Histogen (HSTO) 10-K 10 Mar 22 2021 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Mar. 08, 2022	Jun. 30, 2021
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2021
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	FY
Entity Registrant Name	Histogen Inc.
Entity Central Index Key	0001383701
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Entity Shell Company	false
Title of 12(b) Security	Common Stock, $0.0001 par value
Trading Symbol	HSTO
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	10655 Sorrento Valley Road
Entity Address, Address Line Two	Suite 200
Entity Address, City or Town	San Diego
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	92121
City Area Code	(858)
Local Phone Number	526-3100
Entity File Number	001-36003
Entity Tax Identification Number	20-3183915
Entity Common Stock, Shares Outstanding		49,950,212
Entity Public Float			$ 42.8
Document Annual Report	true
Document Transition Report	false
Auditor Firm ID	199
Auditor Name	Mayer Hoffman McCann P.C.
Auditor Location	San Diego, California
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE The following documents are incorporated by reference into the following parts of the Annual Report on Form 10-K: Certain information required in Part III of this Annual Report on Form 10-K is incorporated from the Registrant’s Proxy Statement for the 2022 Annual Meeting of Stockholders.

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Current assets
Cash and cash equivalents	$ 18,685	$ 6,763
Restricted cash	400	10
Accounts receivable, net	165	144
Inventories		300
Prepaid and other current assets	2,359	1,183
Total current assets	21,609	8,400
Property and equipment, net	399	271
Right-of-use asset	4,432	4,411
Other assets	805	1,931
Total assets	27,245	15,013
Current liabilities
Accounts payable	1,393	539
Accrued liabilities	791	1,880
Current portion of lease liabilities	127	28
Current portion of deferred revenue	19	48
Financed insurance premiums, current	0	193
Payroll protection program loan, current		97
Total current liabilities	2,330	2,785
Lease liabilities, non-current	4,617	4,806
Payroll protection program loan, non-current		369
Noncurrent portion of deferred revenue	98	118
Finance lease liability, non-current	14	22
Total liabilities	7,059	8,100
Commitments and contingencies (Note 10)
Stockholders’ equity
Preferred stock, $0.0001 par value; 10,000,000 shares authorized at December 31, 2021 and 2020; no shares issued and outstanding at December 31, 2021 and 2020
Common stock, $0.0001 par value; 200,000,000 shares authorized at December 31, 2021 and 2020; 49,950,212 and 15,030,757 shares issued and outstanding at December 31, 2021 and 2020, respectively	5	1
Additional paid-in capital	98,839	70,561
Accumulated deficit	(77,652)	(62,702)
Total Histogen Inc. stockholders’ equity	21,192	7,860
Noncontrolling interest	(1,006)	(947)
Total equity	20,186	6,913
Total liabilities and stockholders’ equity	$ 27,245	$ 15,013

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2021	Dec. 31, 2020
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	49,950,212	15,030,757
Common stock, shares outstanding	49,950,212	15,030,757
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Revenue
Total revenue	$ 1,032	$ 2,059
Operating expense
Acquired in-process research and development		7,144
Research and development	8,473	6,219
General and administrative	7,796	6,586
Total operating expense	16,489	20,917
Loss from operations	(15,457)	(18,858)
Other income (expense)
Interest expense, net	(10)	(64)
Other income, net	458	105
Net loss	(15,009)	(18,817)
Loss attributable to noncontrolling interest	59	48
Net loss available to common stockholders	$ (14,950)	$ (18,769)
Net loss per share available to common stockholders, basic and diluted	$ (0.39)	$ (2.08)
Weighted-average number of common shares outstanding used to compute net loss per share, basic and diluted	38,364,711	9,018,376
Product [Member]
Revenue
Total revenue	$ 892	$ 845
Operating expense
Cost of Revenue	220	679
License [Member]
Revenue
Total revenue	27	882
Grant [Member]
Revenue
Total revenue	$ 113	0
Professional Services [Member]
Revenue
Total revenue		332
Operating expense
Cost of Revenue		$ 289

CONSOLIDATED STATEMENTS OF CONV

CONSOLIDATED STATEMENTS OF CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Convertible Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Deficit [Member]	Total Histogen Inc. Stockholders' Deficit [Member]	Noncontrolling Interest [Member]
Beginning balance at Dec. 31, 2019	$ (37,968)			$ 6,864	$ (43,933)	$ (37,069)	$ (899)
Beginning balance, shares at Dec. 31, 2019		5,046,154
Beginning balance at Dec. 31, 2019		$ 39,070
Beginning balance, shares at Dec. 31, 2019			3,343,356
Issuance of common stock to former stockholders of Conatus upon Merger	18,872			18,872		18,872
Issuance of common stock to former stockholders of Conatus upon Merger, shares			3,394,299
Conversion of convertible preferred stock into common stock upon Merger	39,070		$ 1	39,069		39,070
Conversion of convertible preferred stock into common stock upon Merger, shares		(5,046,154)
Conversion of convertible preferred stock into common stock upon Merger		$ (39,070)
Conversion of convertible preferred stock into common stock upon Merger, shares			5,046,154
Issuance of common stock, net of issuance costs	5,098			5,098		5,098
Issuance of common stock, net of issuance costs, shares			3,218,264
Issuance of common stock upon net exercise of stock options	40			40		40
Issuance of common stock upon net exercise of stock options, shares			28,684
Stock-based compensation expense	618			618		618
Net loss	(18,817)				(18,769)	(18,769)	(48)
Ending balance at Dec. 31, 2020	6,913		$ 1	70,561	(62,702)	7,860	(947)
Ending balance, shares at Dec. 31, 2020			15,030,757
Issuance of common stock, net of issuance costs	20,738		$ 3	20,735		20,738
Issuance of common stock, net of issuance costs, shares			28,212,597
Issuance of common stock upon net exercise of warrants	6,840		$ 1	6,839		6,840
Issuance of common stock upon net exercise of warrants, shares			6,721,200
Repurchase of common stock, shares			(14,342)
Stock-based compensation expense	704			704		704
Net loss	(15,009)				(14,950)	(14,950)	(59)
Ending balance at Dec. 31, 2021	$ 20,186		$ 5	$ 98,839	$ (77,652)	$ 21,192	$ (1,006)
Ending balance, shares at Dec. 31, 2021			49,950,212

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS $ in Thousands	12 Months Ended
	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Cash flows from operating activities
Net loss	$ (15,009)	$ (18,817)
Adjustments to reconcile net loss to net cash used in operating activities:
Acquired in-process research and development		7,144
Depreciation and amortization	97	98
Stock-based compensation	704	618
Forgiveness of the Payroll Protection Program Loan	(467)
Loss on disposal of property and equipment	17
Write-off of inventory		202
Changes in operating assets and liabilities:
Accounts receivable	(21)	(34)
Inventories	239	(396)
Prepaid expenses and other current assets	(1,176)	(606)
Other assets	1,187	(259)
Accounts payable	854	(881)
Accrued liabilities	(799)	514
Right-of-use asset and lease liabilities, net	(111)	354
Deferred revenue	(47)	9
Net cash used in operating activities	(14,532)	(12,054)
Cash flows from investing activities
Cash acquired in connection with the Merger		12,835
Cash paid for acquisition costs		(1,817)
Cash paid for property and equipment	(241)	(49)
Net cash provided by (used in) investing activities	(241)	10,969
Cash flows from financing activities
Proceeds from the issuance of common stock, net of issuance costs	20,738	5,098
Costs paid in connection with January 2021 Offering		(7)
Repayment of finance lease obligations	(9)	(7)
Proceeds from promissory notes		500
Payments on promissory notes		(500)
Proceeds from Payroll Protection Program Loan		466
Proceeds from financing of insurance premiums		872
Settlement of forward purchase contract	(290)
Payment on financing of insurance premiums	(193)	(679)
Proceeds from the exercise of warrants	6,839
Proceeds from exercise of stock options		40
Net cash provided by financing activities	27,085	5,783
Net increase in cash, cash equivalents and restricted cash	12,312	4,698
Cash, cash equivalents and restricted cash, beginning of period	6,773	2,075
Cash, cash equivalents and restricted cash, end of period	19,085	6,773
Reconciliation of cash, cash equivalents and restricted cash to the consolidated balance sheets
Cash and cash equivalents	18,685	6,763
Restricted cash	400	10
Total cash, cash equivalents and restricted cash	19,085	6,773
Supplemental disclosure of cash flow information
Cash paid for interest	6	63
Noncash investing and financing activities
Right-of-use asset obtained in exchange for operating lease liability		4,481
Conversion of convertible preferred stock into common stock		39,070
Issuance of common stock to Conatus stockholders		18,872
Net assets acquired in Merger		710
Deferred financing costs included in accounts payable and accrued expenses		701
Fair value of warrants issued to Placement Agent	$ 590	$ 108

Organization and Nature of Oper

Organization and Nature of Operations	12 Months Ended
	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Nature of Operations	1. Organization and Nature of Operations Description of Business Histogen Inc. (the “Company,” “Histogen,” or the “combined company”), formerly known as Conatus Pharmaceuticals Inc. (“Conatus”) clinical-stage therapeutics company focused on developing potential first-in-class restorative therapeutics that ignite the body’s natural process to repair and maintain healthy biological function. Merger between Private Histogen and Conatus Pharmaceuticals Inc. and Name Change On January 28, 2020, the Company, then operating as Conatus, entered into an Agreement and Plan of Merger and Reorganization, as amended (the “Merger Agreement”), with privately-held Histogen, Inc. (“Private Histogen”) and Chinook Merger Sub, Inc., a wholly-owned subsidiary of the Company (“Merger Sub”). Under the Merger Agreement, Merger Sub merged with and into Private Histogen, with Private Histogen surviving as a wholly-owned subsidiary of the Company (the “Merger”). On May 26, 2020, the Merger was completed. Conatus changed its name to Histogen Inc., and Private Histogen, which remains as a wholly-owned subsidiary of the Company, changed its name to Histogen Therapeutics Inc. On May 27, 2020, the combined company’s common stock began trading on The Nasdaq Capital Market under the ticker symbol “HSTO”. Except as otherwise indicated, references herein to “Histogen,” the “Company,” or the “combined company”, refer to Histogen Inc. on a post-Merger basis, and the term “Private Histogen” refers to the business of privately-held Histogen, Inc., prior to completion of the Merger. References to Conatus refer to Conatus Pharmaceuticals Inc. prior to completion of the Merger. Pursuant to the terms of the Merger Agreement, each outstanding share of Private Histogen common stock outstanding immediately prior to the closing of the Merger was converted into approximately 0.14342 shares of Company common stock (the “Exchange Ratio”), after taking into account the Reverse Stock Split, as defined below. Immediately prior to the closing of the Merger, all shares of Private Histogen preferred stock then outstanding were exchanged into shares of common stock of Private Histogen. In addition, all outstanding options exercisable for common stock of Private Histogen and warrants exercisable for common stock of Private Histogen became options and warrants exercisable for the same number of shares of common stock of the Company multiplied by the Exchange Ratio. Immediately following the Merger, stockholders of Private Histogen owned approximately 71.3% of the outstanding common stock of the combined company. The transaction was accounted for as a reverse asset acquisition in accordance with generally accepted accounting principles in the United States of America (“GAAP”). Under this method of accounting, Private Histogen was deemed to be the accounting acquirer for financial reporting purposes. This determination was primarily based on the facts that, immediately following the Merger: (i) Private Histogen’s stockholders owned a substantial majority of the voting rights in the combined company, (ii) Private Histogen designated a majority of the members of the initial board of directors of the combined company, and (iii) Private Histogen’s senior management holds all key positions in the senior management of the combined company. As a result, as of the closing date of the Merger, the net assets of the Company were recorded at their acquisition-date relative fair values in the accompanying consolidated financial statements of the Company and the reported operating results prior to the Merger are those of Private Histogen. Reverse Stock Split and Exchange Ratio On May 26, 2020, in connection with, and prior to the completion of, the Merger, the Company effected a one-for-ten Liquidity The Company has incurred operating losses and negative cash flows from operations and had an accumulated deficit of $77.7 million as of December 31, 2021. The Company expects operating losses and negative cash flows from operations to continue for the foreseeable future. The Company has not yet established ongoing sources of revenues sufficient to cover its operating costs and will need to continue to raise additional capital to support its future operating activities, including progression of its development programs, preparation for commercialization, and other operating costs. Management’s plans with regard to these matters include entering into a combination of additional debt or equity financing arrangements, strategic partnerships, collaboration and licensing arrangements, or other similar arrangements. In addition, the Company may fund its losses from operations through the common stock purchase agreement the Company entered into with Lincoln Park in July 2020, for the purchase of up to $10.0 million of the Company’s common stock over the 24 month period of the purchase agreement, $8.5 million of which remains available for sale as of the date (refer to Note 9 for further information), subject to limitations on the amount of securities the Company may sell under its effective registration statement on Form S-3 within any 12-month period.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation The consolidated financial statements include the accounts of the Company and its controlled subsidiaries, including Histogen Therapeutics, Inc., and have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”). All intercompany balances and transactions have been eliminated upon consolidation. The Company acquired Centro De Investigacion de Medicina Regenerativa, S.A. de C.V. (“CIMRESA”), a company in Mexico, during 2018 to facilitate a potential clinical development program for HST-001, or hair stimulating complex (“HSC”). This is a wholly-owned subsidiary intended to pursue registration with the COFEPRIS (Mexico equivalent to Food and Drug Administration). CIMRESA had no operational or financial activity for the years ended December 31, 2021 and 2020. The Company holds a majority interest (68%) in Adaptive Biologix, Inc. (“AB”, formerly Histogen Oncology, LLC). AB was formed to develop and market applications for the treatment of cancer. The Company consolidates AB into its consolidated financial statements. Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and the disclosure of contingent assets and liabilities and contingencies at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the periods presented. Management believes that these estimates and assumptions are reasonable, however, actual results may differ and could have a material effect on future results of operations and financial position. Though the impact of the COVID-19 pandemic to our business and operating results presents additional uncertainty, the Company continue s to use the best information available to them in their significant accounting estimates. Significant estimates and assumptions include the useful lives of property and equipment, discount rates used in recognizing contracts containing leases, unrecognized tax benefits, reserves for excess or obsolete inventory, stock-based compensation, and best estimate of standalone selling price of revenue deliverables. Actual results may materially differ from those estimates. Variable Interest Entities The Company determined that AB is a variable interest entity (“VIE”) and that the Company is its primary beneficiary. The Company holds greater than 50% of the shares and has the authority to manage the business and affairs of the VIE. AB’s other shareholder does not have a controlling interest. A VIE is typically an entity for which the Company has less than a 100% equity interest but controls the decision making over the business and affairs of the entity, directs the decisions driving the economic performance of such entity and participates in the profit and losses of such an entity. The Company weighed both quantitative and qualitative information about the different risks and reward characteristics of each entity and the significance of that entity to the consolidating group in the aggregate. Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker, the Interim Chief Executive Officer, in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business as one operating segment. Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments purchased with an original maturity date of ninety days or less to be cash equivalents. Cash and cash equivalents include cash in readily available checking, money market accounts and brokerage accounts. The Company’s current restricted cash consists of cash held as collateral for a letter of credit issued as a security deposit for the lease of the Company’s headquarters and is required to be held throughout the lease term. Risks and Uncertainties Credit Risk At certain times throughout the year, the Company may maintain deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institutions in which those deposits are held. Customer Risk During the years ended December 31, 2021 and 2020, one customer accounted for 88% and 100% of total revenues, respectively. Accounts receivable from the customer was $0 and $0.1 million at December 31, 2021 and 2020, respectively. COVID-19 On January 30, 2020, the World Health Organization (“WHO”) announced a global health emergency because of a new strain of coronavirus originating in Wuhan, China (the “COVID-19 outbreak”) and the risks to the international community as the virus spreads globally beyond its point of origin. In March 2020, the WHO classified the COVID-19 outbreak as a pandemic, based on the rapid increase in exposure globally. The cumulative effect the associated disruptions have had, and may continue to have, an adverse impact on the Company’s business and its results of operations. The full impact of the COVID-19 outbreak continues to evolve as of the date these consolidated financial statements were available to be issued and will depend on future developments that are highly uncertain and unpredictable, including efficacy and adoption of vaccines, future resurgences of the virus and its variants, and the speed at which government restrictions are lifted. As such, it is uncertain as to the full magnitude that the pandemic will have on the Company’s financial condition, liquidity, and future results of operations. On March 27, 2020, former President Trump signed into law the Coronavirus Aid, Relief and Economic Security Act (the “CARES Act”). The CARES Act, among other things, includes provisions relating to refundable payroll tax credits, deferment of employer side social security payments, net operating loss carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations, increased limitations on qualified charitable contributions and technical corrections to tax depreciation methods for qualified improvement property. The CARES Act also appropriated funds for the U.S. Small Business Administration Paycheck Protection Program (“PPP”) loans that are forgivable in certain situations to promote continued employment, as well as Economic Injury Disaster Loans to provide liquidity to small businesses harmed by COVID-19. Refer to Note 8 for further information. Accounts Receivable Accounts receivable are generally due within 30 days and are recorded net of the allowance for doubtful accounts, if any. Management considers all accounts receivable to be fully collectible as of December 31, 2021 and 2020, and accordingly, no provision for doubtful accounts was recorded. Inventories Inventories, consisting of raw materials and finished goods, are valued at the lower of cost (first-in, first-out method) or net realizable value. The Company writes down excess and obsolete inventory to its estimated net realizable value based on management’s review of inventories on hand compared to estimated future usage and sales, shelf-life and assumptions about the likelihood of obsolescence. The cost components of finished goods inventories include raw materials, direct labor and an allocation of the Company’s overhead. Property and Equipment Property and equipment are reported net of accumulated depreciation and amortization and are comprised of office furniture and equipment, lab and manufacturing equipment, and leasehold improvements. Ordinary maintenance and repairs are charged to expense, while expenditures that extend the physical or economic life of the assets are capitalized. Furniture and all equipment are depreciated over their estimated useful lives, or five years, using the straight-line method. Software is amortized over its estimated useful lives, or three years, using the straight-line method. Leasehold improvements are amortized over their estimated useful lives and limited by the remaining term of the building lease, using the straight-line method. Deferred Offering Costs Offering costs, consisting of legal, accounting, printer and filing fees related to the public offerings are deferred and offset against proceeds from the public offering upon the closing of the offering. As of December 31, 2021, no offering costs were deferred. As of December 31, 2020, $0.7 million of deferred offering costs related to the Company’s public offering in January 2021 were recorded in the accompanying consolidated balance sheet (refer to Note 9 for further information). Valuation of Long-Lived Assets Long-lived assets to be held and used, including property and equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. As of December 31, 2021 and 2020, the Company has not recognized any impairment to long-lived assets. Forward Purchase Contract In 2011, Private Histogen contracted for research services from EPS Global Research Pte. Ltd. (“EPS”) to conduct clinical trials and compile data from a study that took place in 2011 and 2013. The unpaid amount due for the services was approximately $0.3 million. In 2017, Private Histogen and EPS entered into a Debt Settlement and Conversion Agreement (“Settlement Agreement”) whereby Private Histogen paid $50 thousand and issued EPS 14,342 shares of Series D convertible preferred stock. The Company was required to repurchase the shares at the greater of the remaining balance due of approximately $0.3 million and the market price of the shares at the time of repurchase, but in no event later than December 31, 2021. The Company had the sole option to repurchase of the shares (which were converted from Series D convertible preferred stock into shares of common stock upon the Merger) at any time on or before December 31, 2021. As of December 31, 2020, the Company determined the fair value of the liability to be approximately $0.3 million, which was the value as if the repurchase commitment was exercised immediately. The forward purchase contract was included within accrued liabilities on the accompanying consolidated balance sheet as of December 31, 2020. On December 16, 2021, the Company repurchased from EPS 14,342 shares of common stock in exchange for a cash payment of approximately $0.3 million. The repurchased shares were recorded as treasury stock which the Company intends to retire Fair Value Measurements ASC 820, Fair Value Measurements • Level 1 — Observable inputs such as quoted price (unadjusted) for identical instruments in active markets. • Level 2 — Observable inputs such as quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, or model derived valuations whose significant inputs are observable. • Level 3 — Unobservable inputs that reflect the reporting entity’s own assumptions. At December 31, 2021 and 2020, management believes the carrying amount of financial instruments consisting of cash, cash equivalents, restricted cash, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values due to the short-term nature of those instruments. Comprehensive Loss The Company is required to report all components of comprehensive loss, including net loss, in the accompanying consolidated financial statements in the period in which they are recognized. Comprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources, including unrealized gains and losses on investments and foreign currency translation adjustments. Net loss and comprehensive loss were the same for all periods presented. Revenue Recognition Product and License Revenue The Company records revenue in accordance with ASC 606, Revenue from Contracts with Customers Grant Awards In March 2017, the National Science Foundation (“NSF”), a government agency, awarded the Company a research and development grant to develop a novel wound dressing for infection control and tissue regeneration. The Company has concluded this government grant is not within the scope of ASC 606, as government entities generally do not meet the definition of a “customer” as defined by ASC 606. Payments received under the grant are considered conditional, non-exchange contributions under the scope of ASC 958-605, Not-for-Profit Entities – Revenue Recognition In September 2020, the Company was approved for a grant award from the U.S. Department of Defense (“DoD”) in the amount of approximately $2.0 million to partially fund the Company’s planned Phase 1/2 clinical trial of HST-003 for regeneration of cartilage in the knee. The Company applies International Accounting Standard (“IAS”) 20, Accounting for Government Grants and Disclosure of Government Assistance Professional Services The Company recognizes revenue for professional services which are based upon negotiated rates with the counterparty. Professional services fees are recognized as revenue over time when the underlying services are performed, in accordance with ASC 606, and none of the revenue recognized to date is refundable. Cost of Product Revenue Cost of product revenue represents direct and indirect costs incurred to bring the product to saleable condition. Cost of Professional Services Revenue Cost of professional services revenue represents the Company’s costs for full-time employee equivalents and actual out-of-pocket costs. Research and Development Expenses All research and development costs are charged to expense as incurred. Research and development expenses primarily include (i) payroll and related costs associated with research and development performed, (ii) costs related to clinical and preclinical testing of the Company’s technologies under development, and (iii) other research and development costs including allocations of facility costs, net of reimbursable research and development costs incurred under the DoD grant. Acquired In-Process Research and Development Expense The Company has acquired and may continue to acquire the rights to drug candidates in various stages of development. The up-front payments to acquire a drug candidate are immediately expensed as acquired in-process research and development, provided that the drug candidate has not obtained regulatory approval for marketing and, absent obtaining such approval, have no alternative future use. General and Administrative Expenses General and administrative expenses represent personnel costs for employees involved in general corporate functions, including finance, accounting, legal and human resources, among others. Additional costs included within general and administrative expenses consist of professional fees for legal (including patent costs), audit and other consulting services, travel and entertainment, recruiting, allocated facility and general information technology costs, depreciation and amortization, and other general corporate overhead expenses. Patent Costs The Company expenses all costs as incurred in connection with patent applications (including direct application fees, and the legal and consulting expenses related to making such applications) and such costs are included as a component of general and administrative expenses in the accompanying consolidated statements of operations. Income Taxes Income taxes are accounted for under the asset and liability method. Deferred income taxes are recorded for temporary differences between consolidated financial statement carrying amounts and the tax basis of assets and liabilities. Deferred tax assets and liabilities reflect the tax rates expected to be in effect for the years in which the differences are expected to reverse. No income tax expense or benefit was recorded for the years ended December 31, 2021 and 2020, due to the full valuation allowance on the Company’s net deferred tax assets. A valuation allowance is provided if it is more likely than not that some or all the deferred tax assets will not be realized. The Company also follows the provisions of accounting for uncertainty in income taxes which prescribes a model for the recognition and measurement of a tax position taken or expected to be taken in a tax return, and provides guidance on derecognition, classification, interest and penalties, disclosure and transition. The Company’s policy is to recognize interest or penalties related to income tax matters in income tax expense. Interest and penalties related to income tax matters were not material for the periods presented. Net Loss Per Share Basic net loss per share attributable to common stockholders attributable to common stockholders dilutive securities outstanding for the period. For the years ended December 31, 2021 and 2020 , diluted net loss per share attributable to common stockholders is equal to basic net loss per share attributable to common stockholders as common stock equivalent shares from stock options , warrants and convertible preferred stock were anti-dilutive . The following table sets forth outstanding potentially dilutive shares that have been excluded from the calculation of diluted net loss per share attributable to common stockholders because of their anti-dilutive effect (in common stock equivalents): Years Ended December 31, 2021 2020 Common stock options issued and outstanding 2,326,221 1,708,278 Warrants to purchase common stock 23,726,140 2,023,156 Total anti-dilutive shares 26,052,361 3,731,434 Common Stock Valuations Prior to the Merger, Private Histogen was required to periodically estimate the fair value of common stock with the assistance of an independent third-party valuation expert when issuing stock options and computing its estimated stock-based compensation expense. The assumptions underlying these valuations represented management’s best estimates, which involved inherent uncertainties and the application of significant levels of management judgment. In order to determine the fair value, Private Histogen considered, among other things, contemporaneous valuations of its common stock, business, financial condition and results of operations, including related industry trends affecting its operations; the likelihood of achieving various liquidity events; the lack of marketability of its common stock; the market performance of comparable publicly traded companies; and U.S. and global economic and capital market conditions. Stock-Based Compensation Service-Based Awards The Company recognizes stock-based compensation expense for service-based stock options and restricted stock units (“RSUs”) over the requisite service period on a straight-line basis. Employee and director stock-based compensation for service-based stock options is measured based on estimated fair value as of the grant date using the Black-Scholes option pricing model. The Company estimates the fair value of RSUs based on the closing price of the Company’s common stock on the date of issuance. The Company uses the following assumptions for estimating fair value of service-based option grants: Fair Value of Common Stock – The fair value of common stock underlying the option grant is determined based on observable market prices of the Company’s common stock. Expected Volatility – Volatility is a measure of the amount by which the Company’s share price has historically fluctuated or is expected to fluctuate (i.e., expected volatility) during a period. Due to the lack of an adequate history of a public market for the trading of the Company’s common stock and a lack of adequate company-specific historical and implied volatility data, volatility has been estimated and based on the historical volatility of a group of similar companies that are publicly traded. For these analyses, the Company has selected companies with comparable characteristics, including enterprise value, risk profiles, and position within the industry, and with historical share price information sufficient to meet the expected term of the stock-based awards. Expected Term – This is the period of time during which the options are expected to remain unexercised. Options have a maximum contractual term of ten years. The Company estimates the expected term of stock options using the “simplified method”, whereby the expected term equals the average of the vesting term and the original contractual term of the underlying option. Risk-Free Interest Rate – This is the observed yield on zero-coupon U.S. Treasury securities, as of the day each option is granted, with a term that most closely resembles the expected term of the option. Expected Forfeiture Rate – Forfeitures are recognized as they occur. Performance-Based Options Stock-based compensation expense for performance-based options is recognized based on amortizing the fair market value as of the grant date over the periods during which the achievement of the performance is probable. Performance-based options require certain performance conditions to be achieved in order for these options to vest. These options vest on the date of achievement of the performance condition. Market-Based Options Stock-based compensation expense for market-based options is recognized on a straight-line basis over the derived service period, regardless of whether the market condition is satisfied. Market-based options subject to market-based performance targets require achievement of the performance target in order for these options to vest. The Company estimates the fair value of market-based options as of the grant date and expected term using a Monte Carlo simulation that incorporates option-pricing inputs covering the period from the grant date through the end of the derived service period. Recently Issued Accounting Pronouncements In August 2020, the FASB issued ASU No. 2020-06, Debt – Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40) In November 2021, the FASB issued ASU No. 2021-10, Government Assistance (Topic 832): Disclosure by Business Entities about Government Assistance Recently Adopted Accounting Pronouncements In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes

Inventories

Inventories	12 Months Ended
	Dec. 31, 2021
Inventory Disclosure [Abstract]
Inventories	3. Inventories Inventories consisted of the following components (in thousands): December 31, 2021 2020 Raw materials $ — $ 61 Finished goods — 239 Inventories $ — $ 300 During the year ended December 31, 2020, the Company recorded a write-off of inventory totaling $0.2 million that was recognized as a component of cost of product revenue on the accompanying consolidated statements of operations. As of December 31, 2021, the Company reclassified $0.1 million of cell bank inventory to other assets due to the Company having no additional purchase orders with Allergan for fulfillment.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2021
Property Plant And Equipment [Abstract]
Property and Equipment	4. Property and Equipment Property and equipment, net, consisted of the following (in thousands): December 31, 2021 2020 Leasehold improvements $ — $ 845 Lab and manufacturing equipment 943 1,235 Office furniture and equipment 42 157 Software 48 — Total 1,033 2,237 Less: accumulated depreciation and amortization (634 ) (1,966 ) Property and equipment, net $ 399 $ 271 Depreciation and amortization expense was approximately $0.1

Balance Sheet Details

Balance Sheet Details	12 Months Ended
	Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Balance Sheet Details	5. Balance Sheet Details Prepaid and other current assets consist of the following (in thousands): December 31, 2021 2020 Insurance $ 691 $ 671 Tenant improvement reimbursement receivable 1,057 — Prepaid rent 132 74 Pre-clinical and clinical related expenses 158 42 Prepaid materials 138 — Other 183 396 Total $ 2,359 $ 1,183 Other assets consist of the following (in thousands): December 31, 2021 2020 Insurance $ 732 $ 959 Deferred offering costs — 708 Security deposit — 250 Cell bank material 61 — Other 12 14 Total $ 805 $ 1,931 Accrued liabilities consist of the following (in thousands): December 31, 2021 2020 Current portion of finance lease liabilities $ 9 $ 8 Accrued compensation 346 639 Clinical study related expenses 103 226 Legal fees 144 52 Forward purchase contract — 290 Offering costs — 602 Other 189 63 Total $ 791 $ 1,880

Revenue

Revenue	12 Months Ended
	Dec. 31, 2021
Revenue From Contract With Customer [Abstract]
Revenue	6. Revenue The following is a summary description of the material revenue arrangements, including arrangements that generated revenues during the years ended December 31, 2021 and 2020. Allergan License Agreements 2017 Allergan Amendment In 2017, the Company entered into a series of agreements (collectively, the “2017 Allergan Agreement”), which ultimately transferred Suneva Medical, Inc.’s license and supply rights of Histogen’s cell conditioned media (“CCM”) skin care ingredient in the medical aesthetics market to Allergan Sales LLC (“Allergan”) and granted Allergan an exclusive, royalty-free, perpetual, irrevocable, non-terminable and transferable license, including the right to sublicense to third parties, to use the Company’s CCM skin care ingredient in the medical aesthetics market. The 2017 Allergan Agreement also obligated the Company to deliver CCM to Allergan (the “Supply of CCM to Allergan”) in the future as well as share with Allergan any potential future improvements to the Company’s CCM skin care ingredients identified through the Company’s research and development efforts (“Potential Future Improvements”). In consideration for the execution of the agreements, Histogen received a cash payment of $11.0 million and a potential additional payment of $5.5 million if Allergan’s net sales of products containing the Company’s CCM skin care ingredient exceeds $60.0 million in any calendar year through December 31, 2027. 2019 Allergan Amendment In March 2019, Histogen entered into a separate agreement with Allergan (the “2019 Allergan Amendment”) to amend the 2017 Allergan Agreement in exchange for a one-time payment of $7.5 million to the Company. The agreement broadened Allergan’s license rights, expanding Allergan’s access to certain sales channels where its products incorporating the CCM ingredient can be sold. Specifically, the license was broadened to provide Allergan the exclusive right to sell through the “Amazon Professional” website, or any website or digital platform owned or licensed by Allergan or under the Allergan brand name, and non-exclusive rights to sell on other websites and through brick-and-mortar medical spas and wellness centers (excluding websites and brick-and-mortar stores of luxury brands). The Company evaluated the 2019 Allergan Amendment under ASC 606 and concluded that Allergan continues to be a customer and that the expanded license is distinct from the 2017 Allergan Agreement. The Company determined the expanded license under the 2019 Allergan Amendment to be functional intellectual property as Allergan has the right to utilize the Company’s CCM skin care ingredient, and that ingredient is functional to Allergan at the time the Company transferred the expanded license. The standalone selling price of the expanded license was not readily observable since the Company has not yet established a price for this expanded license and the expanded license has not been sold on a standalone basis to any customer. The Company accounted for the 2019 Allergan Amendment as a modification to the 2017 Allergan Agreement. The contract modification was accounted for as if the 2017 Allergan Agreement had been terminated and the new contract included the expanded license as well as the remaining performance obligations that arose from the 2017 Allergan Agreement related to the Supply of CCM to Allergan and Potential Future Improvements. The total transaction price for the new contract included the $7.5 million from the 2019 Allergan Amendment as well as the amounts deferred as of the 2019 Allergan Amendment execution date for each the Supply of CCM to Allergan and Potential Future Improvements. The standalone selling price for the Supply of CCM to Allergan was determined based on comparable sales transactions. The standalone selling price of the Potential Future Improvements was estimated at the fully burdened rate of research and development employees cost plus a commercially reasonable markup. The amount of the total transaction price allocated to the expanded license was determined using the residual approach, as a result of not having a standalone selling price for the expanded license; that is, the total transaction price less the standalone selling prices of the Supply of CCM to Allergan and Potential Future Improvements. Revenue related to the Supply of CCM to Allergan has been deferred and recognized at the point in time in which deliveries are completed while revenue related to the Potential Future Improvements has been deferred and amortized ratably over the remaining 9-year life of the patent. The Supply of CCM to Allergan under the 2019 Allergan Amendment was entirely fulfilled during the year ended December 31, 2019. The $7.5 million residual amount of the total transaction price allocated to the expanded license was recognized as license revenue upon transfer of the license to Allergan in March 2019. 2020 Allergan Amendment In January 2020, the Company further amended the 2019 Allergan Amendment in exchange for a one-time payment of $1.0 million to the Company (the “2020 Allergan Amendment”). The 2020 Allergan Amendment further broadened Allergan’s exclusive and non-exclusive license rights to include products used for or in connection with microdermabrasion. In addition, the Company agreed to provide Allergan with an additional 200 kilograms of CCM (the “Additional Supply of CCM to Allergan”). The Company evaluated the 2020 Allergan Amendment under ASC 606 and concluded that Allergan continues to be a customer and that the expanded license is distinct from the 2019 Allergan Amendment. The Company determined the expanded license under the 2020 Allergan Amendment to be functional intellectual property as Allergan has the right to utilize the Company’s CCM skin care ingredient, and that ingredient is functional to Allergan at the time the Company transferred the expanded license. The standalone selling price of the expanded license was not readily observable since the Company has not yet established a price for this expanded license and the expanded license has not been sold on a standalone basis to any customer. The Company accounted for the 2020 Allergan Amendment as a modification to the 2019 Allergan Amendment (which had modified the 2017 Allergan Agreement, as noted above). The contract modification was accounted for as if the 2019 Allergan Amendment had been terminated and the new contract included the expanded license and Additional Supply of CCM to Allergan, as well as the remaining performance obligation related to Potential Future Improvements. The total transaction price for the new contract included the $1.0 million from the 2020 Allergan Amendment, the future payment for the Additional Supply of CCM to Allergan, as well as the amounts deferred as of the 2020 Allergan Amendment execution date for Potential Future Improvements. The standalone selling price for the Additional Supply of CCM to Allergan was determined using the observable inputs of historical comparable sales transactions, including the margin from such sales. The Company also considered its reduced expected cost of satisfying this performance obligation based on the current efficiencies within its CCM manufacturing processes. Due to significant efficiencies in the Company’s CCM manufacturing processes, the forecasted cost of CCM production has decreased, while the applied margin was determined by comparison to similar sales transactions in prior years. The standalone selling price of the Potential Future Improvements was estimated at the fully burdened rate of research and development employees cost plus a commercially reasonable markup. The amount of the total transaction price allocated to the expanded license was determined using the residual approach, as a result of not having a standalone selling price for the expanded license; that is, the total transaction price less the standalone selling prices of the Additional Supply of CCM to Allergan and Potential Future Improvements. Revenue related to the Additional Supply of CCM to Allergan has been deferred and will be recognized at the point in time in which deliveries are completed. Revenue related to the Additional Supply of CCM to Allergan was $0.3 million ($28 thousand of which was previously deferred), during the year ended December 31, 2021. All deliveries of Additional Supply of CCM to Allergan have been completed as of March 31, 2021. Revenue related to the Potential Future Improvements has been deferred and amortized ratably over the remaining 9-year life of the patent, for which $19 thousand of previously deferred revenue was recognized in revenue during each of the years ended December 31, 2021 and 2020. The $0.9 million residual amount of the total transaction price allocated to the expanded license was recognized as license revenue upon transfer of the license to Allergan in January 2020. In August 2021, unrelated to the Allergan Agreements, the Company agreed to a sale of CCM under a purchase order with Allergan. The CCM sold to Allergan was initially manufactured by the Company for research and development purposes in support of its product candidates. In September 2021, the Company recognized $0.6 million of product revenue related to the sale. The Company does not have any additional purchase orders with Allergan for fulfillment. Remaining Performance Obligations and Deferred Revenue The remaining performance obligations are the Company’s obligations to (1) deliver Additional Supply of CCM to Allergan and (2) share with Allergan any Potential Future Improvements to CCM identified through the Company’s research and development efforts. Deferred revenue recorded for the Additional Supply of CCM to Allergan was $0 and $28 thousand as of December 31, 2021 and 2020, respectively, while deferred revenue recorded for the Potential Future Improvements was $0.1 million as of December 31, 2021 and 2020. Deferred revenue is classified in current liabilities when the Company’s obligations to supply CCM or provide research for Potential Future Improvements are expected to be satisfied within twelve months of the balance sheet date. Grant Revenue In March 2017, the National Science Foundation, a government agency, awarded the Company a research and development grant to develop a novel wound dressing for infection control and tissue regeneration. Grant revenue recognized was $0.1 million and $0 for the years ended December 31, 2021 and 2020, respectively. As of March 31, 2021, the Company had completed all obligations under the NSF development grant and, as such, no longer generates any revenues in connection with the research and development grant. Professional Services Revenue The Company recognizes revenue for professional services which are based upon negotiated rates with the counterparty and are nonrefundable. Professional services fees are recognized as revenue over time as the underlying services are performed. Professional services revenue related to the Company’s assistance in establishing Allergan’s alternative manufacturing facility was $0 and $0.3 million for the years ended December 31, 2021 and 2020, respectively. Amerimmune Collaborative Development and Commercialization Agreement In October 2020, the Company entered into a Collaborative Development and Commercialization Agreement (“the Collaborative Agreement”) with Amerimmune to jointly develop emricasan for the potential treatment of COVID-19. The FDA approved an investigational new drug application (IND) to initiate a Phase 1 study of emricasan in mild COVID-19 patients to assess safety and tolerability in 2020. Under the Collaborative Agreement, during the agreed upon research term, Amerimmune, at its own expense and in collaboration with the Company, is required to use commercially reasonable efforts to lead the development activities for emricasan, limited to the treatment of COVID-19. Pursuant to the terms of the Collaborative Agreement, each party shall retain ownership of their legacy intellectual property and responsibility for ongoing patent application prosecution and maintenance costs, and will jointly own any intellectual property developed during the term of the agreement. In addition, the Company granted Amerimmune an exclusive option, subject to terms and conditions including completion of a Phase 2 clinical trial by Amerimmune during the research term, to obtain an exclusive license that, if granted by the Company, allows Amerimmune alone, or in conjunction with one or more strategic partners, to use its commercially reasonable efforts to develop, manufacture, and commercialize emricasan and other caspase modulators, including CTS-2090 and CTS-2096, and the Company will share the profits equally with Amerimmune. No consideration will be transferred to the Company until profits, as defined in the Amerimmune Agreement, are generated by Amerimmune from developing or commercializing products. The Company identified multiple promises to deliver goods and services, which include at the inception of the agreement: (i) a license to technology and patents, information, and know-how; (ii) supply of emricasan and (iii) collaboration, including the Company’s participation in a Joint Development Committee and Joint Partnering Committee. At inception and through December 31, 2021, the Company identified one performance obligation for all the deliverables under the Amerimmune Agreement since the delivered elements are either not capable of being distinct or are not distinct within the context of the contract. No upfront consideration was exchanged between the parties and any consideration received will be dependent on the successful execution of a qualifying strategic partnership, as defined, on the successful commercialization of emricasan, or upon a change in control of Amerimmune, as defined. Although the Company will recognize revenue upon the occurrence of one of these events, no such events have occurred as of December 31, 2021. On January 19, 2022, the Company provided a notice of material breach in connection with Amerimmune’s non-performance under the Collaborative Agreement and, on March 3, 2022, filed a demand for arbitration (“Arbitration Demand”) (refer to Note 14 for further information).

Merger

Merger	12 Months Ended
	Dec. 31, 2021
Asset Acquisition [Abstract]
Merger	7. Merger The Merger, which closed on May 26, 2020, was accounted for as a reverse asset acquisition pursuant to Topic 805, Clarifying the Definition of a Business The total purchase price paid in the Merger has been allocated to the net assets acquired and liabilities assumed based on their fair values as of the completion of the Merger. The following summarizes the purchase price paid in the Merger (in thousands, except share and per share amounts): Number of shares of the combined organization owned by the Company’s Pre-Merger stockholders 3,394,299 Multiplied by the fair value per share of Conatus common stock (1) $ 5.56 Fair value of consideration issued to effect the Merger $ 18,872 Transaction costs 1,817 Purchase price $ 20,689 (1) Based on the last reported sale price of the Company’s common stock on the Nasdaq Capital Market on May 26, 2020, the closing date of the Merger, and gives effect to the Reverse Stock Split. The allocation of the purchase price is as follows (in thousands): Cash acquired $ 12,835 Net assets acquired 710 Acquired IPR&D (2) 7,144 Purchase price $ 20,689 (2) Represents the research and development projects of Conatus which were in-process, but not yet completed. This consists primarily of Conatus’ emricasan product candidate. Current accounting standards require that the fair value of IPR&D projects acquired in an asset acquisition with no alternative future use be allocated a portion of the consideration transferred and charged to expense on the acquisition date. The acquired assets did not have outputs or employees.

Debt

Debt	12 Months Ended
	Dec. 31, 2021
Debt Disclosure [Abstract]
Debt	8. Debt Paycheck Protection Program Loan In April 2020, Private Histogen applied for and received loan proceeds in the amount of $0.5 million (the “PPP Loan”) under the PPP as government aid for payroll, rent and utilities. The application for these funds required the Company to, in good faith, certify that the current economic uncertainty made the loan request necessary to support the ongoing operations of the Company. This certification further required the Company to take into account its current business activity and its ability to access other sources of liquidity sufficient to support ongoing operations in a manner that is not significantly detrimental to the business. The certification made by the Company did not contain any objective criteria and is subject to interpretation. Based in part on the Company’s assessment of other sources of liquidity, the uncertainty associated with future revenues created by the COVID-19 pandemic and related governmental responses, and the going concern uncertainty reflected in the Company’s consolidated financial statements as of December 31, 2019, the Company believed in good faith that it met the eligibility requirements for the PPP Loan. If, despite the good-faith belief that given the Company’s circumstances all eligibility requirements for the PPP Loan were satisfied, it is later determined that the Company had violated any applicable laws or regulations or it is otherwise determined that the Company was ineligible to receive the PPP Loan, it may be required to repay the PPP Loan in its entirety and/or be subject to additional penalties and potential liabilities. On June 5, 2020, the Paycheck Protection Program Flexibility Act was signed into law, extending the PPP Loan forgiveness period from eight weeks 24 weeks On March 8, 2021 the Company applied for PPP loan forgiveness with its lender and subsequently received approval from the lender on April 2, 2021. The Company, in good faith, believes it maintained compliance with the requirements of the PPP. On May 21, 2021, the Small Business Administration granted its forgiveness of the PPP Loan, including principal and accrued interest, of $0.5 million. The gain on forgiveness is reported as a component of other income on the accompanying consolidated statement of operations. Financed Insurance Premiums In June 2020, the Company entered into an agreement to finance $0.9 million of its annual insurance premiums

Stockholders_ Equity

Stockholders’ Equity	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Stockholders’ Equity	9. Stockholders’ Equity Common Stock Sales of Common Stock November 2020 Offering In November 2020, the Company completed a registered direct offering (the “November 2020 Offering”) of an aggregate of 2,522,784 shares of common stock, together with accompanying warrants to purchase up to an aggregate of 1,892,088 shares of common stock, at an offering price of $1.78375 per share and accompanying warrant. The common stock was sold in the offering with a warrant that permits the investor to purchase 75% of the number of shares of the Company’s common stock purchased by the investor. The warrants have an exercise price of $1.70 per share, are immediately exercisable, and expire five and a half (5.5) years following the date of issuance. Placement agent warrants were issued to purchase up to 126,139 shares of common stock, are immediately exercisable for an exercise price of $2.2297, and expire on November 11, 2025. The Company received gross proceeds of $4.5 million and incurred placement agent’s fees and other offering expenses of approximately $0.9 million. The placement agent warrants, which are recorded as a component of stockholders’ equity, were valued at an aggregate $0.1 million using the Black-Scholes option pricing model based on the following assumptions: expected volatility of 79.6%, risk-free interest rate of 0.41%, expected dividend yield of 0% and an expected term of 5.0 years. As of December 31, 2021, no warrants have been exercised. As of December 31, 2021, the Company had 1,892,088 shares and 126,139 shares of common stock reserved for issuance pursuant to the warrants and placement agent’s warrants, respectively, issued by the Company in the November 2020 Offering, at an exercise price of $1.78375 per share and $2.2297 per share, respectively. January 2021 Offering In January 2021, the Company completed an S-1 offering (the “January 2021 Offering”) of an aggregate of 11,600,000 shares of common stock, prefunded warrants to purchase up to 2,400,000 shares of its common stock, and common stock warrants to purchase up to an aggregate of 14,000,000 shares of its common stock. To the extent that an investor determines, at their sole discretion, that they would beneficially own in excess of the Beneficial Ownership Limitations (or as such investor may otherwise choose), in lieu of purchasing shares of Common Stock and Common Warrants, such investor may elect to purchase Pre-Funded Warrants and Common Warrants at the Pre-Funded Purchase Price in lieu of the shares of Common Stock and Common Warrants in such a manner to result in the same aggregate purchase price being paid by such investor to the Company. The combined purchase price of one share of common stock and the accompanying common stock warrant was $1.00, and the combined purchase price of one pre-funded warrant and accompanying common stock warrant was $0.9999. The common stock warrants are exercisable for five years at an exercise price of $1.00 per share. The pre-funded warrants are immediately exercisable at an exercise price of $0.0001 per share and may be exercised at any time until all of the prefunded warrants are exercised in full. Placement agent warrants were issued to purchase up to 700,000 shares of common stock, are immediately exercisable for an exercise price of $1.25, and are exercisable for five years following the date of issuance. The Company received gross proceeds of $14.0 million and incurred placement agent’s fees and other offering expenses of approximately $1.9 million. The placement agent warrants, which are recorded as a component of stockholders’ equity, were valued at an aggregate $0.3 million using the Black-Scholes option pricing model based on the following assumptions: expected volatility of 80.08%, risk-free interest rate of 0.38%, expected dividend yield of 0% and an expected term of 5.0 years. As of December 31, 2021, a total of 6,721,200 warrants issued in the January 2021 Offering to purchase shares of common stock have been exercised and the Company issued 6,721,200 shares of its common stock. The Company received gross proceeds of approximately $6.8 million. As of December 31, 2021, the Company had 7,751,300 shares and 227,500 shares of common stock reserved for issuance pursuant to the warrants and placement agent’s warrants, respectively, issued by the Company in the January 2021 Offering, at an exercise price of $1.00 per share and $1.25 per share, respectively. June 2021 Offering In June 2021, the Company completed a registered direct offering (the “June 2021 Offering”) of an aggregate of 5,977,300 shares of common stock, together with accompanying warrants to purchase up to an aggregate of 4,781,840 shares of common stock, at a public offering price of $1.10 per share. The accompanying warrants permit the investor to purchase additional shares equal to 80% of the number of shares of the Company’s common stock purchased by the investor. The warrants have an exercise price of $1.00 per share, are immediately exercisable, and expire five and a half (5.5) years following the date of issuance. In addition, the Company’s placement agent was issued compensatory warrants equal to 5.0%, or 298,865 shares, of the aggregate number of shares of common stock sold in the offering, which are immediately exercisable for an exercise price of $1.375 and expire five (5) years following the date of issuance on June 7, 2026. The Company received gross proceeds of $6.6 million and incurred cash-based placement agent fees and other offering expenses of approximately $0.9 million. The placement agent warrants, which are recorded as a component of stockholders’ equity, were valued at an aggregate $0.2 million using the Black-Scholes option pricing model based on the following assumptions: expected volatility of 80.15%, risk-free interest rate of 0.77%, expected dividend yield of 0% and an expected term of 5.0 years. As of December 31, 2021, no warrants associated with the June 2021 Offering have been exercised. As of December 31, 2021, the Company had 4,781,840 shares and 298,865 shares of common stock reserved for issuance pursuant to the warrants and placement agent’s warrants, respectively, issued by the Company in the June 2021 Offering, at an exercise price of $1.00 per share and $1.375 per share, respectively. December 2021 Offering In December 2021, the Company completed a registered direct offering (the “December 2021 Offering”) of an aggregate of 8,235,297 shares of common stock and 8,235,297 warrants to purchase up to 8,235,297 shares of common stock, at a public offering price of $0.425 per share. The accompanying warrants permit the investor to purchase additional shares equal to the same number of shares of the Company’s common stock purchased by the investor. The warrants have an exercise price of $0.425 per share, may be exercised any time on or after 6 months and one (1) day after the issuance date, and expire five and a half (5.5) years following the date of issuance. In addition, the Company’s placement agent was issued compensatory warrants equal to 5.0%, or 411,765 shares, of the aggregate number of shares of common stock sold in the offering, which are immediately exercisable for an exercise price of $0.5313 and expire five and a half (5.5) years following the date of issuance on June 21, 2027. The Company received gross proceeds of $3.5 million and incurred cash-based placement agent fees and other offering expenses of approximately $0.5 million. The placement agent warrants, which are recorded as a component of stockholders’ equity, were valued at an aggregate $0.1 million using the Black-Scholes option pricing model based on the following assumptions: expected volatility of 79.81%, risk-free interest rate of 1.21%, expected dividend yield of 0% and an expected term of 5.5 years. As of December 31, 2021, no warrants associated with the December 2021 Offering have been exercised. As of December 31, 2021, the Company had 8,235,297 shares and 411,765 shares of common stock reserved for issuance pursuant to the warrants and placement agent’s warrants, respectively, issued by the Company in the December 2021 Offering, at an exercise price of $0.425 per share and $0.5313 per share, respectively. At Market Issuance Sales Agreement with Stifel, Nicolaus & Company, Incorporated Prior to the Merger, Conatus entered into an At Market Issuance Sales Agreement (the “Sales Agreement”) with Stifel, Nicolaus & Company, Incorporated (“Stifel”), pursuant to which the Conatus could sell from time to time, at its option, up to an aggregate of $35.0 million of shares of its common stock through Stifel, as sales agent. In July 2020, the Company terminated the Sales Agreement with Stifel with no shares having been issued pursuant to the Sales Agreement. Common Stock Purchase Agreement with Lincoln Park In July 2020, the Company entered into a common stock purchase agreement (the “2020 Purchase Agreement”) with Lincoln Park which provides that, upon the terms and subject to the conditions and limitations in the 2020 Purchase Agreement, Lincoln Park is committed to purchase up to an aggregate of $10.0 million of shares of the Company’s common stock at the Company’s request from time to time during a 24 month period that began in July 2020 and at prices based on the market price of the Company’s common stock at the time of each sale. Upon execution of the 2020 Purchase Agreement, the Company sold 328,516 shares of common stock at $3.04399 per share to Lincoln Park for gross proceeds of $1.0 million. During the year ended December 31, 2020, the Company sold an additional 300,000 shares of common stock to Lincoln Park for gross proceeds of approximately $0.5 million. As of December 31, 2021, approximately $8.5 million of common stock remains available for sale under the 2020 Purchase Agreement, subject to limitations on the amount of securities the Company may sell under its effective registration statement on Form S-3 within any 12-month period and subject to certain conditions included in the 2020 Purchase Agreement. In addition, in consideration for entering into the 2020 Purchase Agreement and concurrently with the execution of the 2020 Purchase Agreement, the Company issued 66,964 shares of its common stock to Lincoln Park. Common Stock Warrants In 2016, Private Histogen issued warrants to purchase common stock as consideration for settlement of prior liability claims. The warrants for the purchase of up to 3,583 common shares at an exercise price of $23.08 per share expired on July 31, 2021. In addition, at December 31, 2021 and 2020, warrants to purchase 1,346 shares of common stock at an exercise price of $74.30 per share remain outstanding that were issued by Conatus in connection with obtaining financing in 2016. These warrants expire on July 3, 2023. See warrant discussion above in connection with sales of common stock during the years ended December 31, 2021 and 2020, respectively. Stock-Based Compensation Equity Incentive Plans On December 18, 2017, Private Histogen established the Histogen Inc. 2017 Stock Plan (the “2017 Plan”). Under the 2017 Plan, Private Histogen was authorized to issue a maximum aggregate of 837,208 shares of common stock with adjustments for unissued or forfeited shares under the predecessor plan (the Histogen Inc. 2007 Stock Plan). In April 2019, Private Histogen amended the 2017 Plan, which increased the number of common stock available for grants by 326,711 shares. The 2017 Plan permitted the issuance of incentive stock options (“ISOs”), non-statutory stock options (“NSOs”) and Stock Purchase Rights. NSOs could be granted to employees, directors or consultants, while ISOs could be granted only to employees. Options granted vest over a maximum period of four years and expire ten years from the date of grant. In connection with the closing of the Merger, no further awards will be made under the 2017 Plan. In May 2020, in connection with the closing of the Merger, the Company’s stockholders approved the Company’s 2020 Incentive Award Plan (the “2020 Plan”). The maximum number of shares of the Company’s common stock available for issuance under the 2020 Plan equals the sum of (a) 850,000 shares; (b) any shares of common stock of the Company which are subject to awards under the Conatus 2013 Equity Incentive Plan (the “Conatus 2013 Plan”) as of the effective date of the 2020 Plan which become available for issuance under the 2020 Plan after such date in accordance with its terms; and (c) an annual increase on the first day of each calendar year beginning with the January 1 of the calendar year following the effectiveness of the 2020 Plan and ending with the last January 1 during the initial ten year term of the 2020 Plan, equal to the lesser of (i) five percent of the number of shares of the Company’s common stock outstanding (on an as-converted basis) on the final day of the immediately preceding calendar year, and (ii) such lesser number of shares of the Company’s common stock as determined by the Company’s board of directors. Additionally, in connection with the closing of the Merger, no further awards will be made under the Conatus 2013 Plan. As of December 31, 2021, 97,930 fully vested options remain outstanding under the Conatus 2013 Plan with a weighted average exercise price of $42.90 per share. The following summarizes activity related to the Company’s stock options under the 2017 Plan and the 2020 Plan for the year ended December 31, 2021: Options Outstanding Weighted- average Exercise Price Weighted- average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2020 1,592,187 $ 3.06 6.20 $ 108 Granted 1,602,150 0.92 Cancelled / Forfeited (966,046 ) 2.27 Outstanding at December 31, 2021 2,228,291 1.88 6.78 $ — Vested and exercisable at December 31, 2021 1,202,520 $ 2.50 4.56 $ — Chief Executive Officer Stock Options On January 24, 2019, the Company issued 485,178 stock options to its newly appointed Chief Executive Officer. In accordance with the original award agreement, 40% of the options would vest immediately upon an initial public offering or 45 days following a change in control, as defined in the award agreement, while the remaining 60% are subject to vesting, of which 25% vest on the first anniversary of the grant date and then ratably over the remaining 36 months. On January 28, 2020, the award agreement was amended, which became effective upon the close of the Merger in May 2020, whereby the 40% of stock options (“Liquidity Option Shares”) subject to vesting upon an initial public offering or 45 days following a change in control will now vest immediately upon meeting certain performance and market condition-based criteria. The vesting of the Liquidity Option Shares is divided into four separate tranches, each vesting 25% of the Liquidity Option Shares, upon: (1) the closing of the proposed merger with Conatus; (2) the date that the market capitalization of the Company exceeds $200.0 million; (3) the date that the market capitalization of the Company exceeds $275.0 million, and; (4) the date that the market capitalization of the Company exceeds $300.0 million. Each vesting tranche represents a unique derived service period and therefore stock-based compensation expense for each vesting tranche is recognized on a straight-line basis over its respective derived service period. Additionally, in the event that the Chief Executive Officer’s employment with the Company is terminated without cause or he resigns for good reason, an additional portion of the stock options award will vest equal to the number of such options which would have vested in the 12 months following the date of such termination. On May 26, 2020, in connection with the closing of the Merger, 48,517 options of the Liquidity Option Shares became fully vested as the performance condition was achieved. In November 2021, the Company’s President and Chief Executive Officer voluntarily resigned. No further stock-based compensation expense related to the market-based options will be recognized. For the year ended December 31, 2020, the Company recognized $0.2 million in total compensation related to the performance and market-based options. Board of Directors and Employee Stock Options In March 2021, in conjunction with a former Board Member’s voluntary resignation, the Company modified share-based payment awards by accelerating the vesting of all awards that were unvested at the time of his voluntary resignation and by extending the exercise period through December 31, 2021. As a result of the modification, the Company recorded an immaterial amount of additional stock-based compensation expense during the year ended December 31, 2021. As of December 31, 2021, the awards expired unexercised. In June 2021, in conjunction with a former employees’ voluntary resignation, the Company modified share-based payment awards by accelerating the vesting of all awards that were unvested at the time of the voluntary resignation and by extending the exercise period through August 29, 2023. As a result of the modification, the Company recorded $ 0.1 million of additional stock-based compensation expense during the year ended December 31 , 2021. Valuation of Stock Option Awards The following weighted-average assumptions were used to calculate the fair value of awards granted to employees, non-employees and directors: Years Ended December 31, 2021 2020 Expected volatility 78.7 % 76.6 % Risk-free interest rate 0.9 % 0.5 % Expected option life (in years) 6.08 6.25 Expected dividend yield 0.0 % 0.0 % Restricted Stock Units On November 8, 2021, the Company granted 468,449 restricted stock units to the Company’s Interim Chief Executive Officer, Chief Financial Officer, and Senior Vice President of Technical Operations. The fair value of the RSUs was $0.73 per share, which was the closing market price of the Company’s common stock on the date of grant. The RSUs vest in full upon the earlier of (1) 12 months following the grant date and (2) a change of control of the Company, as defined in the Company’s 2020 Plan, and subject to continued service to the Company. In addition, the RSUs awarded to the Company’s Interim Chief Executive Officer are further accelerated in full upon the hiring of a permanent Chief Executive Officer. Stock-based Compensation Expense The compensation cost that has been included in the Company’s consolidated statements of operations for all stock-based compensation arrangements is detailed as follows (in thousands): Years Ended December 31, 2021 2020 General and administrative $ 520 $ 588 Research and development 184 10 Cost of product revenues — 20 Total $ 704 $ 618 As of December 31, 2021, total unrecognized compensation cost related to unvested options and RSUs was approximately $1.0 million which is expected to be recognized over a weighted-average period of 2.3 years. Common Stock Reserved for Future Issuance Common stock reserved for future issuance is as follows: December 31, 2021 2020 Common stock warrants 23,726,140 2,023,156 Common stock options issued and outstanding 2,326,221 1,708,278 Common stock available for issuance under stock plans 46,189 513,141 26,098,550 4,244,575

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. Commitments and Contingencies Leases In January 2020, Private Histogen entered into a long-term operating lease with San Diego Sycamore, LLC (“Sycamore”) for its headquarters that includes office and laboratory space. The lease commenced on March 1, 2020 and expires on August 31, 2031, with no options to renew or extend. The lease was accounted for as a modification of Private Histogen’s existing lease with Sycamore as the lease agreement did not grant Private Histogen an additional right-of-use asset. The terms of the lease agreement include six months of rent abatement at lease commencement and a tenant improvement allowance of up to $2.2 million. The tenant improvements are required to be permanently affixed to the leased office and laboratory space and do not constitute leasehold improvements of the Company. During the construction period of the tenant improvements, the lease agreement requires the Company to relocate its operations to a similar Sycamore property whereby monthly rent is substantially reduced for the duration of the construction period. The lease is subject to additional variable charges for common area maintenance, insurance, taxes and other operating costs. At lease commencement, the Company recognized a right-of-use asset and operating lease liability totaling approximately $4.5 million. The Company used a discount rate based on its estimated incremental borrowing rate to determine the right-of-use asset and operating lease liability amounts to be recognized. The Company determined its incremental borrowing rate based on the term and lease payments of the new operating lease and what it would normally pay to borrow, on a collateralized basis, over a similar term for an amount equal to the lease payments. collateral for a letter of credit issued to be held throughout the lease term. This security deposit is shown as restricted cash on the accompanying consolidated balance sheets. In June 2021, the Company entered into the First Amendment to Lease (the “Amendment”). Pursuant to the Amendment, among other things, the Company and Sycamore agreed (i) to substitute the temporary premises, (ii) to delay the start of construction and the timing of the Company’s relocation to the replacement temporary premises, (iii) to increase the tenant improvement allowance from $2.2 million to $2.3 million, (iv) to increase the letter of credit amount from $0.3 million to $0.4 million upon commencement of the tenant improvements, and (v) to review potential subsequent reductions to the security deposit and related letter of credit requirement at certain time intervals along the lease term provided that the Company is not in default. As a result of the modification, the lease liability was remeasured using the incremental borrowing rate at the modification date and a corresponding reduction of $0.3 million was recorded to both the lease liability and right-of-use-asset. In connection with the closing of the Merger, the Company assumed Conatus’ noncancelable operating lease agreement, as amended, for certain office space with a lease term that expired on September 30, 2020. Upon close of the Merger, the Company recognized a right-of-use asset and operating lease liability in the amount of $0.1 million and $0.2 million, respectively, related to the Conatus lease. Prior to the Merger, Conatus entered into a sub-lease agreement with a third party to lease the whole office space for the remainder of the lease term. Sublease income was not material for all periods presented. The Company leases certain office equipment that is classified as a finance lease. As of December 31, 2021, the weighted-average remaining term of the Company’s operating lease and finance lease was approximately 10 years and two years, respectively. The Company recognizes r ight-of-use assets and lease liabilities at the lease commencement date based on the present value of future minimum lease payments over the lease term. The discount rate used to determine the present value of the lease payments is the rate implicit in the lease unless that rate cannot be readily determined, in which case, the Company utilizes its incremental borrowing rate in determining the present value of the future minimum lease payments. At the inception dates of the leases, the weighted-average discount rate for the Company’s operating and finance lease was 12.2% and 10.0%, respectively. The Company does not record leases with an initial term of 12 months or less on the consolidated balance sheets. Expense for these short-term leases is recognized on a straight-line basis over the lease term. The Company has elected the practical expedient to combine lease and non-lease components into a single component for all classes of underlying assets. The Company’s lease assets and lease liabilities were as follows (in thousands): December 31, Balance Sheet Classification 2021 2020 Assets Operating lease Right-of-use asset $ 4,432 $ 4,411 Finance lease Property and equipment, net 20 28 Total lease assets $ 4,452 $ 4,439 Liabilities Current Operating lease liability Current portion of lease liability $ 127 $ 28 Finance lease liability Accrued liabilities 9 8 Total current liabilities 136 36 Noncurrent Operating lease liability Noncurrent portion of lease liability 4,617 4,806 Finance lease liability Other liabilities 14 22 Total noncurrent liabilities 4,631 4,828 Total lease liabilities $ 4,767 $ 4,864 The components of lease expense were as follows (in thousands): Years Ended December 31, Statement of Operations Classification 2021 2020 Operating lease cost: Cost of product revenue $ — $ 106 Research and development 210 158 General and administrative 428 597 Total operating lease cost $ 638 $ 861 Finance lease cost: Amortization of right-of-use assets Property and equipment, net $ 9 $ 7 Interest on lease liabilities Interest expense 3 3 Total finance lease cost $ 12 $ 10 Supplemental cash flow information related to leases were as follows (in thousands): Years Ended December 31, 2021 2020 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating lease $ 111 $ 299 Operating cash flows from finance lease 3 3 Financing cash flows from finance lease 9 7 Right-of-use asset obtained in exchange for operating lease liability $ — $ 4,481 At December 31, 2021, future minimum payments of lease liabilities were as follows (in thousands): Operating Lease Finance Lease 2022 $ 695 11 2023 780 11 2024 803 4 2025 827 — Thereafter 5,183 — Total minimum lease payments 8,288 26 Less: imputed interest (3,544 ) (3 ) Total future minimum lease payments 4,744 23 Less: current obligations under leases (127 ) (9 ) Noncurrent lease obligations $ 4,617 $ 14 PUR Settlement In April 2019, Private Histogen entered into a Settlement, Release and Termination Agreement (“PUR Settlement”) with PUR Biologics, LLC and its members which terminated the License, Supply and Operating Agreements between Private Histogen and PUR, eliminated Private Histogen’s membership interest in PUR and returned all in-process research and development assets to Private Histogen (the “Development Assets”). The agreement also provided indemnifications and complete releases by and among the parties. The acquisition of the Development Assets was accounted for as an asset acquisition in accordance with ASC 805-50-50, Acquisition of Assets Rather than a Business As consideration for the reacquisition of the Development Assets, Private Histogen compensated PUR with both equity and cash components, including 167,323 shares of Series D convertible preferred stock with a fair value of $1.75 million and a potential cash payout of up to $6.25 million (the “Cap Amount”). Private Histogen paid PUR $0.5 million in upfront cash, forgave approximately $22 thousand of accounts receivable owed by PUR to Private Histogen, and settled an outstanding payable of PUR of approximately $23 thousand owed to a third party. The Company is also obligated to make milestone and royalty payments, including (a) a $0.4 million payment upon the unconditional acceptance and approval of a New Drug Application or Pre-Market Approval Application by the FDA related to the Development Assets, (b) a $0.4 million commercialization milestone upon reaching gross sales (by the Company or licensee) of the $0.5 million of products incorporating the Development Assets, and (c) a five percent (5%) royalty on net revenues collected by Histogen from commercial sales (by the Company or licensee) of products incorporating the Development Assets. The aforementioned cash payments, along with any future milestone and royalty payments, are all applied against the Cap Amount. In accordance with authoritative guidance, amounts for the milestone and royalty payments will be recognized when it is probable that the related contingent liability has been incurred and the amount owed is reasonably estimated. No amounts for the milestone and royalty payments have been recorded during the years ended December 31, 2021 and 2020. Litigation and Legal Matters The Company is subject to claims and legal proceedings that arise in the ordinary course of business. Such matters are inherently uncertain, and there can be no guarantee that the outcome of any such matter will be decided favorably to the Company or that the resolution of any such matter will not have a material adverse effect upon the Company’s consolidated financial statements. The Company accrues a liability for such matters when it is probable that future expenditures will be made, and such expenditures can be reasonably estimated. As of December 31, 2021, no accruals have been made and no liability recognized related to commitments and contingencies.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Income Taxes	11. Income Taxes The reconciliation of income taxes computed using the statutory U.S. income tax rate and the provision is as follows (in thousands): Years Ended December 31, 2021 2020 Tax computed at federal statutory rate $ (3,152 ) $ (3,920 ) State tax, net of federal tax benefits (908 ) (34 ) Tax credits (325 ) 43 Acquired intangible property — 1,513 Valuation allowance 5,320 2,096 PPP loan forgiveness (126 ) — Other (809 ) 302 Provision for income taxes $ — $ — Significant components of the Company’s net deferred tax assets are as follows (in thousands): Years Ended December 31, 2021 2020 Deferred tax assets: Tax loss carryforward $ 18,041 $ 13,519 R&D credits and other tax credits 1,834 1,498 Stock-based compensation 152 82 Compensation 58 135 Deferred revenue 5 10 Lease liability 1,283 1,024 Capitalized research and development 2,607 2,074 Other 80 133 Total deferred tax assets 24,060 18,475 Less: valuation allowance (22,861 ) (17,541 ) Deferred tax assets, net 1,199 934 Deferred tax liability: Right-of-use assets (1,199 ) (934 ) Net deferred tax assets $ — $ — The Company records a valuation allowance against deferred tax assets to the extent that it is more likely than not that some portion, or all, the deferred tax assets will not be realized. Due to the substantial doubt related to the Company’s ability to utilize its deferred tax assets, the Company recorded a valuation allowance against the deferred tax assets. The change in the valuation allowance is an increase of $5.3 million and $4.2 million for the years ended December 31, 2021 and 2020, respectively. As of December 31, 2021, the Company had federal and California net operating loss (“NOL”) carryforwards of approximately $66.3 million and $57.4 million, respectively. Additionally, as of December 31, 2021, Adaptive Biologix has federal and state net operating losses of $0.4 million each. The Company has federal net operating loss carryforwards of $34.0 million that are not subject to expiration. No California NOLs expired in 2021. As of December 31, 2021 , the Company had federal and California research and development ( “ R&D ” ) credit carryforwards of approximately $ 1.4 million. The federal R&D tax credit carryforwards will begin to expire in 2027 unless previously utilized. The California R&D credit carryforwards will carry forward indefinitely. Under Sections 382 and 383 of the Internal Revenue Code (“IRC”), substantial changes in the Company’s ownership may limit the amount of NOL and research and development credit carryforwards that could be used annually in the future to offset taxable income. The tax benefits related to future utilization of federal and state NOL carryforwards, credit carryforwards, and other deferred tax assets may be limited or lost if cumulative changes in ownership exceeds 50% within any three-year Uncertain Tax Positions The FASB ASC Topic 740, Income Taxes The following table summarizes the activity related to our unrecognized tax benefits (in thousands): Years Ended December 31, 2021 2020 Gross unrecognized tax benefits at the beginning of the year $ 561 $ 401 Additions from tax positions taken in the current year 118 37 Additions from tax positions taken in prior years 4 128 Reductions for tax positions from prior year — (5 ) Gross unrecognized tax benefits at end of the year $ 683 $ 561 Due to the existence of the valuation allowance, future changes in the Company’s unrecognized tax benefits will not impact the Company’s effective tax rate. The Company does not anticipate that there will be a substantial change in unrecognized tax benefits within the next twelve months. The Company has not recognized any interest and penalties related to income taxes in the accompanying consolidated balance sheets or statements of operations. The Company is subject to taxation in the U.S. and state jurisdictions. The Company’s income tax returns for all years beginning January 1, 2018 and subsequent are still open to audit by the taxing authorities. CARES ACT On March 27, 2020, the United States enacted the Coronavirus Aid, Relief and Economic Security Act (CARES Act). The Cares Act is an emergency economic stimulus package that includes spending and tax breaks to strengthen the United States economy and fund a nationwide effort to curtail the effect of COVID-19. While the CARES Act provides sweeping tax changes in response to the COVID-19 pandemic, some of the more- significant provisions which are expected to impact the Company’s consolidated financial statements include removal of certain limitations on utilization of net operating losses, increasing the loss carryback period for certain losses to five years, and increasing the ability to deduct interest expense, as well as amending certain provisions of the previously enacted Tax Cuts and Jobs Act. Due to the loss position of the U.S. entities, many provisions of the CARES Act do not impact the Company and the CARES Act did not have an impact on the Company’s income tax provision for the years ended December 31, 2021 and 2020 .

Related Parties

Related Parties	12 Months Ended
	Dec. 31, 2021
Related Party Transactions [Abstract]
Related Parties	12. Related Parties Lordship Lordship, with its predecessor entities along with its principal owner, Jonathan Jackson, have invested and been affiliated with Private Histogen since 2010. As of December 31, 2021 and 2020, Lordship controlled approximately 4.7% and 16% of the Company’s outstanding voting shares, respectively, and currently holds two Board of Director seats. In November 2012, Private Histogen entered into a Strategic Relationship Success Fee Agreement with Lordship (the “Success Fee Agreement”). The Success Fee Agreement causes certain payments to be made from the Company to Lordship equal to 1% of certain product revenues and 10% of certain license and royalty revenues. The Success Fee Agreement also stipulates that if the Company engages in a merger or sale of all or substantially all (defined as 90% or more) of its assets or equity to a third party, then the Company has the option to terminate the agreement by paying Lordship the fair market value of future payments with the minimum payment being at least equal to the most recent annual payments Lordship has received. The Success Fee Agreement was amended in August 2016, but continues to carry the same rights to certain payments. Histogen recognized an expense to Lordship for the years ended December 31, 2021 and 2020 totaling $10 thousand and $0.1 million, respectively, all of which is included in general and administrative expenses on the accompanying consolidated statements of operations. As of December 31, 2021 and 2020, there was a balance of $12 thousand and $14 thousand, respectively, paid to Lordship included as a component of other assets on the accompanying consolidated balance sheets in connection with the deferral of revenue from the Allergan license transfer agreements. Promissory Notes In April 2020, the Company entered into two promissory notes (the “Notes”), each for $0.3 million, with two stockholders, one of which was a principal owner of the Company. The Notes carried a fixed return of $25 thousand, due upon maturity. All outstanding principal and interest were due upon the earlier of (1) June 13, 2020 or (ii) 15 days following the consummation of the Merger. In June 2020, the Notes, including principal and interest, were repaid. Anti-Cancer Inc. Anti-Cancer Inc. (“Anti-Cancer”) is a small early stockholder of the Company who leased space to AB during 2016. Additionally, services were provided to AB by the principal owner of Anti-Cancer. As of December 31, 2021 and 2020, outstanding amounts owed to Anti-Cancer were $22 thousand and are included in the consolidated balance sheets.

Employee Benefit Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2021
Compensation And Retirement Disclosure [Abstract]
Employee Benefit Plans	13. Employee Benefit Plans The Company sponsors a qualified 401(k) savings plan (“401k Plan”) for all eligible employees. Participants may contribute between 1% and 100% of their eligible compensation, subject to IRS regulations. The 401k Plan provides that the Company can make discretionary contributions of 25% of the employees’ salary deferrals up to a maximum of $2,500 per each employee. No employer contributions were made under the 401k Plan for the years ended December 31, 2021 and 2020.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2021
Subsequent Events [Abstract]
Subsequent Events	14. Subsequent Events On or about February 17, 2022, two former employees, each of whom separately resigned and terminated their employment with the Company, filed a complaint in the Superior Court of California, County of San Diego against the Company, its Board of Directors, former Chief Executive Officer, as well as three individuals that are currently employed by the Company. The plaintiffs allege whistleblower status, retaliation, discrimination, unfair business practices, wrongful termination, violation of civil rights, and other California state law claims. Although the complaint lists the “Histogen Board of Directors, a business entity form unknown” as a defendant, the complaint does not specifically list the names of the board members. The Company has tendered the complaint to its liability insurer and engaged outside litigation counsel, as approved by its carrier, to defend the Company, the Board of Directors and the individuals in this matter. The Company objects to the naming of each of the defendants in this matter and deny each of the plaintiffs’ claims. The Company expect s to request an order that the plaintiffs’ claims proceed through arbitration in accordance with contractual obligations set forth in each of the plaintiff’s previously executed employment agreements with the Company. The Company believe s that the defense costs, settlement monies, damages or any other awards would be covered by the Company’s liability insurance; provided, however, insurance may not cover all claims or could exceed our insurance coverage. The Company believes that there are substantial defenses to this lawsuit and intends to vigorously defend against each of these claims. While this litigation matter is in the early stages, the Company believes the action is without merit. Nonetheless, the ultimate outcome is unknown at this time. On March 3, 2022, the Company filed a demand for arbitration (“Arbitration Demand”) with JAMS in the county of San Diego, against Amerimmune LLC (“Amerimmune”) seeking a declaratory judgment that Amerimmune has materially breached the Collaborative Agreement entered into by and between the Company and Amerimmune on October 27, 2020, and that Histogen is therefore entitled to terminate the Collaborative Agreement in accordance with its terms. The Company has further brought the Arbitration Demand for breach of contract, seeking an award of specific performance requiring Amerimmune to comply with the terms of the Agreement, which provide that, in the event of termination for material breach, all rights and licenses granted to Amerimmune by the Company shall terminate, and Amerimmune shall cease any and all development, manufacture and commercialization activities under the Agreement, and any and all rights granted by the Company to Amerimmune revert to the Company. In the event that specific performance is not awarded, the Company is pursuing in the alternative a cause of action for breach of contract, seeking an award of damages for such breach in an amount to be determined at hearing. And finally, the Company is pursuing a claim for misappropriation of trade secrets, seeking an award of damages in an amount to be determined at hearing. During the Arbitration, the Company expects Amerimmune and the Company to continue to support planning of a Phase 2 trial of emricasan for the treatment of COVID-19. In the event that the Company is successful on their claims as set forth in their Arbitration Demand and the Agreement is terminated, the Company intends to develop emricasan for COVID-19 and other infectious and inflammatory diseases independently. There can be no assurances that the Arbitration will result in the Company’s favor. If the Collaborative Agreement is not terminated and the rights granted by the Company to Amerimmune do not revert back to the Company, the Company expects that it will continue to jointly develop emricasan pursuant to the terms of the Collaborative Agreement. The ultimate outcome of this Arbitration is unknown at this time.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The consolidated financial statements include the accounts of the Company and its controlled subsidiaries, including Histogen Therapeutics, Inc., and have been prepared in accordance with accounting principles generally accepted in the United States (“GAAP”). All intercompany balances and transactions have been eliminated upon consolidation. The Company acquired Centro De Investigacion de Medicina Regenerativa, S.A. de C.V. (“CIMRESA”), a company in Mexico, during 2018 to facilitate a potential clinical development program for HST-001, or hair stimulating complex (“HSC”). This is a wholly-owned subsidiary intended to pursue registration with the COFEPRIS (Mexico equivalent to Food and Drug Administration). CIMRESA had no operational or financial activity for the years ended December 31, 2021 and 2020. The Company holds a majority interest (68%) in Adaptive Biologix, Inc. (“AB”, formerly Histogen Oncology, LLC). AB was formed to develop and market applications for the treatment of cancer. The Company consolidates AB into its consolidated financial statements.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities and the disclosure of contingent assets and liabilities and contingencies at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the periods presented. Management believes that these estimates and assumptions are reasonable, however, actual results may differ and could have a material effect on future results of operations and financial position. Though the impact of the COVID-19 pandemic to our business and operating results presents additional uncertainty, the Company continue s to use the best information available to them in their significant accounting estimates. Significant estimates and assumptions include the useful lives of property and equipment, discount rates used in recognizing contracts containing leases, unrecognized tax benefits, reserves for excess or obsolete inventory, stock-based compensation, and best estimate of standalone selling price of revenue deliverables. Actual results may materially differ from those estimates.
Variable Interest Entities	Variable Interest Entities The Company determined that AB is a variable interest entity (“VIE”) and that the Company is its primary beneficiary. The Company holds greater than 50% of the shares and has the authority to manage the business and affairs of the VIE. AB’s other shareholder does not have a controlling interest. A VIE is typically an entity for which the Company has less than a 100% equity interest but controls the decision making over the business and affairs of the entity, directs the decisions driving the economic performance of such entity and participates in the profit and losses of such an entity. The Company weighed both quantitative and qualitative information about the different risks and reward characteristics of each entity and the significance of that entity to the consolidating group in the aggregate.
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker, the Interim Chief Executive Officer, in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business as one operating segment.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash The Company considers all highly liquid investments purchased with an original maturity date of ninety days or less to be cash equivalents. Cash and cash equivalents include cash in readily available checking, money market accounts and brokerage accounts. The Company’s current restricted cash consists of cash held as collateral for a letter of credit issued as a security deposit for the lease of the Company’s headquarters and is required to be held throughout the lease term.
Risks and Uncertainties	Risks and Uncertainties Credit Risk At certain times throughout the year, the Company may maintain deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and believes it is not exposed to significant risk on its cash balances due to the financial position of the depository institutions in which those deposits are held. Customer Risk During the years ended December 31, 2021 and 2020, one customer accounted for 88% and 100% of total revenues, respectively. Accounts receivable from the customer was $0 and $0.1 million at December 31, 2021 and 2020, respectively. COVID-19 On January 30, 2020, the World Health Organization (“WHO”) announced a global health emergency because of a new strain of coronavirus originating in Wuhan, China (the “COVID-19 outbreak”) and the risks to the international community as the virus spreads globally beyond its point of origin. In March 2020, the WHO classified the COVID-19 outbreak as a pandemic, based on the rapid increase in exposure globally. The cumulative effect the associated disruptions have had, and may continue to have, an adverse impact on the Company’s business and its results of operations. The full impact of the COVID-19 outbreak continues to evolve as of the date these consolidated financial statements were available to be issued and will depend on future developments that are highly uncertain and unpredictable, including efficacy and adoption of vaccines, future resurgences of the virus and its variants, and the speed at which government restrictions are lifted. As such, it is uncertain as to the full magnitude that the pandemic will have on the Company’s financial condition, liquidity, and future results of operations. On March 27, 2020, former President Trump signed into law the Coronavirus Aid, Relief and Economic Security Act (the “CARES Act”). The CARES Act, among other things, includes provisions relating to refundable payroll tax credits, deferment of employer side social security payments, net operating loss carryback periods, alternative minimum tax credit refunds, modifications to the net interest deduction limitations, increased limitations on qualified charitable contributions and technical corrections to tax depreciation methods for qualified improvement property. The CARES Act also appropriated funds for the U.S. Small Business Administration Paycheck Protection Program (“PPP”) loans that are forgivable in certain situations to promote continued employment, as well as Economic Injury Disaster Loans to provide liquidity to small businesses harmed by COVID-19. Refer to Note 8 for further information.
Accounts Receivable	Accounts Receivable Accounts receivable are generally due within 30 days and are recorded net of the allowance for doubtful accounts, if any. Management considers all accounts receivable to be fully collectible as of December 31, 2021 and 2020, and accordingly, no provision for doubtful accounts was recorded.
Inventories	Inventories Inventories, consisting of raw materials and finished goods, are valued at the lower of cost (first-in, first-out method) or net realizable value. The Company writes down excess and obsolete inventory to its estimated net realizable value based on management’s review of inventories on hand compared to estimated future usage and sales, shelf-life and assumptions about the likelihood of obsolescence. The cost components of finished goods inventories include raw materials, direct labor and an allocation of the Company’s overhead.
Property and Equipment	Property and Equipment Property and equipment are reported net of accumulated depreciation and amortization and are comprised of office furniture and equipment, lab and manufacturing equipment, and leasehold improvements. Ordinary maintenance and repairs are charged to expense, while expenditures that extend the physical or economic life of the assets are capitalized. Furniture and all equipment are depreciated over their estimated useful lives, or five years, using the straight-line method. Software is amortized over its estimated useful lives, or three years, using the straight-line method. Leasehold improvements are amortized over their estimated useful lives and limited by the remaining term of the building lease, using the straight-line method.
Deferred Offering Costs	Deferred Offering Costs Offering costs, consisting of legal, accounting, printer and filing fees related to the public offerings are deferred and offset against proceeds from the public offering upon the closing of the offering. As of December 31, 2021, no offering costs were deferred. As of December 31, 2020, $0.7 million of deferred offering costs related to the Company’s public offering in January 2021 were recorded in the accompanying consolidated balance sheet (refer to Note 9 for further information).
Valuation of Long-Lived Assets	Valuation of Long-Lived Assets Long-lived assets to be held and used, including property and equipment, are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the assets may not be recoverable. As of December 31, 2021 and 2020, the Company has not recognized any impairment to long-lived assets.
Forward Purchase Contract	Forward Purchase Contract In 2011, Private Histogen contracted for research services from EPS Global Research Pte. Ltd. (“EPS”) to conduct clinical trials and compile data from a study that took place in 2011 and 2013. The unpaid amount due for the services was approximately $0.3 million. In 2017, Private Histogen and EPS entered into a Debt Settlement and Conversion Agreement (“Settlement Agreement”) whereby Private Histogen paid $50 thousand and issued EPS 14,342 shares of Series D convertible preferred stock. The Company was required to repurchase the shares at the greater of the remaining balance due of approximately $0.3 million and the market price of the shares at the time of repurchase, but in no event later than December 31, 2021. The Company had the sole option to repurchase of the shares (which were converted from Series D convertible preferred stock into shares of common stock upon the Merger) at any time on or before December 31, 2021. As of December 31, 2020, the Company determined the fair value of the liability to be approximately $0.3 million, which was the value as if the repurchase commitment was exercised immediately. The forward purchase contract was included within accrued liabilities on the accompanying consolidated balance sheet as of December 31, 2020. On December 16, 2021, the Company repurchased from EPS 14,342 shares of common stock in exchange for a cash payment of approximately $0.3 million. The repurchased shares were recorded as treasury stock which the Company intends to retire
Fair Value Measurements	Fair Value Measurements ASC 820, Fair Value Measurements • Level 1 — Observable inputs such as quoted price (unadjusted) for identical instruments in active markets. • Level 2 — Observable inputs such as quoted prices for similar instruments in active markets, quoted prices for identical or similar instruments in markets that are not active, or model derived valuations whose significant inputs are observable. • Level 3 — Unobservable inputs that reflect the reporting entity’s own assumptions. At December 31, 2021 and 2020, management believes the carrying amount of financial instruments consisting of cash, cash equivalents, restricted cash, accounts receivable, prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values due to the short-term nature of those instruments.
Comprehensive Loss	Comprehensive Loss The Company is required to report all components of comprehensive loss, including net loss, in the accompanying consolidated financial statements in the period in which they are recognized. Comprehensive loss is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources, including unrealized gains and losses on investments and foreign currency translation adjustments. Net loss and comprehensive loss were the same for all periods presented.
Revenue Recognition	Revenue Recognition Product and License Revenue The Company records revenue in accordance with ASC 606, Revenue from Contracts with Customers Grant Awards In March 2017, the National Science Foundation (“NSF”), a government agency, awarded the Company a research and development grant to develop a novel wound dressing for infection control and tissue regeneration. The Company has concluded this government grant is not within the scope of ASC 606, as government entities generally do not meet the definition of a “customer” as defined by ASC 606. Payments received under the grant are considered conditional, non-exchange contributions under the scope of ASC 958-605, Not-for-Profit Entities – Revenue Recognition In September 2020, the Company was approved for a grant award from the U.S. Department of Defense (“DoD”) in the amount of approximately $2.0 million to partially fund the Company’s planned Phase 1/2 clinical trial of HST-003 for regeneration of cartilage in the knee. The Company applies International Accounting Standard (“IAS”) 20, Accounting for Government Grants and Disclosure of Government Assistance Professional Services The Company recognizes revenue for professional services which are based upon negotiated rates with the counterparty. Professional services fees are recognized as revenue over time when the underlying services are performed, in accordance with ASC 606, and none of the revenue recognized to date is refundable.
Cost of Product Revenue	Cost of Product Revenue Cost of product revenue represents direct and indirect costs incurred to bring the product to saleable condition.
Cost of Professional Services Revenue	Cost of Professional Services Revenue Cost of professional services revenue represents the Company’s costs for full-time employee equivalents and actual out-of-pocket costs.
Research and Development Expenses	Research and Development Expenses All research and development costs are charged to expense as incurred. Research and development expenses primarily include (i) payroll and related costs associated with research and development performed, (ii) costs related to clinical and preclinical testing of the Company’s technologies under development, and (iii) other research and development costs including allocations of facility costs, net of reimbursable research and development costs incurred under the DoD grant.
Acquired In-Process Research and Development Expense	Acquired In-Process Research and Development Expense The Company has acquired and may continue to acquire the rights to drug candidates in various stages of development. The up-front payments to acquire a drug candidate are immediately expensed as acquired in-process research and development, provided that the drug candidate has not obtained regulatory approval for marketing and, absent obtaining such approval, have no alternative future use.
General and Administrative Expenses	General and Administrative Expenses General and administrative expenses represent personnel costs for employees involved in general corporate functions, including finance, accounting, legal and human resources, among others. Additional costs included within general and administrative expenses consist of professional fees for legal (including patent costs), audit and other consulting services, travel and entertainment, recruiting, allocated facility and general information technology costs, depreciation and amortization, and other general corporate overhead expenses.
Patent Costs	Patent Costs The Company expenses all costs as incurred in connection with patent applications (including direct application fees, and the legal and consulting expenses related to making such applications) and such costs are included as a component of general and administrative expenses in the accompanying consolidated statements of operations.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Deferred income taxes are recorded for temporary differences between consolidated financial statement carrying amounts and the tax basis of assets and liabilities. Deferred tax assets and liabilities reflect the tax rates expected to be in effect for the years in which the differences are expected to reverse. No income tax expense or benefit was recorded for the years ended December 31, 2021 and 2020, due to the full valuation allowance on the Company’s net deferred tax assets. A valuation allowance is provided if it is more likely than not that some or all the deferred tax assets will not be realized. The Company also follows the provisions of accounting for uncertainty in income taxes which prescribes a model for the recognition and measurement of a tax position taken or expected to be taken in a tax return, and provides guidance on derecognition, classification, interest and penalties, disclosure and transition. The Company’s policy is to recognize interest or penalties related to income tax matters in income tax expense. Interest and penalties related to income tax matters were not material for the periods presented.
Net Loss Per Share	Net Loss Per Share Basic net loss per share attributable to common stockholders attributable to common stockholders dilutive securities outstanding for the period. For the years ended December 31, 2021 and 2020 , diluted net loss per share attributable to common stockholders is equal to basic net loss per share attributable to common stockholders as common stock equivalent shares from stock options , warrants and convertible preferred stock were anti-dilutive . The following table sets forth outstanding potentially dilutive shares that have been excluded from the calculation of diluted net loss per share attributable to common stockholders because of their anti-dilutive effect (in common stock equivalents): Years Ended December 31, 2021 2020 Common stock options issued and outstanding 2,326,221 1,708,278 Warrants to purchase common stock 23,726,140 2,023,156 Total anti-dilutive shares 26,052,361 3,731,434
Common Stock Valuations	Common Stock Valuations Prior to the Merger, Private Histogen was required to periodically estimate the fair value of common stock with the assistance of an independent third-party valuation expert when issuing stock options and computing its estimated stock-based compensation expense. The assumptions underlying these valuations represented management’s best estimates, which involved inherent uncertainties and the application of significant levels of management judgment. In order to determine the fair value, Private Histogen considered, among other things, contemporaneous valuations of its common stock, business, financial condition and results of operations, including related industry trends affecting its operations; the likelihood of achieving various liquidity events; the lack of marketability of its common stock; the market performance of comparable publicly traded companies; and U.S. and global economic and capital market conditions.
Stock-Based Compensation	Stock-Based Compensation Service-Based Awards The Company recognizes stock-based compensation expense for service-based stock options and restricted stock units (“RSUs”) over the requisite service period on a straight-line basis. Employee and director stock-based compensation for service-based stock options is measured based on estimated fair value as of the grant date using the Black-Scholes option pricing model. The Company estimates the fair value of RSUs based on the closing price of the Company’s common stock on the date of issuance. The Company uses the following assumptions for estimating fair value of service-based option grants: Fair Value of Common Stock – The fair value of common stock underlying the option grant is determined based on observable market prices of the Company’s common stock. Expected Volatility – Volatility is a measure of the amount by which the Company’s share price has historically fluctuated or is expected to fluctuate (i.e., expected volatility) during a period. Due to the lack of an adequate history of a public market for the trading of the Company’s common stock and a lack of adequate company-specific historical and implied volatility data, volatility has been estimated and based on the historical volatility of a group of similar companies that are publicly traded. For these analyses, the Company has selected companies with comparable characteristics, including enterprise value, risk profiles, and position within the industry, and with historical share price information sufficient to meet the expected term of the stock-based awards. Expected Term – This is the period of time during which the options are expected to remain unexercised. Options have a maximum contractual term of ten years. The Company estimates the expected term of stock options using the “simplified method”, whereby the expected term equals the average of the vesting term and the original contractual term of the underlying option. Risk-Free Interest Rate – This is the observed yield on zero-coupon U.S. Treasury securities, as of the day each option is granted, with a term that most closely resembles the expected term of the option. Expected Forfeiture Rate – Forfeitures are recognized as they occur. Performance-Based Options Stock-based compensation expense for performance-based options is recognized based on amortizing the fair market value as of the grant date over the periods during which the achievement of the performance is probable. Performance-based options require certain performance conditions to be achieved in order for these options to vest. These options vest on the date of achievement of the performance condition. Market-Based Options Stock-based compensation expense for market-based options is recognized on a straight-line basis over the derived service period, regardless of whether the market condition is satisfied. Market-based options subject to market-based performance targets require achievement of the performance target in order for these options to vest. The Company estimates the fair value of market-based options as of the grant date and expected term using a Monte Carlo simulation that incorporates option-pricing inputs covering the period from the grant date through the end of the derived service period.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In August 2020, the FASB issued ASU No. 2020-06, Debt – Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging – Contracts in Entity’s Own Equity (Subtopic 815-40) In November 2021, the FASB issued ASU No. 2021-10, Government Assistance (Topic 832): Disclosure by Business Entities about Government Assistance
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes
Description of Business	Description of Business Histogen Inc. (the “Company,” “Histogen,” or the “combined company”), formerly known as Conatus Pharmaceuticals Inc. (“Conatus”) clinical-stage therapeutics company focused on developing potential first-in-class restorative therapeutics that ignite the body’s natural process to repair and maintain healthy biological function.
Merger between Private Histogen and Conatus Pharmaceuticals Inc. and Name Change	Merger between Private Histogen and Conatus Pharmaceuticals Inc. and Name Change On January 28, 2020, the Company, then operating as Conatus, entered into an Agreement and Plan of Merger and Reorganization, as amended (the “Merger Agreement”), with privately-held Histogen, Inc. (“Private Histogen”) and Chinook Merger Sub, Inc., a wholly-owned subsidiary of the Company (“Merger Sub”). Under the Merger Agreement, Merger Sub merged with and into Private Histogen, with Private Histogen surviving as a wholly-owned subsidiary of the Company (the “Merger”). On May 26, 2020, the Merger was completed. Conatus changed its name to Histogen Inc., and Private Histogen, which remains as a wholly-owned subsidiary of the Company, changed its name to Histogen Therapeutics Inc. On May 27, 2020, the combined company’s common stock began trading on The Nasdaq Capital Market under the ticker symbol “HSTO”. Except as otherwise indicated, references herein to “Histogen,” the “Company,” or the “combined company”, refer to Histogen Inc. on a post-Merger basis, and the term “Private Histogen” refers to the business of privately-held Histogen, Inc., prior to completion of the Merger. References to Conatus refer to Conatus Pharmaceuticals Inc. prior to completion of the Merger. Pursuant to the terms of the Merger Agreement, each outstanding share of Private Histogen common stock outstanding immediately prior to the closing of the Merger was converted into approximately 0.14342 shares of Company common stock (the “Exchange Ratio”), after taking into account the Reverse Stock Split, as defined below. Immediately prior to the closing of the Merger, all shares of Private Histogen preferred stock then outstanding were exchanged into shares of common stock of Private Histogen. In addition, all outstanding options exercisable for common stock of Private Histogen and warrants exercisable for common stock of Private Histogen became options and warrants exercisable for the same number of shares of common stock of the Company multiplied by the Exchange Ratio. Immediately following the Merger, stockholders of Private Histogen owned approximately 71.3% of the outstanding common stock of the combined company. The transaction was accounted for as a reverse asset acquisition in accordance with generally accepted accounting principles in the United States of America (“GAAP”). Under this method of accounting, Private Histogen was deemed to be the accounting acquirer for financial reporting purposes. This determination was primarily based on the facts that, immediately following the Merger: (i) Private Histogen’s stockholders owned a substantial majority of the voting rights in the combined company, (ii) Private Histogen designated a majority of the members of the initial board of directors of the combined company, and (iii) Private Histogen’s senior management holds all key positions in the senior management of the combined company. As a result, as of the closing date of the Merger, the net assets of the Company were recorded at their acquisition-date relative fair values in the accompanying consolidated financial statements of the Company and the reported operating results prior to the Merger are those of Private Histogen.
Reverse Stock Split and Exchange Ratio	Reverse Stock Split and Exchange Ratio On May 26, 2020, in connection with, and prior to the completion of, the Merger, the Company effected a one-for-ten
Liquidity and Going Concern	Liquidity The Company has incurred operating losses and negative cash flows from operations and had an accumulated deficit of $77.7 million as of December 31, 2021. The Company expects operating losses and negative cash flows from operations to continue for the foreseeable future. The Company has not yet established ongoing sources of revenues sufficient to cover its operating costs and will need to continue to raise additional capital to support its future operating activities, including progression of its development programs, preparation for commercialization, and other operating costs. Management’s plans with regard to these matters include entering into a combination of additional debt or equity financing arrangements, strategic partnerships, collaboration and licensing arrangements, or other similar arrangements. In addition, the Company may fund its losses from operations through the common stock purchase agreement the Company entered into with Lincoln Park in July 2020, for the purchase of up to $10.0 million of the Company’s common stock over the 24 month period of the purchase agreement, $8.5 million of which remains available for sale as of the date (refer to Note 9 for further information), subject to limitations on the amount of securities the Company may sell under its effective registration statement on Form S-3 within any 12-month period.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2021
Accounting Policies [Abstract]
Summary of Outstanding Potentially Dilutive Shares Excluded in Calculation of Diluted Net Loss Per Share	The following table sets forth outstanding potentially dilutive shares that have been excluded from the calculation of diluted net loss per share attributable to common stockholders because of their anti-dilutive effect (in common stock equivalents): Years Ended December 31, 2021 2020 Common stock options issued and outstanding 2,326,221 1,708,278 Warrants to purchase common stock 23,726,140 2,023,156 Total anti-dilutive shares 26,052,361 3,731,434

Inventories (Tables)

Inventories (Tables)	12 Months Ended
	Dec. 31, 2021
Inventory Disclosure [Abstract]
Components of Inventories	Inventories consisted of the following components (in thousands): December 31, 2021 2020 Raw materials $ — $ 61 Finished goods — 239 Inventories $ — $ 300

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2021
Property Plant And Equipment [Abstract]
Schedule of Property and Equipment	Property and equipment, net, consisted of the following (in thousands): December 31, 2021 2020 Leasehold improvements $ — $ 845 Lab and manufacturing equipment 943 1,235 Office furniture and equipment 42 157 Software 48 — Total 1,033 2,237 Less: accumulated depreciation and amortization (634 ) (1,966 ) Property and equipment, net $ 399 $ 271

Balance Sheet Details (Tables)

Balance Sheet Details (Tables)	12 Months Ended
	Dec. 31, 2021
Balance Sheet Related Disclosures [Abstract]
Summary of Prepaid and Other Current Assets	Prepaid and other current assets consist of the following (in thousands): December 31, 2021 2020 Insurance $ 691 $ 671 Tenant improvement reimbursement receivable 1,057 — Prepaid rent 132 74 Pre-clinical and clinical related expenses 158 42 Prepaid materials 138 — Other 183 396 Total $ 2,359 $ 1,183
Summary of Other Assets	Other assets consist of the following (in thousands): December 31, 2021 2020 Insurance $ 732 $ 959 Deferred offering costs — 708 Security deposit — 250 Cell bank material 61 — Other 12 14 Total $ 805 $ 1,931
Summary of Accrued Liabilities	Accrued liabilities consist of the following (in thousands): December 31, 2021 2020 Current portion of finance lease liabilities $ 9 $ 8 Accrued compensation 346 639 Clinical study related expenses 103 226 Legal fees 144 52 Forward purchase contract — 290 Offering costs — 602 Other 189 63 Total $ 791 $ 1,880

Merger (Tables)

Merger (Tables)	12 Months Ended
	Dec. 31, 2021
Asset Acquisition [Abstract]
Summary of Purchase Price Paid in Merger	The total purchase price paid in the Merger has been allocated to the net assets acquired and liabilities assumed based on their fair values as of the completion of the Merger. The following summarizes the purchase price paid in the Merger (in thousands, except share and per share amounts): Number of shares of the combined organization owned by the Company’s Pre-Merger stockholders 3,394,299 Multiplied by the fair value per share of Conatus common stock (1) $ 5.56 Fair value of consideration issued to effect the Merger $ 18,872 Transaction costs 1,817 Purchase price $ 20,689 (1) Based on the last reported sale price of the Company’s common stock on the Nasdaq Capital Market on May 26, 2020, the closing date of the Merger, and gives effect to the Reverse Stock Split.
Summary of Allocation of Purchase Price	The allocation of the purchase price is as follows (in thousands): Cash acquired $ 12,835 Net assets acquired 710 Acquired IPR&D (2) 7,144 Purchase price $ 20,689 (2) Represents the research and development projects of Conatus which were in-process, but not yet completed. This consists primarily of Conatus’ emricasan product candidate. Current accounting standards require that the fair value of IPR&D projects acquired in an asset acquisition with no alternative future use be allocated a portion of the consideration transferred and charged to expense on the acquisition date. The acquired assets did not have outputs or employees.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2021
Equity [Abstract]
Summary of Stock Option Activity	The following summarizes activity related to the Company’s stock options under the 2017 Plan and the 2020 Plan for the year ended December 31, 2021: Options Outstanding Weighted- average Exercise Price Weighted- average Remaining Contractual Term (in years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2020 1,592,187 $ 3.06 6.20 $ 108 Granted 1,602,150 0.92 Cancelled / Forfeited (966,046 ) 2.27 Outstanding at December 31, 2021 2,228,291 1.88 6.78 $ — Vested and exercisable at December 31, 2021 1,202,520 $ 2.50 4.56 $ —
Summary of Valuation of Stock Option Awards	The following weighted-average assumptions were used to calculate the fair value of awards granted to employees, non-employees and directors: Years Ended December 31, 2021 2020 Expected volatility 78.7 % 76.6 % Risk-free interest rate 0.9 % 0.5 % Expected option life (in years) 6.08 6.25 Expected dividend yield 0.0 % 0.0 %
Summary of Compensation Cost Included in the Company's Consolidated Statements of Operations for Stock-based Compensation Arrangements	The compensation cost that has been included in the Company’s consolidated statements of operations for all stock-based compensation arrangements is detailed as follows (in thousands): Years Ended December 31, 2021 2020 General and administrative $ 520 $ 588 Research and development 184 10 Cost of product revenues — 20 Total $ 704 $ 618
Summary of Common Stock Reserved for Future Issuance	Common stock reserved for future issuance is as follows: December 31, 2021 2020 Common stock warrants 23,726,140 2,023,156 Common stock options issued and outstanding 2,326,221 1,708,278 Common stock available for issuance under stock plans 46,189 513,141 26,098,550 4,244,575

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2021
Commitments And Contingencies Disclosure [Abstract]
Summary of Lease Assets and Lease Liabilities	The Company’s lease assets and lease liabilities were as follows (in thousands): December 31, Balance Sheet Classification 2021 2020 Assets Operating lease Right-of-use asset $ 4,432 $ 4,411 Finance lease Property and equipment, net 20 28 Total lease assets $ 4,452 $ 4,439 Liabilities Current Operating lease liability Current portion of lease liability $ 127 $ 28 Finance lease liability Accrued liabilities 9 8 Total current liabilities 136 36 Noncurrent Operating lease liability Noncurrent portion of lease liability 4,617 4,806 Finance lease liability Other liabilities 14 22 Total noncurrent liabilities 4,631 4,828 Total lease liabilities $ 4,767 $ 4,864
Summary of Components of Lease Expense	The components of lease expense were as follows (in thousands): Years Ended December 31, Statement of Operations Classification 2021 2020 Operating lease cost: Cost of product revenue $ — $ 106 Research and development 210 158 General and administrative 428 597 Total operating lease cost $ 638 $ 861 Finance lease cost: Amortization of right-of-use assets Property and equipment, net $ 9 $ 7 Interest on lease liabilities Interest expense 3 3 Total finance lease cost $ 12 $ 10
Summary of Supplemental Cash Flow Information Related to Leases	Supplemental cash flow information related to leases were as follows (in thousands): Years Ended December 31, 2021 2020 Cash paid for amounts included in the measurement of lease liabilities Operating cash flows from operating lease $ 111 $ 299 Operating cash flows from finance lease 3 3 Financing cash flows from finance lease 9 7 Right-of-use asset obtained in exchange for operating lease liability $ — $ 4,481
Schedule of Future Minimum Payments of Lease Liabilities	At December 31, 2021, future minimum payments of lease liabilities were as follows (in thousands): Operating Lease Finance Lease 2022 $ 695 11 2023 780 11 2024 803 4 2025 827 — Thereafter 5,183 — Total minimum lease payments 8,288 26 Less: imputed interest (3,544 ) (3 ) Total future minimum lease payments 4,744 23 Less: current obligations under leases (127 ) (9 ) Noncurrent lease obligations $ 4,617 $ 14

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2021
Income Tax Disclosure [Abstract]
Summary of Reconciliation of Income Taxes Computed using Statutory U.S. Income Tax Rate and Provision	The reconciliation of income taxes computed using the statutory U.S. income tax rate and the provision is as follows (in thousands): Years Ended December 31, 2021 2020 Tax computed at federal statutory rate $ (3,152 ) $ (3,920 ) State tax, net of federal tax benefits (908 ) (34 ) Tax credits (325 ) 43 Acquired intangible property — 1,513 Valuation allowance 5,320 2,096 PPP loan forgiveness (126 ) — Other (809 ) 302 Provision for income taxes $ — $ —
Components of Company's Deferred Tax Assets	Significant components of the Company’s net deferred tax assets are as follows (in thousands): Years Ended December 31, 2021 2020 Deferred tax assets: Tax loss carryforward $ 18,041 $ 13,519 R&D credits and other tax credits 1,834 1,498 Stock-based compensation 152 82 Compensation 58 135 Deferred revenue 5 10 Lease liability 1,283 1,024 Capitalized research and development 2,607 2,074 Other 80 133 Total deferred tax assets 24,060 18,475 Less: valuation allowance (22,861 ) (17,541 ) Deferred tax assets, net 1,199 934 Deferred tax liability: Right-of-use assets (1,199 ) (934 ) Net deferred tax assets $ — $ —
Summary of Activity Related to Unrecognized Tax Benefits	The following table summarizes the activity related to our unrecognized tax benefits (in thousands): Years Ended December 31, 2021 2020 Gross unrecognized tax benefits at the beginning of the year $ 561 $ 401 Additions from tax positions taken in the current year 118 37 Additions from tax positions taken in prior years 4 128 Reductions for tax positions from prior year — (5 ) Gross unrecognized tax benefits at end of the year $ 683 $ 561

Organization and Nature of Op_2

Organization and Nature of Operations - Additional Information (Detail)	May 26, 2020	Jan. 28, 2020shares	Jul. 31, 2020USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Description of Organization and Nature of Operations [Line Items]
Reverse stock split description				one-for-ten
Reverse stock split conversion ratio	0.1
Accumulated deficit				$ (77,652,000)	$ (62,702,000)
Common Stock Purchase Agreement with Lincoln Park [Member]
Description of Organization and Nature of Operations [Line Items]
Common stock shares maximum committed purchase amount			$ 10,000,000
Remaining available for sale common stock shares maximum committed purchase amount			$ 8,500,000	$ 8,500,000
Long-term purchase commitment, period			24 months
Private Histogen [Member]
Description of Organization and Nature of Operations [Line Items]
Exchange Ratio in reverse merger | shares		0.14342
Histogen stockholders' ownership interests post Merger		71.30%

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail)	Dec. 16, 2021USD ($)shares	Jan. 26, 2017USD ($)shares	Sep. 30, 2020USD ($)	Dec. 31, 2021USD ($)Segmentshares	Dec. 31, 2020USD ($)shares
Summary Of Significant Accounting Policies [Line Items]
Percentage ownership not considered variable interest entity				100.00%
Number of operating segment | Segment				1
Deferred Offering Costs				$ 0	$ 708,000
Impairment to long-lived assets				0	$ 0
EPS unpaid services				$ 300,000
Shares issued | shares				0	0
Fair value of liability					$ 300,000
Income tax expense benefit				$ 0	0
U.S. Department of Defense (“DoD”) [Member]
Summary Of Significant Accounting Policies [Line Items]
Accounts receivable from customer				200,000	100,000
Grant funding obtained			$ 2,000,000
Grant award expiration period			2025-09
Qualifying expenses incurred				$ 700,000	100,000
Furniture and All Equipment [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets				5 years
Software [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives of the assets				3 years
Customer Concentration Risk | One Customer [Member]
Summary Of Significant Accounting Policies [Line Items]
Accounts receivable from customer				$ 0	$ 100,000
Revenue Benchmark | Customer Concentration Risk | One Customer [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenues				88.00%	100.00%
Settlement Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Variable interest entity, ownership percentage				50.00%
Cash paid		$ 50,000
Share repurchases, description				The Company was required to repurchase the shares at the greater of the remaining balance due of approximately $0.3 million and the market price of the shares at the time of repurchase, but in no event later than December 31, 2021. The Company had the sole option to repurchase of the shares (which were converted from Series D convertible preferred stock into shares of common stock upon the Merger) at any time on or before December 31, 2021.
Share repurchases, value	$ 300,000			$ 300,000
Repurchase of common stock in cash | shares	14,342
Share repurchase amount due under settlement agreement				$ 0
Settlement Agreement [Member] | Series D Convertible Preferred Stock [Member]
Summary Of Significant Accounting Policies [Line Items]
Shares issued | shares		14,342

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Outstanding Potentially Dilutive Shares Excluded in Calculation of Diluted Net Loss Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding potentially dilutive securities	26,052,361	3,731,434
Common stock options issued and outstanding [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding potentially dilutive securities	2,326,221	1,708,278
Warrants to purchase common stock [Member] | Common Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Outstanding potentially dilutive securities	23,726,140	2,023,156

Inventories - Components of Inv

Inventories - Components of Inventories (Detail) $ in Thousands	Dec. 31, 2020USD ($)
Inventory Disclosure [Abstract]
Raw materials	$ 61
Finished goods	239
Inventories	$ 300

Inventories - Additional Inform

Inventories - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2021
Inventory [Line Items]
Write-off of inventory	$ 202
Cell bank inventory		$ 61
Other Assets [Member]
Inventory [Line Items]
Cell bank inventory		$ 100

Property and Equipment - Schedu

Property and Equipment - Schedule of Property and Equipment, Net (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Property and equipment, gross	$ 1,033	$ 2,237
Less: accumulated depreciation and amortization	(634)	(1,966)
Property and equipment, net	399	271
Leasehold improvements [Member]
Property and equipment, gross		845
Lab and Manufacturing Equipment [Member]
Property and equipment, gross	943	1,235
Office Furniture And Equipment [Member]
Property and equipment, gross	42	$ 157
Software [Member]
Property and equipment, gross	$ 48

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Property Plant And Equipment [Abstract]
Depreciation and amortization	$ 97	$ 98
Property and equipment disposed	$ 1,400

Balance Sheet Details - Summary

Balance Sheet Details - Summary of Prepaid and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Insurance	$ 691	$ 671
Tenant improvement reimbursement receivable	1,057
Prepaid rent	132	74
Pre-clinical and clinical related expenses	158	42
Prepaid materials	138
Other	183	396
Total	$ 2,359	$ 1,183

Balance Sheet Details - Summa_2

Balance Sheet Details - Summary of Other Assets (Detail) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Insurance	$ 732,000	$ 959,000
Deferred Offering Costs	0	708,000
Security deposit		250,000
Cell bank material	61,000
Other	12,000	14,000
Total	$ 805,000	$ 1,931,000

Balance Sheet Details - Summa_3

Balance Sheet Details - Summary of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Balance Sheet Related Disclosures [Abstract]
Current portion of finance lease liabilities	$ 9	$ 8
Accrued compensation	346	639
Clinical study related expenses	103	226
Legal fees	144	52
Forward purchase contract		290
Offering costs		602
Other	189	63
Total	$ 791	$ 1,880

Revenue - Additional Informatio

Revenue - Additional Information (Detail)	1 Months Ended				12 Months Ended
	Sep. 30, 2021USD ($)	Jan. 31, 2020USD ($)kg	Mar. 31, 2019USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Disaggregation of Revenue [Line Items]
Revenue					$ 1,032,000	$ 2,059,000
2017 Allergan Agreement [Member]
Disaggregation of Revenue [Line Items]
Cash payment received				$ 11,000,000
Potential additional payments				5,500,000
2019 Allergan Amendment Agreement [Member]
Disaggregation of Revenue [Line Items]
One-time payment			$ 7,500,000
Remaining life of the patent			9 years
2020 Allergan Amendment Agreement [Member]
Disaggregation of Revenue [Line Items]
Remaining life of the patent		9 years
Revenue	$ 600,000				300,000
Up front payment received		$ 1,000,000
Additional quantity of product to be supplied | kg		200
Deferred revenue					28,000
Revenue recognized					19,000	19,000
CCM Skin Care [Member]
Disaggregation of Revenue [Line Items]
Deferred revenue					0	28,000
CCM Skin Care [Member] | Potential Future Improvements [Member]
Disaggregation of Revenue [Line Items]
Deferred revenue					100,000	100,000
Product [Member]
Disaggregation of Revenue [Line Items]
Revenue					892,000	845,000
Product [Member] | 2017 Allergan Agreement [Member] | Minimum [Member]
Disaggregation of Revenue [Line Items]
Sales target for additional potential payment payout				$ 60,000,000
License [Member]
Disaggregation of Revenue [Line Items]
Revenue					27,000	882,000
License [Member] | 2019 Allergan Amendment Agreement [Member]
Disaggregation of Revenue [Line Items]
Revenue			$ 7,500,000
License [Member] | 2020 Allergan Amendment Agreement [Member]
Disaggregation of Revenue [Line Items]
Revenue		$ 900,000
Grant [Member]
Disaggregation of Revenue [Line Items]
Revenue					113,000	0
Professional Services Revenue [Member]
Disaggregation of Revenue [Line Items]
Revenue					$ 0	$ 300,000

Merger - Additional Information

Merger - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2021
Asset Acquisition [Abstract]
Closing date of Merger	May 26, 2020

Merger - Summary of Purchase Pr

Merger - Summary of Purchase Price Paid in Merger (Detail) $ / shares in Units, $ in Thousands	May 26, 2020USD ($)$ / sharesshares
Asset Acquisition [Abstract]
Number of shares of the combined organization owned by the Company’s Pre-Merger stockholders | shares	3,394,299
Multiplied by the fair value per share of Conatus common stock | $ / shares	$ 5.56	[1]
Fair value of consideration issued to effect the Merger	$ 18,872
Transaction costs	1,817
Purchase price	$ 20,689
[1]	Based on the last reported sale price of the Company’s common stock on the Nasdaq Capital Market on May 26, 2020, the closing date of the Merger, and gives effect to the Reverse Stock Split.

Merger - Summary of Allocation

Merger - Summary of Allocation of Purchase Price (Detail) $ in Thousands	May 26, 2020USD ($)
Asset Acquisition [Abstract]
Cash acquired	$ 12,835
Net assets acquired	710
Acquired IPR&D	7,144	[1]
Purchase price	$ 20,689
[1]	Represents the research and development projects of Conatus which were in-process, but not yet completed. This consists primarily of Conatus’ emricasan product candidate. Current accounting standards require that the fair value of IPR&D projects acquired in an asset acquisition with no alternative future use be allocated a portion of the consideration transferred and charged to expense on the acquisition date. The acquired assets did not have outputs or employees.

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($) $ in Thousands	May 21, 2021	Jun. 05, 2020	Jun. 04, 2020	Jun. 30, 2020	Apr. 30, 2020	Dec. 31, 2020	Dec. 31, 2021
Debt Instrument [Line Items]
Proceeds from financing of insurance premiums				$ 900		$ 872
Percentage of monthly repayments of principal and interest accrued				3.60%
Payment on financing of insurance premiums						$ 193	$ 0
Paycheck Protection Program [Member]
Debt Instrument [Line Items]
Loan proceeds received					$ 500
Loan forgiveness period		168 days	56 days
Deferral period of principal and interest payments extended term		10 months	6 months
Required amount of payroll expenditures, percentage		60.00%	75.00%
Existing loans maturity period		5 years	2 years
Paycheck Protection Program [Member] | Other Income [Member]
Debt Instrument [Line Items]
Loan forgiveness amount	$ 500

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail) - USD ($)

Nov. 08, 2021

May 26, 2020

Jan. 28, 2020

Jan. 24, 2019

Dec. 31, 2021

Jun. 30, 2021

Jan. 31, 2021

Nov. 30, 2020

Jul. 31, 2020

May 31, 2020

Apr. 30, 2019

Dec. 31, 2021

Dec. 31, 2020

Dec. 18, 2017

Dec. 31, 2016

Class Of Stock [Line Items]

Proceeds from the issuance of common stock, net of issuance costs

$ 20,738,000

$ 5,098,000

Expected volatility

78.70%

76.60%

Risk-free interest rate

0.90%

0.50%

Expected dividend yield

0.00%

0.00%

Expected term

6 years 29 days

6 years 3 months

Common stock reserved for issuance

26,098,550

26,098,550

4,244,575

Warrants to purchase common stock

23,726,140

23,726,140

2,023,156

Stock-based total compensation expense

$ 704,000

$ 618,000

Additional stock-based compensation expense

100,000

Unrecognized compensation expense

$ 1,000,000

$ 1,000,000

Weighted-average vesting term

2 years 3 months 18 days

Liquidity Option Shares [Member]

Class Of Stock [Line Items]

Vesting period

12 months

Number of fully vested options

48,517

Vesting percentage

25.00%

Vesting term

The vesting of the Liquidity Option Shares is divided into four separate tranches, each vesting 25% of the Liquidity Option Shares, upon: (1) the closing of the proposed merger with Conatus; (2) the date that the market capitalization of the Company exceeds $200.0 million; (3) the date that the market capitalization of the Company exceeds $275.0 million, and; (4) the date that the market capitalization of the Company exceeds $300.0 million. Each vesting tranche represents a unique derived service period and therefore stock-based compensation expense for each vesting tranche is recognized on a straight-line basis over its respective derived service period. Additionally, in the event that the Chief Executive Officer’s employment with the Company is terminated without cause or he resigns for good reason, an additional portion of the stock options award will vest equal to the number of such options which would have vested in the 12 months following the date of such termination.

Liquidity Option Shares [Member] | Share-based Payment Arrangement, Tranche One [Member]

Class Of Stock [Line Items]

Vesting percentage

40.00%

Liquidity Option Shares [Member] | Share-based Payment Arrangement, Tranche Two [Member]

Class Of Stock [Line Items]

Minimum market capitalization amount required for vesting

$ 200,000,000

Liquidity Option Shares [Member] | Share-based Payment Arrangement, Tranche Three [Member]

Class Of Stock [Line Items]

Minimum market capitalization amount required for vesting

275,000,000

Liquidity Option Shares [Member] | Share-based Payment Arrangement, Tranche Four [Member]

Class Of Stock [Line Items]

Minimum market capitalization amount required for vesting

$ 300,000,000

Market-Based Options [Member]

Class Of Stock [Line Items]

Stock-based total compensation expense

$ 0

Performance and Market-Based Options [Member]

Class Of Stock [Line Items]

Stock-based total compensation expense

200,000

Restricted Stock Units [Member]

Class Of Stock [Line Items]

Vesting term

The RSUs vest in full upon the earlier of (1) 12 months following the grant date and (2) a change of control of the Company, as defined in the Company’s 2020 Plan, and subject to continued service to the Company

Number of restricted stock units granted

468,449

Fair value per share

$ 0.73

Chief Executive Officer [Member] | Stock Options [Member]

Class Of Stock [Line Items]

Vesting period

36 months

Stock options issued

485,178

Vesting term

In accordance with the original award agreement, 40% of the options would vest immediately upon an initial public offering or 45 days following a change in control, as defined in the award agreement, while the remaining 60% are subject to vesting, of which 25% vest on the first anniversary of the grant date and then ratably over the remaining 36 months.

Chief Executive Officer [Member] | Stock Options [Member] | Share-based Payment Arrangement, Tranche One [Member]

Class Of Stock [Line Items]

Vesting percentage

40.00%

Remaining vesting percentage

25.00%

Chief Executive Officer [Member] | Stock Options [Member] | Share-based Payment Arrangement, Tranche Two [Member]

Class Of Stock [Line Items]

Vesting percentage

60.00%

2017 Plan [Member]

Class Of Stock [Line Items]

Number of common stock shares authorized to issue

837,208

Increase in number of common stock available for grant

326,711

Vesting period

4 years

Expiration period

10 years

Stock options issued

0

2020 Stock Plan [Member]

Class Of Stock [Line Items]

Number of common stock shares authorized to issue

850,000

Expiration period

10 years

Percentage of outstanding shares of common stock

5.00%

Conatus 2013 Plan [Member]

Class Of Stock [Line Items]

Stock options issued

0

Number of fully vested options

97,930

Weighted average exercise price of fully vested options

$ 42.90

Common Stock Purchase Agreement with Lincoln Park [Member]

Class Of Stock [Line Items]

Issuance of common stock, net of issuance costs, shares

66,964

Proceeds from the issuance of common stock, net of issuance costs

$ 1,000,000

$ 500,000

Aggregate dollar value of share purchase commitment

$ 10,000,000

Long-term purchase commitment, period

24 months

Number of common stock shares sold

328,516

300,000

Sale of common stock price per share

$ 3.04399

Remaining available for sale common stock shares maximum committed purchase amount

$ 8,500,000

$ 8,500,000

Sales Agreement with Stifel [Member]

Class Of Stock [Line Items]

Number of shares sold under sales agreement

0

Sales Agreement with Stifel [Member] | Maximum [Member]

Class Of Stock [Line Items]

Aggregate value of common shares that can be sold

35,000,000

Common Stock [Member]

Class Of Stock [Line Items]

Issuance of common stock, net of issuance costs, shares

28,212,597

3,218,264

Exercise price of warrant per share

$ 74.30

$ 74.30

$ 74.30

$ 23.08

Warrants to purchase common stock

1,346

1,346

1,346

Warrant expiration date

Jul. 3, 2023

Jul. 3, 2023

Jul. 3, 2023

Common Stock [Member] | Maximum [Member]

Class Of Stock [Line Items]

Warrants to purchase common stock

3,583

Common Stock [Member] | November 2020 Offering [Member]

Class Of Stock [Line Items]

Issuance of common stock, net of issuance costs, shares

2,522,784

Warrants to purchase common stock

1,892,088

Offering price per share

$ 1.78375

Percentage of warrant coverage

75.00%

Exercise price of warrant per share

$ 1.78375

$ 1.70

$ 1.78375

Warrants exercisable expiration period

5 years 6 months

Warrants exercised

0

Common stock reserved for issuance

1,892,088

1,892,088

Common Stock [Member] | November 2020 Offering [Member] | Placement Agent Warrants [Member]

Class Of Stock [Line Items]

Warrants to purchase common stock

126,139

Exercise price of warrant per share

$ 2.2297

$ 2.2297

$ 2.2297

Warrant expiration date

Nov. 11, 2025

Proceeds from the issuance of common stock, net of issuance costs

$ 4,500,000

Placement agent's fees and other offering expenses

900,000

Common stock reserved for issuance

126,139

126,139

Common Stock [Member] | November 2020 Offering [Member] | Placement Agent Warrants [Member] | Black-Scholes Option Pricing Model [Member]

Class Of Stock [Line Items]

Aggregate value of warrants

$ 100,000

Expected volatility

79.60%

Risk-free interest rate

0.41%

Expected dividend yield

0.00%

Expected term

5 years

Common Stock [Member] | January 2021 Offering [Member]

Class Of Stock [Line Items]

Issuance of common stock, net of issuance costs, shares

6,721,200

Exercise price of warrant per share

$ 1

$ 1

Proceeds from the issuance of common stock, net of issuance costs

$ 14,000,000

$ 6,800,000

Placement agent's fees and other offering expenses

$ 1,900,000

Common stock reserved for issuance

7,751,300

7,751,300

Issuance of common stock for warrant exercises, shares

6,721,200

Common Stock [Member] | January 2021 Offering [Member] | Public Offering of Common Stock [Member]

Class Of Stock [Line Items]

Issuance of common stock, net of issuance costs, shares

11,600,000

Warrants to purchase common stock

14,000,000

Exercise price of warrant per share

$ 1

Number of prefunded warrants to be issued

2,400,000

Combined purchase price of one share of common stock and accompanying warrant

$ 1

Combined purchase price of one pre-funded warrant and accompanying warrant

$ 0.9999

Warrant exercisable period

5 years

Common Stock [Member] | January 2021 Offering [Member] | Placement Agent Warrants [Member]

Class Of Stock [Line Items]

Warrants to purchase common stock

700,000

Exercise price of warrant per share

$ 1.25

$ 1.25

$ 1.25

Common stock reserved for issuance

227,500

227,500

Warrant exercisable period

5 years

Common Stock [Member] | January 2021 Offering [Member] | Placement Agent Warrants [Member] | Black-Scholes Option Pricing Model [Member]

Class Of Stock [Line Items]

Aggregate value of warrants

$ 300,000

Expected volatility

80.08%

Risk-free interest rate

0.38%

Expected dividend yield

0.00%

Expected term

5 years

Common Stock [Member] | January 2021 Offering [Member] | Pre-funded Warrants [Member] | Public Offering of Common Stock [Member]

Class Of Stock [Line Items]

Exercise price of warrant per share

$ 0.0001

Common Stock [Member] | June 2021 Offering [Member]

Class Of Stock [Line Items]

Issuance of common stock, net of issuance costs, shares

5,977,300

Warrants to purchase common stock

4,781,840

Offering price per share

$ 1.10

Percentage of warrant coverage

80.00%

Exercise price of warrant per share

$ 1

$ 1

$ 1

Warrants exercisable expiration period

5 years 6 months

Warrants exercised

0

Common stock reserved for issuance

4,781,840

4,781,840

Common Stock [Member] | June 2021 Offering [Member] | Placement Agent Warrants [Member]

Class Of Stock [Line Items]

Warrants to purchase common stock

298,865

Percentage of warrant coverage

5.00%

Exercise price of warrant per share

$ 1.375

$ 1.375

$ 1.375

Warrants exercisable expiration period

5 years

Proceeds from the issuance of common stock, net of issuance costs

$ 6,600,000

Placement agent's fees and other offering expenses

900,000

Common stock reserved for issuance

298,865

298,865

Common Stock [Member] | June 2021 Offering [Member] | Placement Agent Warrants [Member] | Black-Scholes Option Pricing Model [Member]

Class Of Stock [Line Items]

Aggregate value of warrants

$ 200,000

Expected volatility

80.15%

Risk-free interest rate

0.77%

Expected dividend yield

0.00%

Expected term

5 years

Common Stock [Member] | December 2021 Offering [Member]

Class Of Stock [Line Items]

Issuance of common stock, net of issuance costs, shares

8,235,297

Warrants to purchase common stock

8,235,297

8,235,297

Offering price per share

$ 0.425

$ 0.425

Exercise price of warrant per share

$ 0.425

$ 0.425

Warrants exercisable expiration period

5 years 6 months

Warrants exercised

0

Common stock reserved for issuance

8,235,297

8,235,297

Common Stock [Member] | December 2021 Offering [Member] | Placement Agent Warrants [Member]

Class Of Stock [Line Items]

Warrants to purchase common stock

411,765

411,765

Percentage of warrant coverage

5.00%

Exercise price of warrant per share

$ 0.5313

$ 0.5313

Warrants exercisable expiration period

5 years 6 months

Proceeds from the issuance of common stock, net of issuance costs

$ 3,500,000

Placement agent's fees and other offering expenses

$ 500,000

Common stock reserved for issuance

411,765

411,765

Common Stock [Member] | December 2021 Offering [Member] | Placement Agent Warrants [Member] | Black-Scholes Option Pricing Model [Member]

Class Of Stock [Line Items]

Aggregate value of warrants

$ 100,000

$ 100,000

Expected volatility

79.81%

Risk-free interest rate

1.21%

Expected dividend yield

0.00%

Expected term

5 years 6 months

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Stock Option Activity (Details) - 2017 and 2020 Plan [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Options, Beginning balance	1,592,187
Number of Options, Granted	1,602,150
Number of Options, Cancelled / Forfeited	(966,046)
Number of Options, Ending balance	2,228,291	1,592,187
Number of Options, Vested and exercisable	1,202,520
Weighted-Average Exercise Price, Beginning balance	$ 3.06
Weighted-Average Exercise Price, Granted	0.92
Weighted-Average Exercise Price, Cancelled / Forfeited	2.27
Weighted-Average Exercise Price, Ending balance	1.88	$ 3.06
Weighted-Average Exercise Price, Vested and exercisable	$ 2.50
Weighted-Average Remaining Contractual Term Outstanding	6 years 9 months 10 days	6 years 2 months 12 days
Weighted-Average Remaining Contractual Term Outstanding, Vested and exercisable	4 years 6 months 21 days
Aggregate Intrinsic Value Outstanding	$ 108

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Valuation of Stock Option Awards (Detail)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions And Methodology [Abstract]
Expected volatility	78.70%	76.60%
Risk-free interest rate	0.90%	0.50%
Expected option life (in years)	6 years 29 days	6 years 3 months
Expected dividend yield	0.00%	0.00%

Stockholders' Equity - Summar_3

Stockholders' Equity - Summary of Compensation Cost Included in the Company's Consolidated Statements of Operations for Stock-based Compensation Arrangements (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Compensation cost	$ 704	$ 618
General and Administrative [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Compensation cost	520	588
Research and Development [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Compensation cost	$ 184	10
Cost of Product Revenues [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Compensation cost		$ 20

Stockholders' Equity - Summar_4

Stockholders' Equity - Summary of Common Stock Reserved for Future Issuance (Detail) - shares	Dec. 31, 2021	Dec. 31, 2020
Class Of Stock [Line Items]
Common stock warrants	23,726,140	2,023,156
Common stock available for issuance under stock plans	46,189	513,141
Total	26,098,550	4,244,575
Common Stock [Member]
Class Of Stock [Line Items]
Common stock warrants	1,346	1,346
Common stock options issued and outstanding	2,326,221	1,708,278

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Apr. 30, 2019	Dec. 31, 2021	Dec. 31, 2020	Mar. 01, 2020
Operating Leased Assets [Line Items]
Lease commencement date		Mar. 1, 2020
Lease expiration date		Aug. 31, 2031
Lessee, operating lease, existence of option to extend		false
Rent abatement term		6 months
Tenant improvement allowance on modified lease		$ 2,200,000
Right-of-use asset		4,432,000	$ 4,411,000	$ 4,500,000
Operating lease liability		$ 4,744,000		$ 4,500,000
Operating lease remaining term		10 years
Finance lease remaining term		2 years
Operating lease weighted-average discount rate				12.20%
Finance lease weighted-average discount rate				10.00%
Issuance of preferred stock, value		$ 20,738,000	5,098,000
Accrued liabilities		0
Litigation and legal liability		0
PUR Biologics, LLC [Member]
Operating Leased Assets [Line Items]
Upfront cash paid	$ 500,000
Amount forgiven	22,000
Repayments of outstanding payable assumed	23,000
Development Assets [Member]
Operating Leased Assets [Line Items]
Milestone and royalty payment obligations	$ 400,000
Percentage of royalties on net sales	5.00%
Development Assets [Member] | Commercialization Milestone [Member]
Operating Leased Assets [Line Items]
Milestone and royalty payment obligations	$ 400,000
Development Assets [Member] | Product [Member] | Estimated Sales [Member]
Operating Leased Assets [Line Items]
Revenue target for milestone achievement	$ 500,000
Series D Convertible Preferred Stock [Member] | Development Assets [Member] | PUR Biologics, LLC [Member]
Operating Leased Assets [Line Items]
Issuance of preferred stock, shares	167,323
Issuance of preferred stock, value	$ 1,750,000
Contingent Liability [Member]
Operating Leased Assets [Line Items]
Payment for milestone		0	0
Payments for royalties		0	$ 0
Conatus Pharmaceuticals Inc [Member]
Operating Leased Assets [Line Items]
Right-of-use asset		100,000
Operating lease liability		$ 200,000
Office Space [Member]
Operating Leased Assets [Line Items]
Lease expiration date		Sep. 30, 2020
Amendment [Member]
Operating Leased Assets [Line Items]
Tenant improvement allowance on modified lease		$ 2,300,000
Reduction in operating lease liability		300,000
Reduction in right-of-use asset		300,000
Letter of Credit [Member]
Operating Leased Assets [Line Items]
Security Deposit		300,000
Letter of credit		300,000
Letter of Credit [Member] | Amendment [Member]
Operating Leased Assets [Line Items]
Letter of credit		400,000
Maximum [Member]
Operating Leased Assets [Line Items]
Tenant improvement allowance on modified lease		$ 2,200,000
Maximum [Member] | Development Assets [Member] | PUR Biologics, LLC [Member]
Operating Leased Assets [Line Items]
Potential cash payout	$ 6,250,000

Commitments and Contingencies_2

Commitments and Contingencies -Summary of Lease Assets and Lease Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Mar. 01, 2020
Leases [Abstract]
Right-of-use asset	$ 4,432	$ 4,411	$ 4,500
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	RightOfUseAssetMember	RightOfUseAssetMember
Finance lease	$ 20	$ 28
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property and equipment, net	Property and equipment, net
Total lease assets	$ 4,452	$ 4,439
Operating lease liability	$ 127	$ 28
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	CurrentPortionOfLeaseLiabilityMember	CurrentPortionOfLeaseLiabilityMember
Finance lease liability	$ 9	$ 8
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesMember	us-gaap:AccruedLiabilitiesMember
Total current liabilities	$ 136	$ 36
Operating lease liability	$ 4,617	$ 4,806
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	NoncurrentPortionOfLeaseLiabilityMember	NoncurrentPortionOfLeaseLiabilityMember
Finance lease liability	$ 14	$ 22
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesMember	us-gaap:OtherLiabilitiesMember
Total noncurrent liabilities	$ 4,631	$ 4,828
Total lease liabilities	$ 4,767	$ 4,864

Commitments and Contingencies_3

Commitments and Contingencies -Summary of Components of Lease Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Leases [Line Items]
Operating lease cost	$ 638	$ 861
Amortization of right-of-use assets	9	7
Interest on lease liabilities	3	3
Total finance lease cost	12	10
Cost of Product Revenue [Member]
Leases [Line Items]
Operating lease cost		106
Research and Development [Member]
Leases [Line Items]
Operating lease cost	210	158
General and Administrative [Member]
Leases [Line Items]
Operating lease cost	$ 428	$ 597

Commitments and Contingencies_4

Commitments and Contingencies - Summary of Supplemental Cash Flow Information Related to Leases (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating lease	$ 111	$ 299
Operating cash flows from finance lease	3	3
Financing cash flows from finance lease	$ 9	7
Right-of-use asset obtained in exchange for operating lease liability		$ 4,481

Commitments and Contingencies_5

Commitments and Contingencies - Schedule of Future Minimum Payments of Lease Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Mar. 01, 2020
Operating Lease
2022	$ 695
2023	780
2024	803
2025	827
Thereafter	5,183
Total minimum lease payments	8,288
Less: imputed interest	(3,544)
Total future minimum lease payments	4,744		$ 4,500
Less: current obligations under leases	(127)	$ (28)
Noncurrent lease obligations	4,617	4,806
Finance Lease
2022	11
2023	11
2024	4
Total minimum lease payments	26
Less: imputed interest	(3)
Total future minimum lease payments	23
Less: current obligations under leases	(9)	(8)
Noncurrent lease obligations	$ 14	$ 22

Income Taxes - Summary of Recon

Income Taxes - Summary of Reconciliation of Income Taxes Computed using Statutory U.S. Income Tax Rate and Provision (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Expense Benefit Continuing Operations Income Tax Reconciliation [Abstract]
Tax computed at federal statutory rate	$ (3,152)	$ (3,920)
State tax, net of federal tax benefits	(908)	(34)
Tax credits	(325)	43
Acquired intangible property		1,513
Valuation allowance	5,320	2,096
PPP loan forgiveness	(126)
Other	(809)	302
Provision for income taxes	$ 0	$ 0

Income Taxes - Components of Co

Income Taxes - Components of Company's Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Deferred tax assets:
Tax loss carryforward	$ 18,041	$ 13,519
R&D credits and other tax credits	1,834	1,498
Stock-based compensation	152	82
Compensation	58	135
Deferred revenue	5	10
Lease liability	1,283	1,024
Capitalized research and development	2,607	2,074
Other	80	133
Total deferred tax assets	24,060	18,475
Less: valuation allowance	(22,861)	(17,541)
Deferred tax assets, net	1,199	934
Deferred tax liability:
Right-of-use assets	$ (1,199)	$ (934)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Operating Loss Carryforwards [Line Items]
Deferred tax asset, change in valuation allowance amount	$ 5,300,000	$ 4,200,000
Cumulative change in ownership percentage	50.00%
Period for cumulative change in ownership percentage	3 years
Recognized interest or penalties on income tax	$ 0	$ 0
Federal [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	66,300,000
Operating loss carryforwards	34,000,000
Research credit carryforwards	$ 1,400,000
Research credit carryforwards expiration year	2027
Federal [Member] | Adaptive Biologix, Inc. [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 400,000
California [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	57,400,000
Operating loss carryforwards, expired	0
Research credit carryforwards	1,400,000
California [Member] | Adaptive Biologix, Inc. [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 400,000

Income Taxes - Summary of Activ

Income Taxes - Summary of Activity Related to Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Gross unrecognized tax benefits at the beginning of the year	$ 561	$ 401
Additions from tax positions taken in the current year	118	37
Additions from tax positions taken in prior years	4	128
Reductions for tax positions from prior year		(5)
Gross unrecognized tax benefits at end of the year	$ 683	$ 561

Related Parties - Additional In

Related Parties - Additional Information (Detail) $ in Thousands	1 Months Ended		12 Months Ended
	Apr. 30, 2020USD ($)PromissorynoteStockholder	Nov. 30, 2012	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Related Party Transaction [Line Items]
Number of promissory notes | Promissorynote	2
Promissory Note [Member]
Related Party Transaction [Line Items]
Debt instrument, face amount	$ 300
Number of stockholders | Stockholder	2
Debt instrument interest amount	$ 25
Debt instrument, maturity date	Jun. 13, 2020
Number of days post merger that amounts are due	15 days
Lordship Ventures Histogen Holdings LLC [Member]
Related Party Transaction [Line Items]
Percentage of outstanding voting shares controlled			4.70%	16.00%
Lordship Ventures Histogen Holdings LLC [Member] | Success Fee Agreement [Member]
Related Party Transaction [Line Items]
Minimum percentage of asset or equity engaged in merger or sale transaction		90.00%
Related party expense recognized			$ 10	$ 100
Lordship Ventures Histogen Holdings LLC [Member] | Allergan License Agreements [Member]
Related Party Transaction [Line Items]
Amount due to related parties			$ 12	14
Lordship Ventures Histogen Holdings LLC [Member] | Private Histogen [Member] | Success Fee Agreement [Member]
Related Party Transaction [Line Items]
Description of related party transaction			In November 2012, Private Histogen entered into a Strategic Relationship Success Fee Agreement with Lordship (the “Success Fee Agreement”). The Success Fee Agreement causes certain payments to be made from the Company to Lordship equal to 1% of certain product revenues and 10% of certain license and royalty revenues. The Success Fee Agreement also stipulates that if the Company engages in a merger or sale of all or substantially all (defined as 90% or more) of its assets or equity to a third party, then the Company has the option to terminate the agreement by paying Lordship the fair market value of future payments with the minimum payment being at least equal to the most recent annual payments Lordship has received.
Lordship Ventures Histogen Holdings LLC [Member] | Private Histogen [Member] | Success Fee Agreement [Member] | Product Revenue [Member]
Related Party Transaction [Line Items]
Success fee percentage to be paid on certain product revenues		1.00%
Lordship Ventures Histogen Holdings LLC [Member] | Private Histogen [Member] | Success Fee Agreement [Member] | License and Royalty Revenue [Member]
Related Party Transaction [Line Items]
Success fee percentage to be paid on certain license and royalty revenues		10.00%
Anti-Cancer Inc.[Member]
Related Party Transaction [Line Items]
Outstanding amounts owed to related party			$ 22	$ 22

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Postemployment Benefits [Abstract]
Minimum percentage of elgible compensation	1.00%
Maximum percentage of elgible compensation	100.00%
Percentage of contributions of employees salary deferrals up	25.00%
Maximum contribution amount per each employee	$ 2,500
Employee contributions	$ 0	$ 0