operating losses of $175.6 million as of December 31, 2020 and $164.9 million as of December 31, 2019, which are due to expire between 2028 and 2038 and which can be used to offset future taxable income in Canada. As of December 31, 2020 and December 31, 2019, the Company had $11.7 million of net operating losses due to expire in 2035 which can be used to offset future taxable income in the United States. Future use of a portion of the United States loss carryforwards are subject to limitations under Internal Revenue Code Section 382. United States net operating loss carryforwards arising in 2019 and future periods have an indefinite carryforward period. 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. The Company generated $1.8 million and $61.9 million in pre-tax domestic and foreign losses, respectively, for the year ended December 31, 2020. The Company generated $27.1 million and $139.3 million in pre-tax domestic and foreign losses, respectively, for the year ended December 31, 2019. Significant components of the Company’s deferred tax assets and liabilities are shown below: As of December 31, 2020 2019 (in thousands) Deferred tax assets (liabilities): Non-capital losses carryforwards $ 74,351 $ 59,956 Research and development deductions 15,812 16,349 Book amortization in excess of tax (737) (914) Revenue recognized for tax purposes in excess of revenue recognized for accounting purposes 5,279 5,128 Tax value in excess of accounting value in lease inducements 627 705 Federal investment tax credits 5,872 7,325 Provincial investment tax credits 2,644 4,535 Equity accounted for investment 3,375 3,038 Federal R&E credits 3,897 3,897 Deductible stock options 2,457 1,632 Other 1,218 1,111 Total deferred tax assets $ 114,795 $ 102,762 Valuation allowance (114,795) (102,762) Net deferred tax assets (liabilities) $ — $ —

Related party transactions

Related party transactions	12 Months Ended
	Dec. 31, 2020
Related Party Transactions [Abstract]
Related party transactions	Related party transactions On July 31, 2020, Genevant was recapitalized through an equity investment and conversion of previously issued convertible debt securities held by Roivant. Arbutus participated in the recapitalization of Genevant with an investment of $2.5 million. Arbutus determined that this $2.5 million additional investment in Genevant represented the funding of prior losses and accordingly, the Company recorded the amount as an equity investment loss on the Condensed Consolidated Statements of Operations and Comprehensive Loss in 2020. See note 5 for further details. Genevant purchased certain administrative and transitional services from the Company totaling less than $0.1 million and $0.1 million during 2020 and 2019, respectively. These services were billed at agreed hourly rates and reflective of market rates for such services and these costs were netted in research and development in the income statement.

Significant accounting polici_2

Significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Basis of presentation	These consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) and include the accounts of Arbutus Biopharma Corporation and its two wholly-owned subsidiaries, Arbutus Biopharma, Inc. and Arbutus Biopharma U.S. Holdings, Inc.
Principles of consolidation	All intercompany balances and transactions have been eliminated. Certain prior year amounts have been reclassified to conform to the current year presentation. In February 2021, Arbutus Biopharma US Holdings, Inc merged into Arbutus Biopharma, Inc. with Arbutus Biopharma, Inc. continuing its legal existence and Arbutus Biopharma US Holdings, Inc ceasing to exist.
Use of estimates	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 and contingent liabilities as of the end or during the reporting period. Actual results could significantly differ from those estimates. Significant estimates in the accompanying consolidated financial statements impact contingent consideration, income tax recoveries, stock-based compensation, clinical trial accruals and the sale of future royalties liability.
Cash and cash equivalents	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.
Investments in marketable securities	Investments in marketable securities The Company’s short-term investments consist of marketable securities that have original maturities exceeding three months and remaining maturities of less than one year. The Company classifies investments with remaining maturities of one year or longer as non-current. These investments are accounted for as available-for-sale securities and are reported at fair value, with unrealized gains and losses reported in other comprehensive loss, until their disposition. Realized gains and losses from the sale of marketable securities, if any, are calculated using the specific-identification method, and are recorded as a component of other income or loss. The Company reviews its available-for-sale securities at each period end to determine if they remain available-for-sale based on the Company’s current intent and ability to sell the security if it is required to do so. Declines in value judged to be other-than-temporary are included in interest income or expense in the Company’s statements of operations and comprehensive loss. As of December 31, 2020, the recorded value of the Company’s investments in marketable securities was deemed to be recoverable in all respects. All investments are governed by the Company’s Investment Policy approved by the Company’s board of directors.
Foreign currency translation and functional currency conversion	Foreign currency translation and functional currency conversion The Company’s functional currency is the United States dollar. M onetary assets and liabilities denominated in foreign currencies are translated into United States 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.
Investment in Genevant	Investment in Genevant As the result of a recapitalization of Genevant Sciences Ltd. (“Genevant”) in July 2020, Arbutus’ ownership interest in Genevant decreased to approximately 16%. Due to Arbutus’ loss of significant influence with respect to Genevant as a result of the recapitalization, Arbutus discontinued the use of the equity method of accounting for its interest in Genevant. Ownership interests that do not confer the ability to exercise significant influence are accounted for at fair value, except when the investment does not have a readily-determinable fair value. In that case, the investment is carried at cost, less any impairment. The carrying value is subsequently adjusted to fair value based on any observable price changes. Following the recapitalization, Arbutus accounts for its interest in Genevant as equity securities without readily determinable fair values. Accordingly, an estimate of the fair value of the securities is based on the original cost less previously recognized equity method losses, less impairments, plus or minus changes resulting from observable price changes in orderly transactions for identical or a similar Genevant securities. As of December 31, 2020, the carrying value of Arbutus’ investment in Genevant was zero and Arbutus owned approximately 16% of the common equity of Genevant.
Property and equipment	Property and equipment Property and equipment is recorded at cost less impairment losses and accumulated depreciation. 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
Impairment of property and equipment	Property and equipment is reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. If such a review should indicate that the carrying amount of long-lived assets is not recoverable, then such assets are written down to their fair values.
Revenue recognition	Revenue recognition ASC 606, Revenue From Contracts with Customers (“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	Leases As of January 1, 2019, the Company adopted FASB’s Accounting Standards Update 2016-02, Leases
Research and development costs	Research and development costs Research and development costs include compensation and benefits for research and development employees, an allocation of overhead expenses and costs associated with materials and supplies used in clinical trials and research and development, outside contracted services including clinical and pre-clinical study costs, legal, regulatory compliance and fees paid to consultants or outside parties for research and development activities performed on the Company’s behalf. Such costs are charged to expense in the period in which they are incurred.
Net loss attributable to common shareholders per share	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 Series A participating convertible preferred shares (“Preferred Shares”), as further described in note 13, that meet the definition of participating securities. The Company’s 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.
Deferred income taxes	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.
Stock-based compensation	Stock-based compensation We measure and recognize compensation expense for all share-based compensation arrangements based on estimated fair values. We use the Black-Scholes option valuation model to estimate the fair value of stock options at the date of grant. The Black-Scholes option valuation model requires the input of subjective assumptions to calculate the value of stock options. For those assumptions, we use historical data and other information to estimate the expected price volatility and risk free interest rate for all awards. The expected life of stock options granted are estimated to be five years for employees and seven years for directors and executives, based on our historical experience. 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. Expense is recognized over the vesting period for all awards and commences at the grant date for time-based awards and upon the Company’s determination that the achievement of such performance conditions is probable for performance-based awards. Forfeitures are recognized as they occur. For the Company’s Employee Stock Purchase Plan, the fair value of the right to acquire stock at a discounted price under the plan is calculated using the Black-Scholes valuation model. Expense is recognized over the period the employee contributes to the plan through payroll deductions. 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. As of January 1, 2016, the Company changed its functional currency to US dollars, which resulted in certain stock option awards with exercise prices denominated in Canadian dollars having an exercise price that is not denominated in the Company’s functional currency. 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 a liability.
Preferred Shares	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	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 the United States.
Comprehensive loss	Comprehensive loss Comprehensive loss is comprised of net loss, the impact of foreign currency translation adjustments and adjustments for the change in unrealized gains and losses on investments in available-for-sale marketable securities. The Company displays comprehensive loss and its components in the consolidated statements of operations and comprehensive loss, net of tax effects if any.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments which potentially subject the Company to credit risk consist primarily of cash, cash equivalents and marketable securities. The Company holds these investments in highly rated financial institutions, and, by policy, limits the amounts of credit exposure to any one financial institution. These amounts at times may exceed federally insured limits. The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds. The Company has no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements.
Recent accounting pronouncements	Recent accounting pronouncements In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2016-13, Financial Instruments - Credit Losses: Measurement of Credit Losses on Financial Instruments (ASC 326). The guidance is effective for the Company beginning January 1, 2023 and it changes how entities account for credit losses on financial assets and other instruments that are not measured at fair value through net income, including available-for-sale debt securities. The Company is currently evaluating the impact of the new standard on its consolidated financial statements.
Fair value measurements	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, accounts receivable, accounts payable and accrued liabilities approximate their fair values due to the immediate or short-term maturity of these financial instruments.

Significant accounting polici_3

Significant accounting policies (Tables)	12 Months Ended
	Dec. 31, 2020
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, 2020 2019 (in thousands, except share and per share amounts) Numerator: Allocation of distributable earnings $ — $ — Allocation of undistributable loss (75,868) (164,872) Allocation of net loss attributed to common shareholders $ (75,868) $ (164,872) Denominator: Weighted average number of common shares - basic and diluted 75,835,378 57,093,454 Basic and diluted net loss attributable to common shareholders per share $ (1.00) $ (2.89)

Fair value measurements (Tables

Fair value measurements (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of assets and liabilities measured at fair value on a recurring basis	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 Total As of December 31, 2020 (in thousands) Assets Cash and cash equivalents $ 52,251 $ — $ — $ 52,251 Investments in marketable securities 71,017 — — 71,017 Total $ 123,268 $ — $ — $ 123,268 Liabilities Liability-classified options $ — $ — $ 250 $ 250 Contingent consideration — — 3,426 3,426 Total $ — $ — $ 3,676 $ 3,676 Level 1 Level 2 Level 3 Total As of December 31, 2019 (in thousands) Assets Cash and cash equivalents $ 31,799 $ — $ — $ 31,799 Investments in marketable securities 59,035 — — 59,035 Total $ 90,834 $ — $ — $ 90,834 Liabilities Liability-classified options $ — $ — $ 253 $ 253 Contingent consideration — — 2,953 2,953 Total $ — $ — $ 3,206 $ 3,206
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 options exercised in the period Increase (decrease) in fair value of liability Liability at end of the period (in thousands) Year ended December 31, 2020 $ 253 $ — $ (3) $ 250 Year ended December 31, 2019 $ 479 $ — $ (226) $ 253
Schedule of changes in fair value of contingent consideration	The following table presents the changes in fair value of the Company’s contingent consideration: Liability at beginning of the period Increase (decrease) in fair value of liability Liability at end of the period (in thousands) Year ended December 31, 2020 $ 2,953 $ 473 $ 3,426 Year ended December 31, 2019 $ 3,126 $ (173) $ 2,953

Investments in marketable sec_2

Investments in marketable securities (Tables)	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Investments in marketable securities	Investments in marketable securities consisted of the following: Amortized Cost Gross Unrealized Gain (1) Gross Unrealized Loss (1) Fair Value As of December 31, 2020 (in thousands) Cash equivalents Money market fund $ 13,703 $ — $ — $ 13,703 US government agency bonds — — — — US treasury bills 2,000 — — 2,000 Total $ 15,703 $ — $ — $ 15,703 Investments in marketable securities US government agency bonds $ 11,550 $ 7 $ — $ 11,557 US treasury bills 21,990 2 — 21,992 US government bonds 37,463 6 (1) 37,468 Total $ 71,003 $ 15 $ (1) $ 71,017 (1) Gross unrealized gain (loss) is pre-tax. Amortized Cost Gross Unrealized Gain (1) Gross Unrealized Loss (1) Fair Value As of December 31, 2019 (in thousands) Cash equivalents Money market fund $ 4,106 $ — $ — $ 4,106 US government agency bonds 1,511 — — 1,511 US treasury bills 1,499 — — 1,499 Total $ 7,116 $ — $ — $ 7,116 Investments in marketable securities Us government agency bonds $ 19,863 $ 2 $ (1) $ 19,864 US treasury bills 15,926 2 (1) 15,927 US government bonds 23,246 — (2) 23,244 Total $ 59,035 $ 4 $ (4) $ 59,035 (1) Gross unrealized gain (loss) is pre-tax.

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Schedule of lease cost	Weighted average remaining lease term and discount rate were as follows: As of December 31, 2020 Weighted-average remaining lease term (years) 6.1 Weighted average discount rate 9.0% The Company did not include options to extend its lease terms as part of its ROU asset and lease liabilities. Supplemental cash flow information related to the Company’s operating leases was as follows: 2020 2019 (in thousands) Cash paid for amounts included in the measurement of lease liabilities $ 657 $ 1,116
Schedule of lease maturity	Future minimum lease payments under operating leases that have remaining terms as of December 31, 2020 are as follows: As of December 31, 2020 (in thousands) 2021 $ 677 2022 581 2023 598 2024 616 2025 635 Thereafter 787 Total lease payments $ 3,894 Less: interest (911) Present value of lease payments $ 2,983

Property and equipment (Tables)

Property and equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Schedule of property and equipment	Cost Accumulated depreciation Net book value December 31, 2020 (in thousands) Lab equipment $ 5,669 $ (4,369) $ 1,300 Leasehold improvements 8,555 (3,017) 5,538 Computer hardware and software 324 (235) 89 $ 14,548 $ (7,621) $ 6,927 Cost Accumulated depreciation Net book value December 31, 2019 (in thousands) Lab equipment $ 5,511 $ (3,316) $ 2,195 Leasehold improvements 8,521 (2,152) 6,369 Computer hardware and software 286 (174) 112 $ 14,318 $ (5,642) $ 8,676

Accounts payable and accrued _2

Accounts payable and accrued liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
Schedule of accounts payable and accrued liabilities	Accounts payable and accrued liabilities are comprised of the following: December 31, 2020 December 31, 2019 (in thousands) Trade accounts payable $ 2,994 $ 2,398 Payroll accruals 3,566 2,314 Research and development accruals 1,653 1,433 Professional fee accruals 679 809 Site consolidation accrual — 137 Other accrued liabilities 9 144 Total $ 8,901 $ 7,235

Sale of future royalties (Table

Sale of future royalties (Tables)	12 Months Ended
	Dec. 31, 2020
Other Liabilities Disclosure [Abstract]
Activity related to net liability	The table below shows the activity related to the net liability for the years ended December 31, 2020 and December 31, 2019: Twelve Months Ended December 31, 2020 2019 (in thousands) Net liability related to sale of future royalties - beginning balance $ 18,992 $ — Initial recognition of liability — 30,000 Debt discount and issuance costs — (11,451) Non-cash royalty revenue (3,395) (1,656) Non-cash interest expense 3,957 2,099 Net liability related to sale of future royalties - ending balance $ 19,554 $ 18,992

Collaborations, contracts and_2

Collaborations, contracts and licensing agreements (Tables)	12 Months Ended
	Dec. 31, 2020
Revenue from Contract with Customer [Abstract]
Schedule of revenue recognized under collaborations, contracts and licensing agreements	Revenues are summarized in the following table: Year ended December 31, 2020 2019 (in thousands) Revenue from collaborations and licenses Acuitas Therapeutics, Inc. $ 3,259 $ 1,931 Gritstone Oncology, Inc. — 1,819 Acrotech Biopharma, LLC 269 605 Non-cash royalty revenue Alnylam Pharmaceuticals, Inc. 3,386 1,656 Total revenue $ 6,914 $ 6,011

Stock-based compensation (Table

Stock-based compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of stock option activity	The following table summarizes additional information related to the Company’s equity-classified stock options, including its performance options, as of December 31, 2020: As of December 31, 2020 Options outstanding and expected to vest Number of stock options outstanding 10,391,676 Weighted-average exercise price $ 4.53 Intrinsic value (in $000s) $ 3,532 Weighted-average term remaining 6.7 years Vested stock options Number of vested stock options 6,384,386 Weighted-average exercise price $ 5.11 Intrinsic value (in $000s) $ 1,758 Weighted-average term remaining 5.5 years
Schedule of weighted average Black-Scholes option-pricing assumptions and resultant fair values	The assumptions used in the Black-Scholes option-pricing for grants made during the years ended December 31, 2020 and 2019 are as follows: December 31, 2020 December 31, 2019 Expected average option term 6.2 years 7.3 years Expected volatility 80.2 % 75.9 % Expected dividends — % — % Risk-free interest rate 1.2 % 2.27 %
Schedule of weighted average option pricing assumptions and the resultant fair values	The weighted average Black-Scholes option-pricing assumptions and the resultant fair values as of December 31, 2020 and December 31, 2019, are presented in the following table: December 31, 2020 December 31, 2019 Stock price $ 3.55 $ 2.78 Expected average option term 0.9 years 1.6 years Expected volatility 105.66 % 113.1 % Expected dividends — % — % Risk-free interest rate 0.11 % 1.59 % Weighted-average fair value per share $ 1.30 $ 1.11 Total fair value of vested liability-classified options (in $000s) $ 250 $ 253
Schedule of allocation of stock-based compensation	Stock-based compensation has been recorded in the consolidated statement of operations and comprehensive income (loss) as follows: Year Ended December 31 2020 2019 (in thousands) Research and development $ 3,090 $ 2,971 General and administrative 3,071 3,828 Total $ 6,161 $ 6,799
Arbutus Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of stock option activity	The following table summarizes activity related to the Company’s equity-classified stock options, including its performance options, for the year ended December 31, 2020: Stock Options Outstanding Vested Stock Options Non-Vested Stock Options Number Weighted-Average Exercise Price Number Number Weighted-Average Grant-Date Fair Value Balance as of December 31, 2019 8,249,093 $ 5.00 4,294,649 3,954,444 $ 2.86 Options granted 2,865,350 $ 3.21 — 2,865,350 $ 2.20 Options exercised (125,649) $ 3.04 (125,649) — $ — Options forfeit, canceled or expired (597,118) $ 5.10 (313,861) (283,257) $ 2.53 Options vested — $ — 2,529,247 (2,529,247) $ 2.69 Balance as of December 31, 2020 10,391,676 $ 4.53 6,384,386 4,007,290 $ 2.51
OnCore Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of stock option activity	The following table summarizes additional information related to the OnCore stock options as of December 31, 2020: As of December 31, 2020 Vested stock options Intrinsic value (in $000s) $ 241 Weighted-average term remaining 3.8 years
Schedule of option activity	The following table summarizes activity related to the OnCore stock options for the year ended December 31, 2020: Stock Options Vested and Outstanding Number of OnCore Options Number of Equivalent Company Common Shares Weighted-Average Exercise Price Balance as of December 31, 2019 99,290 99,991 $ 0.56 Options exercised (19,255) (19,391) $ 0.56 Options forfeit, canceled or expired — — $ — Balance as of December 31, 2020 80,035 80,600 $ 0.56
Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Schedule of stock option activity	The following table summarizes activity related to the Company’s liability-classified stock options for the year ended December 31, 2020: Stock Options Vested and Outstanding Number Weighted-Average Exercise Price Balance as of December 31, 2019 227,500 $ 5.49 Options exercised (25,000) $ 3.02 Options forfeit, canceled or expired (5,000) $ 3.02 Balance as of December 31, 2020 197,500 $ 6.00 The following table summarizes additional information related to the Company’s liability-classified stock options as of December 31, 2020: As of December 31, 2020 Options outstanding and expected to vest Intrinsic value (in $000s) $ 158 Weighted-average term remaining 0.9 years

Income taxes (Tables)

Income taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of effective income tax rate reconciliation	Income tax (benefit) expense varies from the amounts that would be computed by applying the combined Canadian federal and provincial income tax rate of 27% (2019 - 27%) to the loss before income taxes as shown in the following tables: Year ended December 31, 2020 2019 (in thousands) Computed taxes (benefits) at Canadian federal and provincial tax rates $ (17,211) $ (44,922) Difference due to change in tax rate on opening deferred taxes — 8,356 Adjustment to prior year 390 (525) Permanent and other differences 622 3,458 Change in valuation allowance - other 12,033 19,078 Difference due to income taxed at foreign rates 3,716 (3,343) Stock-based compensation 450 523 Impairment of goodwill — 4,719 Income tax expense (recovery) $ — $ (12,656)
Schedule of components of deferred tax assets	Significant components of the Company’s deferred tax assets and liabilities are shown below: As of December 31, 2020 2019 (in thousands) Deferred tax assets (liabilities): Non-capital losses carryforwards $ 74,351 $ 59,956 Research and development deductions 15,812 16,349 Book amortization in excess of tax (737) (914) Revenue recognized for tax purposes in excess of revenue recognized for accounting purposes 5,279 5,128 Tax value in excess of accounting value in lease inducements 627 705 Federal investment tax credits 5,872 7,325 Provincial investment tax credits 2,644 4,535 Equity accounted for investment 3,375 3,038 Federal R&E credits 3,897 3,897 Deductible stock options 2,457 1,632 Other 1,218 1,111 Total deferred tax assets $ 114,795 $ 102,762 Valuation allowance (114,795) (102,762) Net deferred tax assets (liabilities) $ — $ —

Organization (Details)

Organization (Details) $ in Thousands	2 Months Ended	12 Months Ended
	Mar. 03, 2021USD ($)	Dec. 31, 2020USD ($)product	Dec. 31, 2019USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of lead products | product		2
Cash, cash equivalents and short-term investments		$ 123,300
Class of Stock [Line Items]
Issuance of common shares pursuant to the Open Market Sales Agreement		86,297	$ 18,601
Jefferies LLC | Common Shares | Sale Agreement
Class of Stock [Line Items]
Issuance of common shares pursuant to the Open Market Sales Agreement		$ 86,300	$ 19,500
Jefferies LLC | Common Shares | Sale Agreement | Subsequent event
Class of Stock [Line Items]
Issuance of common shares pursuant to the Open Market Sales Agreement	$ 24,300

Significant accounting polici_4

Significant accounting policies - Narrative (Details) - USD ($) shares in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Jul. 31, 2020
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Equity method investments	$ 0
Anti-dilutive common shares excluded from calculation of income per common share (in shares)	31.8	28.4
Preferred dividend percentage	8.75%
Directors and Executives | Stock Option
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Expected average option term	7 years
Employee | Stock Option
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Expected average option term	5 years
Stock Option
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Anti-dilutive common shares excluded from calculation of income per common share (in shares)	10.7
Convertible Preferred Shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Anti-dilutive common shares excluded from calculation of income per common share (in shares)	21.1
Genevant
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Ownership interest in equity method investment (as a percent)	16.00%		16.00%
Equity method investments	$ 0

Significant accounting polici_5

Significant accounting policies - Estimated useful lives of property and equipment (Details)	12 Months Ended
	Dec. 31, 2020
Laboratory equipment
Property, Plant and Equipment [Line Items]
Useful lives	5 years
Computer and office equipment | Minimum
Property, Plant and Equipment [Line Items]
Useful lives	2 years
Computer and office equipment | Maximum
Property, Plant and Equipment [Line Items]
Useful lives	5 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Useful lives	5 years

Significant accounting polici_6

Significant accounting policies - Computation of basic and diluted net income (loss) per common share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dividend accretion of convertible preferred shares	$ (12,123)	$ (11,149)
Net loss attributable to common shares	$ (75,868)	$ (164,872)
Weighted average number of shares - basic diluted (in shares)	75,835,378	57,093,454
Basic and diluted (in USD per share)	$ (1)	$ (2.89)
Common Shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Dividend accretion of convertible preferred shares	$ 0	$ 0
Allocation of undistributable loss	(75,868)	(164,872)
Net loss attributable to common shares	$ (75,868)	$ (164,872)
Weighted average number of shares - basic diluted (in shares)	75,835,378	57,093,454
Basic and diluted (in USD per share)	$ (1)	$ (2.89)

Fair value measurements_ - Narr

Fair value measurements  - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair value of contingent consideration	$ 3,426	$ 2,953	$ 3,126
Increase in fair value of contingent consideration	$ 473	$ (173)

Fair value measurements_ - Asse

Fair value measurements  - Assets and liabilities measured at fair value on recurring basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Liabilities
Contingent consideration	$ 3,426	$ 2,953	$ 3,126
Fair Value, Measurements, Recurring
Assets
Cash and cash equivalents	52,251	31,799
Investments in marketable securities	71,017	59,035
Total	123,268	90,834
Liabilities
Liability-classified options	250	253
Contingent consideration	3,426	2,953
Total	3,676	3,206
Fair Value, Measurements, Recurring | Level 1
Assets
Cash and cash equivalents	52,251	31,799
Investments in marketable securities	71,017	59,035
Total	123,268	90,834
Liabilities
Liability-classified options	0	0
Contingent consideration	0	0
Total	0	0
Fair Value, Measurements, Recurring | Level 2
Assets
Cash and cash equivalents	0	0
Investments in marketable securities	0	0
Total	0	0
Liabilities
Liability-classified options	0	0
Contingent consideration	0	0
Total	0	0
Fair Value, Measurements, Recurring | Level 3
Assets
Cash and cash equivalents	0	0
Investments in marketable securities	0	0
Total	0	0
Liabilities
Liability-classified options	250	253
Contingent consideration	3,426	2,953
Total	$ 3,676	$ 3,206

Fair value measurements_ - Chan

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, 2020	Dec. 31, 2019
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Liability at beginning of the period	$ 253	$ 479
Fair value of liability-classified options exercised in the period	0	0
Increase (decrease) in fair value of liability	(3)	(226)
Liability at end of the period	$ 250	$ 253

Fair value measurements_- Chang

Fair value measurements - Changes in fair value of contingent consideration (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Liability at beginning of the period	$ 2,953	$ 3,126
Increase (decrease) in fair value of liability	473	(173)
Liability at end of the period	$ 3,426	$ 2,953

Investments in marketable sec_3

Investments in marketable securities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Securities, Available-for-sale [Line Items]
Cash Equivalents, Amortized Cost	$ 52,251	$ 31,799
Amortized Cost	71,003	59,035
Gross Unrealized Gain	15	4
Gross Unrealized Loss	(1)	(4)
Fair Value	71,017	59,035
Cash Equivalents
Debt Securities, Available-for-sale [Line Items]
Cash Equivalents, Amortized Cost	15,703	7,116
Cash Equivalents, Fair Value	15,703	7,116
Money market fund | Cash Equivalents
Debt Securities, Available-for-sale [Line Items]
Cash Equivalents, Amortized Cost	13,703	4,106
Cash Equivalents, Fair Value	13,703	4,106
US government agency bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	11,550	19,863
Gross Unrealized Gain	7	2
Gross Unrealized Loss	0	(1)
Fair Value	11,557	19,864
US government agency bonds | Cash Equivalents
Debt Securities, Available-for-sale [Line Items]
Cash Equivalents, Amortized Cost	0	1,511
Cash Equivalents, Fair Value	0	1,511
US treasury bills
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	21,990	15,926
Gross Unrealized Gain	2	2
Gross Unrealized Loss	0	(1)
Fair Value	21,992	15,927
US treasury bills | Cash Equivalents
Debt Securities, Available-for-sale [Line Items]
Cash Equivalents, Amortized Cost	2,000	1,499
Cash Equivalents, Fair Value	2,000	1,499
US government bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	37,463	23,246
Gross Unrealized Gain	6	0
Gross Unrealized Loss	(1)	(2)
Fair Value	$ 37,468	$ 23,244

Investment in Genevant (Details

Investment in Genevant (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Jul. 31, 2020
Schedule of Equity Method Investments [Line Items]
Gain (loss) on investments		$ (2,545,000)	$ (22,522,000)
Net equity investment loss		2,545,000	22,522,000
Equity method investments	$ 0	$ 0
Genevant
Schedule of Equity Method Investments [Line Items]
Sub-licensing revenue, percentage	20.00%	20.00%
Investments				$ 2,500,000
Gain (loss) on investments	$ 2,500,000		(14,900,000)
Ownership interest in equity method investment (as a percent)	16.00%	16.00%		16.00%
Impairment charge			$ 7,600,000
Equity method investments	$ 0	$ 0

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020USD ($)leaserenewal_option	Dec. 31, 2019USD ($)
Lessee, Lease, Description [Line Items]
Number of operating leases | lease	2
Renewal term	5 years
Operating lease expense	$ 0.7	$ 1.2
Fixed lease payment	0.6	0.9
Variable lease payment	$ 0.1	0.3
Sublease income		$ 0.2
Corporate Headquarters Located 701 Veterans Circle, Warminster, Pennsylvania
Lessee, Lease, Description [Line Items]
Number of renewal options | renewal_option	2
Discount rate	9.00%
Offices Located at 626 Jacksonville Rd., Warminster, Pennsylvania
Lessee, Lease, Description [Line Items]
Discount rate	7.60%
Burnaby Facility
Lessee, Lease, Description [Line Items]
Discount rate	5.00%

Leases - Lease cost (Details)

Leases - Lease cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Weighted-average remaining lease term (years)	6 years 1 month 6 days
Weighted average discount rate	9.00%
Cash paid for amounts included in the measurement of lease liabilities	$ 657	$ 1,116

Leases - Maturity of lease liab

Leases - Maturity of lease liability (Details) $ in Thousands	Dec. 31, 2020USD ($)
Leases [Abstract]
2021	$ 677
2022	581
2023	598
2024	616
2025	635
Thereafter	787
Total lease payments	3,894
Less: interest	(911)
Present value of lease payments	$ 2,983

Property and equipment - Schedu

Property and equipment - Schedule (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Property, Plant and Equipment [Line Items]
Cost	$ 14,548	$ 14,318
Accumulated depreciation	(7,621)	(5,642)
Net book value	6,927	8,676
Lab equipment
Property, Plant and Equipment [Line Items]
Cost	5,669	5,511
Accumulated depreciation	(4,369)	(3,316)
Net book value	1,300	2,195
Leasehold improvements
Property, Plant and Equipment [Line Items]
Cost	8,555	8,521
Accumulated depreciation	(3,017)	(2,152)
Net book value	5,538	6,369
Computer hardware and software
Property, Plant and Equipment [Line Items]
Cost	324	286
Accumulated depreciation	(235)	(174)
Net book value	$ 89	$ 112

Property and equipment - Narrat

Property and equipment - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2019USD ($)
Property, Plant and Equipment [Abstract]
Disposed equipment, furniture, and leasehold improvements	$ 3.4
Net book value of disposal assets	$ 0.1

Intangible assets and goodwill

Intangible assets and goodwill (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Indefinite-lived Intangible Assets [Line Items]
Impairment of intangible assets	$ 0	$ 43,836,000
Tax benefit related to decrease in deferred tax liability for indefinite delay of further development		12,700,000
Impairment of goodwill	$ 0	22,471,000
Goodwill		0
IPR&D – cccDNA Sterilizers
Indefinite-lived Intangible Assets [Line Items]
Impairment of intangible assets		43,800,000
Intangible assets		$ 0

Accounts payable and accrued _3

Accounts payable and accrued liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Trade accounts payable	$ 2,994	$ 2,398
Payroll accruals	3,566	2,314
Research and development accruals	1,653	1,433
Professional fee accruals	679	809
Site consolidation accrual	0	137
Other accrued liabilities	9	144
Accounts payable and accrued liabilities	$ 8,901	$ 7,235

Sale of future royalties - Narr

Sale of future royalties - Narrative (Details) - USD ($)	Jul. 02, 2019	Jan. 01, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020
Other Liabilities Disclosure [Line Items]
Royalty guarantees commitments percentage			2.50%
Non-cash royalty revenue			$ 3,395,000	$ 1,656,000
Non-cash interest expense			3,957,000	2,099,000
OMERS
Other Liabilities Disclosure [Line Items]
Royalty interest sold, percentage of sales, annual revenue threshold of highest tier	$ 500,000,000
Gross proceeds from royalty interest sold		$ 20,000,000
Royalty interest sold, maximum royalties for buyer	$ 30,000,000
Royalty guarantees commitments percentage	100.00%
Royalty payable	$ 30,000,000
Debt discount and issuance costs	$ 1,500,000		$ 0	11,451,000
Effective annual interest rate of royalty liability			16.00%
Non-cash royalty revenue			$ 3,400,000	1,700,000	$ 5,100,000
Non-cash interest expense			$ 4,000,000	$ 2,100,000
OMERS | Minimum
Other Liabilities Disclosure [Line Items]
Royalty, percentage of interest sold	1.00%
OMERS | Maximum
Other Liabilities Disclosure [Line Items]
Royalty, percentage of interest sold	2.33%

Sale of future royalties - Acti

Sale of future royalties - Activity (Details) - USD ($) $ in Thousands	Jul. 02, 2019	Dec. 31, 2020	Dec. 31, 2019
Liability Related To Future Royalties [Roll Forward]
Net liability related to sale of future royalties - beginning balance		$ 18,992	$ 0
Non-cash royalty revenue		(3,395)	(1,656)
Non-cash interest expense		3,957	2,099
Net liability related to sale of future royalties - ending balance		19,554	18,992
OMERS
Liability Related To Future Royalties [Roll Forward]
Initial recognition of liability		0	30,000
Debt discount and issuance costs	$ (1,500)	0	(11,451)
Non-cash interest expense		$ 4,000	$ 2,100

Contingencies and commitments (

Contingencies and commitments (Details) $ in Thousands, $ in Millions	Dec. 18, 2020USD ($)	Aug. 20, 2019USD ($)	Sep. 30, 2019USD ($)	Dec. 31, 2020USD ($)	Dec. 31, 2020CAD ($)	Dec. 31, 2019USD ($)	Mar. 31, 2004USD ($)	Mar. 31, 2004CAD ($)	Dec. 31, 2020CAD ($)	Dec. 31, 2018USD ($)	Oct. 31, 2014USD ($)
Contingencies and Commitments [Line Items]
Percent of costs funded by TPC							27.00%	27.00%
Maximum contribution for product							$ 7,200	$ 9.3
Cumulative contribution for product				$ 2,700	$ 3.7
Royalty guarantees commitments percentage				2.50%	2.50%
Contingent consideration				$ 3,426		$ 2,953				$ 3,126
Fair Value, Measurements, Recurring
Contingencies and Commitments [Line Items]
Contingent consideration				3,426		2,953
Arbutus Inc. | Enantigen
Contingencies and Commitments [Line Items]
Business combination, regulatory, development and sales milestone payments estimated fair value				3,400
Blumberg and Drexel | Fair Value, Measurements, Recurring | Enantigen
Contingencies and Commitments [Line Items]
Contingent consideration				0
Blumberg and Drexel | Arbutus Inc.
Contingencies and Commitments [Line Items]
Development and regulatory milestones payment per licensed compound series, maximum											$ 102,500
Maximum royalty payment											$ 1,000
Royalty
Contingencies and Commitments [Line Items]
Collaborations and contracts				300		$ 300
Royalties paid or accrued				100
Contractual obligation				$ 2,700					$ 3.7
Arbitration with the University of British Columbia
Contingencies and Commitments [Line Items]
Payments for legal settlements		$ 5,900	$ 5,900
Litigation settlement interest		$ 2,600
Loss contingency, loss in period			6,300
Amount awarded to other party			5,900
Loss contingency, damages sought for allegedly unpaid royalties	$ 2,000
Arbitration with the University of British Columbia | Minimum
Contingencies and Commitments [Line Items]
Estimate of possible loss			$ 400

Collaborations, contracts and_3

Collaborations, contracts and licensing agreements - Narrative (Details)	Jul. 02, 2019USD ($)	Jan. 01, 2019USD ($)	Dec. 31, 2020USD ($)product	Dec. 31, 2013USD ($)	Apr. 11, 2018	May 06, 2006chemotherapy_products
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Number of royalty entitlements | product			2
Royalty guarantees commitments percentage			2.50%
Number of chemotherapy products with worldwide licenses | chemotherapy_products						3
Marqibo Commercial Sales
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Contracts revenue				$ 1,000,000
Assembly
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Costs related to collaboration			$ 200,000
OMERS
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Royalty interest sold, percentage of sales, annual revenue threshold of highest tier	$ 500,000,000
Gross proceeds from royalty interest sold		$ 20,000,000
Royalty interest sold, maximum royalties for buyer	$ 30,000,000
Royalty guarantees commitments percentage	100.00%
Royalty payable	$ 30,000,000
OMERS | Minimum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Royalty, percentage of interest sold	1.00%
OMERS | Maximum
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Royalty, percentage of interest sold	2.33%
Gritstone Oncology, Inc. | License | Genevant
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Equity method investment, percentage or revenue entitled					50.00%
Talon Therapeutics
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Non-cash royalty revenue				$ 18,000,000

Collaborations, contracts and_4

Collaborations, contracts and licensing agreements - Summary of revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Disaggregation of Revenue [Line Items]
Revenues	$ 6,914	$ 6,011
License | Acuitas Therapeutics, Inc.
Disaggregation of Revenue [Line Items]
Revenues	3,259	1,931
License | Gritstone Oncology, Inc.
Disaggregation of Revenue [Line Items]
Revenues	0	1,819
License | Acrotech Biopharma, LLC
Disaggregation of Revenue [Line Items]
Revenues	269	605
Non-cash royalty revenue
Disaggregation of Revenue [Line Items]
Revenues	3,395	1,656
Non-cash royalty revenue | Alnylam Pharmaceuticals, Inc.
Disaggregation of Revenue [Line Items]
Revenues	$ 3,386	$ 1,656

Shareholders_ equity (Details)

Shareholders’ equity (Details) - USD ($)	Jan. 12, 2018	Oct. 16, 2017	Oct. 02, 2017	Mar. 03, 2021	Dec. 31, 2020	Dec. 31, 2019	Aug. 31, 2020	Jun. 30, 2020	Dec. 31, 2018
Class of Stock [Line Items]
Proceeds from issuance of common stock					$ 86,297,000	$ 18,601,000
Issuance of common shares in conjunction with the private offering, net of issuance costs					$ 86,297,000	18,601,000
Shares price (in USD per share)								$ 1.82
Preferred dividend percentage					8.75%
Roivant
Class of Stock [Line Items]
Noncontrolling interest, ownership percentage by owners after conversion			33.00%
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	$ 75,000,000		$ 50,000,000
Number of shares issued under agreement					24,728,368	9,138,232
Proceeds from issuance of common stock					$ 86,300,000	$ 19,500,000
Common Shares | Sale Agreement | Jefferies LLC | Subsequent event
Class of Stock [Line Items]
Number of shares issued under agreement				5,800,000
Proceeds from issuance of common stock				$ 24,300,000
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 (in USD per share)			$ 7.13
Premium percentage on closing stock price			15.00%
Shares price (in USD per share)			$ 6.20
Preferred dividend percentage			8.75%			8.75%
Noncontrolling interest, investment commitment period			4 years
Convertible Preferred Stock, Shares Of Common Stock Issued upon Conversion			23,000,000
Preferred Shares
Class of Stock [Line Items]
Shares issued					1,164,000	1,164,000			1,164,000

Stock-based compensation - Narr

Stock-based compensation - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2019	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common shares reserved for issuance		1,500,000
Discount rate on shares		15.00%
Stock-based compensation expense related to ESPP		$ 200
Non-cash stock-based compensation expense			$ 1,100
Unearned compensation expense		$ 7,800
Unearned compensation expense, recognition period		2 years 3 months 18 days
Stock-based compensation expense		$ 6,161	$ 6,799
Collier Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted (in shares)	1,112,000
Arbutus Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected average option term		6 years 2 months 12 days	7 years 3 months 18 days
Intrinsic value of options exercised		$ 300	$ 100
OnCore Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options outstanding (in shares)		80,035	99,290
Intrinsic value of options exercised		$ 100	$ 100
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock-based compensation awards approved to be issued (in shares)		15,790,202
Number of options outstanding (in shares)		10,669,776
Number of additional shares authorized (in shares)		3,161,471
Stock Option | 2016 and 2011 Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected average option term		10 years
Stock Option | Minimum | 2016 and 2011 Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period		3 years
Stock Option | Maximum | 2016 and 2011 Plans
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option vesting period		4 years
Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options outstanding (in shares)		197,500	227,500
Expected average option term		10 months 24 days	1 year 7 months 6 days
Intrinsic value of options exercised		$ 100
Performance shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 300

Stock-based compensation - Stoc

Stock-based compensation - Stock option activity under the Arbutus Plan (Details) - Arbutus Plans	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Stock Option
Number of optioned common shares
Balance - Number of optioned common shares (in shares)	8,249,093
Options granted (in shares)	2,865,350
Options exercised (in shares)	(125,649)
Options forfeited, canceled or expired (in shares)	(597,118)
Options vested (in shares)	0
Balance - Number of optioned common shares (in shares)	10,391,676
Weighted average exercise price
Balance - Weighted average exercise price (in CAD and USD per share) | $ / shares	$ 5
Options granted - Weighted average exercise price (in CAD and USD per share) | $ / shares	3.21
Options exercised - Weighted average exercise price (in CAD and USD per share) | $ / shares	3.04
Options forfeited, canceled or expired - Weighted average exercise price (in CAD and USD per share) | $ / shares	5.10
Options vested (USD per share) | $ / shares	0
Balance - Weighted average exercise price (in CAD and USD per share) | $ / shares	$ 4.53
Vested Stock Options
Number of optioned common shares
Balance - Number of optioned common shares (in shares)	4,294,649
Options granted (in shares)	0
Options exercised (in shares)	(125,649)
Options forfeited, canceled or expired (in shares)	(313,861)
Options vested (in shares)	2,529,247
Balance - Number of optioned common shares (in shares)	6,384,386
Non-Vested Stock Options
Number of optioned common shares
Balance - Number of optioned common shares (in shares)	3,954,444
Options granted (in shares)	2,865,350
Options exercised (in shares)	0
Options forfeited, canceled or expired (in shares)	(283,257)
Options vested (in shares)	2,529,247
Balance - Number of optioned common shares (in shares)	4,007,290
Weighted average exercise price
Balance - Weighted average exercise price (in CAD and USD per share) | $ / shares	$ 2.86
Options granted - Weighted average exercise price (in CAD and USD per share) | $ / shares	2.20
Options exercised - Weighted average exercise price (in CAD and USD per share) | $ / shares	0
Options forfeited, canceled or expired - Weighted average exercise price (in CAD and USD per share) | $ / shares	2.53
Options vested (USD per share) | $ / shares	2.69
Balance - Weighted average exercise price (in CAD and USD per share) | $ / shares	$ 2.51

Stock-based compensation - St_2

Stock-based compensation - Stock options outstanding under the Arbutus Plan (Details) - Arbutus Plans $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020USD ($)$ / sharesshares
Stock Option
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of options outstanding (in shares) | shares	10,391,676
Options outstanding, Weighted average exercise price (in USD per share) | $ / shares	$ 4.53
Intrinsic value (in $000s) | $	$ 3,532
Weighted-average term remaining	6 years 8 months 12 days
Vested Stock Options
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of options outstanding (in shares) | shares	6,384,386
Options outstanding, Weighted average exercise price (in USD per share) | $ / shares	$ 5.11
Intrinsic value (in $000s) | $	$ 1,758
Weighted-average term remaining	5 years 6 months

Stock-based compensation - Valu

Stock-based compensation - Valuation assumptions for stock options under the Arbutus Plan (Details) - Arbutus Plans	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected average option term	6 years 2 months 12 days	7 years 3 months 18 days
Expected volatility	80.20%	75.90%
Expected dividends	0.00%	0.00%
Risk-free interest rate	1.20%	2.27%

Stock-based compensation - St_3

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, 2020USD ($)$ / sharesshares
Number of optioned common shares
Balance - Number of optioned common shares (in shares) | shares	227,500
Options exercised (in shares) | shares	(25,000)
Options forfeited, canceled or expired (in shares) | shares	(5,000)
Balance - Number of optioned common shares (in shares) | shares	197,500
Weighted average exercise price
Balance - Weighted average exercise price (in CAD and USD per share) | $ / shares	$ 5.49
Options exercised - Weighted average exercise price (in CAD and USD per share) | $ / shares	3.02
Options forfeited, canceled or expired - Weighted average exercise price (in CAD and USD per share) | $ / shares	3.02
Balance - Weighted average exercise price (in CAD and USD per share) | $ / shares	$ 6
Intrinsic value (in $000s) | $	$ 158
Weighted-average term remaining	10 months 24 days

Stock-based compensation - Va_2

Stock-based compensation - Valuation assumptions for liability-classified options (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Jun. 30, 2020	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares price (in USD per share)			$ 1.82
Liability classified stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares price (in USD per share)	$ 3.55	$ 2.78
Expected average option term	10 months 24 days	1 year 7 months 6 days
Expected volatility	105.66%	113.10%
Expected dividends	0.00%	0.00%
Risk-free interest rate	0.11%	1.59%
Weighted average fair value per share of options outstanding (in USD per share)	$ 1.30	$ 1.11
Total fair value of vested liability-classified options (in $000s)	$ 250	$ 253		$ 479

Stock-based compensation - Outs

Stock-based compensation - Outstanding options under the Oncore Option Plan (Details) - OnCore Option Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Number of optioned common shares
Balance - Number of optioned common shares (in shares)	99,290
Options exercised (in shares)	(19,255)
Options forfeited, canceled or expired (in shares)	0
Balance - Number of optioned common shares (in shares)	80,035	99,290
Weighted average exercise price
Balance - Weighted average exercise price (in CAD and USD per share)	$ 0.56
Options exercised - Weighted average exercise price (in CAD and USD per share)	0.56
Options forfeited, canceled or expired - Weighted average exercise price (in CAD and USD per share)	0
Balance - Weighted average exercise price (in CAD and USD per share)	$ 0.56	$ 0.56
Intrinsic value (in $000s)	$ 241
Weighted average remaining contractual life (years)	3 years 9 months 18 days
Intrinsic value of options exercised	$ 100	$ 100
Equivalent number of Company common shares
Number of optioned common shares
Balance - Number of optioned common shares (in shares)	99,991
Options exercised (in shares)	(19,391)
Options forfeited, canceled or expired (in shares)	0
Balance - Number of optioned common shares (in shares)	80,600	99,991

Stock-based compensation - St_4

Stock-based compensation - Stock-based compensation expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 6,161	$ 6,799
OnCore Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised	100	100
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	3,090	2,971
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 3,071	$ 3,828

Income taxes - Narrative (Detai

Income taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Canadian federal and provincial income tax rate	27.00%	27.00%
Research and development credits	$ 3,900	$ 3,900
Scientific research and experimental development expenditures available for indefinite carry-forward	74,351	59,956
Deferred tax assets, operating loss carryforwards, subject to expiration	11,700	11,700
Pre-tax domestic losses	1,800	27,100
Pre-tax foreign losses	61,900	139,300
Investment tax credit carryforward
Income Taxes [Line Items]
Investment tax credits available to reduce Canadian federal income taxes	8,000	10,000
Investment tax credits available to reduce provincial income taxes	2,600	4,500
Research tax credit carryforward
Income Taxes [Line Items]
Scientific research and experimental development expenditures available for indefinite carry-forward	58,600	60,600
Deferred tax assets, operating loss carryforwards, subject to expiration	$ 175,600	$ 164,900

Income taxes - Income tax recon

Income taxes - Income tax reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Computed taxes (benefits) at Canadian federal and provincial tax rates	$ (17,211)	$ (44,922)
Difference due to change in tax rate on opening deferred taxes	0	8,356
Adjustment to prior year	390	(525)
Permanent and other differences	622	3,458
Change in valuation allowance - other	12,033	19,078
Difference due to income taxed at foreign rates	3,716	(3,343)
Stock-based compensation	450	523
Impairment of goodwill	0	4,719
Income tax expense (recovery)	$ 0	$ (12,656)

Income taxes - Deferred tax ass

Income taxes - Deferred tax assets and liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Components of Deferred Tax Assets [Line Items]
Non-capital losses carryforwards	$ 74,351	$ 59,956
Research and development deductions	15,812	16,349
Book amortization in excess of tax	(737)	(914)
Revenue recognized for tax purposes in excess of revenue recognized for accounting purposes	5,279	5,128
Tax value in excess of accounting value in lease inducements	627	705
Equity accounted for investment	3,375	3,038
Federal R&E credits	3,897
Deductible stock options	2,457	1,632
Other	1,218	1,111
Total deferred tax assets	114,795	102,762
Valuation allowance	(114,795)	(102,762)
Net deferred tax assets (liabilities)	0	0
Federal
Components of Deferred Tax Assets [Line Items]
Investment tax credits	5,872	7,325
Provincial
Components of Deferred Tax Assets [Line Items]
Investment tax credits	$ 2,644	$ 4,535

Related party transactions (Det

Related party transactions (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2020USD ($)ft²	Dec. 31, 2020USD ($)ft²	Dec. 31, 2019USD ($)	Jul. 31, 2020USD ($)
Related Party Transaction [Line Items]
Gain (loss) on investments		$ (2,545)	$ (22,522)
Genevant
Related Party Transaction [Line Items]
Investments				$ 2,500
Gain (loss) on investments	$ 2,500		(14,900)
Genevant | Equity Method Investee | Administrative and transitional services
Related Party Transaction [Line Items]
Income from related party		100	$ 100
Genevant | Equity Method Investee | Sublease Burnaby facility
Related Party Transaction [Line Items]
Income from related party		$ 200
Area of sublease facility | ft²	17,900	17,900