Altimmune, Inc. 10-K

Item 8. Financial Statements and Supplementary Data ​ ALTIMMUNE, INC. INDEX TO CONSOLIDATED FINANCIAL STATEMENTS ​ ​ Report of Independent Registered Public Accounting Firm — Ernst & Young LLP (PCAOB ID: 42 ) 95 Consolidated Balance Sheets as of December 31, 2021 and 2020 97 Consolidated Statements of Operations and Comprehensive Loss for the years ended December 31, 2021 and 2020 98 Consolidated Statements of Stockholders’ Equity for the years ended December 31, 2021 and 2020 99 Consolidated Statements of Cash Flows for the years ended December 31, 2021 and 2020 100 Notes to Consolidated Financial Statements 101 ​ ​ ​ ​ 94 REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM The Shareholders and the Board of Directors of Altimmune, Inc. Opinion on the Financial Statements We have audited the accompanying consolidated balance sheets of Altimmune, Inc. (the Company) as of December 31, 2021 and 2020, the related consolidated statements of operations and comprehensive loss, changes in stockholders’ equity and cash flows for each of the two years in the period ended December 31, 2021, and the related notes (collectively referred to as the “consolidated financial statements”). In our opinion, the consolidated financial statements present fairly, in all material respects, the financial position of the Company at December 31, 2021 and 2020, and the results of its operations and its cash flows for each of the two years in the period ended December 31, 2021, in conformity with U.S. generally accepted accounting principles. Basis for opinion These financial statements are the responsibility of the Company’s management. Our responsibility is to express an opinion on the Company’s financial statements based on our audits. We are a public accounting firm registered with the Public Company Accounting Oversight Board (United States) (PCAOB) and are required to be independent with respect to the Company in accordance with the U.S. federal securities laws and the applicable rules and regulations of the Securities and Exchange Commission and the PCAOB. We conducted our audits in accordance with standards of the PCAOB. Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement, whether due to error or fraud. The Company is not required to have, nor were we engaged to perform, an audit of its internal control over financial reporting. As part of our audits we are required to obtain an understanding of internal control over financial reporting but not for the purpose of expressing an opinion on the effectiveness of the Company’s internal control over financial reporting. Accordingly, we express no such opinion. Our audits included performing procedures to assess the risks of material misstatement of the financial statements, whether due to error or fraud, and performing procedures that respond to those risks. Such procedures included examining, on a test basis, evidence regarding the amounts and disclosures in the financial statements. Our audits also included evaluating the accounting principles used and significant estimates made by management, as well as evaluating the overall presentation of the financial statements. We believe that our audits provide a reasonable basis for our opinion. Critical Audit Matters The critical audit matter communicated below is a matter arising from the current period audit of the financial statements that was communicated or required to be communicated to the audit committee and that: (1) relates to accounts or disclosures that are material to the financial statements and (2) involved our especially challenging, subjective or complex judgments. The communication of the critical audit matter does not alter in any way our opinion on the consolidated financial statements, taken as a whole, and we are not, by communicating the critical audit matter below, providing a separate opinion on the critical audit matter or on the account or disclosure to which it relates. ​ ​ ​ ​ ​ Accounting for the Lonza manufacturing agreement, including related long-lived asset impairment assessment Description of the Matter ​ As explained in Note 3 to the consolidated financial statements, the Company capitalized costs related to the procurement of long-lead equipment and build out of the suite associated with the Company’s manufacturing collaboration with Lonza Houston, Inc. (“Lonza”) for the manufacture of AdCOVID or other adenovirus-based vaccines. In June 2021, the Company announced the discontinuation of further development of AdCOVID and in the fourth quarter terminated its agreement with Lonza. For the year ended December 31, 2021, the Company recorded $11.4 million of impairment loss on construction-in-progress. The fair value of the assets related to construction-in-progress was primarily determined utilizing the cost approach, which determines the current replacement cost of the asset being appraised and then deducts for the loss in value caused by 95 contractual restrictions on the asset, the probability of satisfying the contractual restrictions, physical deterioration, functional obsolescence and economic obsolescence. Auditing the Company's accounting conclusions for the Lonza Manufacturing Agreement and related impairment loss was complex due to the unusual and non-recurring nature of the transaction which required extensive audit effort. In particular, the accounting for the agreement involved an assessment of the relevant accounting guidance to determine whether the costs incurred qualified for capitalization and an evaluation of the fair value of the construction-in-progress in order to determine the impairment loss to be recorded. How We Addressed the Matter in Our Audit ​ To test the accounting for the Lonza manufacturing agreement, our audit procedures included, among others, inspecting the agreements and evaluating the completeness and accuracy of the Company’s technical accounting analyses of the transactions and application of relevant accounting guidance. This also included the involvement of subject matter resources to assist in evaluating the Company’s conclusion on the interpretation and application of the relevant accounting literature. It also included recalculating the estimate of fair value of the construction-in-progress and impairment loss recorded. ​ /s/ Ernst & Young LLP We have served as the Company’s auditor since 2017. Tysons, Virginia March 15, 2022 ​ 96 ALTIMMUNE, INC. CONSOLIDATED BALANCE SHEETS ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2021 ​ 2020 ASSETS ​ ​ Current assets: ​ ​ Cash and cash equivalents ​ $ 190,300,776 ​ $ 115,917,807 Restricted cash ​ 34,174 ​ 34,174 Total cash, cash equivalents and restricted cash ​ 190,334,950 ​ 115,951,981 Short-term investments ​ — ​ 100,005,558 Accounts receivable ​ 428,836 ​ 4,610,202 Income tax and R&D incentive receivables ​ 5,409,639 ​ 7,762,793 Prepaid expenses and other current assets ​ 7,952,690 ​ 1,926,675 Total current assets ​ 204,126,115 ​ 230,257,209 Property and equipment, net ​ 1,447,786 ​ 1,056,920 Intangible assets, net ​ 12,418,967 ​ 12,823,846 Other assets ​ 871,976 ​ 977,238 Total assets ​ $ 218,864,844 ​ $ 245,115,213 LIABILITIES AND STOCKHOLDERS’ EQUITY ​ ​ Current liabilities: ​ ​ Accounts payable ​ $ 2,034,493 ​ $ 612,293 Contingent consideration ​ ​ 6,090,000 ​ ​ — Accrued expenses and other current liabilities ​ 10,151,437 ​ 11,408,154 Total current liabilities ​ 18,275,930 ​ 12,020,447 Contingent consideration ​ — ​ 5,390,000 Other long-term liabilities ​ 1,454,203 ​ 1,828,443 Total liabilities ​ 19,730,133 ​ 19,238,890 Commitments and contingencies (Note 17) ​ ​ Stockholders’ equity: ​ ​ Common stock, $ 0.0001 par value; 200,000,000 shares authorized; 40,993,768 and 37,142,946 shares issued and outstanding at December 31, 2021 and December 31, 2020, respectively ​ ​ 4,090 ​ ​ 3,697 Additional paid-in capital ​ 497,342,207 ​ 417,337,742 Accumulated deficit ​ ( 293,171,423 ) ​ ( 186,420,599 ) Accumulated other comprehensive loss, net ​ ( 5,040,163 ) ​ ( 5,044,517 ) Total stockholders’ equity ​ 199,134,711 ​ 225,876,323 Total liabilities and stockholders’ equity ​ $ 218,864,844 ​ $ 245,115,213 ​ The accompanying notes are an integral part of the consolidated financial statements. ​ 97 ALTIMMUNE, INC. CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2021 ​ 2020 Revenues ​ $ 4,410,356 ​ $ 8,185,027 Operating expenses: ​ ​ Research and development ​ 74,541,115 ​ 49,774,328 General and administrative ​ 15,413,282 ​ 13,209,440 Impairment loss on construction-in-progress ​ 11,370,000 ​ — Total operating expenses ​ 101,324,397 ​ 62,983,768 Loss from operations ​ ( 96,914,041 ) ​ ( 54,798,741 ) Other income (expense): ​ ​ Interest expense ​ ( 5,656 ) ​ ( 9,421 ) Interest income ​ 202,741 ​ 322,514 Other (expense) income, net ​ ( 373,868 ) ​ 24,147 Total other (expense) income, net ​ ( 176,783 ) ​ 337,240 Net loss before income tax benefit ​ ( 97,090,824 ) ​ ( 54,461,501 ) Income tax benefit ​ — ​ 5,417,024 Net loss ​ ( 97,090,824 ) ​ ( 49,044,477 ) Other comprehensive income (loss) — unrealized gain (loss) on short-term investments ​ 4,354 ​ ( 24,361 ) Comprehensive loss ​ $ ( 97,086,470 ) ​ $ ( 49,068,838 ) Net loss per share, basic and diluted ​ $ ( 2.35 ) ​ $ ( 1.91 ) Weighted-average common shares outstanding, basic and diluted ​ 41,283,498 ​ 25,637,023 ​ The accompanying notes are an integral part of the consolidated financial statements ​ ​ ​ ​ 98 ​ ALTIMMUNE, INC. CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Additional ​ ​ ​ ​ Other ​ Total ​ Common Stock Paid-In Accumulated Comprehensive Stockholders’ ​ ​ Shares ​ Amount ​ Capital ​ Deficit ​ Loss ​ Equity Balance at December 31, 2019 ​ 15,312,167 $ 1,508 $ 187,914,916 $ ( 137,376,122 ) $ ( 5,020,156 ) ​ $ 45,520,146 Stock-based compensation — ​ — ​ 2,576,006 ​ — ​ — ​ 2,576,006 Exercise of stock options 46,966 ​ 4 ​ 128,892 ​ — ​ — ​ 128,896 Vesting of restricted stock awards including withholding, net 84,320 ​ 16 ​ ( 262,729 ) ​ — ​ — ​ ( 262,713 ) Issuance of common stock from Employee Stock Purchase Plan 92,661 ​ 8 ​ 135,463 ​ — ​ — ​ 135,471 Issuance of common stock and pre-funded warrants in public offering, net 4,119,564 ​ 412 ​ 124,027,403 ​ — ​ — ​ 124,027,815 Issuance of common stock in at-the-market offerings, net 5,594,455 ​ 560 ​ 48,155,512 ​ — ​ — ​ 48,156,072 Issuance of common stock upon exercise of warrants ​ 10,197,907 ​ 1,020 ​ 41,037,438 ​ — ​ — ​ ​ 41,038,458 Issuance of common stock related to contingent consideration liability ​ 1,694,906 ​ 169 ​ 13,624,841 ​ — ​ — ​ ​ 13,625,010 Unrealized loss on short term investments ​ — ​ — ​ — ​ — ​ ( 24,361 ) ​ ​ ( 24,361 ) Net loss — ​ — ​ — ​ ( 49,044,477 ) ​ — ​ ( 49,044,477 ) Balance at December 31, 2020 37,142,946 ​ 3,697 ​ 417,337,742 ​ ( 186,420,599 ) ​ ( 5,044,517 ) ​ 225,876,323 Stock-based compensation — ​ — ​ 5,518,890 ​ — ​ — ​ 5,518,890 Exercise of stock options 54,068 ​ 6 ​ 176,448 ​ — ​ — ​ 176,454 Vesting of restricted stock awards including withholding, net ( 28,850 ) ​ 4 ​ ( 400,341 ) ​ — ​ — ​ ( 400,337 ) Issuance of common stock from Employee Stock Purchase Plan 24,100 ​ ​ 3 ​ ​ 224,469 ​ ​ — ​ ​ — ​ 224,472 Retirement of common stock in exchange for common stock warrant ( 1,000,000 ) ​ ( 100 ) ​ ( 7,539,900 ) ​ ( 9,660,000 ) ​ — ​ ( 17,200,000 ) Issuance of common stock warrant in exchange for retirement of common stock — ​ — ​ 17,200,000 ​ — ​ — ​ 17,200,000 Issuance of common stock in at-the-market offerings, net ​ 4,800,454 ​ ​ 480 ​ ​ 64,814,899 ​ ​ — ​ ​ — ​ ​ 64,815,379 Issuance of common stock upon cashless exercise of warrants 1,050 ​ — ​ 10,000 ​ — ​ — ​ 10,000 Unrealized gain on short-term investments — ​ — ​ — ​ — ​ 4,354 ​ 4,354 Net loss — ​ — ​ — ​ ( 97,090,824 ) ​ — ​ ( 97,090,824 ) Balance at December 31, 2021 40,993,768 ​ $ 4,090 ​ $ 497,342,207 ​ $ ( 293,171,423 ) ​ $ ( 5,040,163 ) ​ $ 199,134,711 ​ The accompanying notes are an integral part of the consolidated financial statement ​ ​ ​ 99 ​ ALTIMMUNE, INC. CONSOLIDATED STATEMENTS OF CASH FLOWS ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2021 ​ 2020 CASH FLOWS FROM OPERATING ACTIVITIES: ​ ​ Net loss ​ $ ( 97,090,824 ) ​ $ ( 49,044,477 ) Adjustments to reconcile net loss to net cash used in operating activities: ​ ​ Change in fair value of contingent consideration liability ​ 700,000 ​ 16,265,010 Impairment loss on construction-in-progress ​ 11,370,000 ​ — Impairment loss on intangible assets ​ 579,497 ​ — Stock-based compensation expense ​ 5,518,890 ​ 2,576,006 Depreciation and amortization ​ 551,301 ​ 428,878 Unrealized losses (gains) on foreign currency exchange ​ 383,721 ​ ( 19,073 ) Changes in operating assets and liabilities: ​ ​ Accounts receivable ​ 4,181,366 ​ ( 3,589,024 ) Prepaid expenses and other current assets ​ ( 5,907,878 ) ​ ( 1,371,312 ) Accounts payable ​ 1,422,200 ​ 594,060 Accrued expenses and other liabilities ​ ( 2,299,368 ) ​ 6,987,815 Income tax and R&D incentive receivables ​ 2,353,154 ​ ( 7,133,698 ) Net cash used in operating activities ​ ( 78,237,941 ) ​ ( 34,305,815 ) CASH FLOWS FROM INVESTING ACTIVITIES: ​ ​ Proceeds from sales and maturities of short-term investments ​ 107,426,876 ​ 56,406,564 Purchases of short-term investments ​ ( 7,592,100 ) ​ ( 128,289,919 ) Purchases of property and equipment, net ​ ( 12,117,111 ) ​ ( 203,957 ) Cash paid for internally developed patents ​ ( 194,538 ) ​ ( 138,464 ) Net cash provided by (used in) investing activities ​ 87,523,127 ​ ( 72,225,776 ) CASH FLOWS FROM FINANCING ACTIVITIES: ​ ​ Payments of deferred offering costs ​ ​ ( 118,522 ) ​ ​ — Proceeds from exercises of warrants ​ — ​ 41,038,458 Proceeds from issuance of common stock in at-the-market offerings, net ​ 64,815,379 ​ 48,156,072 Proceeds from issuance of common stock and pre-funded warrants in public offering, net ​ — ​ 124,027,815 Proceeds from issuance of notes payable ​ — ​ 632,000 Payments of notes payable ​ — ​ ( 632,000 ) Proceeds from issuance of common stock from Employee Stock Purchase Plan ​ 224,472 ​ 135,471 Proceeds from exercises of stock options ​ 176,454 ​ 128,896 Net cash provided by financing activities ​ 65,097,783 ​ 213,486,712 Net increase in cash and cash equivalents and restricted cash ​ 74,382,969 ​ 106,955,121 Cash, cash equivalents and restricted cash at beginning of period ​ 115,951,981 ​ 8,996,860 Cash, cash equivalents and restricted cash at end of period ​ $ 190,334,950 ​ $ 115,951,981 ​ ​ ​ ​ ​ ​ ​ SUPPLEMENTAL CASH FLOW INFORMATION: ​ ​ Cash paid for interest ​ $ — ​ $ 1,791 SUPPLEMENTAL NON-CASH ACTIVITIES: ​ ​ Fair value of common stock retired in exchange for issuance of common stock warrant ​ $ 17,200,000 ​ $ — Common stock issued related to contingent consideration liability ​ $ — ​ $ 13,625,010 Operating lease liability and right of use asset addition ​ $ 72,047 ​ $ 338,212 ​ The accompanying notes are an integral part of the consolidated financial statements. ​ 100 ALTIMMUNE, INC. NOTES TO CONSOLIDATED FINANCIAL STATEMENTS 1. Nature of Business and Organization Altimmune, Inc., headquartered in Gaithersburg, Maryland, United States, together with its subsidiaries (collectively, the “Company” or “Altimmune”) is a clinical stage biopharmaceutical company incorporated under the laws of the State of Delaware. The Company is focused on developing treatments for obesity and liver diseases. The Company’s pipeline includes next generation peptide therapeutics for obesity and non-alcoholic steatohepatitis (“NASH”) (for both, pemvidutide [proposed INN], formerly known as ALT-801), and for chronic hepatitis B (HepTcell). Since its inception, the Company has devoted substantially all of its efforts to business planning, research and development, recruiting management and technical staff and raising capital, and has financed its operations through the issuance of common and preferred stock, long-term debt and proceeds from research grants and government contracts. The Company has not generated any revenues from the sale of any products to date, and there is no assurance of any future revenues from product sales. 2. Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation The accompanying consolidated financial statements are prepared in conformity with generally accepted accounting principles in the United States (“U.S. GAAP”) and in accordance with the rules and regulations of the United States Securities and Exchange Commission (“SEC”). The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All significant intercompany accounts and transactions have been eliminated in consolidation. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets, liabilities, revenue and expenses, and the disclosure of contingent assets and liabilities as of and during the reporting period. The Company bases estimates and assumptions on historical experience when available and on various factors that it believes to be reasonable under the circumstances. Significant estimates relied upon in preparing the accompanying consolidated financial statements were related to revenue recognition, the fair value of common stock and other equity instruments, accounting for stock-based compensation, income taxes, useful lives of long-lived assets, fair value of contingent consideration, impairment of long-lived assets, and accounting for project development and certain accruals. The Company assesses the above estimates on an ongoing basis; however, actual results could differ materially from those estimates. Segment Information The Company is managed and operates as a single business focused on the research and development of treatments for various diseases and disorders, and vaccines. The Company is managed by a single management team, and consistent with its organizational structure, the Chief Executive Officer manages and allocates resources at a consolidated level. Accordingly, the Company views its business as one operating segment. Cash Equivalents The Company considers all highly liquid investments purchased with remaining maturities of 90 days or less on the purchase date to be cash equivalents, and include amounts held in money market funds which are actively traded (a Level 1 input). 101 Restricted Cash The Company had restricted cash of $ 34,174 at both December 31, 2021 and 2020, held in money market savings accounts as collateral. The restricted cash as of December 31, 2021 and 2020 is for the Company’s facility lease obligation. Restricted cash is classified as a component of cash, cash equivalents, and restricted cash in the accompanying consolidated balance sheets and consolidated statements of cash flows. Short-term Investments The Company’s short-term investments are comprised of U.S. Treasury, corporate debt securities and certificate of deposit that have original maturities less than or equal to one year and are classified as available-for-sale securities. Such securities are carried at estimated fair value, with any unrealized holding gains or losses reported as accumulated other comprehensive income or loss, which is a separate component of stockholders’ equity. Realized gains and losses and declines in value judged to be other-than-temporary, if any, are included in other income (expenses), net in the consolidated results of operations. The Company reviews its investment portfolio for impairment quarterly or more frequently if circumstances warrant. In determining whether a decline in the value of an investment is other-than-temporary, the Company evaluates currently available factors that may include, among others: (1) general market conditions; (2) the duration and extent to which fair value has been less than the carrying value; (3) the investment issuer’s financial condition and business outlook; and (4) its assessment as to whether it is more likely than not that the Company will be required to sell a security prior to recovery of its amortized cost basis. A decline in the market value of any available-for-sale security below cost that is deemed to be other-than-temporary results in a reduction in fair value charged to earnings in that period, and a new cost basis for the security is established. Dividend and interest income are recognized in other income when earned. The cost of securities sold is calculated using the specific identification method. The Company places all investments with government agencies, or corporate institutions whose debt is rated as investment grade. Fair Value Measurements The Company records certain financial assets and liabilities at fair value in accordance with the guidance in Financial Accounting Standards Board (“FASB”) Accounting Standard Codification Topic 820, Fair Value Measurements and Disclosures (“ASC 820”), which defines fair value and establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy are described below: Level 1 — Quoted prices (unadjusted) in active markets for identical assets or liabilities that the Company can access at the measurement date. Level 2 — Inputs other than quoted prices included within Level 1 that are either directly or indirectly observable. If the asset or liability has a specified (contractual) term, a Level 2 input must be observable for substantially the full term. Level 3 — Unobservable inputs developed using estimates of assumptions developed by the Company, which reflect those that a market participant would use. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Fair value is a market-based measure considered from the perspective of a market participant rather than an entity-specific measure. Therefore, even when market assumptions are not readily available, the Company’s own assumptions are set to reflect those that market participants would use in pricing the asset or liability at the measurement date. The Company uses prices and inputs that are current as of the measurement date, including during periods of market dislocation. In periods of market dislocation, the observability of prices and inputs may change for many instruments. This condition could cause an instrument to be reclassified within levels in the fair value hierarchy. If applicable, the Company will recognize transfers into and out of Level 3 within the fair value hierarchy at the end of the reporting period in which the 102 actual event or change in circumstance occurs. There were no transfers into or out of Level 3 of the fair value hierarchy during the years ended December 31, 2021 and 2020. Financial Instruments The Company’s financial instruments consist of cash, cash equivalents, restricted cash, accounts receivable, short-term investments, notes payable, accounts payable, accrued expenses, contingent consideration, common stock warrants classified as a liability, and common stock warrants classified as equity. The carrying amounts of cash, cash equivalents, restricted cash, accounts receivable, accounts payable, and accrued expenses approximate their fair value due to the short-term nature of those financial instruments. Short-term investments are recorded at fair value, with any unrealized holding gains or losses reported as accumulated other comprehensive income or loss. Notes payable, prior to their redemption or cancellation, are recorded at their repayment value which approximates fair value. Contingent payments classified as a liability are recorded at fair value estimated using the Monte Carlo simulation valuation model. Common stock warrants classified as equity are initially recorded at their grant date fair value. For those warrants with a down round feature, if the down round feature is triggered, the Company would remeasure those instruments at that time with changes recorded as a deemed dividend all within equity. Common stock warrants classified as a liability are recorded at fair value and are remeasured every reporting period with the changes in fair value recorded as a component of other income (expenses), net until their settlement or exercise. Accounts Receivable Accounts receivable includes both billed and unbilled amounts. The Company makes judgments as to its ability to collect outstanding receivables and provides an allowance for receivables when collection becomes doubtful. Provisions are made based upon a specific review of all significant outstanding invoices and the overall quality and age of those invoices not specifically reviewed. The Company’s receivables represent amounts reimbursed under its government grants and contracts. The Company believes that credit risks associated with these government grants and contracts is not significant. To date, the Company has not experienced any losses associated with accounts receivable and does not maintain an allowance for doubtful accounts. Concentrations of Credit Risk Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents, restricted cash, and accounts receivable. Periodically, the Company maintains deposits in financial institutions in excess of government insured limits. Management believes that the Company is not exposed to significant credit risk as the Company’s deposits are held at financial institutions that management believes to be of high credit quality. The Company has not experienced any losses in these deposits. The Company recognizes research grants and contracts earned in connection with the services provided on research and development projects. The Company provides credit in the normal course of providing such services based on evaluations of the grantors’ financial condition and generally does not require collateral. To manage accounts receivable credit risk, the Company monitors the creditworthiness of its grantors. The U.S. government accounts for 97 % of revenue for both of the years ended December 31, 2021 and 2020. The U.S. government accounts for 100 % of accounts receivable for both of the years ended December 31, 2021 and 2020. Property and Equipment, Net The Company records property and equipment at cost less accumulated depreciation and amortization. Expenditures for maintenance and repairs are charged to operations as incurred, whereas major improvements are capitalized as additions to property and equipment. Costs of assets under construction are capitalized but are not depreciated until the construction is substantially complete and the assets being constructed are ready for their intended use. 103 Depreciation and amortization are recorded using the straight-line method over the estimated useful lives of the assets, as follows: ​ ​ ​ Asset Category Estimated Useful Life Computer and telecommunications 3 – 5 years Software 3 years Furniture, fixtures and equipment 5 years Laboratory equipment 7 years Leasehold improvements Lesser of lease term or estimated useful lives ​ Intangible Assets Intangible assets acquired in a business combination consist primarily of in-process research and development (“IPR&D”) assets. The value attributable to IPR&D projects at the time of acquisition is capitalized as an indefinite-lived intangible asset and tested for impairment until the project is completed or abandoned. Upon completion of the project, the indefinite-lived intangible asset will be accounted for as a finite-lived intangible asset and amortized on a straight-line basis over its estimated useful life. If the project is abandoned, the indefinite-lived intangible asset will be charged to expense. Intangible assets, including patents and licenses, acquired in other transactions are recorded at cost. Intangible assets with finite useful lives consist of legal and patent costs incurred in the course of obtaining patents and license issuance fees for the use of proprietary technologies. Costs incurred for obtaining patents are amortized on a straight-line basis over the estimated useful lives of the assets from the time of approval of the patent. Prior to approval, these costs are carried on the balance sheets and not amortized. In the event approval is denied, the cost of the denied application is expensed. License issuance fees are amortized on a straight-line basis over the estimated useful lives of the underlying licensed technology. Intangible assets with finite useful lives are being amortized over 6 to 20 years . These amortization costs are classified as research and development expenses in the accompanying statements of operations and comprehensive loss. Impairment of Long-lived Assets The Company evaluates its long-lived tangible and intangible assets for impairment whenever events or changes in circumstances indicate that the carrying amount of such assets may not be recoverable. Impairment of long-lived assets other than goodwill and indefinite lived intangibles is assessed by comparing the undiscounted cash flows expected to be generated by the asset group to its carrying value. During the year ended December 31, 2021, the Company recorded non-cash impairment charges for assets that were previously capitalized in connection with the discontinuation of AdCOVID (see Note 3). In addition, the Company recorded an impairment loss of $ 0.6 million on intangible assets associated with the Company’s discontinued development programs (see Note 5). The Company has indefinite lived intangible assets associated with in-process research and development (“IPR&D”). The Company’s IPR&D assets are currently non-amortizing. Until such time as the projects are either completed or abandoned, the Company test those assets for impairment at least annually at year end, or more frequently at interim periods, by evaluating qualitative factors which could be indicative of impairment. Qualitative factors being considered include, but are not limited to, the current project status, forecasted changes in the timing or amounts required to complete the project, forecasted changes in timing or changes in the future cash flows to be generated by the completed products, a probability of success of the ultimate project and changes to other market-based assumptions, such as discount rates. If impairment indicators are present as a result of the Company’s qualitative assessment, the Company will test those assets for impairment by comparing the fair value of the assets to their carrying value. Upon completion or abandonment, the value of the IPR&D assets will be amortized to expense over the anticipated useful life of the developed products, if completed, or charged to expense when abandoned if no alternative future use exists. Key assumptions used in the Company’s impairment analysis tests include projected cash flows, a probability of success of the ultimate project, and the discount rate. 104 The Company has one IPR&D asset, HepTcell, that was acquired in 2015. This candidate is a viral pathogen immunotherapy product for the treatment of chronic HBV. The Company performed a qualitative assessment for the IPR&D impairment testing for 2021 and 2020 and determined that no impairment indicators were present. Leases The Company’s headquarters lease is the primary lease, accounted for as an operating lease under FASB Accounting Standards Codification Topic 842, Leases (“ASC 842”), utilizing the prospective optional transition method. The Company elected the package of practical expedients permitted. Accordingly, the Company accounted for its existing operating leases as operating leases under ASC 842, without reassessing (a) whether the contracts contain a lease, (b) whether classification of the operating leases would be different in accordance with ASC 842, or (c) whether the unamortized initial direct costs before transition adjustments would have met the definition of initial direct costs at lease commencement. In addition, the Company does not allocate the consideration between lease and non-lease components. The Company determines if an arrangement is a lease at inception. Operating leases are recorded as a current and long-term lease obligation, with a corresponding right of use lease assets. The lease obligations represent the Company’s obligation to make lease payments arising from the lease. The right of use lease assets represent the Company’s right to use an underlying asset for the lease term. The lease obligations and the operating right of use lease assets are recognized at the commencement date based on the present value of lease payments over the lease term. As most of the Company’s leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date in determining the present value of lease payments. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. Lease expense for lease payments is recognized on a straight-line basis over the lease term. Short-term leases are leases having a term of twelve months or less. The Company recognizes short-term leases on a straight-line basis and does not record a related lease asset or liability for such leases. Lease incentives and allowance provided by our landlord for the construction of leasehold improvements are recorded as lease incentive obligations as the related construction costs are incurred, up to the maximum allowance. Contingent Consideration The Company records contingent consideration associated with development and regulatory milestones that meets the definition of a liability under FASB Accounting Standards Codification Topic 480, Distinguishing Liabilities From Equity (“ASC 480”) at fair value. The fair value model used to calculate this obligation is based on the Monte Carlo simulation that has been risk adjusted based on the probability of achievement of the milestones. The inputs the Company uses for determining the fair value of the contingent consideration associated with development and regulatory milestones are Level 3 fair value measurements. The Company re-evaluates the fair value on a quarterly basis. Changes in the fair value can result from adjustments to the probability of achievement of the milestones, stock price, volatility and the risk-free interest rate. The change in Company’s estimates associated with the timing of payments which will become due and payable for development and regulatory milestones will change the fair value of contingent consideration, resulting in a charge or contra expense to research and development expense in the period in which the increase or decrease is determined. Warrants Common stock warrants issued in connection with the 2018 Unit Offering, the 2018 and 2019 Registered Direct Offerings, and the 2020 Public Offering (all terms defined in Note 10 and Note 11), were classified as a component of permanent equity because they are freestanding financial instruments that were legally detachable and separately exercisable from other debt and equity instruments, are contingently exercisable, do not embody an obligation for the Company to repurchase its shares, and permits the holders to receive a fixed number of common shares upon exercise. In addition, such warrants did not provide any guarantee of value or return. The 2018 Registered Direct Offering and 2019 Registered Direct Offering triggered down round adjustments to the exercise price of warrants issued in connection with 105 the 2018 Unit Offering. In 2019, the Company treated the value of the effect of the reduction in exercise price as a deemed dividend, resulting in a reduction to income available to common shareholders (see Note 11). There was a reduction in exercise price in 2020 due to the At-the-Market Offering which triggered an anti-dilution provision under the warrant agreement with the Company’s holders of redeemable preferred stock (see Note 11). Stock-based Compensation The Company accounts for all stock-based compensation granted to employees and non-employees using a fair value method. Stock-based compensation awarded to employees is measured at the grant date fair value of stock option grants and is recognized over the requisite service period of the awards, usually the vesting period, on a straight-line basis, net of estimated forfeitures. If awards are modified, the Company compares the fair value of the affected award measured immediately prior to modification to its value after modification. To the extent that the fair value of the modified award exceeds the original award, the incremental fair value of the modified award is recognized as compensation expense on the date of modification for vested awards, and over the remaining vesting period for unvested awards. Revenue The Company’s revenue consists primarily of government and foundation grants and contracts that support the Company’s efforts on specific research projects. The Company has determined that the government agencies and foundations providing grants and contracts to the Company are not customers. These grants and contracts generally provide for reimbursement of approved costs as those costs are incurred by the Company. Research grants and contracts and the related accounts receivable are recognized as earned in proportion to when reimbursable expenses are incurred in performance of the contract. Payments received in advance of services being provided are recorded as deferred revenue. The Company anticipates that these government and foundation grants will decline in future periods. Research and Development Research and development costs are expensed as incurred. Research and development costs consist of payroll and personnel expense, consulting costs, external contract research and development expenses, which includes fees paid to other entities that conduct certain research and development activities on the Company’s behalf, such as clinical research organizations (“CROs”) and contract manufacturing organizations (“CMOs”), raw materials, drug product manufacturing costs, laboratory supplies and allocated overhead, including depreciation and amortization, rent and utilities. Material research and development costs that are paid in advance of performance are capitalized as a prepaid expense and amortized over the service period as the services are provided. Clinical trial costs are a significant component of research and development expenses, and the Company outsources a significant portion of these costs to third parties. Third party clinical trial expenses include investigator fees, site and patient costs, CRO costs, costs for central laboratory testing, data management and CMO costs. The accrual for site and patient costs includes inputs such as estimates of patient enrollment, patient cycles incurred, clinical site activations and other pass-through costs. These inputs are required to be estimated due to a lag in receiving the actual clinical information from third parties. Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected on the consolidated balance sheets as a prepaid asset or accrued expenses. These third-party agreements are generally cancelable, and related costs are recorded as research and development expenses as incurred. Material advance payments for goods or services that will be used or rendered for future research and development activities are recorded as a prepaid asset and recognized as expense as the related goods are delivered or the related services are performed. When evaluating the adequacy of the accrued expenses, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Significant judgments and estimates may be made in determining the accrued balances at the end of any reporting period. Research and Development Incentive Credits The Company is eligible to obtain certain research and development (“R&D”) incentive credits, through the participation in the U.K. R&D Small and Medium Enterprise tax relief program (“U.K. R&D credit”) and the Australian 106 research and development incentive credit (the “Australia R&D credit”) program administered through the Australian Tax Office (the “ATO”). The U.K. R&D credits are calculated as a percentage of qualifying R&D expenses and are payable in cash by the U.K. government to the Company. Qualifying R&D expenses consist of employment costs for research staff, consumables, a proportion of relevant, permitted sub-contract costs and certain internal overhead costs incurred as part of research projects for which the Company does not receive income. The Australia R&D credits provide for a cash refund based on a percentage of certain research and development activities undertaken in Australia by the Company’s wholly owned subsidiary, Altimmune AU Pty, Limited. Qualifying R&D expenses must be incurred within the country. The Company will record a reduction to R&D expense in the consolidated statement of operations and comprehensive loss when there is reasonable assurance that the Company will comply with the conditions attached to the incentive credits and that the incentive credits will be received. The U.K. and Australian incentive credits are available on the basis of specific criteria with which the Company must comply. The incentive credits are subject to future audits by the government authorities and a four-year statute of limitations. Although the incentive credits may be administered through the local tax authority, the Company has accounted for the incentives outside of the scope of FASB Accounting Standards Codification Topic 740, Income Taxes (“ASC 740”), since the incentives are not linked to the Company’s taxable income and can be realized regardless of whether the Company has generated taxable income in the respective jurisdictions. The Company accounts for these incentive credits as a government grant which analogizes with International Accounting Standards 20 (“IAS 20”), Accounting for Government Grants and Disclosure of Government Assistance . As of and for the year ended December 31, 2021 and 2020, the Company recognized $ 1.8 million and $ 2.3 million, respectively, of R&D credits included in “Income tax and R&D incentive receivables” on the accompanying consolidated balance sheets and a corresponding reduction to R&D expense in the consolidated statement of operations and comprehensive loss. Income Taxes The Company accounts for income taxes in accordance with ASC 740. ASC 740 uses the asset and liability approach, which requires the recognition of future tax benefits or liabilities on the temporary differences between the financial reporting and tax bases of our assets and liabilities. Deferred tax assets and liabilities represent future tax consequences of temporary differences between the financial statement carrying amounts and the tax basis of assets and liabilities and for loss carryforwards using enacted tax rates expected to be in effect in the years in which the differences reverse. A valuation allowance is established when necessary to reduce deferred tax assets to the amounts expected to be realized. The Company also recognizes a tax benefit from uncertain tax positions only if it is “more likely than not” that the position is sustainable based on its technical merits. The Company accounts for interest and penalties related to uncertain tax positions as part of its provision for income taxes. To date, the Company has not incurred interest and penalties related to uncertain tax positions. Should such costs be incurred, they would be classified as a component of provision for income taxes. The Company conducts R&D activities potentially qualified to claim research tax credits for U.S. federal and state purposes under Internal Revenue Code Section 41. The Company has not performed a formal study claiming these credits in the tax returns because the Company does not yet have taxable profits. Once the Company becomes profitable, it will likely have a study prepared, and the amount of R&D tax credits available could generate income tax benefit, subject to an annual Section 383 limitation and valuation allowance for realizability of the deferred tax asset. As of December 31, 2021 and 2020, the Company recognized $ 3.6 million and $ 5.4 million of income tax receivables included in “Income tax and R&D incentive receivables” on the accompanying consolidated balance sheets. Comprehensive Loss For the years presented, the total comprehensive loss includes net loss and other comprehensive income (loss) which represents unrealized gains or losses on investments. 107 Net Loss per Share Basic net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding for the period without consideration for potentially dilutive securities. The Company computes diluted net loss per common share after giving consideration to all potentially dilutive common equivalents, including all unvested restricted stock, common stock warrants, and common stock options outstanding during the period except where the effect of such non-participating securities would be anti-dilutive. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and dilutive common stock equivalents outstanding for the period determined using the treasury-stock and if-converted methods. Recently Issued Accounting Pronouncements Recently Adopted : In December 2019, the FASB issued Accounting Standards Update (“ASU”) No. 2019-12, Income Taxes (Topic 740), Simplifying the Accounting for Income Taxes (“ASU No. 2019-12”). ASU No. 2019-12 amends the approaches and methodologies in accounting for income taxes during interim periods and makes changes to certain income tax classifications. The new standard allows exceptions to the use of the incremental approach for intra-period tax allocation, when there is a loss from continuing operations and income or a gain from other items, and to the general methodology for calculating income taxes in an interim period, when a year-to-date loss exceeds the anticipated loss for the year. The standard also requires franchise or similar taxes partially based on income to be reported as income tax and the effects of enacted changes in tax laws or rates to be included in the annual effective tax rate computation from the date of enactment. Lastly, in any future acquisition, the Company would be required to evaluate when the step-up in the tax basis of goodwill is part of the business combination and when it should be considered a separate transaction. The Company adopted the standard as of January 1, 2021 and determined that the adoption did not have a material impact on the Company’s consolidated financial statements. In November 2021, the FASB issued ASU No. 2021-10, Government Assistance (Topic 832): Disclosures by Business Entities about Government Assistance (“ASU No. 2021-10”). ASU No. 2021-10 has an effective and transition date of January 1, 2022. This standard increases the transparency of transactions with the government that are accounted for by applying a grant or contribution accounting model and aims to reduce diversity that currently exists in the recognition, measurement, presentation, and disclosure of government assistance received by business entities due to the lack of specific authoritative guidance in GAAP. This standard requires an entity to provide information regarding the nature of the transaction with a government and the related accounting policy used to account for this transaction, the line item on the consolidated balance sheets and consolidated statement of operations and comprehensive loss that are affected by the transaction and the amounts applicable to each financial statement line item, and the significant terms and conditions of the transaction, including commitments and contingencies. The Company early adopted the standard as of December 31, 2021 and determined that the adoption of this standard did not have a material impact on the Company's consolidated financial statements. Not Yet Adopted : In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (“ASU No. 2016-13”). ASU No. 2016-13 requires entities to measure all expected credit losses for financial assets held at the reporting date based on historical experience, current conditions and reasonable and supportable forecasts. This update also required enhanced disclosures to help financial statement users better understand significant estimates and judgments used in estimating credit losses, as well as the credit quality and underwriting standards of an entity’s portfolio. This standard is effective for the Company as a smaller reporting company beginning January 1, 2023. Adoption is not expected to have a material impact on the Company’s consolidated financial statements. 108 3. Fair Value Measurement The Company records cash equivalents, short-term investments, contingent consideration and warrant liability at fair value on a recurring basis. Fair value is an exit price, representing the amount that would be received from the sale of an asset or paid to transfer a liability in an orderly transaction between market participants based on assumptions that market participants would use in pricing an asset or liability. The Company’s assets and liabilities measured at fair value on a recurring basis at December 31, 2021 consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement at December 31, 2021 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents - money market funds ​ $ 65,634,137 ​ $ 65,634,137 ​ $ — ​ $ — Total ​ ​ 65,634,137 ​ ​ 65,634,137 ​ ​ — ​ ​ — Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration liability (see Note 8) ​ 6,090,000 ​ — ​ — ​ 6,090,000 Total ​ $ 6,090,000 ​ $ — ​ $ — ​ $ 6,090,000 ​ The Company’s assets and liabilities measured at fair value on a recurring basis at December 31, 2020 consisted of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement at December 31, 2020 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents - money market funds ​ $ 90,389,473 $ 90,389,473 $ — $ — Short-term investments ​ 100,005,558 ​ — ​ 100,005,558 ​ — Total ​ ​ 190,395,031 ​ ​ 90,389,473 ​ ​ 100,005,558 ​ ​ — Liabilities: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Contingent consideration liability (see Note 8) ​ 5,390,000 ​ — ​ — ​ 5,390,000 Warrant liability ​ 10,000 ​ — ​ — ​ 10,000 Total ​ $ 5,400,000 ​ $ — ​ $ — ​ $ 5,400,000 ​ There was no warrant liability at December 31, 2021. The warranty liability is included in Other long-term liabilities in the consolidated balance sheet at December 31, 2020. The warrant liability was valued using the Monte Carlo simulation valuation model with Level 3 inputs. Short-term investments have been initially valued at the transaction price and subsequently valued at the end of each reporting period utilizing third party pricing services or other market observable data (Level 2). The pricing services utilize industry standard valuation models, including both income and market-based approaches and observable market inputs to determine value. There were no short-term investments at December 31, 2021. Short-term investments with quoted prices at December 31, 2020 as shown below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ Unrealized Gain ​ ​ ​ ​ ​ Amortized Cost ​ (Loss) ​ Market Value United States treasury securities $ 20,052,757 $ 1,843 $ 20,054,600 Commercial paper and corporate debt securities ​ ​ 47,521,344 ​ ​ ( 5,440 ) ​ ​ 47,515,904 Asset backed securities ​ 7,414,619 ​ ( 757 ) ​ 7,413,862 Certificate of deposit ​ ​ 25,021,192 ​ ​ — ​ ​ 25,021,192 Total ​ $ 100,009,912 ​ $ ( 4,354 ) ​ $ 100,005,558 ​ The fair value of contingent payments classified as a liability is based on the regulatory milestones described in Note 8 and estimated using the Monte Carlo simulation valuation model with Level 3 inputs. 109 The assumptions used to estimate the fair value of contingent payments that were classified as a liability at December 31, 2021 include the following significant unobservable inputs: ​ ​ ​ ​ ​ Unobservable input ​ Value or Range Weighted-Average Expected volatility 80.1 % ​ 80.1 % Risk-free interest rate 0.26 % ​ 0.26 % Cost of capital 30 % ​ 30 % Discount for lack of marketability 8 %‑ 13 % ​ 11 % Probability of payment 88 % ​ 88 % Projected year of payment 2022 2022 ​ The assumptions used to estimate the fair value of contingent payments that were classified as a liability at December 31, 2020 include the following significant unobservable inputs: ​ ​ ​ ​ ​ Unobservable input ​ Value or Range Weighted-Average Expected volatility 114.9 % ​ 114.9 % Risk-free interest rate 0.11 % ​ 0.11 % Cost of capital 30 % ​ 30 % Discount for lack of marketability 9 %‑ 15 % ​ 12 % Probability of payment 63 % ​ 63 % Projected year of payment 2022 2022 ​ If applicable, the Company will recognize transfers into and out of Level 3 within the fair value hierarchy at the end of the reporting period in which the actual event or change in circumstance occurs. There were no transfers into and out of Level 3 of the fair value hierarchy during the years ended December 31, 2021 or 2020. Separate disclosure is required for assets and liabilities measured at fair value on a recurring basis from those measured at fair value on a non-recurring basis. Assets recorded at fair value on a non-recurring basis, such as property and equipment and intangible assets are recognized at fair value when they are impaired. During the year ended December 31, 2021, the Company recorded non-cash impairment charges to property and equipment, net on a non-recurring basis (see below). During the year ended December 31, 2020, the Company had no significant assets or liabilities that were measured at fair value on a non-recurring basis. Lonza Manufacturing Agreement ​ In March 2021, the Company expanded its manufacturing collaboration with Lonza Houston, Inc. (“Lonza”) for the manufacture of AdCOVID or other adenovirus-based vaccines. Under the expanded agreement, the Company has committed approximately $ 23.0 million to Lonza to procure long-lead equipment and construct a dedicated manufacturing suite for clinical and commercial production of adenovirus-based vaccines. This work was completed during the fourth quarter of 2021. The Company capitalized a total of $ 11.4 million as construction-in-progress (“CIP”) during the year ended December 31, 2021 under this expanded agreement. In June 2021, the Company announced the discontinuation of further development of AdCOVID following the Company’s review of findings from the Phase 1 clinical trial. Construction continued at Lonza, and the Company assessed its strategic options with respect to the suite. Should Lonza contract a replacement project with another customer for the suite within 12 months of termination, Lonza shall reimburse the Company for 75 % of the price paid for any equipment that can be utilized for the other customer. The Company’s expectation was that, more likely than not, the suite would be disposed of significantly before the end of its previously estimated useful life. ​ During the nine months ended September 30, 2021, the Company recorded a non-cash impairment charge of $ 8.1 million to property and equipment, net associated with the construction of the Lonza facility. The fair value of the CIP related assets was $ 3.3 million at September 30, 2021. At September 30, 2021, the fair value of the CIP related assets was primarily determined utilizing the cost approach, which reflects the current replacement cost of the asset being appraised, adjusted for contractual restrictions on the assets, the probability of satisfying the contractual restrictions, physical 110 deterioration, functional obsolescence and economic obsolescence. The fair value measurement was considered a Level 3 measurement within the valuation hierarchy. During the fourth quarter of 2021, due to the failure of negotiations with the lead potential replacement customer for the CIP related assets and potential negotiations with other prospective customers failing to materialize, and due to other specific competitive and market conditions, as well as the termination of the manufacturing agreement with Lonza in December 2021, along with the remote probability of recovering cost after termination, the Company considered these triggering events and reassessed the CIP related assets for impairment and determined that the assets had no potential value and recorded an additional impairment charge of $ 3.3 million for the full remaining value of the CIP related assets. For the year ended December 31, 2021, the Company recorded a total of $ 11.4 million in non-cash impairment charges associated with CIP in the accompanying audited consolidated statements of operations and comprehensive loss. Following the discontinuation of AdCOVID, incremental costs incurred under the construction contract have been recorded to research and development expenses in the accompanying audited consolidated statements of operations and comprehensive loss. Research and development expenses related to the Lonza manufacturing agreement was approximately $ 11.6 million, less $ 1.0 million of credit issued by Lonza, for the year ended December 31, 2021. ​ 4. Property and Equipment, Net Property and equipment, net consists of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2021 ​ 2020 Furniture, fixtures and equipment $ 222,430 $ 125,538 Laboratory equipment ​ 1,040,199 ​ 959,585 Computers and telecommunications ​ 291,302 ​ 220,316 Software ​ 147,556 ​ 64,409 Leasehold improvements ​ 1,793,179 ​ 1,285,883 Property and equipment, at cost ​ 3,494,666 ​ 2,655,731 Less: accumulated depreciation and amortization ​ ​ ( 2,046,880 ) ​ ​ ( 1,598,811 ) Property and equipment, net ​ $ 1,447,786 ​ $ 1,056,920 ​ Depreciation expense related to property and equipment for the years ended December 31, 2021 and 2020 was $ 0.4 million and $ 0.3 million, respectively. 5. Intangible Assets The Company’s intangible assets consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2021 ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Estimated ​ Carrying ​ Accumulated ​ ​ ​ ​ Net Book ​ ​ Useful Lives ​ Value ​ Amortization ​ Impairment ​ Value Internally developed patents 6 – 20 years $ 1,079,325 $ ( 499,828 ) $ ( 579,497 ) $ — Acquired licenses 16 – 20 years ​ 285,000 ​ ( 285,000 ) ​ — ​ — Total intangible assets subject to amortization ​ 1,364,325 ​ ( 784,828 ) ​ ( 579,497 ) ​ — IPR&D assets Indefinite ​ 12,418,967 ​ — ​ — ​ 12,418,967 Total ​ $ 13,783,292 ​ $ ( 784,828 ) ​ $ ( 579,497 ) ​ $ 12,418,967 ​ 111 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2020 ​ ​ ​ ​ Gross ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Estimated ​ Carrying ​ Accumulated ​ ​ ​ ​ Net Book ​ Useful Lives Value Amortization Impairment Value Internally developed patents 6 – 10 years ​ $ 884,787 ​ $ ( 479,908 ) ​ $ — ​ $ 404,879 Acquired licenses 16 – 20 years ​ 285,000 ​ ( 285,000 ) ​ — ​ — Total intangible assets subject to amortization ​ 1,169,787 ​ ( 764,908 ) ​ — ​ 404,879 IPR&D assets Indefinite ​ 12,418,967 ​ — ​ — ​ 12,418,967 Total ​ $ 13,588,754 ​ $ ( 764,908 ) ​ $ — ​ $ 12,823,846 ​ Amortization expense of intangible assets subject to amortization totaled $ 19,920 and $ 46,813 for the years ended December 31, 2021 and 2020, respectively. Amortization expense was classified as research and development expenses in the accompanying consolidated statements of operations and comprehensive loss. Intangible assets subject to amortization, which represent incomplete technologies, was amortized to expense over their estimated useful lives once the underlying technologies were substantially complete. In the event that in the future the Company ceases the development of these assets, the remaining carrying value would be written off at that time. IPR&D assets are periodically assessed for impairment by considering the state of completion of the projects, the remaining activities required to complete development, the anticipated market for the completed products and anticipated future cash required to complete development. As of December 31, 2021, the Company recorded an impairment loss of $ 0.6 million for the remaining net book value of the internally developed patents that are associated with the Company's discontinued development programs. The impairment loss has been recorded to research and development expenses in the accompanying audited consolidated statements of operations and comprehensive loss. There was no IPR&D impairment loss during the year ended December 31, 2021 and 2020. 6. Leases The Company rents office and laboratory space in the United States. The Company also leases office equipment under non-cancellable equipment leases through June 2026 . Rent expense during the years ended December 31, 2021 and 2020 under all of the Company’s operating leases was $ 0.5 million and $ 0.4 million, respectively, which includes short-term leases and variable lease costs that are not included in the lease obligation. The office space lease provides for increases in future minimum annual rental payments as defined in the lease agreements. The office space lease also includes an option to renew the lease as of the end of the term. The Company has determined that the lease renewal option is not reasonably certain of being exercised. The cash paid for operating lease liabilities for the year ended December 31, 2021 and 2020 was $ 0.5 million and $ 0.4 million, respectively. Supplemental balance sheet information related to the operating leases is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2021 ​ 2020 Operating lease obligations (see Note 7 and 9) $ 1,535,112 $ 1,824,840 ​ Operating lease right-of-use assets (included in "Other assets" in Balance Sheet) ​ $ 798,178 ​ $ 903,825 ​ Weighted-average remaining lease term (years) ​ 3.3 ​ 4.33 ​ Weighted-average discount rate ​ 7.2 % 7.3 % ​ 112 Maturities of operating lease liabilities are as follows: ​ ​ ​ ​ Year ending December 31, ​ 2022 ​ $ 505,305 2023 ​ 515,314 2024 ​ 525,623 2025 ​ 176,365 Total operating lease payments ​ 1,722,607 Less: imputed interest ​ ( 187,495 ) Total operating lease liabilities (see Note 7 and 9) ​ $ 1,535,112 ​ ​ 7. Accrued Expenses and Other Current Liabilities Accrued expense and other current liabilities consist of the following: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2021 ​ 2020 Accrued professional services $ 395,940 $ 1,350,194 Accrued payroll and employee benefits ​ 2,313,436 ​ 2,351,599 Accrued research and development ​ 6,987,598 ​ 7,316,876 Lease obligation, current portion (see Note 6) ​ 411,450 ​ 356,716 Accrued interest and other ​ 43,013 ​ 32,769 Total accrued expenses and other current liabilities ​ $ 10,151,437 ​ $ 11,408,154 ​ ​ 8. Contingent Consideration The Company entered into an Agreement and Plan of Merger and Reorganization, dated July 8, 2019 , by and among the Company, Springfield Merger Sub, Inc., Springfield Merger Sub, LLC, Spitfire Pharma, Inc. and David Collier, as the Stockholder Representative (the “Spitfire Merger Agreement”) to acquire all of the equity interests of Spitfire Pharma, Inc. (“Spitfire”). Spitfire was a privately held, preclinical pharmaceutical company developing a novel dual GLP-1/glucagon receptor agonist for the treatment of non-alcoholic steatohepatitis. The transaction closed on July 12, 2019. The Company issued 1,887,250 unregistered shares of its common stock (the “shares”) as upfront consideration to certain former securityholders of Spitfire (collectively, the “Spitfire Equityholders”), representing an amount equal to $ 5.0 million less working capital and transaction expense adjustment amounts as defined in the agreement. The acquisition of Spitfire was accounted for as an asset acquisition instead of a business combination because substantially all of the fair value of the gross assets acquired was concentrated in a single identifiable asset or group of similar identifiable assets, and therefore, the asset was not considered a business. The Company expensed the acquired intellectual property as of the acquisition date as in-process research and development with no alternative future uses. The Spitfire Merger Agreement also includes future contingent payments up to $ 88.0 million in cash and shares of the Company’s common stock as follows (each, a “Milestone Event”): ● a one-time payment of $ 5.0 million (the “IND Milestone Consideration Amount”) within sixty days of the submission of an Investigational New Drug Application (“IND”) to the United States Food and Drug Administration (the “FDA”) or other applicable governmental authority in a foreign jurisdiction, which IND has not been rejected or placed on clinical hold by the FDA or such applicable foreign governmental authority within time specified in the Spitfire Merger Agreement; ● a one-time payment of $ 3.0 million (the “Phase 2 Milestone Consideration Amount” and together with the IND Milestone Consideration Amount, the “Regulatory Milestones”) within sixty days of the initiation (first patient, first dosing) of the first Phase 2 clinical trial of a product candidate anywhere in the world; and 113 ● payments of up to $ 80.0 million upon the achievement of specified worldwide net sales (the “Sales Milestones”) of all products developed using the technology acquired in the License Agreement within ten years following the approval of a new drug application filed with the FDA. The Regulatory Milestones will be payable in shares of the Company’s Common Stock, with the number of shares of the Company’s Common Stock to be issued in connection with each milestone amount, if any, dependent on the share price at the time of achievement. The number of any shares issued in consideration for the IND Milestone Consideration Amount will be determined based on lower of (A) the average of the closing prices of our Common Stock as reported on the Nasdaq Global Market for the twenty (20) consecutive trading days prior to the IND Reference Date or (B) $ 2.95 . The value of any shares issued in consideration for the Phase 2 Milestone Consideration Amount shall be determined based the lower of (A) on the average of the closing trading prices of our Common Stock as reported on the Nasdaq Global Market for the twenty (20) consecutive trading days immediately preceding the date of the occurrence of the Phase 2 Milestone Event or (B) $ 3.54 . The future contingent payments related to the Regulatory Milestones are stock-based payments accounted for under ASC 480. Such stock-based payments are subject to a lock-up whereby 50 % of the shares are released at 3 months and 50 % are released at 6 months. The future contingent payments related to the Sales Milestones are predominately cash-based payments accounted for under FASB Accounting Standards Codification Topic 450, Contingencies . Accordingly, the Company will recognize the Sales Milestones when the contingency is probable and the amount is reasonably estimated. On November 3, 2020, the Company received acknowledgement from the Australian Government Department of Health on the Company’s submitted clinical trial notification (“CTN”) which triggered the obligation to settle the IND Milestone payment to the former owners. As a result, on November 19, 2020, the Company issued 1,694,906 shares of its Common Stock valued at $ 9.57 per share for the amount value of $ 13.6 million to the former Spitfire stockholders. Pursuant to the Spitfire Merger Agreement, the Company issued the shares within sixty days of the submission of the CTN, which was October 29, 2020 . From September 30, 2020 through the date of issuance, the Company recognized a decrease in the fair value of the IND Milestone payment of $ 5.4 million to research and development expense and reclassified the balance in the contingent consideration liability associated with the fair value of the IND Milestone payment to equity in the Company’s consolidated balance sheet. No Regulatory Milestones were achieved during the year ended December 31, 2021; however, the milestone which would trigger the Phase 2 Milestone Consideration Amount remains outstanding. The Company estimates the future contingent consideration for the Regulatory Milestones based upon a Monte Carlo simulation valuation model that is risk adjusted based on the probability of achieving the milestones and a discount for lack of marketability. The Company remeasures the fair value of the contingent consideration at each reporting period. During the fourth quarter of 2020, the Company achieved the IND Milestone and paid the obligation in shares according to the calculation discussed above. Below is a summary of the contingent consideration activity: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2021 ​ 2020 Beginning balance $ 5,390,000 $ 2,750,000 Change in fair value ​ 700,000 ​ 16,265,010 Fair value of payments settled in common stock (IND Milestone) ​ — ​ ( 13,625,010 ) Ending balance ​ $ 6,090,000 ​ $ 5,390,000 ​ The net increase in fair value throughout 2021 was primarily attributable to timing of the probability of milestone achievement. The net increase in fair value throughout the year ended December 31, 2020 was primarily attributable to an increase in the closing share price of the Company’s common stock and in the probability of milestone achievement, partially offset by the fair value of the IND Milestone payment settled in common stock. Any changes in fair value have been recorded within research and development expense during the respective periods presented. As of December 31, 2021, we classified the total contingent consideration of $ 6.1 million as current liabilities. The balance sheet classification between current and non-current liabilities was based upon our reasonable expectation as to the timing of settlement of the Phase 2 Milestone payment to the former owners. 114 9. Notes Payable and Other Liabilities Paycheck Protection Program On April 7, 2020, the Company applied for a loan from ServisFirst Bank, as lender, pursuant to the Paycheck Protection Program of the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) as administered by the U.S. Small Business Administration (the "SBA"). On April 13, 2020, the Loan was approved and the Company received the proceeds from a loan in the amount of $ 632,000 (the “PPP Loan”). The PPP Loan, which took the form of a promissory note (the “Promissory Note”), was set to mature on April 7, 2022 and bore interest at a rate of 1 % per annum. Monthly principal and interest payments, less the amount of any potential forgiveness, was to commence on November 7, 2020. All or a portion of the Loan may have been forgiven by the SBA and lender upon application by the Company upon documentation of expenditures in accordance with the SBA requirements. On July 21, 2020, the Company voluntarily extinguished the Promissory Note by paying the outstanding principal and accrued interest in cash. The Company’s other long-term liabilities are summarized as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2021 ​ 2020 Lease obligation, long-term portion (see Note 6) $ 1,123,662 $ 1,468,124 Conditional economic incentive grants ​ 250,000 ​ 250,000 Other ​ 80,541 ​ 110,319 Total other long-term liabilities ​ $ 1,454,203 ​ $ 1,828,443 ​ Economic Incentive Grants The Company has two conditional economic incentive grants for a total of $ 250,000 from Montgomery County, Maryland and the State of Maryland. The Montgomery County grant was received in May 2018, with a term expiring on February 28, 2028 . The State of Maryland grant was received in October 2019, with a 10 -year term expiring on December 31, 2029 . These grants are conditional primarily based on the Company maintaining its current headquarter locations in addition to employing a required number of employees at different reporting dates through the term of the grants. The Company is accruing 3 % interest on both grants and has recorded $ 7,563 and $ 7,583 in interest expense for the years ended December 31, 2021 and 2020, respectively. ​ 10. Common Stock At-the-Market Offerings On February 25, 2021, the Company entered into an Equity Distribution Agreement (the “2021 Agreement”) with Piper Sandler & Co., Evercore Group L.L.C., and B. Riley Securities, Inc., serving as sales agents (the “Sales Agents”) with respect to an at-the-market offerings program under which the Company may offer and sell, from time to time at its sole discretion, shares of its common stock, par value $ 0.0001 per share (the “Common Stock”), having an aggregate offering price of up to $ 125.0 million (the “Shares”) through the Sale Agents (the “2021 ATM Offering”). Any Shares offered and sold in the 2021 ATM Offering will be issued pursuant to the Company’s Registration Statement on Form S-3 filed with the SEC on December 31, 2020, which was declared effective on January 11, 2021, the prospectus supplement relating to the 2021 ATM Offering filed with the SEC on February 25, 2021 and any applicable additional prospectus supplements related to the 2021 ATM Offering that form a part of the Registration Statement. As of December 31, 2021, the Company has sold 4,800,454 shares of Common Stock under the 2021 Agreement resulting in approximately $ 64.8 million in net proceeds, with $ 58.0 million remaining available to be sold under the 2021 Agreement. As of December 31, 2021, the Company recorded approximately $ 0.1 million of offering costs which offset the proceeds received from the shares sold through December 31, 2021. The Company capitalized approximately $ 0.1 million of deferred offering costs which will offset future proceeds received under the 2021 Agreement. 115 O n March 27, 2020, the Company entered into an Equity Distribution Agreement (the “2020 Agreement”) with JMP Securities LLC, serving as placement agent (the “Placement Agent”) with respect to an at-the-market offerings program under which the Company may offer and sell, from time to time at its sole discretion, shares of its common stock, par value $ 0.0001 per share, having an aggregate offering price of up to $ 50.0 million (the “Shares”) through the Placement Agent (the “2020 ATM Offering”). Any Shares offered and sold in the 2020 ATM Offering were issued pursuant to the Company’s Registration Statement on Form S-3 filed with the SEC on April 4, 2019, which was declared effective on April 12, 2019, the prospectus supplement relating to the 2020 ATM Offering filed with the SEC on March 27, 2020 and any applicable additional prospectus supplements related to the 2020 ATM Offering that form a part of the Registration Statement. The aggregate market value of Shares eligible for sale in the 2020 ATM Offering and under the 2020 Agreement were subject to the limitations of General Instruction I.B.6 of Form S-3, to the extent required under such instruction. The Company offered Shares having an aggregate offering price of $ 18.9 million pursuant to the prospectus supplement filed with the SEC on March 27, 2020. On June 1, 2020, the Company filed an amendment to the 2020 Agreement which amended the prospectus supplement dated March 27, 2020 to increase the aggregate offering price to $ 50.0 million. As of December 31, 2020, the Company sold 5,594,455 shares of Common Stock under the amended 2020 Agreement resulting in $ 48.2 million in net proceeds. The 2020 Agreement was fully utilized during the year ended December 31, 2020, and no Shares were sold under the 2020 Agreement during the year ended December 31, 2021. Exchange Agreement On February 25, 2021, the Company entered into an exchange agreement (the “Exchange Agreement”) with an Investor and its affiliates (the “Exchanging Stockholders”), pursuant to which the Company exchanged an aggregate of 1,000,000 shares of the Company’s common stock, par value $ 0.0001 per share, owned by the Exchanging Stockholders for pre-funded warrants (the “Exchange Warrants”) to purchase an aggregate of 1,000,000 shares of common stock (subject to adjustment in the event of any stock dividends and splits, reverse stock split, recapitalization, reorganization or similar transaction, as described in the Exchange Warrants), with an exercise price of $ 0.0001 per share. The Exchange Warrants do not expire and are exercisable at any time except that the Exchange Warrants cannot be exercised by the Exchanging Stockholders if, after giving effect thereto, the Exchanging Stockholders would beneficially own more than 9.99 % of the Company’s common stock, subject to certain exceptions. In accordance with FASB Accounting Standards Codification Topic 505, Equity , the Company recorded the retirement of the common stock exchanged as a reduction of common shares outstanding and a corresponding debit to additional paid-in-capital and accumulated deficit at the fair value of the Exchange Warrants on the issuance date. The Exchange Warrants were classified as equity in accordance with ASC 480 and the fair value of the Exchange Warrants was recorded as a credit to additional paid-in-capital and is not subject to remeasurement. The Company determined that the fair value of the Exchange Warrants is substantially similar to the fair value of the retired shares on the issuance date due to the negligible exercise price for the Exchange Warrants. As of December 31, 2021, none of the Exchange Warrants have been exercised. Public Offering On July 16, 2020, the Company offered and sold (i) 3,369,564 shares of common stock, at a price to the public of $ 23.00 per share, and (ii) pre-funded warrants of the Company to purchase 1,630,436 shares of common stock at an exercise price equal to $ 0.0001 per share (the “Pre-Funded Warrants”), at a price to the public of $ 22.9999 per share of common stock underlying the Pre-Funded Warrants (equal to the public offering price per share of Common Stock, minus the exercise price of each Pre-Funded Warrant). The Pre-Funded Warrants are exercisable at any time, provided that each Pre-Funded Warrant holder will be prohibited from exercising such Pre-Funded Warrants into shares of the Company’s common stock if, as a result of such exercise, the holder, together with its affiliates, would own more than 4.99 % of the total number of shares of the Company’s common stock then issued and outstanding, which percentage may change at the holders’ election to any other number less than or equal to 19.99 % upon 61 days ’ notice to the Company. The gross proceeds of this offering were approximately $ 132.2 million, which includes the exercise in full of the underwriters’ option to purchase an additional 750,000 shares of common stock, before deducting underwriting discounts and commissions and offering expenses during the third quarter of 2020. The net proceeds of this offering were approximately $ 124.0 million, after deducting underwriting discounts and commissions and offering expenses payable by the Company. The Company has assessed the Pre-Funded Warrants for appropriate equity or liability classification and determined that the Pre-Funded Warrants are freestanding instruments that do not meet the definition of a liability pursuant 116 to ASC 480 and do not meet the definition of a derivative pursuant to FASB Accounting Standards Codification Topic 815, Derivatives and Hedging (“ASC 815”). The Pre-Funded Warrants are indexed to the Company’s common stock and meet all other conditions for equity classification under ASC 480 and ASC 815. Accordingly, the Pre-Funded Warrants are classified as equity and are accounted for as a component of additional paid-in capital at the time of issuance. As of December 31, 2021, no Pre-Funded Warrants were exercised. Registered Direct Offering On March 12, 2019 , the Company issued a combined total of 4,361,370 common units and pre-funded units to certain institutional investors in a registered direct offering (the “Registered Direct Offering”). Each common unit in the Registered Direct Offering was sold at a price of $ 3.21 and consisted of one share of common stock and 0.70 of a warrant to purchase one share of common stock at an exercise price of $ 3.21 . Each warrant sold in the Registered Direct Offering was exercisable immediately and expired five years from the date of issuance. Each pre-funded unit in the Registered Direct Offering was sold at a public offering price of $ 3.20 and consisted of a pre-funded warrant to purchase one share of common stock at an exercise price of $ 0.01 per share and 0.70 of a warrant to purchase one share of common stock at an exercise price of $ 3.21 . All of the pre-funded warrants were exercised during 2019. The net proceeds of the Registered Direct Offering were $ 12.7 million, after deducting the underwriting discount and estimated offering expenses payable by the Company. The warrants issued in the Registered Direct Offering were recognized as equity classified freestanding financial instruments. The Registered Direct Offering triggered a down round adjustment to the exercise price of the warrants issued in the 2018 Unit Offering (refer to Note 11) from $ 4.1798 to $ 2.7568 . During the year ended December 31, 2019, the Company treated the value of the effect of the reduction in exercise price as a deemed dividend of $ 452,925 which reduced income available to common shareholders. The value of a down round feature is measured as the difference between the financial instrument’s fair value (without the down round feature) using the pre-trigger exercise price and the financial instrument’s fair value (without the down round feature) using the reduced exercise price. 11. Warrants The following common stock warrants were outstanding at December 31, 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of ​ ​ ​ ​ ​ ​ ​ ​ ​ Common ​ Per Share ​ ​ ​ ​ ​ ​ Stock ​ Exercise ​ ​ ​ ​ ​ ​ Warrants ​ Price ​ Issuance Date ​ Expiration Date Replacement warrants 155 $ 483.00 March 3, 2012 March 3, 2022 Issued with common units in the 2018 Unit Offering 3,300 ​ 2.7568 October 2, 2018 October 2, 2023 Issued with common units in the 2018 Registered Direct Offering 92,300 ​ 5.40 October 10, 2018 October 10, 2023 Issued with common units in the 2019 Registered Direct Offering (see Note 10) 50,000 ​ 3.21 March 12, 2019 March 12, 2024 Issued with common units in the 2020 Public Offering (see Note 10) 1,630,436 ​ 0.0001 July 16, 2020 — Issued in exchange for retirement of common stock per the Exchange Agreement (see Note 10) ​ 1,000,000 ​ ​ 0.0001 ​ February 25, 2021 ​ — Total 2,776,191 ​ ​ ​ ​ 117 The following common stock warrants were outstanding at December 31, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Number of ​ ​ ​ ​ ​ ​ ​ ​ ​ Common ​ Per Share ​ ​ ​ ​ ​ ​ Stock ​ Exercise ​ ​ ​ ​ ​ ​ Warrants ​ Price ​ Issuance Date ​ Expiration Date Replacement warrants 155 $ 483.00 March 3, 2012 March 3, 2022 Issued with redeemable preferred stock* 1,420 ​ 3.50 August 16, 2017 August 16, 2022 Issued with common units in the 2018 Unit Offering 3,300 ​ 2.7568 October 2, 2018 October 2, 2023 Issued with common units in the 2018 Registered Direct Offering 92,300 ​ 5.40 October 10, 2018 October 10, 2023 Issued with common units in the 2019 Registered Direct Offering (see Note 10) 50,000 ​ 3.21 March 12, 2019 March 12, 2024 Issued with common units in the 2020 Public Offering (see Note 10) 1,630,436 ​ 0.0001 July 16, 2020 — Total 1,777,611 ​ *Liability classified warrants ​ ​ The following is a description of the common stock warrants issued prior to January 1, 2019: Replacement Warrants In May 2017, the Company issued 155 common stock warrants to replace outstanding common stock warrants in connection with the Company’s merger with PharmAthene, Inc. Redeemable Preferred Stock Warrants In August 2017, in connection with a redeemable preferred stock issuance, the Company granted warrants to holders of redeemable preferred stock to purchase up to 78,181 shares of the Company’s common stock. Warrants issued with the redeemable preferred stock are classified as a liability and were initially recorded at their grant date fair value, and remeasured on each subsequent balance sheet date. The warrant liability is classified as a component of other long-term liabilities on the consolidated balance sheets. During the year ended December 31, 2019, the Company exchanged 1,550 of these warrants for a combination of common stock and cash, leaving 62 of these warrants outstanding as of December 31, 2019. During the second quarter of 2020, the 62 common stock warrants were repriced to 1,420 common stock warrants due to the at-the-market offerings which triggered an anti-dilution provision under the warrant agreement with the Company’s holders of redeemable preferred stock. As of December 31, 2021, all of the redeemable preferred stock warrants were exercised. 2018 Unit Offering On October 2, 2018 , the Company issued a combined total of 2,400,000 common units and pre-funded units in a public offering (the “2018 Unit Offering”). Each common unit in the 2018 Unit Offering was sold at a public offering price of $ 5.00 and consisted of one share of common stock and a warrant to purchase one share of common stock at an exercise price of $ 6.00 . Each warrant sold in the 2018 Unit Offering was exercisable immediately and expired five years from the date of issuance. Each pre-funded unit in the 2018 Unit Offering was sold at a public offering price of $ 4.99 and consisted of a pre-funded warrant to purchase one share of common stock at an exercise price of $ 0.01 per share and a warrant to purchase one share of common stock at an exercise price of $ 6.00 . The pre-funded warrants were immediately exercisable and were able to be exercised at any time until all of the pre-funded warrants were exercised in full. All of the pre-funded warrants were exercised prior to December 31, 2018. The warrants issued in the 2018 Unit Offering are each subject to anti-dilution protection. Accordingly, to the extent the Company was to issue additional common stock or securities convertible into common stock at an issuance price lower than exercise price of the warrants, the exercise price of the warrants would be adjusted to the lower of (i) the issuance price or (ii) the lowest volume weighted-average price of the Company’s common stock on the five trading days following the announcement of the new offering. 118 In conjunction with the 2018 Unit Offering, the Company issued 196,650 warrants to the underwriter. The underwriter warrants had an exercise price per share equal to 125 % of the public offering price per common unit in this offering and could be exercised on a cashless basis. As of December 30, 2021, all of the underwriter warrants were exercised in full. 2018 Registered Direct Offering On October 10, 2018 , the Company issued a combined total of 4,629,630 common units and pre-funded units to certain institutional investors in a registered direct offering (the “2018 Registered Direct Offering”). Each common unit in the 2018 Registered Direct Offering was sold at a price of $ 5.40 and consisted of one share of common stock and a warrant to purchase one share of common stock at an exercise price of $ 5.40 . Each warrant sold in the 2018 Registered Direct Offering was exercisable immediately and expired five years from the date of issuance. Each pre-funded unit in the 2018 Registered Direct Offering was sold at a public offering price of $ 5.39 and consisted of a pre-funded warrant to purchase one share of common stock at an exercise price of $ 0.01 per share and a warrant to purchase one share of common stock at an exercise price of $ 5.40 . The pre-funded warrants were immediately exercisable and were able to be exercised at any time until all of the pre-funded warrants are exercised in full. All of the pre-funded warrants were exercised prior to December 31, 2018. The 2018 Registered Direct Offering triggered a down round adjustment to the exercise price of the warrants issued in the 2018 Unit Offering from $ 6.00 to $ 4.1798 . A summary of warrant activity is as follows: ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2021 2020 Warrants outstanding, December 31, 2020 1,777,611 10,384,706 Issuances — 1,631,794 Exchanges (see Note 10) ​ 1,000,000 ​ — Exercises ( 1,420 ) ( 10,238,889 ) Warrants outstanding, December 31, 2021 2,776,191 1,777,611 ​ ​ 12. Stock-Based Compensation Stock Options The Company established the 2001 Employee Stock Option Plan to provide incentive stock options and non-qualified stock options to employees, and the 2001 Non-employee Stock Option Plan to provide non-qualified stock options to the members of the board of directors and advisory board, and non-employees. The 2001 Employee Stock Option Plan and the 2001 Non-employee Stock Option Plan are collectively referred to as the “2001 Plans.” In connection with the PharmAthene Merger Agreement in 2017, the Company issued options from its 2001 Plans to replace options previously granted. The Company de-designated common stock available for issuance under the 2001 Plans. No additional options or restricted stock will be granted under these plans. Options outstanding and unvested restricted stock granted or replaced under these plans will continue to vest over the remaining vesting period through the earlier of exercise, expiration, or forfeiture. The replacement options issued after the 2017 mergers will continue to vest over the remaining vesting period through the earlier of exercise, expiration, or forfeiture. Also, in connection with the 2017 mergers, the 2001 Plans were assumed by the Company. In addition, the Company assumed the PharmAthene, Inc. Amended and Restated 2007 Long-Term Incentive Compensation Plan (the “2007 Plan”). Awards outstanding under the 2007 Plan remained outstanding in accordance with their applicable terms and conditions. No additional awards will be made under the 2007 Plan. The Company established the 2017 Omnibus Incentive Plan (the “Omnibus Plan”) to provide incentive stock options, non-qualified stock options, restricted stock, and other stock-based awards denominated in shares of the Company’s common stock, and performance-based cash awards to eligible employees, consultants, and directors. In 2018, the Company’s shareholders approved an amendment to the Omnibus Plan to increase the number of shares reserved for 119 issuance from 1,500,000 to 5,000,000 . The aggregate share reserve will be increased on January 1 of each year commencing in 2018 and ending on and including January 1, 2027 up to an amount equal to the lowest of (i) 4 % of the total number of shares of common stock outstanding on a fully diluted basis as of December 31 of the immediately preceding calendar year, and (ii) such number of shares of common stock, if any, determined by the Company’s board of directors. The maximum shares of common stock that may be granted to each employee or consultant in any fiscal year under the Omnibus Plan is the lesser of 800,000 shares per type of award or a maximum compensation amount of $ 5,000,000 under a Black-Scholes valuation model. The maximum common stock that may be granted to directors under the Omnibus Plan during any fiscal year is 500,000 shares. On November 29, 2018, the Board approved and adopted the Altimmune Inc. 2018 Inducement Grant Plan (the “Inducement Plan”). The Inducement Plan provides for the grant of equity or equity-based awards in the form of non-qualified stock options, restricted stock awards and other stock-based awards. The Inducement Plan was adopted by the Board without stockholder approval pursuant to Rule 5635(c)(4) of the NASDAQ Listing Rules. The Board has reserved 2,000,000 shares of the Company’s common stock for issuance pursuant to awards granted under the Inducement Plan (subject to customary adjustments in the event of a change in capital structure of the Company), and the Inducement Plan will be administered by the Compensation Committee. In accordance with Rule 5635(c)(4) of the NASDAQ Listing Rules, awards under the Inducement Plan may be only made to an employee who has not previously been an employee or member of the Board or any parent or subsidiary, or following a bona fide period of non-employment by the Company or a parent or subsidiary, if he or she is granted such award in connection with his or her commencement of employment with the Company or a subsidiary and such grant is an inducement material to his or her entering into employment with the Company or such subsidiary. The 2001 Plans, the 2007 Plan, the Omnibus Plan and the Inducement Plan are collectively referred to as the “Plans.” During the year ended December 31, 2021 under the Plans, a total of 1,225,700 options to purchase shares of common stock were granted. As of December 31, 2021, there were 990,819 and 1,394,206 shares of common stock available for future grants under the Omnibus Plan and the Inducement Plan, respectively. The fair value of stock option issued to employees was estimated at the date of grant using Black-Scholes with the following weighted-average assumptions: ​ ​ ​ ​ ​ ​ ​ ​ For the Year Ended December 31, ​ 2021 2020 Expected volatility 109.6 % 102.4 % Expected term (years) 6.0 5.9 ​ Risk-free interest rate 0.8 % 1.2 % Expected dividend yield 0.0 % 0.0 % ​ Expected volatility: As there is not sufficient historical volatility for the expected term of the stock options, the Company uses an average historical share price volatility, inclusive of its own volatility, based on an analysis of reported data for a peer group of comparable companies which were selected based upon industry similarities. Expected term (years): Expected term represents the number of years that the Company’s option grants are expected to be outstanding. There is not sufficient historical share exercise data to calculate the expected term of the stock options; therefore, the Company elected to utilize the simplified method to value option grants. Under this approach, the weighted-average expected life is presumed to be the average of the vesting term and the contractual term of the option. Risk-free interest rate: The Company determined the risk-free interest rate by using a weighted-average equivalent to the expected term based on the daily U.S. Treasury yield curve rate in effect as of the date of grant. Expected dividend yield: The Company does not anticipate paying any dividends in the foreseeable future. The fair value of each non-employee stock option is estimated at the date of grant using Black-Scholes with assumptions generally consistent with those used for employee stock options, with the exception of expected term, which is over the contractual life. 120 A summary of stock option activity under the Plans is presented below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ ​ ​ Weighted- ​ Remaining ​ ​ ​ ​ ​ Number of ​ Average ​ Contractual Term ​ Aggregate Intrinsic ​ ​ Stock Options ​ Exercise Price ​ (Years) ​ Value Outstanding, December 31, 2020 1,626,752 ​ $ 4.58 5.9 ​ $ 12,234,740 Granted 1,225,700 ​ $ 14.34 ​ Exercised ( 54,068 ) ​ $ 3.26 ​ Forfeited or expired ( 214,941 ) ​ $ 11.93 ​ Outstanding, December 31, 2021 2,583,443 ​ $ 8.63 5.9 ​ $ 8,460,273 Exercisable, December 31, 2021 1,097,101 ​ $ 5.66 5.8 ​ $ 5,570,354 Vested and expected to vest, December 31, 2021 1,334,735 ​ $ 10.81 6.0 ​ $ 2,889,919 ​ The per share weighted-average grant date fair value of stock options granted during the years ended December 31, 2021 and 2020 were $ 11.79 and $ 4.75 per share, respectively. The total intrinsic value of stock options exercised during the years ended December 31, 2021 and 2020 was $ 0.7 million and $ 0.9 million, respectively. The total fair value of awards vested during the years ended December 31, 2021 and 2020 was $ 4.7 million and $ 1.1 million, respectively. At December 31, 2021, there was $ 10.0 million of unrecognized compensation cost related to stock options, which is expected to be recognized over a weighted-average period of 2.3 years. Restricted Stock In October 2016, the Company authorized and granted a restricted stock award of 2,651 shares at an aggregate purchase price of $ 1,067 . The weighted-average grant date fair value of the restricted stock award was $ 310.80 per share. The restricted stock vested ratably at the end of each quarter over four years starting on December 31, 2016 with 50 % of the original issued shared subject to accelerated vesting upon a deemed liquidation event. During the year ended December 31, 2020, 213 of the restricted shares fully vested, which completed the vesting of this share award. In November 2018, the Company authorized and granted the Chief Executive Officer a restricted stock award of 322,907 shares on his date of hire. The weighted-average grant date fair value of the restricted stock award was $ 3.59 per share. The restricted stock vests over a four-year period, 25 % of the shares vesting on the one-year anniversary, and the remaining 75 % vesting in 36 substantially equal monthly installments and will be fully vested on December 1, 2022 ; provided, however, that the executive officer has not experienced a termination prior to the applicable vesting date. The fair value of the 80,726 restricted shares that vested during the year ended December 31, 2021 totaled $ 1.0 million. In June 2020, the Company authorized and granted 109,525 shares of restricted stock awards which vested over three months . The weighted-average grant date fair value of the restricted stock award was $ 9.19 per share. During the year ended December 31, 2020, all of the 109,525 of restricted shares fully vested, which completed the vesting of this share award. In September 2020, the Company authorized and granted 15,000 shares of restricted stock units which vest over a four-year period, 25 % of the shares vesting on the one-year anniversary, and the remaining 75 % vesting in 36 substantially equal monthly installments and will be fully vested on September 22, 2024 . The weighted-average grant date fair value of the restricted stock award was $ 14.35 per share. The fair value of the 4,687 restricted shares that vested during the year ended December 31, 2021 totaled $ 0.1 million. In February 2021, the Company authorized and granted 181,279 shares of restricted stock units which vest over four years and will be fully vested on February 1, 2025 . The weighted-average grant date fair value of the restricted stock award was $ 16.71 per share. No restricted shares vested during the year ended December 31, 2021. In June 2021, the Company authorized and granted 15,000 shares of restricted stock units which vest over a four-year period, 25 % of the shares vesting on the one-year anniversary, and the remaining 75 % vesting in 36 substantially equal monthly installments and will be fully vested on June 30, 2025 . The weighted-average grant date fair value of the restricted stock award was $ 9.85 per share. No restricted shares vested during the year ended December 31, 2021. 121 In December 2021, the Company authorized and granted 50,000 shares of restricted stock units which vest over four years and will be fully vested on December 31, 2025 . The weighted-average grant date fair value of the restricted stock award was $ 9.16 per share. No restricted shares vested during the year ended December 31, 2021. A summary of restricted stock activities is presented below: ​ ​ ​ ​ ​ ​ ​ ​ Weighted- ​ ​ ​ ​ average ​ ​ ​ ​ Grant Date ​ ​ Shares ​ Fair Value Unvested, December 31, 2020 169,726 ​ $ 4.54 Granted 246,279 ​ 14.76 Vested ( 85,413 ) ​ 4.18 Forfeited or expired ​ ( 24,664 ) ​ ​ 16.71 Unvested, December 31, 2021 305,928 ​ $ 11.89 ​ As of December 31, 2021, total unrecognized compensation expense related to restricted stock awards was $ 2.7 million, which the Company expects to recognize over a weighted-average period of approximately 2.7 years. 2019 Employee Stock Purchase Plan On March 29, 2019, the board of directors adopted the 2019 Employee Stock Purchase Plan (the “2019 ESPP”). A total of 403,500 shares of the Company’s common stock have been reserved for issuance under the 2019 ESPP. Subject to any plan limitations, the 2019 ESPP allows eligible employees to contribute through payroll deductions up to 10 % of their earnings for the purchase of the Company’s common stock at a discounted price per share. The offering periods begin in February and August of each year, with the initial offering period started on August 1, 2019. The common shares issuable under the 2019 ESPP were registered pursuant to a registration statement on Form S-8 on April 4, 2019. Unless otherwise determined by the administrator, the Company’s common stock will be purchased for the accounts of employees participating in the 2019 ESPP at a price per share that is the lesser of 85 % of the fair market value of the Company’s common stock on the first trading day of the offering period or 85 % of the fair market value of the Company’s common stock on the last trading day of the offering period. The 2019 ESPP estimated shares to be purchased fair value is included in the stock-based compensation expense. Employees have the ability to purchase shares of the Company’s common stock at a price equal to the lower of the first or last trading day of the offering period, which represents an option and, therefore, the 2019 ESPP is a compensatory plan under ASC 718-50, Employee Stock Purchase Plans . Accordingly, stock-based compensation expense is determined based on the option’s grant-date fair value, employee contributions, and the Company’s stock price and is recognized over the requisite service period of the option. The Company used the Black-Scholes valuation model. During the year ended December 31, 2021, employees purchased 24,100 shares for $ 0.2 million under the 2019 ESPP. The Company recognized stock-based compensation expense related to this plan of $ 0.3 million and $ 0.2 million for the years ended December 31, 2021 and 2020, respectively. Stock-based Compensation Expense Stock-based compensation expense is classified in the accompanying consolidated statements of operations and comprehensive loss for the years ended December 31, 2021 and 2020 as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2021 ​ 2020 Research and development ​ $ 1,655,982 ​ $ 357,762 General and administrative ​ 3,862,908 ​ 2,218,244 Total ​ $ 5,518,890 ​ $ 2,576,006 ​ ​ 122 13. U.S. Government Contracts and Grants In June 2020, the Company was awarded $ 4.7 million from the U.S. Army Medical Research & Development Command (“USAMRDC”) to fund its Phase 1/2 clinical trial of T-COVID. The competitive award was granted by USAMRDC in collaboration with the Medical Technology Enterprise Consortium (“MTEC”), a 501(c)(3) biomedical technology consortium working in partnership with the Department of Defense (“DoD”). Under the contract, MTEC paid the Company a firm fixed fee based upon the achievement of certain milestones for conduct and completion of a Phase 1/2 study and research and development work on the replication-deficient adenovirus 5 (“RD-Ad5”) vector vaccine platform. For the years ended December 31, 2021 and 2020, the Company has recognized $ 0.5 million and $ 4.2 million of grant revenue under this contract, respectively. In July 2016, the Company signed a five-year contract with Biomedical Advanced Research and Development Authority (“BARDA”). The contract, as amended, has a total value of up to $ 136.8 million and is used to fund clinical development of NasoShield. Under the contract, BARDA paid the Company a fixed fee and reimburses certain costs for the research and development of an Ad5-vectored, protective antigen-based intranasal anthrax vaccine through cGMP manufacture and conduct of a Phase 1 clinical trial dose ranging assessment of safety and immunogenicity. The contract consisted of an initial base performance period providing approximately $ 30.9 million in funding for the period July 2016 through December 2021. BARDA had seven options to extend the contract to fund certain continued development and manufacturing activities for the anthrax vaccine, including Phase 2 clinical studies. Each option, if exercised by BARDA, would have provided additional funding ranging from approximately $ 1.1 million to $ 34.4 million for a three-year period beginning in 2021. For the years ended December 31, 2021 and 2020, the Company has recognized $ 3.7 million and $ 3.1 million of grant revenue under the current BARDA contract, respectively. At December 31, 2021, BARDA had not elected to extend the contract. The Company accounts for these contracts as a government grant which analogizes with International Accounting Standards 20 (“IAS 20”), Accounting for Government Grants and Disclosure of Government Assistance . 14. Employee Benefit Plans The Company has a 401(k)-retirement plan in which substantially all of our employees in the United States are eligible to participate in. Eligible employees may elect to contribute up to the maximum limits, as set by the Internal Revenue Service, of their eligible compensation. During the years ended December 31, 2021 and 2020, the Company made discretionary plan contributions of $ 0.3 million and $ 0.2 million, respectively. 15. Income Taxes The components of net loss before income tax benefit are as follows: ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2021 ​ 2020 U.S. operations ​ $ ( 78,583,331 ) ​ $ ( 50,735,735 ) Non-U.S. operations ​ ( 18,507,493 ) ​ ( 3,725,766 ) Net loss before income tax benefit ​ $ ( 97,090,824 ) ​ $ ( 54,461,501 ) ​ The components of the income tax benefit are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2021 2020 U.S. federal ​ ​ Current ​ $ — ​ $ 4,706,092 Deferred ​ — ​ — U.S. state and local ​ ​ Current ​ — ​ 710,932 Deferred ​ — ​ — Income tax benefit ​ $ — ​ $ 5,417,024 ​ 123 Reconciliation between the effect of applying the federal statutory rate and the effective income tax rate used to calculate the Company’s income tax benefit is as follows: ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2021 ​ 2020 Federal statutory rate 21.00 % 21.00 % State income taxes, net of federal benefit 4.71 4.10 ​ Research and development tax credit ( 2.30 ) ( 0.84 ) ​ Acquired in process research and development ( 0.15 ) ( 6.27 ) ​ CARES Act U.S. federal and state carryback claim — 1.81 ​ Other ( 0.47 ) 0.29 ​ Change in valuation allowance ( 22.79 ) ( 10.14 ) ​ Effective tax rate — % 9.95 % ​ Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income and for tax carryforwards. Significant components of the Company’s deferred tax assets and liabilities are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ 2021 2020 Deferred tax assets: ​ ​ Net operating losses ​ $ 37,229,317 ​ $ 18,978,410 Accrued expenses ​ 352,040 ​ 495,301 Amortization ​ 745,676 ​ 785,523 Stock compensation ​ 1,275,987 ​ 584,507 Lease liability ​ 422,424 ​ 502,151 Asset impairment ​ 3,128,740 ​ — Other ​ 109,015 ​ 106,197 Total deferred tax assets ​ 43,263,199 ​ 21,452,089 Valuation allowance ​ ( 40,584,149 ) ​ ( 18,671,086 ) Deferred tax assets, net ​ 2,679,050 ​ 2,781,003 Deferred tax liabilities: ​ ​ IPR&D assets ​ ( 2,359,604 ) ​ ( 2,386,667 ) Right of use asset ​ ( 219,639 ) ​ ( 248,710 ) Depreciation ​ ( 99,807 ) ​ ( 145,626 ) Total deferred tax liabilities ​ ( 2,679,050 ) ​ ( 2,781,003 ) Total deferred tax assets (liabilities), net ​ $ — ​ $ — ​ The Company assesses the need for a valuation allowance against our deferred tax assets and considers both positive and negative evidence related to the likelihood of realization of the deferred tax assets to determine, based on the weight of available evidence, whether it is more-likely-than-not that some or all of the deferred tax assets will not be realized. This determination requires significant judgment, including assumptions about future taxable income that are based on historical and projected information. The increase in the valuation allowance during the year ended December 31, 2021 primarily relates to increases for current year losses in both the U.S. and foreign locations which the Company concluded needed a full valuation allowance. The Company has recorded a valuation allowance against its net U.S. deferred tax assets it believes are not more likely than not realizable and the net non-U.S. deferred tax assets. Deferred tax liabilities, consist primarily of indefinite life IPR&D assets located in a foreign subsidiary, which will be applied in the future to offset against net operating losses (“NOLs”) that have an indefinite life. The Company has U.S. federal and state net operating loss carryforwards of approximately $ 107.8 million and $ 110.3 million, respectively, as of December 31, 2021, of which a portion of the federal and state amount of $ 6.6 million and $ 110.3 million, respectively, has a 20-year carry forward period that will expire at various dates beginning in 2024 . Under current law, the remaining federal amount of $ 101.2 million has an indefinite life and amounts utilized in the future may not exceed 80% of taxable income. The Company also has foreign net operating loss carryforward of approximately $ 37.2 million which carryforward indefinitely. 124 Under Section 382 of the Internal Revenue Code of 1986 (“IRC 382”), as amended, substantial changes in the Company’s ownership may limit the amount of NOLs that can be utilized annually in the future to offset its U.S. federal and state taxable income. Specifically, this limitation may arise in the event of a cumulative change in ownership of the Company of more than 50 % within any three-year period. The amount of the annual limitation is determined based on the value of the Company immediately before the ownership change. The Company has reduced the NOL and related valuation allowance in historical periods. Our existing NOLs are subject to limitations arising from previous ownership changes from 2020 and prior that impact the timing and amount. In addition, future changes in our stock ownership, many of which are outside of our control, could result in an ownership change. While we do not believe we have experienced ownership changes in 2021, it is possible we may have incurred a change as no new IRC 382 study was performed in 2021 to determine if there was another ownership change. Accordingly, we may not be able to utilize a material portion of our NOLs and this could harm our future operating results by effectively increasing our future tax obligations. Significant judgment is required in evaluating tax positions and determining the provision for income taxes. The Company establishes liabilities for tax-related uncertainties based on estimates of whether, and the extent to which, additional taxes may be due. These liabilities are established when the Company believes that certain positions might be challenged despite its belief that its tax return positions are fully supportable. The Company adjusts these liabilities in light of changing facts and circumstances, such as the outcome of a tax audit. The provision for income taxes includes the impact of changes to these liabilities. The amount of unrecognized tax benefits was $ 0.2 million and $ 0.7 million as of December 31, 2021 and 2020, respectively. Any changes in the next twelve months are not anticipated to have a significant impact on the results of operations, financial position or cash flows of the Company. All of the Company’s uncertain tax positions, if recognized, would affect its income tax expense. The Company has elected an accounting policy to classify interest and penalties related to unrecognized tax benefits as a component of income tax expense. As of December 31, 2021 and 2020, potential interest and penalties on unrecognized tax benefits were not significant. The following is a tabular reconciliation of the total amounts of unrecognized tax benefits excluding related interest and penalties: ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ ​ 2021 ​ 2020 Beginning balance ​ $ 710,783 ​ $ — Increases for current year tax positions ​ ​ — ​ ​ 710,783 Decreases for prior year tax positions ​ ( 474,458 ) ​ — Ending balance ​ $ 236,325 ​ $ 710,783 ​ The Company files income tax returns in the United States, various U.S. states, U.K. and Australia. The Company is still open to examination by the applicable taxing authorities from 2010 forward, although tax attributes that were generated prior to 2010 may still be adjusted upon examination by federal, state, foreign or local tax authorities if they either have been or will be used in a future period. 16. Net Loss Per Share Because the Company has reported net loss attributable to common stockholders for the years ended December 31, 2021 and 2020, basic and diluted net loss per share attributable to common stockholders are the same for both years. Basic net loss per share attributable to common stockholders is computed by dividing the net loss attributable to common stockholders by the weighted-average numbers of shares of common stock outstanding for the period. Basic shares outstanding includes the weighted-average effect of the Company’s outstanding pre-funded warrants, the exercise of which requires little or no consideration for the delivery of shares of common stock. 125 Diluted net loss per share is calculated by adjusting weighted-average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period. As such, all unvested restricted stock, common stock warrants, and stock options have been excluded from the computation of diluted weighted-average shares outstanding because such securities would have an anti-dilutive impact for all periods presented. Potential common shares issuable upon conversion, vesting or exercise of unvested restricted stock, common stock warrants, and stock options that are excluded from the computation of diluted weighted-average shares outstanding, as they are anti-dilutive, are as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, ​ ​ 2021 ​ 2020 Common stock warrants 145,755 145,755 Common stock options 2,594,177 1,631,898 Restricted stock 305,928 169,726 ​ ​ 17. Commitments and Contingencies License Obligations PER.C6 Cell Line - Janssen Vaccines & Prevention B.V. The Company has a royalty-bearing, worldwide non-exclusive license agreement with Janssen Vaccines & Prevention B.V. (formerly known as Crucell Holland B.V.) (“Janssen”) for use of its vaccine technology. The Company may terminate the license agreement without cause, and the agreement contains customary provisions for either party to terminate prior to the expiration of the agreement. The amended license agreement expires on a product-by-product and country-by-country basis on the later of the date upon which the last of the licensed patents applicable to the relevant product expires or 15 years from the date of first commercial sale of the relevant product. The Janssen patent rights include patents issued in the United States with an expected expiration date no earlier than April 2020, in each case not giving effect to any potential extensions and assuming payment of all associated fees. Upon expiration of the amended license agreement, or if the Company terminates the amended license agreement for Janssen’s material breach, the Company retains the right to exploit the rights granted. Under the agreement, the Company is required to pay an annual license fee and annual royalty fees upon reaching certain milestones in an amount that equals the greater of a low single digit percentage of net sales or $ 150,000 . On April 2, 2020, the Company entered into Amendment No. 3 to the Second Restated License Agreement and additionally entered into Amendment No. 4, 5 and 6 throughout 2020 (collectively, the “Amendments”), by and between the Company and Janssen (as amended by Amendment No. 1 to Second Restated License Agreement and Amendment No. 2 to Second Restated License Agreement, together with the Amendments, the “License Agreement”). Pursuant to the Amendment, the field of licenses granted to the Company for the use of the PER.C6 cell line under the License Agreement is expanded to cover COVID-19 caused by SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), in addition to the existing licenses related to Bacillus anthracis and influenza virus. All capitalized terms not defined herein shall have the meanings assigned to them in the Amendment or the License Agreement, as applicable. Pursuant to the Amendment, the Company agreed to pay certain additional development-based milestone payments through approval of licensed products by the FDA for the treatment or prevention of COVID-19, up to an aggregate amount of $ 1.2 million. The Company also agreed to pay royalty payments as a percentage of net sales of products to a royalty stacking reduction and minimum annual royalty payments, until the expiration of the term of the License Agreement, as amended. Fees incurred under the Janssen agreement totaled $ 0.2 million and $ 0.3 million for the years ended December 31, 2021 and 2020, respectively, and are included in research and development expenses in the accompanying consolidated statements of operations and comprehensive loss. 126 Spitfire Acquisition As disclosed in Note 8, the Company is obligated to make payments of up to $ 80.0 million upon the achievement of specified worldwide net sales of all products developed using the technology acquired from Spitfire Pharma Inc. within ten years following the approval of a new drug application filed with the FDA. Litigation In December 2019, a complaint was filed by Dr. De-Chu Christopher Tang (“Plaintiff”) against the Company, which the Company removed to the United States District Court for the Eastern District of Texas. The Plaintiff amended the complaint in February 2020 to include Vipin K. Garg and David J. Drutz as defendants, in addition to the Company (Dr. Garg, Dr. Drutz, and the Company are collectively referred to as “Defendants”). In March 2020 the Defendants filed a motion to dismiss the complaint. The Court denied the motion without prejudice and allowed Plaintiff an opportunity to file an amended complaint. Plaintiff’s second amended complaint was filed on April 17, 2020, and Defendants filed a motion to dismiss that complaint on May 1, 2020. A hearing on Defendants’ motion to dismiss was held on May 20, 2020. Plaintiff, who is representing himself, alleges five causes of action as follows: (1) Defendants’ alleged retention of Plaintiff’s lab notebooks after the termination of his employment in 2012; (2) alleged plagiarism based on publishing an article without naming Plaintiff as an author; (3) use of the Adhigh System, which Plaintiff alleges he developed; (4) allegations that Defendants manipulated the Company’s stock and caused a decrease in value; and (5) allegations that the Defendants “wast[ed] government grant money and poison[ed] science by leaving data to rot.” On September 30, 2020, Plaintiff filed a motion titled “Motion to Proscribe Defendants’ Allegedly Illegal Use of Plaintiff’s AdHigh System in Altimmune’s Human Clinical Trials,” to which Defendants filed an opposition on October 13, 2020. The court has not yet ruled on that motion, which also remains pending. On November 6, 2020, Defendants filed a motion for summary judgment on the basis of lack of personal jurisdiction, insufficient service of process, and failure to state a claim. The court ruled on that motion on March 25, 2021, which dismissed the case on the basis of lack of personal jurisdiction. On December 1, 2020, the magistrate judge assigned to the case issued a report and recommendation that Defendants’ motion to dismiss of May 1, 2020 be granted and that this action be dismissed for lack of personal jurisdiction. Plaintiff filed objections to the report and recommendation on December 14, 2020, and the resolution of those objections by the district court remains pending. In December 2021, the Plaintiff refiled the complaint in the United States District Court for the District of Maryland. The Company believes the allegations in the complaint are without merit and intends to vigorously defend the litigation. However, the outcome of this legal proceeding is uncertain at this time and the Company cannot reasonably estimate a range of loss, if any. Accordingly, the Company has not accrued any liability associated with this action. The Company is a party in various contracts and subject to disputes, litigation, and potential claims arising in the ordinary course of business none of which are currently reasonably possible or probable of material loss. 18. Subsequent Events Exchange Agreement On January 20, 2022, Exchange Warrants to purchase 1,000,000 shares were net exercised, resulting in the issuance of 999,984 shares of common stock. All of the Exchange Warrants were exercised in full. See Note 10 for further details. Public Offering On January 20, 2022, warrant holders exercised 760,870 of the Pre-Funded Warrants and were issued 760,870 shares of common stock, leaving 869,566 remaining Pre-Funded Warrants unexercised. See Note 10 for further details. 127 Item 9. Changes in and Disagreements with Accountants on Accounting and Financial Disclosure None.