What changed in this filing

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Item 1. Financial Statements

2026-05-13 compared with 2025-11-06 · 118 added, 151 removed, 253 unchanged (52% of the section changed)

3 unchanged sentences

(In thousands, except share and per-share amounts)

September 30,

Current assets:

20 unchanged sentences

200,000,000 shares authorized;

95,598,665 and 72,352,701 shares issued and outstanding as of September 30, 2025 and December 31 2024, respectively

130,221,154 and 110,882,735 shares issued and outstanding as of March 31, 2026 and December 31, 2025, respectively

Additional paid-in capital

8 unchanged sentences

Three Months Ended

Nine Months Ended

September 30,

Operating expenses:

10 unchanged sentences

Income tax expense (benefit)

Other comprehensive income — unrealized gain (loss) on short-term investments

Other comprehensive income — unrealized loss on short-term investments

Comprehensive loss

13 unchanged sentences

Issuance of common stock in at-the-market offerings, net

Unrealized (loss) gain on short-term investments

Issuance of common stock in direct offering, net

Issuance of common stock upon exercise of pre-funded warrants

Unrealized loss on short-term investments

Balance at March 31, 2026

Stock-based compensation

Exercise of stock options

Vesting of restricted stock awards including withholding, net

Issuance of common stock in at-the-market offerings, net

Unrealized (loss) gain on short-term investments

Balance at June 30, 2025

Stock-based compensation

Exercise of stock options

Issuance of common stock from Employee Stock Purchase Plan

Issuance of common stock in at-the-market offerings, net

Unrealized (loss) gain on short-term investments

Balance at September 30, 2025

The accompanying notes are an integral part of the unaudited consolidated financial statements.

9 unchanged sentences

Issuance of common stock from Employee Stock Purchase Plan

Issuance of common stock upon exercise of warrants

Unrealized (loss) gain on short-term investments

Issuance of common stock in at-the-market offerings, net

Unrealized loss on short-term investments

Balance at March 31, 2025

Stock-based compensation

Exercise of stock options

Vesting of restricted stock awards including withholding, net

Unrealized (loss) gain on short-term investments

Balance at June 30, 2024

Stock-based compensation

Exercise of stock options

Vesting of restricted stock awards including withholding, net

Issuance of common stock from Employee Stock Purchase Plan

Unrealized (loss) gain on short-term investments

Balance at September 30, 2024

The accompanying notes are an integral part of the unaudited consolidated financial statements.

2 unchanged sentences

(In thousands)

Nine Months Ended

September 30,

Three Months Ended

CASH FLOWS FROM OPERATING ACTIVITIES:

5 unchanged sentences

Loss on foreign currency exchange

Impairment loss on long-lived asset

Deferred income tax benefit

13 unchanged sentences

Payments of deferred offering costs

Proceeds from exercises of warrants

Proceeds from term loan

Payment for debt issuance costs

Proceeds from issuance of common stock in at-the-market offerings, net

Proceeds from issuance of common stock and pre-funded warrants in direct offering, net

Proceeds from issuance of common stock from Employee Stock Purchase Plan

Proceeds from exercises of stock options

Payments for tax withholding in share-based compensation

Net cash provided by (used in) financing activities

Other financing activities

Net cash provided by financing activities

Net increase (decrease) in cash and cash equivalents and restricted cash

3 unchanged sentences

Cash paid for interest

Cash received from income tax refunds

SUPPLEMENTAL NON-CASH ACTIVITIES:

Operating lease liability and right-of-use asset addition

Deferred offering costs in accrued expenses and other current liabilities

The accompanying notes are an integral part of the unaudited consolidated financial statements.

4 unchanged sentences

Altimmune, Inc., headquartered in Gaithersburg, Maryland, United States, together with its subsidiaries (collectively, the “Company” or “Altimmune”) is a late clinical-stage biopharmaceutical company incorporated under the laws of the State of Delaware.

The Company is developing novel peptide-based therapeutics for liver and cardiometabolic diseases.

The Company’s lead program is pemvidutide (formerly known as ALT-801), a balanced 1:1 glucagon/GLP-1 dual receptor agonist for the treatment of metabolic dysfunction-associated steatohepatitis (“MASH”), alcohol use disorder (“AUD”) and alcohol-associated liver disease (“ALD”).

The Company is developing novel therapies for serious liver diseases.

The Company’s lead product candidate is pemvidutide (formerly known as ALT-801), a balanced 1:1 glucagon/GLP-1 dual receptor agonist in development for the treatment of metabolic dysfunction-associated steatohepatitis (“MASH”), alcohol use disorder (“AUD”) and alcohol-associated liver disease (“ALD”).

The Company may also pursue additional indications for pemvidutide that leverage its differentiated clinical profile.

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.

Since its inception, the Company has devoted substantially all of its efforts to business strategy and 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.

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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, 2024, included in the Annual Report on Form 10-K which was filed with the SEC on February 27, 2025.

GAAP”) for complete consolidated financial statements and should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2025, included in the Annual Report on Form 10-K, which was filed with the SEC on March 6, 2026.

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.

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Summary of Significant Accounting Policies

During the nine months ended September 30, 2025, 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, 2024, as filed with the SEC on February 27, 2025.

During the three months ended March 31, 2026, 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, 2025, as filed with the SEC on March 6, 2026.

Use of Estimates

1 unchanged sentence

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, the valuation of share-based awards, income taxes, prepaids, and accruals for research and development activities.

Significant estimates and assumptions made in the accompanying condensed consolidated financial statements include, but are not limited to, the valuation of share-based awards, income taxes, prepaids, 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.

During the nine months ended September 30, 2025, the Company has recorded a discrete tax benefit of approximately $ 0.7 million, related to a portion of carryback claims with the State of Maryland of which the Company previously held an uncertain tax position against.

Other than the discrete tax benefit discussed above, due to a full valuation allowance, the Company did no t record an income tax expense (benefit) for either of the three and nine months ended September 30, 2025 and 2024.

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.

On July 4, 2025, the One Big Beautiful Bill Act (“OBBBA”) was enacted in the U.S.

The OBBBA includes significant provisions, such as the permanent extension of certain expiring provisions of the Tax Cuts and Jobs Act, modifications to the international tax framework and the restoration of favorable tax treatment for certain business provisions.

The legislation has multiple effective dates, with certain provisions effective in 2025 and others implemented through 2027.

The Company is currently assessing its impact on our consolidated financial statements and will continue to evaluate the full impact of these legislative changes as additional guidance becomes available;

however, it does not expect the OBBBA to have a material impact on our estimated annual effective tax rate in 2025.

Debt discount and issuance costs

The Company accounts for fees paid to lenders, as compensation for services beyond their role as a creditor, and third parties whose costs are directly related to issuing debt as debt issuance cost.

Amounts paid to the lender as a reduction in the proceeds received are considered a discount on the issuance.

Debt issuance costs and discounts related to term loans are reported as a direct deduction from the outstanding debt and amortized over the term of the loan using the effective interest method as an additional interest expense.

Impairment or Disposal of Long-lived Assets

Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate the carrying value of such assets may not be recoverable in accordance with the guidance in Financial Accounting Standards Board (“FASB”) Accounting Standard Codification Topic 360, Property, Plant and Equipment (“ASC 360”) .

The Company’s long-lived assets include properties and equipment and right of use (“ROU”) assets.

For long-lived assets, impairment is recognized when the undiscounted cash flows used in the test for recoverability is less than their carrying value, and the fair value of the long-lived asset is below the carrying value.

In the event impairment exists, the long-lived asset will be written down to its fair value, and an impairment loss is recorded as the difference between the carrying value and fair value.

During the three months ended March 31, 2026, the Company recognized an impairment charge of $ 0.7 million related to its office and laboratory lease ROU asset and underlying leasehold improvements and equipment.

The Company determined the fair value of each asset group using a discounted cash flow model based on the expected sublease income utilizing its current borrowing rate.

The inputs utilized for fair value measurement are unobservable and considered level 3 in the fair value hierarchy.

The impairment charge was recorded in “Research and development expense” in the Consolidated Statement of Operations and Comprehensive Loss, and reduced the carrying amount of the underlying long-lived assets to fair value.

Fair Value Measurements

The Company’s assets measured at fair value on a recurring basis as of September 30, 2025 consisted of the following (in thousands):

Fair Value Measurement at September 30, 2025

The Company’s assets measured at fair value on a recurring basis as of March 31, 2026, consisted of the following (in thousands):

Fair Value Measurement at March 31, 2026

Cash equivalents - money market funds

Cash equivalents - agency debt securities

Cash equivalents - commercial paper

Cash equivalents - US treasury

Short-term investments

2 unchanged sentences

Cash equivalents - money market funds

Cash equivalents - commercial paper

Short-term investments

2 unchanged sentences

The Company’s short-term investments have a maturity date of one year or less.

Short-term investments with quoted prices as of September 30, 2025 as shown below (in thousands):

September 30, 2025

Short-term investments with quoted prices as of March 31, 2026, as shown below (in thousands):

March 31, 2026

Unrealized Gain

16 unchanged sentences

Agency debt securities

During the nine months ended September 30, 2025, the Company recognized approximately $ 0.1 million realized net loss from the sales of available-for-sale debt securities that were classified as short-term investments.

These investments had an insignificant amount of unrealized net loss that was reclassified out of other comprehensive income.

As of September 30, 2025 and December 31, 2024, none of the unrealized losses on the Company’s short-term investments were a result of credit loss;

therefore, any unrealized losses were recognized in other comprehensive income.

As of September 30, 2025 and December 31, 2024, the Company had $ 0.7 million and $ 0.4 million, respectively, accrued interest on short-term investments included in “Accounts and other receivables” on the accompanying Consolidated Balance Sheets.

As of March 31, 2026 and December 31, 2025, 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 other comprehensive income (OCI).

As of March 31, 2026 and December 31, 2025, the Company had $ 1.4 million and $ 1.1 million, respectively, accrued interest on short-term investments included in “Accounts and other receivables” on the accompanying Consolidated Balance Sheets.

The carrying amounts of the Company’s debt approximate fair value because the rates are floating rates based on the prime lending rate, which approximates market rates (see Note 5) and represents a Level 2 fair value measurement.

1 unchanged sentence

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 nine months ended September 30, 2025 and year ended December 31, 2024, the Company had no assets or liabilities that were measured at fair value on a non-recurring basis.

As of March 31, 2026 and December 31, 2025, the Company had no other assets or liabilities that were measured at fair value on a non-recurring basis.

Accrued Expenses

Accrued expenses and other current liabilities consist of the following (in thousands):

September 30, 2025

March 31, 2026

December 31, 2025

8 unchanged sentences

Under the terms of the Loan Agreement, the first Term Loan tranche was drawn down on the Closing Date in an aggregate principal amount of $ 15.0 million.

Upon the achievement of certain milestones and subject to other terms and conditions set out in the Loan Agreement, (i) the second Term Loan tranche will be made available in an aggregate principal amount of up to $ 25.0 million and (ii) the third Term Loan tranche will be made available in an aggregate principal amount of up to $ 15.0 million.

Upon the achievement of certain milestones and subject to other terms and conditions set out in the Loan Agreement, (i) the second Term Loan tranche was to be made available in an aggregate principal amount of up to $ 25.0 million and (ii) the third Term Loan tranche was to be made available in an aggregate principal amount of up to $ 15.0 million.

The fourth Term Loan tranche was to be made available in an aggregate principal amount of up to $ 45.0 million subject to the approval of the lenders.

The Term Loan had interest rate equal to the greater of (a) the prime rate as reported in The Wall Street Journal plus 2.45 % and (b) (i) 9.95 % until December 31, 2025, and (ii) 9.45 % thereafter.

On November 5, 2025, (the “Amendment Closing”), the Company 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 described 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.

The Term Loan will mature on January 1, 2029 (the “Maturity Date”).

The Term Loan bears interest equal to the greater of (a) the prime rate as reported in The Wall Street Journal plus 2.45 % and (b) (i) 9.95 % until December 31, 2025, and (ii) 9.45 % thereafter (the “Interest Rate”).

The Company may make payments of interest only through June 1, 2027, which will be extended to December 1, 2027, June 1, 2028, or December 1, 2028, if certain conditions described in the Loan Agreement are met.

The Company may make payments of interest only through December 1, 2027, which will be extended to June 1, 2028, or December 1, 2028, if certain conditions described in the Loan Agreement, as amended, are met.

Thereafter, the Company is obligated to make payments that will include installments of principal and interest through the Maturity Date.

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The Loan Agreement includes customary events of default, including payment defaults, breaches of representations and warranties, breaches of covenants following any applicable cure period and the occurrence of certain events that could reasonably be expected to have a “material adverse effect” as set forth in the Loan Agreement.

As of September 30, 2025, the Company was in compliance with the covenants under the Loan Agreement.

As of March 31, 2026, the Company was in compliance with the covenants under the Loan Agreement.

The obligation under the Loan Agreement is secured by a security interest in substantially all of the Company’s assets and the assets of its subsidiaries that are co-borrowers or guarantors.

Upon the occurrence of an event of default, Hercules will be entitled to exercise remedies, including acceleration of the Term Loan obligations and foreclosure on collateral.

The Loan Agreement provides for a prepayment charge equal to 3.0 % of the outstanding principal balance of the Term Loan if prepayment is made within the twelve months after closing, 2.0 % if within the twenty-four months after closing, 1.0 % if within the thirty-six months after closing and 0.0 % thereafter.

The Loan Agreement, as amended, provides for a prepayment charge equal to 3.0 % of the outstanding principal balance of the Term Loan if prepayment is made within the twelve months after Amendment Closing, 2.0 % if within the twenty-four months after Amendment Closing, 1.0 % if within the thirty-six months after Amendment Closing and 0.0 % thereafter.

The Loan Agreement provides for an end of term charge of 6.25 % of the funded loan amount, due at the earlier of prepayment or maturity.

Pro-rata payment of any earned end of term charge will be due upon any partial prepayment (the “End of Term Charge”).

In addition, the Loan Agreement requires the Company to pay a facility charge of 1.0 % of the Term Loan funded due at the Closing Date and of each subsequent Term Loan tranche at the time such tranche is funded.

The Company accounted for the End of Term Charge, Facility Charge, and other direct costs incurred in connection with the Loan Agreement as a debt discount and issuance costs, and they are being amortized over the term of the loan using the effective interest method.

The effective interest rate on the Term Loan is 14.4 %.

The Company incurred interest expense on the Term Loan, including debt discount and issuance costs amortization, of $ 0.5 million and $ 0.8 million during the three and nine months ended September 30, 2025, respectively.

In addition, the Loan Agreement requires the Company to pay a facility charge of 1.0 % of

the Term Loan funded due at the Closing Date and of each subsequent Term Loan tranche at the time such tranche is funded.

The Company accounted for the End of Term Charge, Facility Charge, and other direct costs incurred in connection with the Loan Agreement and its amendment as a debt discount and issuance costs, and they are being amortized over the term of the loan using the effective interest method.

The weighted-average effective interest rate on the Term Loan is 13.37 %.

The Company incurred interest expense on the Term Loan, including debt discount and issuance costs amortization, of $ 1.1 million during the three months ended March 31, 2026.

The Term Loan consists of the following (in thousands):

September 30, 2025

March 31, 2026

December 31, 2025

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Total term loan, net of current portion

Future principal loan payments on the currently outstanding Term Loan as of September 30, 2025 are as follows (in thousands):

2025 - remainder of the year

Future principal loan payments on the currently outstanding Term Loan as of March 31, 2026 are as follows (in thousands):

Total future principal payments

5 unchanged sentences

The Company’s other noncurrent liabilities are summarized as follows (in thousands):

September 30, 2025

March 31, 2026

December 31, 2025

5 unchanged sentences

The Amended and Restated Certificate of Incorporation, as amended (“Charter”), authorized the Company to issue 200,000,000 shares of common stock, par value $ 0.0001 per share.

As of September 30, 2025, the Company had 95,598,665 shares of common stock issued and outstanding .

As of March 31, 2026, the Company had 130,221,154 shares of common stock issued and outstanding .

Each share of common stock entitles the holder to one vote on all matters submitted to a vote of the Company’s stockholders.

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The Charter also authorized the Company to issue 1,000,000 shares of preferred stock, par value $ 0.0001 per share.

As of September 30, 2025, the Company had no shares of preferred stock issued and outstanding .

At-the-Market Offerings

On February 27, 2025, the Company entered into an Equity Distribution Agreement (the “2025 Agreement”) with Leerink Partners LLC, Piper Sandler & Co.

and Stifel, Nicolaus & Company, Incorporated, serving as sales agents (the “2025 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 “2025 Shares”) through the 2025 Sales Agents (the “2025 Offering”).

All Shares offered and sold in the 2025 Offering will be issued pursuant to the Company’s Registration Statement on Form S-3 filed with the SEC on February 27, 2025, which was declared effective on March 13, 2025, and the prospectus supplements related to the 2025 Offering that form a part of the Registration Statement.

The Company capitalized approximately $ 0.3 million of other offering costs which will offset the proceeds received from the shares sold under the 2025 Agreement.

During the nine months ended September 30, 2025, the Company has sold 18,524,709 shares of common stock under the 2025 Agreement resulting in approximately $ 81.9 million in proceeds, net of $ 2.7 million commission and other offering costs, and as of September 30, 2025, $ 65.4 million remained available to be sold under the 2025 Agreement.

As of September 30, 2025, there was $ 0.1 million deferred offering costs included in prepaid expenses and other current assets on the accompanying consolidated balance sheets.

As of March 31, 2026, the Company had no shares of preferred stock issued and outstanding .

At-the-Market (ATM) Offerings

On November 6, 2025, the Company entered into an Equity Distribution Agreement (the “November 2025 Agreement”) with Leerink Partners LLC serving as sales agent (the “November 2025 Sales Agent”) with respect to an ATM 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 $ 200.0 million (the “November 2025 Shares”) through the November 2025 Sales Agent (the “November 2025 Offering”).

All Shares offered and sold in the November 2025 Offering will be issued pursuant to the Company’s Registration Statement on Form S-3 filed with the SEC on February 27, 2025, which was declared effective on March 13, 2025, and the prospectus supplements related to the November 2025 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 November 2025 Agreement.

Since inception through March 31, 2026, the Company has sold 7,920,228 shares of common stock under the November 2025 Agreement resulting in approximately $ 34.2 million in proceeds, net of $ 0.6 million commission and other offering costs.

During the three months ended March 31, 2026, the Company sold 2,021,169 shares of common stock under the November 2025 Agreement resulting in approximately $ 8.7 million in proceeds, net of $ 0.1 million commission and other offering costs, and as of March 31, 2026, $ 165.3 million remained available to be sold under the November 2025 Agreement.

As of March 31, 2026, there was $ 0.2 million deferred offering costs included in prepaid expenses and other current assets on the accompanying consolidated balance sheets.

On February 27, 2025, the Company 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 (the “February 2025 Sales Agents”) with respect to an ATM offerings program under which the Company offered and sold shares of its common stock, having an aggregate offering price of up to $ 150.0 million (the “February 2025 Shares”) through the February 2025 Sales Agents (the “February 2025 Offering”).

All Shares offered and sold in the 2025 Offering were issued pursuant to the Company’s Registration Statement on Form S-3 filed with the SEC on February 27, 2025, which was declared effective on March 13, 2025, and the prospectus supplements related to the February 2025 Offering that form a part of the Registration Statement.

During the three months ended March 31, 2025, the Company sold 805,502 shares of common stock under the February 2025 Agreement for net proceeds of approximately $ 4.6 million.

Since inception through the termination of the February 2025 Agreement in November 2025, the Company sold 27,896,642 shares of common stock resulting in approximately $ 118.1 million in proceeds, net $ 3.9 million commission and other offering costs.

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 “2023 Sales Agents”), with respect to an at-the-market offerings program under which the Company offered and sold shares of its common stock, having an aggregate offering price of up to $ 150.0 million (the “2023 Shares”) through the 2023 Sales Agents (the “2023 Offering”).

Riley Securities, Inc., serving as sales agents (the “2023 Sales Agents”), with respect to an ATM offerings program under which the Company offered and sold shares of its common stock, having an aggregate offering price of up to $ 150.0 million (the “2023 Shares”) through the 2023 Sales Agents (the “2023 Offering”).

All 2023 Shares offered and sold in the 2023 Offering were issued pursuant to the Company’s Registration Statement on Form S-3 filed with the SEC on February 28, 2023.

During the nine months ended September 30, 2025, the Company has sold 4,467,866 shares of common stock under the 2023 Agreement resulting in approximately $ 30.2 million in proceeds, net of $ 1.0 million commission and other offering costs.

Since inception through the expiration of the 2023 Agreement in February 2025, the Company sold 26,129,903 shares of common stock under the 2023 Agreement, resulting in approximately $ 126.8 million in proceeds, As of September 30, 2025, there were no remaining shares available under the 2023 Agreement as the 2023 Agreement was terminated.

During the three months ended March 31, 2025, the Company sold 4,467,866 shares of common stock under the 2023 Agreement for net proceeds of approximately $ 30.2 million.

Since inception through the termination of the 2023 Agreement in February 2025, the Company sold 26,129,903 shares of common stock under the 2023 Agreement resulting in approximately $ 126.8 million in proceeds, net of $ 4.1 million commission and other offering costs.

Registered Direct Offering (“RDO”)

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 $ 70.3 million (the “January 2026 RDO”).

All Shares offered and sold in the January 2026 RDO were issued pursuant to the Company’s Registration Statement on Form S-3 filed with the SEC on November 13, 2025, which was declared effective on December 5, 2025.

The pre-funded warrants were fully exercised on February 13, 2026 at an exercise price of $ 0.001 per share, resulting in the issuance of 4,647,534 shares of the Company’s common stock.

The pre-funded warrants are indexed to the Company’s common stock and meet the criteria to be classified as equity.

Proceeds from the issuance of pre-funded warrants are recorded within additional paid-in capital.

Stock-Based Compensation

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The Company’s stock option awards generally vest over four years and typically have a contractual life of ten years .

As of September 30, 2025, there was $ 20.2 million of unrecognized compensation cost related to stock options, which is expected to be recognized over a weighted-average period of 2.6 years.

During the nine months ended September 30, 2025, the Company granted 2,672,150 stock options with a weighted average exercise price of $ 5.86 and per share weighted average grant date fair value of $ 4.74 .

Information related to stock options outstanding as of September 30, 2025 is as follows (in thousands, except share, exercise price, and contractual term):

As of March 31, 2026, there was $ 20.6 million of unrecognized compensation cost related to stock options, which is expected to be recognized over a weighted-average period of 3.2 years.

During the three months ended March 31, 2026, the Company granted 1,607,663 stock options with a weighted average exercise price of $ 4.52 and per share weighted average grant date fair value of $ 3.75 .

Information related to stock options outstanding as of March 31, 2026, is as follows (in thousands, except share, exercise price, and contractual term):

Weighted-Average

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Forfeited or expired

Outstanding, September 30, 2025

Exercisable, September 30, 2025

Vested and expected to vest, September 30, 2025

Outstanding, March 31, 2026

Exercisable, March 31, 2026

Vested and expected to vest, March 31, 2026

Restricted Stock Units (RSUs)

During the nine months ended September 30, 2025, the Company granted 577,700 shares of RSUs with a weighted average grant date fair value of $ 6.31 which vest over four years .

As of September 30, 2025, the Company had unvested RSUs of 1,135,950 shares with total unrecognized compensation expense of $ 6.3 million, which the Company expects to recognize over a weighted average period of approximately 2.7 years.

During the nine months ended September 30, 2025, the Company issued 167,880 shares of unrestricted common stock as a result of the vesting of 267,903 RSUs net of 100,023 shares of common stock withheld to satisfy tax withholding obligations.

During the three months ended March 31, 2026, the Company granted 672,517 shares of RSUs with a weighted average grant date fair value of $ 4.52 which vest over four years .

As of March 31, 2026, the Company had unvested RSUs of 2,159,982 shares with total unrecognized compensation expense of $ 7.9 million, which the Company expects to recognize over a weighted average period of approximately 3.4 years.

During the three months ended March 31, 2026, the

Company issued 209,537 shares common stock as a result of the vesting of 333,575 RSUs, net of 124,038 shares of common stock withheld to satisfy tax withholding obligations.

2019 Employee Stock Purchase Plan (“ESPP”)

Under the ESPP, employees purchased 71,342 shares of the Company’s common stock for $ 0.3 million during the nine months ended September 30, 2025.

Under the ESPP, employees purchased 57,801 shares for $ 0.2 million during the three months ended March 31, 2026.

Stock-based Compensation Expense

Stock-based compensation expense is classified in the unaudited consolidated Statements of Operations and Comprehensive Loss for the three and nine months ended September 30, 2025 and 2024 as follows (in thousands):

During the three months ended March 31, 2026, the Company recorded $ 0.3 million in incremental stock-based compensation expense as a result of the modifications of stock awards upon termination of a former executive officer.

The modification extended the option exercise period of a former executive officer’s fully vested stock options by a period of twelve months from the termination date.

Stock-based compensation expense is classified in the unaudited consolidated statements of operations and comprehensive loss for the three months ended March 31, 2026 and 2025 as follows (in thousands):

Three Months Ended

Nine Months Ended

September 30,

Research and development

1 unchanged sentence

Net Loss Per Share

Because the Company has reported net loss attributable to common stockholders for the three and nine months ended September 30, 2025 and 2024, basic and diluted net loss per share attributable to common stockholders in each period are the same.

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.

Because the Company has reported net loss attributable to common stockholders for the three months ended March 31, 2026 and 2025, basic and diluted net loss per share attributable to common stockholders in each period are the same.

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.

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Potential common shares issuable upon conversion, vesting, or exercise of unvested RSUs 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 Nine Months Ended

September 30,

Three Months Ended

Common stock options

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(“Spitfire”).

Spitfire was a privately held, preclinical pharmaceutical company developing novel peptide products for pharmaceutical indications, including pemvidutide for the treatment of MASH.

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.

(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”).

1 unchanged sentence

Accordingly, the Company will recognize the Sales Milestones when the contingency is probable and the amount can be reasonably estimated.

On August 5, 2025, a class action complaint was filed in federal district court in the District of Maryland, Southern Division, naming as defendants the Company and two of the Company’s executive officers, which is now captioned In re Altimmune, Inc.

Securities Litigation , Case No.

8:25-cv-02581 (D.

Md.) (the “Securities Class Action”).

The Securities Class Action 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 August 10, 2023 and June 25, 2025, including relating to pemvidutide and our IMPACT Phase 2b trial of pemvidutide in MASH.

The plaintiff and class members seek, among other things, 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 October 16, 2025, the court appointed lead plaintiffs for the litigation.

On October 29, 2025, the court entered an order requiring lead plaintiffs to file an amended complaint by November 26, 2025, and for defendants to file an answer or notice of intent to file a motion to dismiss such amended complaint by December 10, 2025.

The Company intends to defend vigorously against this litigation.

On September 29, 2025, a shareholder derivative complaint was filed in federal district court in the District of Maryland, purportedly on behalf of the Company, naming as defendants two of the Company’s then-executive officers and eight of the Company’s current and former board members, captioned Alaraidah v.

Altimmune, Inc., et al ., No.

8:25-cv-03223 (D.

Md.) (the “Derivative Action”).

The complaint is based upon allegations that are similar to those alleged in a class action complaint previously filed against us in the Securities Class Action and alleges claims for violations of

Section 14(a) of the Securities Exchange Act of 1934, breaches of fiduciary duty, unjust enrichment, abuse of control, gross mismanagement, waste of corporate assets, and contribution under Sections 10(b) and 21D of the Securities Exchange Act of 1934 based on the defendants purportedly making or causing to be made false and misleading statements and omissions of material fact between August 10, 2023 and June 25, 2025.

The complaint seeks unspecified monetary relief, restitution, costs, and equitable relief.

The Company intends to defend vigorously against this litigation.

The Company is a party to various contracts that are subject to potential disputes, litigation, and claims arising in the ordinary course of business, none of which are currently reasonably possible or probable of material loss.

The Company from time to time may be 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.

Segment Information

The Company is a late clinical-stage biopharmaceutical company developing novel peptide-based therapeutics for liver and cardiometabolic diseases.

The Company’s lead program is pemvidutide, a balanced 1:1 glucagon/GLP-1 dual receptor agonist for the treatment of MASH, AUD and ALD.

The Company is a late clinical-stage biopharmaceutical company developing novel therapies for serious liver diseases.

The Company’s lead product candidate is pemvidutide, a balanced 1:1 glucagon/GLP-1 dual receptor agonist in development for the treatment of MASH, AUD and ALD.

To date, the Company has not generated any revenue from the sale of any products.

The chief operating decision maker assesses the performance of the Company and decides how to allocate resources based solely on net (loss) income, which is also reported on the consolidated statements of operations and consolidated loss as net (loss) income.

The measure of segment assets is reported on the consolidated balance sheet as total assets.

Subsequent Events

The Company evaluated subsequent events through the issuance date of the financial statements on this quarterly report on Form 10-Q.

During October 2025 and through the date of the issuance of the financial statements, the Company raised $ 33.8 million in net proceeds through the issuance of 8,743,720 shares of common stock pursuant to the 2025 Offering.

The Term Loan, as amended, is structured in four tranches.

As disclosed in Note 5, 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.

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.

The Company evaluated subsequent events through the issuance date of the financial statements.

On April 16, 2026, the Company amended its Charter by filing a Certificate of Amendment with the Secretary of State of Delaware.

The Certificate of Amendment reflected an amendment to increase the number of authorized shares of common stock from 200,000,000 to 400,000,000 and was approved by the holders of more than a majority of the votes cast at the 2026 Annual Meeting of Shareholders.

In addition, the Company also amended its ESPP to increase the number of shares of common stock reserved under the ESPP from 403,500 to 1,108,827 .

On April 22, 2026, the Company entered into an underwriting agreement with certain underwriters pursuant to which the Company offered and sold securities consisting of (i) 64,250,000 shares of its common stock and accompanying common stock warrants to purchase an aggregate of 64,250,000 shares of common stock (or pre-funded warrants in lieu thereof) and (ii) in lieu of common stock, to certain investors that so choose, pre-funded warrants to purchase an aggregate of up to 10,750,000 shares of its common stock and accompanying common stock warrants to purchase an aggregate of 10,750,000 shares of common stock (or pre-funded warrants in lieu thereof), at an exercise price of $ 0.001 per pre-funded warrant (the “April 2026 Offering”).

The common stock and pre-funded warrants were sold in combination with an accompanying common stock warrant to purchase one share of common stock (or pre-funded warrant in lieu thereof) issued for each share of common stock or pre-funded warrant sold.

The accompanying common stock warrant has an exercise price of $ 3.00 per share and is immediately exercisable from the date of issuance.

The combined offering price of each share of common stock and accompany common stock warrant is $ 3.00 .

The combined offering price of each pre-funded warrant and accompanying common stock warrant is $ 2.999 .

The net proceeds of the April 2026 Offering were approximately $ 211.2 million, after deducting the underwriting discount and estimated offering expenses.

If all of the common stock warrants sold in the April 2026 Offering were to be exercised in cash at their exercise price, the Company would receive additional gross proceeds of $ 225 million.

All shares of common stock, pre-funded warrants and common stock warrants offered and sold in the April 2026 Offering were issued pursuant to the February 2025 Shelf and November

2025 Shelf and a related registration statement that was filed with the SEC on April 22, 2026 pursuant to Rule 462(b) under the Securities Act of 1933, as amended, and became automatically effective upon filing as permitted under Rule 429.

Compared sentence by sentence after normalising whitespace, quotation marks, case and digits, so re-formatting and restated figures do not read as changed language. Wording changes appear as one removal and one addition. The current filing and the prior one are authoritative.

What changed 10-Q

Item 1. Financial Statements