Annual Report for Fiscal Year Ending 12-31, 2025 (Form 10-K)

Management's Discussion and Analysis of Financial Condition and Results of Operations

The following discussion and analysis of our financial condition and results of operations should be read together with our consolidated financial statements and related notes appearing elsewhere in this Annual Report. Some of the information contained in this discussion and analysis contains forward-looking statements that involve substantial risks and uncertainties. See "Forward-looking statements" in Part I of this Annual Report and the section entitled "Risk Factors" in Part I, Item 1A of this Annual Report for a discussion of certain factors that could cause actual results or events to differ materially from the forward-looking statements that we make.

Overview

Altimmune, Inc. is a late clinical-stage biopharmaceutical company developing novel therapies for serious liver diseases. Our lead product candidate, pemvidutide (formerly known as ALT-801), is a balanced 1:1 glucagon/GLP-1 dual receptor agonist in development for the treatment of MASH, AUD and ALD. We may also pursue additional indications for pemvidutide that leverage its differentiated clinical profile. Except where the context indicates otherwise, references to "we," "us," "our," "Altimmune", or the "Company" refer to the company and its subsidiaries.

Fiscal Year 2025 Business Update

MASH

On June 26, 2025, we released 24-week topline efficacy results from IMPACT, a Phase 2b trial of pemvidutide in patients with MASH. The Phase 2b trial enrolled 212 subjects with biopsy-confirmed MASH and fibrosis stages F2/F3 with and without diabetes randomized 1:2:2 to receive weekly subcutaneous doses of pemvidutide at 1.2 mg, 1.8 mg or placebo. The topline 24-week data showed that treatment with pemvidutide achieved statistically significant improvements in MASH resolution without worsening of fibrosis, improvements in fibrosis without worsening of MASH, and statistically significant changes in well-established NITs of fibrosis, including ELF score and LSM compared with placebo at both doses.

On December 11, 2025, we held an End-of-Phase 2 meeting with the FDA to discuss and align on the parameters for a registrational Phase 3 trial of pemvidutide for MASH patients with moderate to advanced fibrosis with biopsy driven endpoints. The FDA agreed to the use of AIM-MASH AI Assist, the first FDA-qualified AI pathology tool for MASH clinical trials, in our Phase 3 trial. We received final minutes from the End-of-Phase 2 meeting in January 2026, which we believe describe a clear regulatory path for a Phase 3 trial in MASH. We also intend to seek scientific advice from European regulators to further inform the final Phase 3 protocol. See Item 1. Business for additional information.

On December 19, 2025, we announced positive 48-week topline results from the IMPACT Phase 2b trial of pemvidutide in patients with MASH. The topline 48-week data from the IMPACT trial showed that treatment with pemvidutide achieved statistically significant improvements across treatment arms versus placebo in the key anti-fibrosis NITs of ELF and LSM.

Additional Indications for Pemvidutide

On March 13, 2025, we announced that we are pursuing two additional indications for our lead product candidate, pemvidutide. The new indications are AUD and ALD.

AUD

On May 19, 2025, we announced the enrollment of the first subject in the RECLAIM Phase 2 trial evaluating the efficacy and safety of pemvidutide in subjects with AUD. RECLAIM is a randomized, placebo-controlled trial conducted across approximately 15 sites in the United States, targeting enrollment of approximately 100 subjects.

On August 19, 2025, we announced that the U.S. Food and Drug Administration has granted Fast Track designation to pemvidutide for the treatment of AUD. Fast Track designation is intended to accelerate the development and review of new drugs that target serious conditions and address unmet medical needs.

On November 3, 2025, we announced the completion of enrollment in the RECLAIM Phase 2 trial. Enrollment completed ahead of schedule, underscoring strong interest from the patient community in a new therapeutic option for AUD. We are on track to complete the 24-week treatment period and announce topline results in 2026.

ALD

On July 9, 2025, we announced the enrollment of the first patient in the RESTORE Phase 2 trial evaluating the efficacy and safety of pemvidutide in subjects with ALD. RESTORE is a randomized, placebo-controlled trial enrolling approximately 100 patients across 34 sites in the United States. See Item 1. Business for additional information.

Recent Global Events

Tariffs and Inflation

The United States recently imposed reciprocal and additional tariffs on many countries around the world. Such tariffs and counter tariffs by other countries against the U.S. have been causing uncertainties in the global markets and supply chain. If the tariffs and counter tariffs continue or escalate, they could have a significant negative effect on the global economy or on our operations, including continued inflationary pressures on raw materials, supply chain and logistics disruptions, and volatility in the capital markets, foreign exchange rates and interest rates.

Inflation generally affects us by increasing our employee-related costs and clinical trial expenses, as well as other operating expenses. Our financial condition and results of operations may also be impacted by other factors we may not be able to control, such as public health crises, global supply chain disruptions, uncertain global economic conditions, global trade disputes or political instability as further discussed in the section "Risk Factors" in this Annual Report on Form 10-K.

Financial Operations Overview

The consolidated financial information presented below includes the accounts of Altimmune, Inc., Altimmune UK, Ltd, Spitfire Pharma, LLC. and Altimmune AU Pty, Ltd. All intercompany accounts and transactions have been eliminated in consolidation.

Revenue

We have not generated any revenue from the sale of any products to date. Our revenues in previous years consisted primarily of government and foundation grants and contracts that supported our efforts on specific research projects.

Research and development expenses

Research and development expenses consist primarily of costs incurred for the development of our product candidates, which include:

Research and development costs are expensed as incurred. Costs for certain development activities are recognized based on an evaluation of the progress to completion of specific tasks using information and data provided to us by our vendors, CROs and clinical sites.

We cannot determine with certainty the duration and completion costs of the current or future clinical trials of our product candidates or if, when or to what extent we will generate sales from the commercialization of any of our product candidates if they receive regulatory approval. The successful development of our product candidates is highly uncertain and may never result in approved products. The duration, costs and timing of clinical trials and development of our product candidates will depend on a variety of factors, including:

A change in the outcome of any of these variables with respect to the development of a product candidate could mean a significant change in the costs and timing associated with the development of that product candidate. For example, if the FDA, or another regulatory authority were to require us to conduct clinical trials beyond those that we currently anticipate will be required for the completion of clinical development of a product candidate, we could be required to expend significant additional financial resources and time on the completion of clinical development. Additionally, we may conduct additional trials in support of sales and marketing of our product candidates.

We plan to increase our research and development expenses for the foreseeable future as we continue the development of clinical and preclinical candidates. Our current active and planned research and development activities include the following:

A significant portion of our research and development efforts have been related to the development of pemvidutide. We do not allocate personnel-related costs, costs associated with our general research platform improvements, depreciation or other indirect costs to specific programs.

General and Administrative Expenses

General and administrative expenses consist primarily of salaries and related costs for personnel, including stock-based compensation and travel expenses for our employees in executive, operational, finance and human resource functions. Other general and administrative expenses include insurance expenses, facility-related costs and professional fees for directors, accounting and legal services, and expenses associated with obtaining and maintaining our intellectual property.

We anticipate that our general and administrative expenses will increase in the future as we increase our headcount to support our continued research and development activities. We also anticipate increased expenses related to audit, legal, regulatory and tax-related services associated with maintaining compliance with exchange listing and the SEC requirements, director and officer insurance, investor relations costs and other costs associated with being a public company. Additionally, if and when we believe a regulatory approval of the first product candidate appears likely, we anticipate an increase in staffing and related expenses as a result of our preparation for commercial operations, especially as it relates to the sales and marketing of our product candidates.

Results of Operations

Comparison of years ended December 31, 2025 and December 31, 2024 (in thousands):

*Indicates the percentage change period over period is not meaningful due to zero or negligible amount in the prior period.

Research and development expenses

Research and development expenses for the years ended December 31, 2025 and 2024 consisted primarily of expenses related to product candidate development, summarized as follows:

*indicates the percentage change period over period is not meaningful due to zero amount in the prior period.

The decrease in research and development expenses for MASH was primarily due to ongoing enrollment for the IMPACT Phase 2b trial in MASH during 2024 which was completed in early 2025. The decrease in other pemvidutide expenses was primarily due to a $5.7 million decrease in manufacturing expenses and a $2.1 million decrease due to winding down of GLP-1 and other nonclinical activities. These decreases were partially offset by the increase in expense associated with the start of the AUD and ALD trials.

The decrease in research and development expenses for HepTcell was due to the termination of HepTcell in March 2024.

General and administrative expenses

General and administrative expenses increased by $7.1 million, or 34%, during the year ended December 31, 2025 as compared to the year ended December 31, 2024, primarily due to a $2.7 million increase in professional services and a $4.9 million increase in stock compensation and other labor-related expenses, including the $1.4 million severance costs for our former executives.

Total other income (expense), net

Total other income (expense), net decreased by $2.4 million during the year ended December 31, 2025 as compared to the year ended December 31, 2024. The net decrease was primarily due to a $1.6 million increase in interest expense related to our Term Loan and a $0.5 million decrease in interest income earned on our cash equivalents and short-term investments.

Income tax expense (benefit)

During the year ended December 31, 2025, we have recorded a discrete tax benefit of approximately $0.7 million related to a portion of carryback claims with the State of Maryland, which we previously held an uncertain tax position against. Other than the discrete tax benefit discussed above, due to a full valuation allowance, the Company did not record an income tax expense (benefit) for either of the years ended December 31, 2025 and 2024.

Liquidity and Capital Resources

Overview

Our primary sources of cash for the year ended December 31, 2025 were from equity transactions, debt, interest income from our money market funds and short-term investments, and proceeds from maturity of our short-term investments. Our cash, cash equivalents, restricted cash and short-term investments were $273.5 million as of December 31, 2025. We believe, based on the operating cash requirements and capital expenditures expected for 2026 and 2027, our cash on hand as of December 31, 2025, together with expected cash receipts from our equity transactions and research and development incentives, are sufficient to fund operations for at least a twelve-month period from the issuance date of our December 31, 2025 consolidated financial statements.

We have not generated any revenues from the sale of any products to date, and there is no assurance of any future revenues from product sales. We have incurred significant losses since we commenced operations. As of December 31, 2025, we had an accumulated deficit of $649.5 million. In addition, we have not generated positive cash flows from operations. We have had to rely on a variety of financing sources, including the issuance of debt and equity securities. As capital resources are consumed to fund our research and development activities, we may require additional capital beyond our currently anticipated amounts. In order to address our capital needs, including our planned clinical trials, we must continue to actively pursue additional equity or debt financing, and monetization of our existing programs through partnership arrangements or sales to third parties.

Sources of Liquidity

Loan Financing

On May 13, 2025 ("Closing Date"), we entered into a Loan and Security Agreement ("Loan Agreement") with Hercules Capital, Inc. ("Hercules") and the lenders party thereto, pursuant to which the lenders will make available up to four tranches of term loans in an aggregate principal amount of $100.0 million (the "Term Loan"), subject to certain terms and conditions. The first Term Loan tranche was drawn down on the Closing Date in an aggregate principal amount of $15.0 million.

On November 5, 2025, (the "Amendment Closing"), we entered into an amendment to the Loan Agreement with Hercules and the lenders party thereto, pursuant to which the lenders will, subject to certain terms and conditions, increase the availability under the Term Loan from an aggregate principal amount of $100.0 million to $125.0 million. The Term Loan, as amended, is structured in four tranches. As disclosed above, the first Term Loan tranche was drawn down on the

Closing Date in an aggregate principal amount of $15.0 million. The second Term Loan tranche was drawn down on the Amendment Closing in an aggregate principal amount of $20.0 million. Upon the achievement of certain milestones and subject to other terms and conditions set out in the Loan Agreement, as amended, the third Term Loan tranche will be made available in an aggregate principal amount of up to $10.0 million. The fourth Term Loan tranche will be made available in an aggregate principal amount of up to $80.0 million subject to the approval of the lenders. The Term Loan, as amended, bears interest equal to the greater of (a) 9.70% per annum and (b) the prime rate as reported in The Wall Street Journal plus 2.45% per annum. The interest-only period has been extended to 30 months from May 13, 2025.

Shelf Registrations

On November 13, 2025, we filed a shelf registration statement on Form S-3, as amended, which was declared effective on December 5, 2025. This shelf registration allows us to offer and sell up to $400.0 million of our common stock, preferred stock, debt securities, warrants, rights and units (the "November 2025 Shelf") for a period of 3 years from effectiveness.

On February 27, 2025, we filed a shelf registration statement on Form S-3, which was declared effective on March 13, 2025. This shelf registration allows us to offer and sell up to $400.0 million of our common stock, preferred stock, debt securities, warrants, rights and units (the "February 2025 Shelf") for a period of 3 years from effectiveness.

On February 28, 2023, we filed a shelf registration statement on Form S-3ASR, which was declared effective immediately. This shelf registration allowed us to offer and sell any amount of our common stock, preferred stock, debt securities, warrants, rights and units (the "2023 Shelf"). The 2023 Shelf expired on February 27, 2025

At-the-Market Offerings

On November 6, 2025, we entered into an Equity Distribution Agreement (the "November 2025 Agreement") with Leerink Partners LLC serving as sales agent, with respect to an at-the-market offerings program under which we may offer and sell shares of our common stock having an aggregate offering price of up to $200.0 million through the sales agent from the February 2025 Shelf. Since inception through December 31, 2025, we raised approximately $25.4 million in net proceeds, with $174.2 million remaining available to be sold under the November 2025 Agreement.

On February 27, 2025, we entered into an Equity Distribution Agreement (the "February 2025 Agreement") with Leerink Partners LLC, Piper Sandler & Co. and Stifel, Nicolaus & Company, Incorporated, serving as sales agents, with respect to an at-the-market offerings program under which we offered and sold shares of our common stock having an aggregate offering price of up to $150.0 million through the sales agents from the February 2025 Shelf. Since inception, through the termination of the February 2025 Agreement in November 2025, we raised approximately $118.3 million in net proceeds.

On February 28, 2023, we entered 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, with respect to an at-the-market offerings program under which we offered and sold shares of our common stock having an aggregate offering price of up to $150.0 million through the Sale Agents from the 2023 Shelf. Since inception through the termination of the 2023 Agreement in February 2025, we raised approximately $126.8 million in net proceeds.

Registered Direct Offering

On January 27, 2026, the Company entered into a securities purchase agreement with a new fundamental institutional investor pursuant to a registered direct offering under the November 2025 Shelf for the purchase and sale of 12,397,920 shares of its common stock and 4,647,534 pre-funded warrants for net proceeds of approximately $70.4 million. The pre-funded warrants were fully exercised on February 13, 2026, resulting in the issuance of 4,647,534 shares of our common stock.

Cash Flows

The following table provides information regarding our cash flows for the years ended December 31, 2025 and 2024:

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Operating Activities

Net cash used in operating activities was $67.5 million for the year ended December 31, 2025 compared to $79.8 million during the year ended December 31, 2024. Our sources of cash provided by operations during the year ended December 31, 2025 were primarily cash receipts of research and development incentive credits. The primary uses of cash from our operating activities include payments for labor and labor-related costs, professional fees, research and development costs associated with our clinical trials and other general corporate expenditures. The decrease in cash used in operating activities of $12.3 million was due to a $10.0 million decrease in net loss as adjusted for noncash items and a $2.3 million change in working capital accounts.

Investing Activities

Net cash used in investing activities was $132.5 million for the year ended December 31, 2025 compared to $28.4 million net cash provided by investing activities during the year ended December 31, 2024. The net cash used in investing activities during the year ended December 31, 2025 was primarily due to $285.4 million purchase of short-term investments, partially offset by $153.0 million proceeds from sale and maturities of short-term investments. The net cash used in investing activities during the year ended December 31, 2024 was primarily due to $115.7 million purchase of short-term investments, partially offset by $87.3 million proceeds from sale and maturities of short-term investments.

Financing Activities

Net cash provided by financing activities was $206.8 million for the year ended December 31, 2025 compared to $10.0 million during the year ended December 31, 2024. The net cash provided by financing activities during the year ended December 31, 2025 was primarily the result of the receipt of $173.3 million in net proceeds from the issuance of common stock from our at-the-market offerings program, $33.9 million in net proceeds from the Term Loan and $0.3 million in proceeds from our ESPP, partially offset by a $0.7 million payment for tax withholding obligations related to share-based compensation. The net cash provided by financing activities during the year ended December 31, 2024 was primarily the result of the receipt of $10.0 million in net proceeds from the issuance of common stock from our at-the-market offerings program, $0.4 million in proceeds from exercise of stock options, $0.3 million in proceeds from our ESPP and $0.2 million proceeds from exercises of stock warrants, partially offset by $0.9 million payment for tax withholding obligations related to share-based compensation.

Capital Resources

We have financed our operations to date principally through our equity offerings and proceeds from issuances of our preferred stock, common stock and warrants. As of December 31, 2025, we had $273.5 million of cash, cash equivalents, restricted cash and short-term investments. Accordingly, management believes that we have sufficient capital to fund our plan of operations for at least a twelve-month period from the issuance date of our December 31, 2025 consolidated financial statements. However, in order to address our capital needs in the long-term, including our planned

clinical trials, we must continue to actively pursue additional equity or debt financing and monetization of our existing programs through partnership arrangements or sales to third parties.

Critical Accounting Estimates

Our management's discussion and analysis of our financial condition and results of operations is based on our consolidated financial statements, which have been prepared in accordance with U.S. generally accepted accounting principles, or GAAP. The preparation of our consolidated financial statements requires us to make judgments and estimates that affect the reported amounts of assets, liabilities, revenues and expenses, and the disclosure of contingent liabilities in our consolidated financial statements. We base our estimates on historical experience, known trends and events, and various other factors that we believe to be reasonable under the circumstances. Actual results may differ from these estimates under different assumptions or conditions. On an ongoing basis, we evaluate our judgments and estimates in light of changes in circumstances, facts and experience. The effects of material revisions in estimates, if any, will be reflected in the consolidated financial statements prospectively from the date of change in estimates.

While our significant accounting policies are described in more detail in the notes to our consolidated financial statements appearing elsewhere in this Annual Report, we believe the following accounting policies used in the preparation of our consolidated financial statements require the most significant judgments and estimates.

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 our 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 we outsource 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, we analyze 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 prepaid and accrued balances at the end of any reporting period.

Stock-based Compensation

We account for all stock-based compensation granted to employees and non-employees using a fair value method. Compensation expense related to stock-based awards is recognized over the requisite service period of the awards, usually the vesting period, on a straight-line basis, net of estimated forfeitures. The fair value of stock option awards to employees and directors is estimated using the Black-Scholes option pricing model, which requires the input of subjective assumptions, including (1) the expected stock price volatility, (2) the expected term of the award, (3) the risk-free interest rate and (4) expected dividends.

We estimate forfeitures at the time of grant and, if necessary, revise the estimate in subsequent periods if actual forfeitures differ from those estimates. Estimates are based on our historical analysis of actual stock option forfeitures.

The actual expense recognized over the vesting period is only for those options that vest. For each of the years ended December 31, 2025 and 2024, forfeiture rates were approximately 9%.

We calculated the fair value of stock option awards using the Black-Scholes option pricing model. The Black-Scholes option pricing model requires the input of subjective assumptions, including stock price volatility and the expected life of stock options. The application of this valuation model involves assumptions that are highly subjective, judgmental and sensitive in the determination of compensation cost. Our stock started being publicly traded under ALT beginning in June 2017, and as such we do not have sufficient history to estimate the volatility of our common stock price or the expected life of our options. The expected stock price volatility for stock option awards is based on a weighted-average volatility rate of historical volatility from a representative peer group of comparable companies and our stock price volatility until such time that we have sufficient history to rely on the volatility of our own stock. The average expected life of stock options was determined according to the "simplified method" as described in SAB 107, which is the midpoint between the vesting date and the end of the contractual term. The risk-free interest rate was determined by reference to implied yields available from U.S. Treasury securities with a remaining term equal to the expected life assumed at the date of grant. We have not paid and do not anticipate paying cash dividends. Therefore, the expected dividend rate is assumed to be 0%.

Modification of stock awards are evaluated and recorded based on the fair value of the award on the modification date. Depending on the type of modifications, we estimate the fair value of modified stock options using the Black-Scholes option pricing model. The fair value of modified restricted stock units is determined based on our stock price at the modification date.

There is a high degree of subjectivity involved when using option pricing models to estimate stock-based compensation. If factors change and we employ different assumptions when valuing our options, the compensation expense that we record in the future may differ significantly from what we have historically reported.