Altimmune, Inc. 10-Q

Item 1. Financial Statements ALTIMMUNE, INC. CONSOLIDATED BALANCE SHEETS (In thousands, except share and per-share amounts) ​ ​ ​ ​ ​ ​ ​ ​ June 30, ​ December 31, ​ ​ 2024 ​ 2023 ​ ​ (Unaudited) ​ ​ ​ ASSETS ​ ​ ​ Current assets: ​ ​ Cash and cash equivalents ​ $ 57,128 ​ $ 135,117 Restricted cash ​ 41 ​ 41 Total cash, cash equivalents and restricted cash ​ 57,169 ​ 135,158 Short-term investments ​ 107,780 ​ 62,698 Accounts and other receivables ​ 424 ​ 1,111 Income tax and R&D incentive receivables ​ 2,588 ​ 3,742 Prepaid expenses and other current assets ​ 3,225 ​ 6,917 Total current assets ​ 171,186 ​ 209,626 Property and equipment, net ​ 483 ​ 651 Other assets ​ 1,677 ​ 363 Total assets ​ $ 173,346 ​ $ 210,640 LIABILITIES AND STOCKHOLDERS’ EQUITY ​ ​ Current liabilities: ​ ​ Accounts payable ​ $ 2,688 ​ $ 2,070 Accrued expenses and other current liabilities ​ 12,467 ​ 10,073 Total current liabilities ​ 15,155 ​ 12,143 Noncurrent liabilities ​ 5,660 ​ 4,398 Total liabilities ​ 20,815 ​ 16,541 Commitments and contingencies (Note 10) ​ ​ Stockholders’ equity: ​ ​ Common stock, $ 0.0001 par value; 200,000,000 shares authorized; 71,046,267 and 70,677,400 shares issued and outstanding as of June 30, 2024 and December 31, 2023, respectively ​ ​ 7 ​ ​ 7 Additional paid-in capital ​ 673,081 ​ 665,427 Accumulated deficit ​ ( 515,365 ) ​ ( 466,331 ) Accumulated other comprehensive loss, net ​ ( 5,192 ) ​ ( 5,004 ) Total stockholders’ equity ​ 152,531 ​ 194,099 Total liabilities and stockholders’ equity ​ $ 173,346 ​ $ 210,640 ​ The accompanying notes are an integral part of the unaudited consolidated financial statements. ​ 1 Table of Contents ALTIMMUNE, INC. CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS (Unaudited) (In thousands, except share and per-share amounts) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended ​ Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2024 2023 2024 2023 Revenues ​ $ 5 ​ $ 6 ​ $ 10 ​ $ 27 Operating expenses: ​ ​ ​ ​ Research and development ​ 21,155 ​ 13,253 ​ 42,642 ​ 30,502 General and administrative ​ 5,595 ​ 4,760 ​ 10,907 ​ 9,291 Total operating expenses ​ 26,750 ​ 18,013 ​ 53,549 ​ 39,793 Loss from operations ​ ( 26,745 ) ​ ( 18,007 ) ​ ( 53,539 ) ​ ( 39,766 ) Other income (expense): ​ ​ ​ ​ Interest expense ​ ( 1 ) ​ ( 2 ) ​ ( 2 ) ​ ( 4 ) Interest income ​ 2,182 ​ 1,835 ​ 4,595 ​ 3,503 Other income (expense), net ​ ( 76 ) ​ 113 ​ ( 88 ) ​ 132 Total other income (expense), net ​ 2,105 ​ 1,946 ​ 4,505 ​ 3,631 Net loss ​ ( 24,640 ) ​ ( 16,061 ) ​ ( 49,034 ) ​ ( 36,135 ) Other comprehensive income — unrealized (loss) gain on short-term investments ​ ( 31 ) ​ ( 79 ) ​ ( 188 ) ​ 47 Comprehensive loss ​ $ ( 24,671 ) ​ $ ( 16,140 ) ​ $ ( 49,222 ) ​ $ ( 36,088 ) Net loss per share, basic and diluted ​ $ ( 0.35 ) ​ $ ( 0.32 ) ​ $ ( 0.69 ) ​ $ ( 0.72 ) Weighted-average common shares outstanding, basic and diluted ​ 70,924,371 ​ 50,691,558 ​ 70,863,042 ​ 50,410,184 ​ The accompanying notes are an integral part of the unaudited consolidated financial statements. ​ ​ 2 Table of Contents ​ ALTIMMUNE, INC. CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY (Unaudited) (In thousands, except share amounts) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Additional ​ ​ ​ ​ Other ​ Total ​ Common Stock Paid-In Accumulated Comprehensive Stockholders’ ​ ​ Shares ​ Amount ​ Capital ​ Deficit ​ Loss ​ Equity Balance at December 31, 2023 ​ 70,677,400 ​ $ 7 ​ $ 665,427 ​ $ ( 466,331 ) ​ $ ( 5,004 ) ​ $ 194,099 Stock-based compensation — ​ — ​ 3,650 ​ — ​ — ​ 3,650 Exercise of stock options 1,250 ​ — ​ 9 ​ — ​ — ​ 9 Vesting of restricted stock awards including withholding, net ​ 107,875 ​ ​ — ​ ​ ( 600 ) ​ ​ — ​ ​ — ​ ​ ( 600 ) Issuance of common stock from Employee Stock Purchase Plan 62,609 ​ — ​ 169 ​ — ​ — ​ 169 Issuance of common stock upon exercise of warrants ​ 50,000 ​ ​ — ​ ​ 161 ​ ​ — ​ ​ — ​ ​ 161 Unrealized (loss) gain on short-term investments — ​ — ​ — ​ — ​ ( 157 ) ​ ( 157 ) Net loss ​ — ​ ​ — ​ ​ — ​ ​ ( 24,394 ) ​ ​ — ​ ​ ( 24,394 ) Balance at March 31, 2024 70,899,134 $ 7 $ 668,816 $ ( 490,725 ) $ ( 5,161 ) $ 172,937 Stock-based compensation — $ — $ 4,311 $ — $ — $ 4,311 Exercise of stock options ​ 64,433 ​ — ​ 198 ​ — ​ — ​ 198 Vesting of restricted stock awards including withholding, net 82,700 ​ — ​ ( 244 ) ​ — ​ — ​ ( 244 ) Unrealized (loss) gain on short-term investments — ​ — ​ — ​ — ​ ( 31 ) ​ ( 31 ) Net loss — ​ — ​ — ​ ( 24,640 ) ​ — ​ ( 24,640 ) Balance at June 30, 2024 71,046,267 $ 7 $ 673,081 $ ( 515,365 ) $ ( 5,192 ) $ 152,531 ​ The accompanying notes are an integral part of the unaudited consolidated financial statements. ​ 3 Table of Contents ​ ​ ALTIMMUNE, INC. CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY (Unaudited) (In thousands, except share amounts) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Accumulated ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Additional ​ ​ ​ ​ Other ​ Total ​ Common Stock Paid-In Accumulated Comprehensive Stockholders’ ​ ​ Shares ​ Amount ​ Capital ​ Deficit ​ Loss ​ Equity Balance at December 31, 2022 ​ 49,199,845 ​ $ 5 ​ $ 568,399 ​ $ ( 377,884 ) ​ $ ( 5,227 ) ​ $ 185,293 Stock-based compensation — ​ — ​ 2,675 ​ — ​ — ​ 2,675 Exercise of stock options 19,303 ​ — ​ 61 ​ — ​ — ​ 61 Vesting of restricted stock awards including withholding, net 54,347 ​ ​ — ​ ​ ( 484 ) ​ ​ — ​ ​ — ​ ( 484 ) Issuance of common stock from Employee Stock Purchase Plan 13,215 ​ — ​ 135 ​ — ​ — ​ 135 Unrealized (loss) gain on short-term investments — ​ — ​ — ​ — ​ 126 ​ 126 Net loss ​ — ​ ​ — ​ ​ — ​ ​ ( 20,074 ) ​ ​ — ​ ​ ( 20,074 ) Balance at March 31, 2023 49,286,710 $ 5 $ 570,786 $ ( 397,958 ) $ ( 5,101 ) $ 167,732 Stock-based compensation — $ — $ 2,786 $ — $ — $ 2,786 Vesting of restricted stock awards including withholding, net 6,320 ​ — ​ ( 16 ) ​ — ​ — ​ ( 16 ) Issuance of common stock in at-the-market offerings, net 3,364,631 ​ ​ — ​ ​ 13,352 ​ ​ — ​ ​ — ​ 13,352 Unrealized (loss) gain on short-term investments — ​ — ​ — ​ — ​ ( 79 ) ​ ( 79 ) Net loss — ​ — ​ — ​ ( 16,061 ) ​ — ​ ( 16,061 ) Balance at June 30, 2023 52,657,661 $ 5 $ 586,908 $ ( 414,019 ) $ ( 5,180 ) $ 167,714 ​ The accompanying notes are an integral part of the unaudited consolidated financial statements. ​ ​ 4 Table of Contents ​ ALTIMMUNE, INC. CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (In thousands) ​ ​ ​ ​ ​ ​ ​ ​ Six Months Ended ​ ​ June 30, ​ ​ 2024 ​ 2023 CASH FLOWS FROM OPERATING ACTIVITIES: ​ ​ Net loss ​ $ ( 49,034 ) ​ $ ( 36,135 ) Adjustments to reconcile net loss to net cash used in operating activities: ​ ​ ​ Stock-based compensation expense ​ 7,961 ​ 5,461 Depreciation of property and equipment ​ 168 ​ 246 Accretion of discounts on short-term investments ​ ​ ( 2,052 ) ​ ​ ( 1,107 ) Loss (gain) on foreign currency exchange ​ 81 ​ ( 132 ) Changes in operating assets and liabilities: ​ ​ ​ ​ Accounts receivable ​ 687 ​ 37 Prepaid expenses and other assets ​ 3,692 ​ ( 250 ) Accounts payable ​ 618 ​ ( 769 ) Accrued expenses and other liabilities ​ 2,260 ​ ( 4,930 ) Income tax and R&D incentive receivables ​ 1,154 ​ ( 1,211 ) Net cash used in operating activities ​ ( 34,465 ) ​ ( 38,790 ) CASH FLOWS FROM INVESTING ACTIVITIES: ​ ​ Proceeds from sales and maturities of short-term investments ​ 33,500 ​ 60,565 Purchases of short-term investments ​ ( 76,717 ) ​ ( 43,229 ) Purchases of property and equipment, net ​ — ​ ( 47 ) Net cash (used in) provided by investing activities ​ ( 43,217 ) ​ 17,289 CASH FLOWS FROM FINANCING ACTIVITIES: ​ ​ Payments of deferred offering costs ​ ​ — ​ ​ ( 195 ) Proceeds from exercises of warrants ​ 161 ​ — Proceeds from issuance of common stock in at-the-market offerings, net ​ — ​ 13,352 Payment of conditional economic incentive ​ — ​ ( 90 ) Proceeds from issuance of common stock from Employee Stock Purchase Plan ​ 169 ​ 135 Proceeds from exercises of stock options ​ 207 ​ 61 Payments for tax withholding in share-based compensation ​ ( 844 ) ​ ( 500 ) Net cash used in financing activities ​ ( 307 ) ​ 12,763 Net decrease in cash and cash equivalents and restricted cash ​ ( 77,989 ) ​ ( 8,738 ) Cash, cash equivalents and restricted cash at beginning of period ​ 135,158 ​ 111,131 Cash, cash equivalents and restricted cash at end of period ​ $ 57,169 ​ $ 102,393 ​ ​ ​ ​ ​ ​ ​ SUPPLEMENTAL NON-CASH ACTIVITIES: ​ ​ ​ ​ Operating lease liability and right-of-use asset addition ​ $ 1,409 ​ $ — ​ The accompanying notes are an integral part of the unaudited consolidated financial statements. ​ 5 Table of Contents ALTIMMUNE, INC. NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Unaudited) 1. Nature of Business and Basis of Presentation Nature of Business 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 lead product candidate, pemvidutide (formerly known as ALT-801), is a novel, investigational, peptide-based GLP-1/glucagon dual receptor agonist in development for the treatment of obesity and metabolic dysfunction-associated steatohepatitis (“MASH”), previously termed non-alcoholic steatohepatitis (“NASH”). 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. Basis of Presentation The accompanying unaudited consolidated financial statements are prepared pursuant to the rules and regulations of the U.S. Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Accordingly, they do not include all of the information and disclosures required by accounting principles generally accepted in the United States (“U.S. GAAP”) for complete consolidated financial statements and should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2023, included in the Annual Report on Form 10-K which was filed with the SEC on March 27, 2024. In the opinion of management, the Company has prepared the accompanying unaudited consolidated financial statements on the same basis as the audited consolidated financial statements, and these consolidated financial statements include all adjustments, consisting only of normal recurring adjustments, necessary for a fair presentation of the results of the interim periods presented. The operating results for the interim periods presented are not necessarily indicative of the results expected for the full year 2024 or any future years or periods. The accompanying unaudited 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. The accompanying unaudited consolidated financial statements have been prepared on the basis of continuity of operations, realization of assets, and the satisfaction of liabilities in the ordinary course of business. The financial statements do not include any adjustments relating to the recoverability and classification of recorded assets and liabilities that might be necessary should the Company be unable to continue as a going concern. 2. Summary of Significant Accounting Policies During the six months ended June 30, 2024, there have been no significant changes to the Company’s summary of significant accounting policies contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023, as filed with the SEC on March 27, 2024. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Significant estimates and assumptions made in the accompanying condensed consolidated financial statements include, but are not limited to, 6 Table of Contents the valuation of share-based awards, income taxes, and accruals for research and development activities. The Company bases its estimates on historical experience and on various other assumptions that are believed to be reasonable. However, actual results could differ from those estimates. Income Taxes Due to a full valuation allowance, the Company did no t record an income tax expense (benefit) for either of the three and six months ended June 30, 2024 or 2023. The Company calculates its quarterly income tax provision based on estimated, annual effective tax rates applied to ordinary income (or loss) and other known items computed and recognized as they occur. The Company’s total provision is based on the United States statutory rate, increased by state and foreign taxes and reduced by a full valuation allowance on the Company’s deferred tax assets. 3. Fair Value Measurements The Company’s assets measured at fair value on a recurring basis as of June 30, 2024 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement at June 30, 2024 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents - money market funds ​ $ 52,131 ​ $ 52,131 ​ $ — ​ $ — Short-term investments ​ 107,780 ​ — ​ 107,780 ​ — Total ​ $ 159,911 ​ $ 52,131 ​ $ 107,780 ​ $ — ​ The Company’s assets measured at fair value on a recurring basis as of December 31, 2023 consisted of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurement at December 31, 2023 ​ Total Level 1 Level 2 Level 3 Assets: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Cash equivalents - money market funds ​ $ 123,233 $ 123,233 ​ $ — ​ $ — Short-term investments ​ 62,698 ​ — ​ 62,698 ​ — Total ​ $ 185,931 ​ $ 123,233 ​ $ 62,698 ​ $ — ​ ​ 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. Short-term investments with quoted prices as of June 30, 2024 as shown below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2024 ​ ​ Amortized Cost ​ Unrealized (Loss) Gain ​ Credit loss ​ Market Value United States treasury securities $ 22,625 $ ( 32 ) $ — $ 22,593 Commercial paper and corporate debt securities ​ ​ 64,062 ​ ​ ( 95 ) ​ ​ — ​ ​ 63,967 Asset backed securities ​ 5,494 ​ ( 11 ) ​ — ​ 5,483 Agency debt securities ​ ​ 15,751 ​ ​ ( 14 ) ​ ​ — ​ ​ 15,737 Total ​ $ 107,932 ​ $ ( 152 ) ​ $ — ​ $ 107,780 ​ 7 Table of Contents Short-term investments with quoted prices as of December 31, 2023 as shown below (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, 2023 ​ ​ Amortized Cost ​ Unrealized (Loss) Gain ​ Credit Loss ​ Market Value United States treasury securities $ 19,472 $ 12 $ — $ 19,484 Commercial paper and corporate debt securities ​ ​ 31,301 ​ ​ 24 ​ ​ — ​ ​ 31,325 Asset backed securities ​ 2,966 ​ ( 4 ) ​ — ​ 2,962 Agency debt securities ​ ​ 8,923 ​ ​ 4 ​ ​ — ​ ​ 8,927 Total ​ $ 62,662 ​ $ 36 ​ $ — ​ $ 62,698 ​ As of June 30, 2024 and December 31, 2023, none of the unrealized losses on the Company’s short-term investments are a result of credit loss; therefore, any unrealized losses were recognized in OCI. As of June 30, 2024 and December 31, 2023, the Company had $ 0.3 million and $ 0.1 million, respectively, accrued interest on short-term investments included in “Accounts and other receivables” on the accompanying Consolidated Balance Sheets. 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 six months ended June 30, 2024 and year ended December 31, 2023, the Company had no significant assets or liabilities that were measured at fair value on a non-recurring basis. 4. Operating Leases The Company’s operating lease for office and laboratory space in the United States was set to expire on April 30, 2025. On May 20, 2024, the Company exercised its one-time 60 -month renewal option to renew its lease for an additional 60 months. As of May 1, 2024, the Company remeasured its lease liability and recorded $ 1.4 million additional lease liability and right-of-use asset using an updated incremental borrowing rate of 9.5 %. The renewed lease has a term of 72 months and expires on April 30, 2030. The Company reassessed that the renewed lease remains an operating lease under Topic 842. Rent expense under the Company’s operating leases was $ 0.1 million and $ 0.3 million during the three and six months ended June 30, 2024. During the three and six months ended June 30, 2023, rent expense under the Company’s operating leases was $ 0.1 million and $ 0.3 million, respectively. Rent expense includes short-term leases and variable lease costs that are not included in the lease obligation. 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. The cash paid for operating lease liabilities for each of the six months ended June 30, 2024 and 2023 was $ 0.3 million. 8 Table of Contents Supplemental other information related to the operating leases balance sheet information is as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2024 ​ December 31, 2023 ​ Balance Sheet Classification Operating lease obligations, current (see Note 5) $ 345 $ 496 ​ ​ Accrued expenses and other current liabilities Operating lease obligations, noncurrent (see Note 6) ​ $ 1,517 ​ $ 175 ​ ​ Noncurrent liabilities Operating lease right-of-use assets ​ $ 1,677 ​ $ 363 ​ ​ Other assets Weighted-average remaining lease term (years) ​ 5.8 ​ 1.3 ​ ​ ​ Weighted-average discount rate ​ 9.5 % 7.2 % ​ ​ ​ Maturities of operating lease liabilities as of June 30, 2024 are as follows (in thousands): ​ ​ ​ ​ 2024 - remainder of the year ​ $ 264 2025 ​ 422 2026 ​ 376 2027 ​ 387 2028 ​ ​ 398 2029 ​ ​ 410 2030 ​ 138 Total operating lease payments ​ 2,395 Less: imputed interest ​ ( 533 ) Total operating lease liabilities ​ $ 1,862 ​ ​ 5. Accrued Expenses Accrued expenses and other current liabilities consist of the following (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2024 ​ December 31, 2023 Accrued professional services $ 357 ​ $ 293 Accrued payroll and employee benefits ​ 2,029 ​ 3,315 Accrued research and development ​ 9,667 ​ 5,845 Lease obligation, current portion (see Note 4) ​ 345 ​ ​ 496 Accrued interest and other ​ 69 ​ 124 Total accrued expenses and other current liabilities ​ $ 12,467 ​ $ 10,073 ​ ​ ​ 6. Noncurrent Liabilities The Company’s noncurrent liabilities are summarized as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ June 30, 2024 ​ December 31, 2023 Research and development incentive credit ​ $ 3,952 ​ $ 4,023 Lease obligation, long-term portion (see Note 4) ​ 1,517 ​ ​ 175 Conditional economic incentive grants ​ 160 ​ 160 Other ​ 31 ​ 40 Total noncurrent liabilities ​ $ 5,660 ​ $ 4,398 ​ ​ 7. Stockholders’ Equity The Amended and Restated Certificate of Incorporation, as amended (“Charter”), authorizes the Company to issue 200,000,000 shares of common stock, par value $ 0.0001 per share. As of June 30, 2024, the Company had 71,046,267 shares of common stock issued and outstanding . 9 Table of Contents Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders. Common stockholders are not entitled to receive dividends, unless declared by the board of directors. The Charter also authorizes the Company to issue 1,000,000 shares of preferred stock, par value $ 0.0001 per share. As of June 30, 2024, the Company had no shares of preferred stock issued and outstanding . At-the-Market Offerings On February 28, 2023, the Company entered into an Equity Distribution Agreement (the “2023 Agreement”) with Evercore Group L.L.C., JMP Securities LLC 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, having an aggregate offering price of up to $ 150.0 million (the “Shares”) through the Sales Agents (the “2023 Offering”). All Shares offered and sold in the 2023 Offering will be issued pursuant to the Company’s Registration Statement on Form S-3 filed with the SEC on February 28, 2023, which was declared effective immediately, the prospectus supplement relating to the 2023 Offering filed with the SEC on February 28, 2023, and any applicable additional prospectus supplements related to the 2023 Offering that form a part of the Registration Statement. The Company capitalized approximately $ 0.2 million of other offering costs which will offset the proceeds received from the shares sold under the 2023 Agreement. Since inception through June 30, 2024, the Company has sold 20,454,516 shares of common stock under the 2023 Agreement, resulting in approximately $ 86.6 million in proceeds, net of $ 2.8 million commission and other offering costs. No shares were sold under the 2023 Agreement during the six months ended June 30, 2024, and as of June 30, 2024, $ 60.6 million remained available to be sold under the 2023 Agreement. As of June 30, 2024, there was $ 0.1 million deferred offering costs included in prepaid expenses and other current assets on the accompanying consolidated balance sheets. Warrants On March 5, 2024, warrant holders exercised 50,000 warrants with an exercise price of $ 3.21 , resulting in the issuance of 50,000 shares of common stock. As of June 30, 2024, the Company had no outstanding warrants. ​ 8. Stock-Based Compensation 2017 Omnibus Incentive Plan (Omnibus Plan) The Company’s Omnibus Plan provides for an annual increase on January 1 of each year, commencing in 2019 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. Accordingly, on January 1, 2024, the number of shares of Common Stock reserved and available for issuance under the Omnibus Plan increased by 3,055,006 shares of common stock. Stock Options The Company’s stock option awards generally vest over four years and typically have a contractual life of ten years . As of June 30, 2024, there was $ 19.8 million of unrecognized compensation cost related to stock options, which is expected to be recognized over a weighted-average period of 2.8 years. During the six months ended June 30, 2024, the Company granted 1,566,575 stock options with a weighted average exercise price of $ 9.32 and per share weighted average grant date fair value of $ 7.55 . 10 Table of Contents Information related to stock options outstanding as of June 30, 2024 is as follows (in thousands, except share, exercise price and contractual term): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted-Average ​ ​ ​ ​ ​ ​ Weighted- ​ Remaining ​ ​ ​ ​ ​ Number of ​ Average ​ Contractual Term ​ Aggregate Intrinsic ​ ​ Stock Options ​ Exercise Price ​ (Years) ​ Value Outstanding, December 31, 2023 5,043,593 ​ $ 9.33 5.9 ​ $ 16,919 Granted 1,566,575 ​ $ 9.32 ​ Exercised ( 65,683 ) ​ $ 3.16 ​ Forfeited or expired ( 260,825 ) ​ $ 8.36 ​ Outstanding, June 30, 2024 6,283,660 ​ $ 9.43 6.0 ​ $ 5,199 Exercisable, June 30, 2024 3,302,235 ​ $ 9.30 5.9 ​ $ 4,182 Vested and expected to vest, June 30, 2024 6,015,332 ​ $ 9.42 6.0 ​ $ 5,108 ​ Restricted Stock Units (RSUs) During the six months ended June 30, 2024, the Company granted 484,600 shares of RSUs with a weighted average grant date fair value of $ 9.32 which vest over four years . As of June 30, 2024, the Company had unvested RSUs of 786,102 shares with total unrecognized compensation expense of $ 6.3 million, which the Company expects to recognize over a weighted average period of approximately 2.9 years. During the six months ended June 30, 2024, the Company issued 190,575 shares of unrestricted common stock as a result of the vesting of 286,165 RSUs net of 95,590 shares of common stock withheld to satisfy tax withholding obligations. 2019 Employee Stock Purchase Plan (ESPP) Under the ESPP, employees purchased 62,609 shares for $ 0.2 million during the six months ended June 30, 2024. During each of the three and six months ended June 30, 2024, the Company recognized compensation expense of $ 0.1 million. During the three and six months ended June 30, 2023, the Company recognized compensation expense of $ 0.1 million and $ 0.2 million, respectively. Stock-Based Compensation Expense During the three months ended June 30, 2024, the Company recorded $ 1.0 million incremental stock-based compensation expense as a result of the modifications of stock awards upon termination of the former Chief Financial Officer. The modification changed the vesting conditions of the awards by accelerating the vesting of certain unvested awards that would have otherwise been forfeited upon termination. The incremental costs are included in the Statements of Operations and Comprehensive Loss under general and administrative expense. Stock-based compensation expense is classified in the unaudited consolidated Statements of Operations and Comprehensive Loss for the three and six months ended June 30, 2024 and 2023 as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three Months Ended Six Months Ended ​ ​ June 30, ​ June 30, ​ ​ 2024 2023 ​ 2024 2023 Research and development ​ $ 1,574 ​ $ 1,209 ​ $ 3,249 ​ $ 2,396 General and administrative ​ 2,737 ​ 1,577 ​ 4,712 ​ 3,065 Total ​ $ 4,311 ​ $ 2,786 ​ $ 7,961 ​ $ 5,461 ​ ​ ​ 9. Net Loss Per Share Because the Company has reported net loss attributable to common stockholders for the three and six months ended June 30, 2024 and 2023, basic and diluted net loss per share attributable to common stockholders in each period are the same. 11 Table of Contents 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. 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, RSUs, common stock 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 RSUs, 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: ​ ​ ​ ​ ​ ​ ​ Three and Six Months Ended ​ ​ June 30, ​ ​ 2024 ​ 2023 Common stock warrants — 145,600 Common stock options 6,328,463 4,838,961 Restricted stock units 786,102 ​ 620,417 ​ ​ ​ 10. Commitments and Contingencies Spitfire Acquisition In July 2019, the Company entered into 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 novel peptide products for pharmaceutical indications, including pemvidutide for the treatment of MASH. As part of the agreement, 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. (the “Sales Milestone”) within ten years following the approval of a new drug application filed with the U. S. Food and Drug Administration (the “FDA”). Litigation On May 6, 2024, a class action complaint was filed in federal district court in the District of Maryland, Southern Division, naming as defendants the Company and three of the Company’s executive officers, captioned Mogan v. Altimmune, Inc., et al., No. 24-cv-01315 (D. Md.) (the “Class Action”). The complaint alleges that the defendants violated Sections 10(b) and 20(a) of the Securities Exchange Act of 1934, as amended, and Rule 10b-5 thereunder, by making false and misleading statements and omissions of material fact to the investing public including the plaintiff and class members, who purchased or otherwise acquired the Company’s common stock between December 1, 2023 and April 26, 2024. The plaintiff and class members seek to have the action maintained as a class action under Rule 23 of the Federal Rules of Civil Procedure and for the defendants to pay damages, interest, and an award of costs, including attorneys’ fees. On June 14, 2024, the Court entered an order stating that defendants were not required to answer, move to dismiss, or otherwise respond to the initial complaint filed on May 6, 2024, and that within 14 days of the Court’s entry of an order appointing a lead plaintiff the parties are to confer and submit a proposed schedule to the court for the filing of an amended complaint (if any) and the filing of a motion to dismiss or other response to the amended complaint. A substantially similar complaint, captioned Campanile v. Altimmune, Inc., et al. , No. 8:24-cv-01918 (D. Md.), was also filed in the same court by another plaintiff on July 1, 2024 against the Company and three of its executive officers, based upon the same general set of allegations and class period. On July 5, 2024, two movants moved to consolidate the two actions and to be appointed lead plaintiff. On July 12, 2024, these movants filed a stipulation and proposed order to consolidate the related actions, and to be appointed co-lead plaintiffs. The Company intends to vigorously defend against this class action litigation. On June 4, 2024, a shareholder derivative complaint was filed in federal district court in the District of Delaware, purportedly on behalf of the Company, naming as defendants three of the Company’s executive officers and eight of the Company’s board members, captioned Stourbridge Investments LLC v. Garg, et al. , No. 1:24-cv-669-GBW (D. Del.). The complaint is based upon allegations that are similar to those alleged in the Class Action and alleges claims for contribution, 12 Table of Contents breaches of fiduciary duty, unjust enrichment, and waste of corporate assets based on the defendants purportedly making or causing to be made false and misleading statements and omissions of material fact between December 1, 2023 and April 26, 2024. The complaint seeks unspecified monetary relief, exemplary damages, restitution, contribution, and costs, as well as equitable relief. A similar shareholder derivative complaint was filed in the same court by another plaintiff on July 1, 2024, based upon substantially similar allegations, and alleges claims for contribution, breach of fiduciary duties, unjust enrichment, abuse of control, gross mismanagement, and waste of corporate assets. The complaint, captioned Alaraidah v. Garg, et al. , No. 1:24-cv-00772-GBW (D. Del.), seeks unspecified monetary relief, restitution, costs, and equitable relief. These actions were consolidated on July 18, 2024 into case no. 1:24-cv-669-GBW (the “Derivative Action”). The Company intends to vigorously defend against the Derivative 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. ​ 13 Table of Contents