# EDGAR Filing Document

**Accession Number:** 0001326190
**File Stem:** 0001326190-25-000064
**Filing Date:** 2025-11
**Character Count:** 121335
**Document Hash:** 7c73da9c30906b3b28f7c4a7105568e0
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001326190-25-000064.hdr.sgml**: 20251106

**ACCESSION NUMBER**: 0001326190-25-000064

**CONFORMED SUBMISSION TYPE**: 10-Q

**PUBLIC DOCUMENT COUNT**: 62

**CONFORMED PERIOD OF REPORT**: 20250930

**FILED AS OF DATE**: 20251106

**DATE AS OF CHANGE**: 20251106

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Altimmune, Inc.
- **CENTRAL INDEX KEY:** 0001326190
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 202726770
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 10-Q
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-32587
- **FILM NUMBER:** 251458359

**BUSINESS ADDRESS:**
- **STREET 1:** 910 CLOPPER ROAD
- **STREET 2:** SUITE 201S
- **CITY:** GAITHERSBURG
- **STATE:** MD
- **ZIP:** 20878
- **BUSINESS PHONE:** 2406541450

**MAIL ADDRESS:**
- **STREET 1:** 910 CLOPPER ROAD
- **STREET 2:** SUITE 201S
- **CITY:** GAITHERSBURG
- **STATE:** MD
- **ZIP:** 20878

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** PHARMATHENE, INC
- **DATE OF NAME CHANGE:** 20071016

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** HEALTHCARE ACQUISITION CORP
- **DATE OF NAME CHANGE:** 20050505

?xml version='1.0' encoding='ASCII'? ALTIMMUNE, INC._September 30, 2025

[**Table of Contents**](#TOC)

------

**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION**

**Washington, D.C. 20549**

**FORM 10-Q**

**(Mark One)**

&nbsp;&nbsp;&nbsp;&nbsp;☒ **QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934** 

**For the quarterly period ended September 30, 2025**

**or**

☐ **TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934**

**For the transition period from &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; to &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;** 

**Commission file number 001-32587**

![Graphic](alt-20250930x10q002.jpg)

**ALTIMMUNE, INC.**

**(Exact Name of Registrant as Specified in its Charter)**

---

| | |
|:---|:---|
| **Delaware** | **20-2726770** |
| **(State or Other Jurisdiction of**<br>**Incorporation or Organization)** | **(I.R.S. Employer**<br>**Identification No.)** |
| **910 Clopper Road Suite 201S, Gaithersburg, Maryland** | **20878** |
| **(Address of Principal Executive Offices)** | **(Zip Code)** |

---

**(240) 654-1450**

**(Registrant's Telephone Number, Including Area Code)**

**Securities registered pursuant to Section 12(b) of the Act:**

---

| | | |
|:---|:---|:---|
| *Title of each class* | *Trading Symbol(s)* | *Name of each exchange on which registered* |
| Common stock, par value $0.0001 per share | ALT | The NASDAQ Global Market |

---

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ⌧&nbsp;&nbsp;&nbsp;&nbsp;No ◻

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ⌧&nbsp;&nbsp;&nbsp;&nbsp;No ◻

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, smaller reporting company, or an emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company," and "emerging growth company" in Rule 12b-2 of the Exchange Act.

---

| | | | |
|:---|:---|:---|:---|
| Large accelerated filer | ◻ | Accelerated filer | ◻ |
| Non-accelerated filer | ⌧ | Smaller reporting company | ⌧ |
|  |  | Emerging growth company | ◻ |

---

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ◻

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). Yes ☐&nbsp;&nbsp;&nbsp;&nbsp;No ⌧

As of October 31, 2025 there were 104,254,173 shares of the registrant's common stock, par value $0.0001 per share, outstanding.

------

[**Table of Contents**](#TOC)

#### ALTIMMUNE, INC.

#### **TABLE OF CONTENTS**

---

| | | |
|:---|:---|:---|
|  |  | **Page** |
| [**PART I. FINANCIAL INFORMATION**](#PARTIFINANCIALINFORMATION_8053) | [**PART I. FINANCIAL INFORMATION**](#PARTIFINANCIALINFORMATION_8053) |  |
| [Item 1.](#Item1FinancialStatements_961784) | [Financial Statements](#Item1FinancialStatements_961784) | 1 |
|  | &nbsp;&nbsp;&nbsp;&nbsp;[Consolidated Balance Sheets as of September 30, 2025 (unaudited) and December 31, 2024](#CONSOLIDATEDBALANCESHEETS_242482) | 1 |
|  | &nbsp;&nbsp;&nbsp;&nbsp;[Consolidated Statements of Operations and Comprehensive Loss for the three and nine months ended September 30, 2025 and 2024 (unaudited)](#CONSOLIDATEDSTATEMENTSOFOPERATIONSANDCOM) | 2 |
|  | &nbsp;&nbsp;&nbsp;&nbsp;[Consolidated Statements of Changes in Stockholders' Equity for the three and nine months ended September 30, 2025 and 2024 (unaudited)](#CONSOLIDATEDSTATEMENTSOFCHANGESINSTOCKHO) | 3 |
|  | &nbsp;&nbsp;&nbsp;&nbsp;[Consolidated Statements of Cash Flows for the nine months ended September 30, 2025 and 2024 (unaudited)](#CONSOLIDATEDSTATEMENTSOFCASHFLOWS_490285) | 5 |
|  | &nbsp;&nbsp;&nbsp;&nbsp;[Notes to Consolidated Financial Statements (unaudited)](#NOTESTOCONSOLIDATEDFINANCIALSTATEMENTS_4) | 6 |
| [Item 2.](#Item2ManagementsDiscussionandAnalysisofF) | [Management's Discussion and Analysis of Financial Condition and Results of Operations](#Item2ManagementsDiscussionandAnalysisofF) | 15 |
| [Item 3.](#Item3QuantitativeandQualitativeDisclosur) | [Quantitative and Qualitative Disclosures about Market Risk](#Item3QuantitativeandQualitativeDisclosur) | 23 |
| [Item 4.](#Item4ControlsandProcedures_640907) | [Controls and Procedures](#Item4ControlsandProcedures_640907) | 23 |
| [**PART II. OTHER INFORMATION**](#PARTIIOTHERINFORMATION_760989) | [**PART II. OTHER INFORMATION**](#PARTIIOTHERINFORMATION_760989) |  |
| [Item 1.](#Item1LegalProceedings_974488) | [Legal Proceedings](#Item1LegalProceedings_974488) | 23 |
| [Item 1A.](#Item1ARiskFactors_350839) | [Risk Factors](#Item1ARiskFactors_350839) | 24 |
| [Item 2.](#Item2UnregisteredSalesofEquitySecurities) | [Unregistered Sales of Equity Securities and Use of Proceeds](#Item2UnregisteredSalesofEquitySecurities) | 24 |
| [Item 3.](#Item3DefaultuponSeniorSecurities_41291) | [Defaults Upon Senior Securities](#Item3DefaultuponSeniorSecurities_41291) | 24 |
| [Item 4.](#Item4MineSafetyDisclosures_637902) | [Mine Safety Disclosures](#Item4MineSafetyDisclosures_637902) | 24 |
| [Item 5.](#Item5OtherInformation_359177) | [Other Information](#Item5OtherInformation_359177) | 24 |
| [Item 6.](#Item6Exhibits_593392) | [Exhibits](#Item6Exhibits_593392) | 25 |
|  | [Signatures](#SIGNATURES_71153) | 26 |

---

[**Table of Contents**](#TOC)

#### PART I. FINANCIAL INFORMATION

#### Item 1. Financial Statements

#### ALTIMMUNE, INC.

#### CONSOLIDATED BALANCE SHEETS

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

---

| | | |
|:---|:---|:---|
|  | **September 30,** <br>**2025** | **December 31,** <br>**2024** |
|  | **(Unaudited)** |  |
| **ASSETS** |  |  |
| Current assets: |  |  |
| &nbsp;&nbsp;Cash and cash equivalents | $61236 | $36926 |
| &nbsp;&nbsp;Restricted cash | 42 | 42 |
| &nbsp;&nbsp;&nbsp;&nbsp;Total cash, cash equivalents and restricted cash | 61278 | 36968 |
| &nbsp;&nbsp;Short-term investments | 149540 | 94965 |
| &nbsp;&nbsp;Accounts and other receivables | 845 | 544 |
| &nbsp;&nbsp;Income tax and R&D incentive receivables  | 547 | 2573 |
| &nbsp;&nbsp;Prepaid expenses and other current assets | 4405 | 2204 |
| &nbsp;&nbsp;&nbsp;&nbsp;Total current assets | 216615 | 137254 |
| Property and equipment, net | 337 | 413 |
| Other assets | 1495 | 1639 |
| &nbsp;&nbsp;&nbsp;&nbsp;Total assets | $218447 | $139306 |
| **LIABILITIES AND STOCKHOLDERS' EQUITY** |  |  |
| Current liabilities: |  |  |
| &nbsp;&nbsp;Accounts payable | $4804 | $211 |
| &nbsp;&nbsp;Accrued expenses and other current liabilities | 7802 | 10257 |
| &nbsp;&nbsp;&nbsp;&nbsp;Total current liabilities | 12606 | 10468 |
| Term loan, noncurrent | 14445 |  |
| Other noncurrent liabilities | 5795 | 5330 |
| &nbsp;&nbsp;&nbsp;&nbsp;Total liabilities | 32846 | 15798 |
| Commitments and contingencies (Note 10) |  |  |
| Stockholders' equity: |  |  |
| &nbsp;&nbsp;Common stock, $0.0001 par value; 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 | 10 | 7 |
| &nbsp;&nbsp;Additional paid-in capital | 812732 | 689864 |
| &nbsp;&nbsp;Accumulated deficit | (622125) | (561390) |
| &nbsp;&nbsp;Accumulated other comprehensive loss, net | (5016) | (4973) |
| &nbsp;&nbsp;&nbsp;&nbsp;Total stockholders' equity | 185601 | 123508 |
| &nbsp;&nbsp;&nbsp;&nbsp;Total liabilities and stockholders' equity | $218447 | $139306 |

---

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

[**Table of Contents**](#TOC)

#### ALTIMMUNE, INC.

#### CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
(Unaudited)

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

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Three Months Ended**  | **Three Months Ended**  | **Nine Months Ended**  | **Nine Months Ended**  |
|  | **September 30,**  | **September 30,**  | **September 30,**  | **September 30,**  |
|  | **2025** | **2024** | **2025** | **2024** |
| Revenues | $5 | $5 | $15 | $15 |
| Operating expenses: |  |  |  |  |
| &nbsp;&nbsp;Research and development | 14960 | 19803 | 48023 | 62445 |
| &nbsp;&nbsp;General and administrative | 5904 | 4969 | 17588 | 15876 |
| &nbsp;&nbsp;&nbsp;&nbsp;Total operating expenses | 20864 | 24772 | 65611 | 78321 |
| Loss from operations | (20859) | (24767) | (65596) | (78306) |
| Other income (expense): |  |  |  |  |
| &nbsp;&nbsp;Interest expense | (495) | (6) | (760) | (8) |
| &nbsp;&nbsp;Interest income | 2426 | 1910 | 5103 | 6505 |
| &nbsp;&nbsp;Other income (expense), net | (86) | 18 | (163) | (70) |
| &nbsp;&nbsp;&nbsp;&nbsp;Total other income (expense), net | 1845 | 1922 | 4180 | 6427 |
| Net loss before income taxes | (19014) | (22845) | (61416) | (71879) |
| Income tax expense (benefit) |  |  | (681) |  |
| Net loss | (19014) | (22845) | (60735) | (71879) |
| Other comprehensive income — unrealized gain (loss) on short-term investments | 23 | 347 | (43) | 159 |
| Comprehensive loss | $(18991) | $(22498) | $(60778) | $(71720) |
| Net loss per share, basic and diluted | $(0.21) | $(0.32) | $(0.74) | $(1.01) |
| Weighted-average common shares outstanding, basic and diluted | 89418028 | 71084787 | 82198581 | 70927222 |

---

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

[**Table of Contents**](#TOC)

#### ALTIMMUNE, INC.

#### CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY
(Unaudited)

#### (In thousands, except share amounts)

---

| | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|
|  | **Common Stock** | **Common Stock** | | | | |
|  | **Shares** | **Amount** | <br>**Additional** <br>**Paid-In**<br>**Capital** | <br>**Accumulated**<br>**Deficit** | **Accumulated**<br> **Other** <br>**Comprehensive**<br>**Loss** | <br>**Total** <br>**Stockholders'**<br>**Equity** |
| **Balance at December 31, 2024** | 72352701 | $7 | $689864 | $(561390) | $(4973) | $123508 |
| &nbsp;&nbsp;Stock-based compensation |  |  | 4015 |  |  | 4015 |
| &nbsp;&nbsp;Exercise of stock options | 1250 |  | 4 |  |  | 4 |
| &nbsp;&nbsp;Vesting of restricted stock awards including withholding, net | 165259 |  | (678) |  |  | (678) |
| &nbsp;&nbsp;Issuance of common stock from Employee Stock Purchase Plan | 32872 |  | 170 |  |  | 170 |
| &nbsp;&nbsp;Issuance of common stock in at-the-market offerings, net | 5273368 | 1 | 34747 |  |  | 34748 |
| &nbsp;&nbsp;Unrealized (loss) gain on short-term investments |  |  |  |  | (30) | (30) |
| &nbsp;&nbsp;Net loss |  |  |  | (19575) |  | (19575) |
| **Balance at March 31, 2025** | 77825450 | $8 | $728122 | $(580965) | $(5003) | $142162 |
| &nbsp;&nbsp;Stock-based compensation |  | $— | $3566 | $— | $— | $3566 |
| &nbsp;&nbsp;Exercise of stock options | 1667 |  | 4 |  |  | 4 |
| &nbsp;&nbsp;Vesting of restricted stock awards including withholding, net | 2621 |  | (6) |  |  | (6) |
| &nbsp;&nbsp;Issuance of common stock in at-the-market offerings, net | 7246562 | 1 | 37822 |  |  | 37823 |
| &nbsp;&nbsp;Unrealized (loss) gain on short-term investments |  |  |  |  | (36) | (36) |
| &nbsp;&nbsp;Net loss |  |  |  | (22146) |  | (22146) |
| **Balance at June 30, 2025** | 85076300 | $9 | $769508 | $(603111) | $(5039) | $161367 |
| &nbsp;&nbsp;Stock-based compensation |  | $— | $3554 | $— | $— | $3554 |
| &nbsp;&nbsp;Exercise of stock options | 11250 |  | 33 |  |  | 33 |
| &nbsp;&nbsp;Issuance of common stock from Employee Stock Purchase Plan | 38470 |  | 121 |  |  | 121 |
| &nbsp;&nbsp;Issuance of common stock in at-the-market offerings, net | 10472645 | 1 | 39516 |  |  | 39517 |
| &nbsp;&nbsp;Unrealized (loss) gain on short-term investments |  |  |  |  | 23 | 23 |
| &nbsp;&nbsp;Net loss |  |  |  | (19014) |  | (19014) |
| **Balance at September 30, 2025** | 95598665 | $10 | $812732 | $(622125) | $(5016) | $185601 |

---

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

[**Table of Contents**](#TOC)

#### ALTIMMUNE, INC.

#### CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY
(Unaudited)

#### (In thousands, except share amounts)

---

| | | | | | | |
|:---|:---|:---|:---|:---|:---|:---|
|  | **Common Stock** | **Common Stock** | | | | |
|  | **Shares** | **Amount** | <br>**Additional** <br>**Paid-In**<br>**Capital** | <br>**Accumulated**<br>**Deficit** | **Accumulated**<br> **Other** <br>**Comprehensive**<br>**Loss** | <br>**Total** <br>**Stockholders'**<br>**Equity** |
| **Balance at December 31, 2023** | 70677400 | $7 | $665427 | $(466331) | $(5004) | $194099 |
| &nbsp;&nbsp;Stock-based compensation |  |  | 3650 |  |  | 3650 |
| &nbsp;&nbsp;Exercise of stock options | 1250 |  | 9 |  |  | 9 |
| &nbsp;&nbsp;Vesting of restricted stock awards including withholding, net | 107875 |  | (600) |  |  | (600) |
| &nbsp;&nbsp;Issuance of common stock from Employee Stock Purchase Plan | 62609 |  | 169 |  |  | 169 |
| &nbsp;&nbsp;Issuance of common stock upon exercise of warrants | 50000 |  | 161 |  |  | 161 |
| &nbsp;&nbsp;Unrealized (loss) gain on short-term investments |  |  |  |  | (157) | (157) |
| &nbsp;&nbsp;Net loss |  |  |  | (24394) |  | (24394) |
| **Balance at March 31, 2024** | 70899134 | $7 | $668816 | $(490725) | $(5161) | $172937 |
| &nbsp;&nbsp;Stock-based compensation |  | $— | $4311 | $— | $— | $4311 |
| &nbsp;&nbsp;Exercise of stock options | 64433 |  | 198 |  |  | 198 |
| &nbsp;&nbsp;Vesting of restricted stock awards including withholding, net | 82700 |  | (244) |  |  | (244) |
| &nbsp;&nbsp;Unrealized (loss) gain on short-term investments |  |  |  |  | (31) | (31) |
| &nbsp;&nbsp;Net loss |  |  |  | (24640) |  | (24640) |
| **Balance at June 30, 2024** | 71046267 | $7 | $673081 | $(515365) | $(5192) | $152531 |
| &nbsp;&nbsp;Stock-based compensation |  | $— | $3078 | $— | $— | $3078 |
| &nbsp;&nbsp;Exercise of stock options | 52584 |  | 139 |  |  | 139 |
| &nbsp;&nbsp;Vesting of restricted stock awards including withholding, net | 1308 |  | (4) |  |  | (4) |
| &nbsp;&nbsp;Issuance of common stock from Employee Stock Purchase Plan | 24248 |  | 131 |  |  | 131 |
| &nbsp;&nbsp;Unrealized (loss) gain on short-term investments |  |  |  |  | 347 | 347 |
| &nbsp;&nbsp;Net loss |  |  |  | (22845) |  | (22845) |
| **Balance at September 30, 2024** | 71124407 | $7 | $676425 | $(538210) | $(4845) | $133377 |

---

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

[**Table of Contents**](#TOC)

#### ALTIMMUNE, INC.

#### CONSOLIDATED STATEMENTS OF CASH FLOWS
(Unaudited)

#### (In thousands)

---

| | | |
|:---|:---|:---|
|  | **Nine Months Ended**  | **Nine Months Ended**  |
|  | **September 30,**  | **September 30,**  |
|  | **2025** | **2024** |
| **CASH FLOWS FROM OPERATING ACTIVITIES:** |  |  |
| &nbsp;&nbsp;Net loss | $(60735) | $(71879) |
| &nbsp;&nbsp;Adjustments to reconcile net loss to net cash used in operating activities: |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Stock-based compensation expense | 11135 | 11039 |
| &nbsp;&nbsp;&nbsp;&nbsp;Depreciation of property and equipment | 86 | 205 |
| &nbsp;&nbsp;&nbsp;&nbsp;Accretion of discounts on short-term investments | (1313) | (3031) |
| &nbsp;&nbsp;&nbsp;&nbsp;Amortization of debt discount and costs | 171 |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Loss on foreign currency exchange | 116 | 69 |
| &nbsp;&nbsp;&nbsp;&nbsp;Deferred income tax benefit | (681) |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Changes in operating assets and liabilities: |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Accounts receivable | (301) | 683 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Prepaid expenses and other assets | (1903) | 3920 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Accounts payable | 4593 | (937) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Accrued expenses and other liabilities | (1962) | (2482) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Income tax and R&D incentive receivables | 2707 | 830 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Net cash used in operating activities | (48087) | (61583) |
| **CASH FLOWS FROM INVESTING ACTIVITIES:** |  |  |
| &nbsp;&nbsp;Proceeds from sales and maturities of short-term investments | 143589 | 60500 |
| &nbsp;&nbsp;Purchases of short-term investments | (196894) | (102518) |
| &nbsp;&nbsp;Purchases of property and equipment | (10) |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Net cash used in investing activities | (53315) | (42018) |
| **CASH FLOWS FROM FINANCING ACTIVITIES:** |  |  |
| &nbsp;&nbsp;Payments of deferred offering costs | (298) |  |
| &nbsp;&nbsp;Proceeds from exercises of warrants |  | 161 |
| &nbsp;&nbsp;Proceeds from term loan | 15000 |  |
| &nbsp;&nbsp;Payment for debt issuance costs | (726) |  |
| &nbsp;&nbsp;Proceeds from issuance of common stock in at-the-market offerings, net | 112088 |  |
| &nbsp;&nbsp;Proceeds from issuance of common stock from Employee Stock Purchase Plan | 291 | 300 |
| &nbsp;&nbsp;Proceeds from exercises of stock options | 41 | 346 |
| &nbsp;&nbsp;Payments for tax withholding in share-based compensation | (684) | (848) |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Net cash provided by (used in) financing activities | 125712 | (41) |
| Net increase (decrease) in cash and cash equivalents and restricted cash | 24310 | (103642) |
| Cash, cash equivalents and restricted cash at beginning of period | 36968 | 135158 |
| Cash, cash equivalents and restricted cash at end of period | $61278 | $31516 |
| **SUPPLEMENTAL CASH FLOW INFORMATION:** |  |  |
| &nbsp;&nbsp;Cash paid for interest | $460 | $— |
| &nbsp;&nbsp;Cash received from income tax refunds | $1422 | $— |
| **SUPPLEMENTAL NON-CASH ACTIVITIES:** |  |  |
| &nbsp;&nbsp;Operating lease liability and right-of-use asset addition | $— | $1409 |

---

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

[**Table of Contents**](#TOC)

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

*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

[**Table of Contents**](#TOC)

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.

*Income Taxes*

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 not 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.

3. 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** | **Fair Value Measurement at September 30, 2025** | **Fair Value Measurement at September 30, 2025** | **Fair Value Measurement at September 30, 2025** |
|  | **Total** | **Level 1** | **Level 2** | **Level 3** |
| Assets: |  |  |  |  |
| Cash equivalents - money market funds | $16640 | $16640 | $— | $— |
| Cash equivalents - agency debt securities | 1990 |  | 1990 |  |
| Cash equivalents - commercial paper | 11621 |  | 11621 |  |
| Cash equivalents - US treasury | 5964 |  | 5964 |  |
| Short-term investments | 149540 |  | 149540 |  |
| &nbsp;&nbsp;Total | $185755 | $16640 | $169115 | $— |

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The Company's assets measured at fair value on a recurring basis as of December 31, 2024 consisted of the following (in thousands):

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Fair Value Measurement at December 31, 2024** | **Fair Value Measurement at December 31, 2024** | **Fair Value Measurement at December 31, 2024** | **Fair Value Measurement at December 31, 2024** |
|  | **Total** | **Level 1** | **Level 2** | **Level 3** |
| Assets: |  |  |  |  |
| Cash equivalents - money market funds | $27279 | $27279 | $— | $— |
| Short-term investments | 94965 |  | 94965 |  |
| &nbsp;&nbsp;Total | $122244 | $27279 | $94965 | $— |

---

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. 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** | **September 30, 2025** | **September 30, 2025** | **September 30, 2025** |
|  | <br>**Amortized Cost** | **Unrealized Gain**<br>**Unrealized (Loss) Gain** | **Unrealized Gain**<br>**Credit loss** | <br>**Market Value** |
| United States treasury securities | $49233 | $7 | $— | $49240 |
| Commercial paper and corporate debt securities | 86356 | 8 |  | 86364 |
| Asset backed securities | 8001 | 5 |  | 8006 |
| Agency debt securities | 5927 | 3 |  | 5930 |
| &nbsp;&nbsp;Total | $149517 | $23 | $— | $149540 |

---

Short-term investments with quoted prices as of December 31, 2024 as shown below (in thousands):

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **December 31, 2024** | **December 31, 2024** | **December 31, 2024** | **December 31, 2024** |
|  | <br>**Amortized Cost** | **Unrealized Gain**<br>**Unrealized (Loss) Gain** | **Unrealized Gain**<br>**Credit Loss** | <br>**Market Value** |
| United States treasury securities | $21375 | $16 | $— | $21391 |
| Commercial paper and corporate debt securities | 52641 | 15 |  | 52656 |
| Asset backed securities | 5951 | 14 |  | 5965 |
| Agency debt securities | 14931 | 22 |  | 14953 |
| &nbsp;&nbsp;Total | $94898 | $67 | $— | $94965 |

---

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.

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.

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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 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.

4. Accrued Expenses

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

---

| | | |
|:---|:---|:---|
|  | **September 30, 2025** | **December 31, 2024** |
| Accrued professional services | $403 | $401 |
| Accrued payroll and employee benefits | 2411 | 3079 |
| Accrued research and development | 4564 | 6443 |
| Lease obligation, current portion | 247 | 279 |
| Accrued interest and other | 177 | 55 |
| &nbsp;&nbsp;Total accrued expenses and other current liabilities | $7802 | $10257 |

---

5. Term Loan

On May 13, 2025 ("Closing Date"), the Company and certain of its subsidiaries 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.

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

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

The Loan Agreement includes customary representations and warranties and covenants associated with the Term Loan. Such terms include (1) covenants concerning financial and other reporting obligations, and (2) certain limitations on indebtedness, liens, investments, distributions (including dividends), collateral, transfers, mergers or acquisitions, taxes, corporate changes, and deposit accounts. Compliance with the financial covenant will be conditionally waived pursuant to the terms of the Loan Agreement when the Company's market capitalization exceeds $800 million. 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.

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.

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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 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.

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

---

| | | |
|:---|:---|:---|
|  | **September 30, 2025** | **December 31, 2024** |
| Term loan principal amount | $15000 | $— |
| End of term charge | 937 |  |
| Unamortized discount and issuance costs | (1492) |  |
| Total term loan | 14445 |  |
| Less: current portion of term loan |  |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Total term loan, net of current portion | $14445 | $— |

---

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

---

| | |
|:---|:---|
| &nbsp;&nbsp;2025 - remainder of the year | $— |
| &nbsp;&nbsp;2026 |  |
| &nbsp;&nbsp;2027 | 4449 |
| &nbsp;&nbsp;2028 | 7266 |
| &nbsp;&nbsp;2029 | 3285 |
| &nbsp;&nbsp;&nbsp;&nbsp;Total future principal payments | 15000 |
| &nbsp;&nbsp;Add: End of term charge | 937 |
| &nbsp;&nbsp;Less: Unamortized discount and issuance costs | (1492) |
| &nbsp;&nbsp;Less: Current portion of term loan |  |
| &nbsp;&nbsp;&nbsp;&nbsp;Total term loan, net of current portion | $14445 |

---

6. Other Noncurrent Liabilities

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

---

| | | |
|:---|:---|:---|
|  | **September 30, 2025** | **December 31, 2024** |
| Research and development incentive credit | $4416 | $3746 |
| Lease obligation, long-term portion | 1213 | 1402 |
| Conditional economic incentive grants | 160 | 160 |
| Other | 6 | 22 |
| &nbsp;&nbsp;Total other noncurrent liabilities | $5795 | $5330 |

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7. Stockholders' Equity

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.

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 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.

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"). 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.

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, 2025, the number of shares of Common Stock reserved and available for issuance under the Omnibus Plan increased by 3,193,659 shares of common stock.

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*Stock Options*

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):

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | <br>**Number of**<br>**Stock Options** | <br>**Weighted-**<br>**Average**<br>**Exercise Price** | **Weighted-Average**<br>**Remaining**<br>**Contractual Term**<br>**(Years)** | <br>**Aggregate Intrinsic**<br>**Value**  |
| Outstanding, December 31, 2024 | 6630477 | $9.32 | 6.0 | $5839 |
| &nbsp;&nbsp;Granted | 2672150 | $5.86 |  |  |
| &nbsp;&nbsp;Exercised | (14167) | $2.91 |  |  |
| &nbsp;&nbsp;Forfeited or expired | (627103) | $9.56 |  |  |
| Outstanding, September 30, 2025 | 8661357 | $8.24 | 5.9 | $1076 |
| Exercisable, September 30, 2025 | 4502219 | $9.23 | 5.9 | $1036 |
| Vested and expected to vest, September 30, 2025 | 8287035 | $8.29 | 5.9 | $1072 |

---

*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.

*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.

*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):

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Three Months Ended**  | **Three Months Ended**  | **Nine Months Ended**  | **Nine Months Ended**  |
|  | **September 30,**  | **September 30,**  | **September 30,**  | **September 30,**  |
|  | **2025** | **2024** | **2025** | **2024** |
| Research and development | $1522 | $1545 | $4851 | $4794 |
| General and administrative | 2032 | 1533 | 6284 | 6245 |
| &nbsp;&nbsp;Total | $3554 | $3078 | $11135 | $11039 |

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9. 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.

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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 RSUs 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 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**  | **Three and Nine Months Ended**  |
|  | **September 30,**  | **September 30,**  |
|  | **2025** | **2024** |
| Common stock options | 8725956 | 6435016 |
| Restricted stock units | 1135950 | 784227 |

---

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").

The contingent payments related to the Sales Milestones are predominately cash-based payments accounted for under FASB Accounting Standards Codification Topic 450, Contingencies. Accordingly, the Company will recognize the Sales Milestones when the contingency is probable and the amount can be reasonably estimated.

*Litigation*

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

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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.

11. 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. 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.

12. 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.

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 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. 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.

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#### Item 2. 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 Quarterly Report on Form 10-Q and our consolidated financial statements and related notes for the year ended December 31, 2024 included in our Annual Report on Form 10-K, which was filed with the SEC on February 27, 2025.*

*This Quarterly Report on Form 10-Q contains forward-looking statements that involve substantial risks and uncertainties. The words "expect," "anticipate," "intend," "plan," "believe," "estimate," "may," "will," "should," "could," "target," "strategy," "intend," "project," "guidance," "likely," "usually," "potential," or the negative of these words or variations of such words, similar expressions, or comparable terminology are intended to identify such forward-looking statements, although not all forward-looking statements contain these identifying words. There are a number of important risks and uncertainties that could cause our actual results to differ materially from those indicated by forward-looking statements. We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. A further list and description of risks, uncertainties and other factors that could cause actual results or events to differ materially from the forward-looking statements that we make is included in the cautionary statements herein and in our other filings with the SEC, including those set forth under Part I, Item 1A, Risk Factors in our Annual Report on Form 10-K for the year ended December 31, 2024. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments that we may make.*

*We have based the forward-looking statements included in this Quarterly Report on Form 10-Q on information available to us on the date of this quarterly report, and we assume no obligation to update any such forward-looking statements, other than as required by law. Although we undertake no obligation to revise or update any forward-looking statements, whether as a result of new information, future events or otherwise, you are advised to consult any additional disclosures that we may make directly to you or through reports that we, in the future, may file with the SEC, including Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K.*

***Overview***

Altimmune, Inc. is a late clinical-stage biopharmaceutical company developing novel peptide-based therapeutics for liver and cardiometabolic diseases. Our lead program is pemvidutide (formerly known as ALT-801), a balanced 1:1 glucagon/GLP-1 dual receptor agonist for the treatment of MASH, AUD and ALD. We may also pursue additional indications for pemvidutide that leverage our 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.

***Recent Business Update***

#### MASH
On June 26, 2025, we released planned, 24-week topline efficacy results from IMPACT, a Phase 2b trial in 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 either weekly subcutaneous pemvidutide at 1.2 mg or 1.8 mg doses or placebo for 48 weeks.

In an intent-to-treat ("ITT") analysis, in which subjects with missing biopsies were considered non-responders, the proportions of subjects achieving MASH resolution without worsening of fibrosis at 24 weeks were 58% and 52%, for pemvidutide 1.2 mg and 1.8 mg, respectively versus 20% for placebo (p< 0.0001 both doses). The effects on fibrosis improvement without worsening of MASH in an ITT analysis were 33% and 36% for pemvidutide 1.2 mg and 1.8 mg, respectively compared with 28% for placebo (differences not statistically significant). A supplemental AI-based analysis demonstrated statistically significant reductions in fibrosis, including 31% of subjects receiving pemvidutide 1.8 mg achieving a 60% or more reduction in fibrosis compared to 8% receiving placebo (p< 0.001). Statistically significant changes in well-established non-invasive tests of fibrosis, including ELF score and VCTE were also observed compared

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with placebo at both doses. Together, this data suggests strong evidence of anti-fibrotic activity of pemvidutide in the MASH population. At 24 weeks, mean weight loss in pemvidutide-treated subjects was 4.8% and 5.8% at the 1.2 mg and 1.8 mg doses, respectively, versus 0.5% in the placebo arm (p< 0.001, both doses). The numerical values here are slightly different than originally announced as part of the topline data, but do not impact statistical significance across any of the results.

Pemvidutide also demonstrated favorable safety and tolerability, with low overall treatment discontinuation rates due to adverse events of less than 1% and 1.2% in the pemvidutide 1.2 mg and 1.8 mg groups versus 2.4% in the placebo group, an important finding given that no dose titration was used in the trial. There were no serious adverse events related to study medication.

#### AUD and ALD
On March 13, 2025, we announced that we are pursuing two additional indications for our lead product candidate, pemvidutide. The new indications are alcohol use disorder ("AUD") and alcohol-associated liver disease ("ALD"), also known as Alcohol Liver Disease.

AUD is a chronic disease characterized by excessive drinking. In addition to the underlying alcohol misuse by AUD patients, AUD patients have comorbidities that pose significant treatment and management challenges (including liver steatosis, obesity, hypertension and hyperlipidemia). 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. Subjects will be randomized 1:1 to receive either 2.4 mg pemvidutide or placebo weekly for 24 weeks. The trial's primary endpoint is a change in alcohol consumption, measured by the change from baseline in the average number of heavy drinking days per week at Week 24, with the key secondary endpoints including the proportion of subjects achieving a 2-level reduction in World Health Organization ("WHO") risk drinking level and the absolute change from baseline in average levels of phosphatidylethanol ("PEth"), a serum biomarker of alcohol intake.

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. Enrollment completed ahead of schedule, underscoring strong interest from patient community in a new therapeutic option for AUD. We noted that we are on track to complete the 24-week treatment period and announce topline results in 2026.

ALD is a disease characterized by damage to the liver due to excessive and chronic alcohol use. ALD progression (like MASH progression) begins with liver steatosis, which may lead to inflammation, fibrosis and, ultimately, to cirrhosis. 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. Subjects will be randomized 1:1 to receive either 2.4mg pemvidutide or placebo weekly for 48 weeks. The trial's primary endpoint is the change from baseline in liver stiffness measurement ("LSM") by Vibration Controlled Transient Elastography ("VCTE") at Week 24. Key secondary endpoints include the change from baseline in LSM by VCTE at Week 48, changes in Enhanced Liver Fibrosis ("ELF") score at Weeks 24 and 48, and changes in alcohol consumption and body weight at the same time points.

***Recent Global Events***

#### Tariffs
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

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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.

#### U.S. Government Shutdown
On October 1, 2025, the U.S. federal government entered a shutdown suspending services deemed non-essential as a result of the failure by Congress to enact regular appropriations for the 2026 fiscal year. If the shutdown continues for a prolonged period of time, it could result in significant delays in the SEC's and FDA's ability to timely review and process any submissions we have filed or may file or cause other regulatory delays, which could have a material adverse effect on our business.

***Results of Operations***

***Comparison of the three months ended September 30, 2025 and 2024***

The following table summarizes our results of operations for the three months ended September 30, 2025 and 2024 (in thousands):

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Three Months Ended September 30,**  | **Three Months Ended September 30,**  | **Three Months Ended September 30,**  | **Three Months Ended September 30,**  |
|  | **2025** | **2024** | **Increase (Decrease)** | **Increase (Decrease)** |
| Revenues | $5 | $5 | $— | —% |
| Operating expenses: |  |  |  |  |
| &nbsp;&nbsp;Research and development | 14960 | 19803 | (4843) | (24)% |
| &nbsp;&nbsp;General and administrative | 5904 | 4969 | 935 | 19% |
| &nbsp;&nbsp;&nbsp;&nbsp;Total operating expenses | 20864 | 24772 | (3908) | (16)% |
| Loss from operations | (20859) | (24767) | (3908) | (16)% |
| Other income (expense): |  |  |  |  |
| &nbsp;&nbsp;Interest expense | (495) | (6) | 489 |  |
| &nbsp;&nbsp;Interest income | 2426 | 1910 | 516 | 27% |
| &nbsp;&nbsp;Other income (expense), net | (86) | 18 | (104) | (578)% |
| &nbsp;&nbsp;&nbsp;&nbsp;Total other income (expense), net | 1845 | 1922 | (77) | (4)% |
| Net loss | $(19014) | $(22845) | $(3831) | (17)% |

---

#### Revenues
We have not generated any revenues 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.

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#### Research and development expenses
Research and development expenses consisted primarily of expenses related to product candidate development. Research and development expenses decreased by $4.8 million, or 24%, for the three months ended September 30, 2025, as compared to the same period ended September 30, 2024:

---

| | | | | |
|:---|:---|:---|:---|:---|
| | **Three Months Ended September 30,**  | **Three Months Ended September 30,**  | **Three Months Ended September 30,**  | **Three Months Ended September 30,**  |
| <br>(in thousands) | **2025** | **2024** | **Increase (Decrease)** | **Increase (Decrease)** |
| Pemvidutide |  |  |  |  |
| &nbsp;&nbsp;MASH | $4327 | $8380 | $(4053) | (48)% |
| &nbsp;&nbsp;ALD | 1481 |  | 1481 | 100% |
| &nbsp;&nbsp;AUD | 1874 |  | 1874 | 100% |
| &nbsp;&nbsp;Other pemvidutide expenses | 1514 | 3996 | (2482) | (62)% |
| &nbsp;&nbsp;&nbsp;&nbsp;Total pemvidutide expenses | 9196 | 12376 | (3180) | (26)% |
| HepTcell |  | 334 | (334) | 100% |
| Non-project costs | 5764 | 7093 | (1329) | (19)% |
| &nbsp;&nbsp;Total research and development expenses | $14960 | $19803 | $(4843) | (24)% |

---

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. The decrease in other pemvidutide expenses was primarily due to a $1.2 million decrease in manufacturing expenses. 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.

The decrease in non-project costs were primarily due to a $0.8 million initial cost for additional research and discovery projects during 2024 which were not pursued in 2025 and a $0.3 million reduction in overhead costs.

#### General and administrative expenses
General and administrative expenses increased by $0.9 million, or 19%, for the three months ended September 30, 2025, as compared to the three months ended September 30, 2024, primarily due to a $0.7 million increase in stock compensation and other labor-related expenses and a $0.4 million increase in expenses for professional services.

#### Total other income (expense), net
Total other income (expense), net decreased by $0.1 million, or 4%, for the three months ended September 30, 2025, as compared to the three months ended September 30, 2024.

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***Comparison of the nine months ended September 30, 2025 and 2024***

The following table summarizes our results of operations for the nine months ended September 30, 2025 and 2024 (in thousands):

---

| | | | | |
|:---|:---|:---|:---|:---|
|  | **Nine Months Ended September 30,**  | **Nine Months Ended September 30,**  | **Nine Months Ended September 30,**  | **Nine Months Ended September 30,**  |
|  | **2025** | **2024** | **Increase (Decrease)** | **Increase (Decrease)** |
| Revenues | $15 | $15 | $— | —% |
| Operating expenses: |  |  |  |  |
| &nbsp;&nbsp;Research and development | 48023 | 62445 | (14422) | (23)% |
| &nbsp;&nbsp;General and administrative | 17588 | 15876 | 1712 | 11% |
| &nbsp;&nbsp;&nbsp;&nbsp;Total operating expenses | 65611 | 78321 | (12710) | (16)% |
| Loss from operations | (65596) | (78306) | (12710) | (16)% |
| Other income (expense): |  |  |  |  |
| &nbsp;&nbsp;Interest expense | (760) | (8) | 752 |  |
| &nbsp;&nbsp;Interest income | 5103 | 6505 | (1402) | (22)% |
| &nbsp;&nbsp;Other income (expense), net | (163) | (70) | (93) | 133% |
| &nbsp;&nbsp;&nbsp;&nbsp;Total other income (expense), net | 4180 | 6427 | (2247) | (35)% |
| Net loss before income taxes | (61416) | (71879) | 10463 | (15)% |
| Income tax expense (benefit) | (681) |  | (681) | 100% |
| Net loss | $(60735) | $(71879) | $(11144) | (16)% |

---

#### Revenues
We have not generated any revenues 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 consisted primarily of expenses related to product candidate development. Research and development expenses decreased by $14.4 million, or 23%, for the nine months ended September 30, 2025, as compared to the same period ended September 30, 2024:

---

| | | | | |
|:---|:---|:---|:---|:---|
| | **Nine Months Ended September 30,**  | **Nine Months Ended September 30,**  | **Nine Months Ended September 30,**  | **Nine Months Ended September 30,**  |
| <br>(in thousands) | **2025** | **2024** | **Increase (Decrease)** | **Increase (Decrease)** |
| Pemvidutide |  |  |  |  |
| &nbsp;&nbsp;MASH | $17113 | $27292 | $(10179) | (37)% |
| &nbsp;&nbsp;ALD | 3077 |  | 3077 | 100% |
| &nbsp;&nbsp;AUD | 3286 |  | 3286 | 100% |
| &nbsp;&nbsp;Other pemvidutide expenses | 6112 | 12373 | (6261) | (51)% |
| &nbsp;&nbsp;&nbsp;&nbsp;Total pemvidutide expenses | 29588 | 39665 | (10077) | (25)% |
| HepTcell |  | 2359 | (2359) | (100)% |
| Non-project costs | 18435 | 20421 | (1986) | (10)% |
| &nbsp;&nbsp;Total research and development expenses | $48023 | $62445 | $(14422) | (23)% |

---

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. The decrease in other pemvidutide expenses was primarily due to a $4.5 million decrease in manufacturing expenses. These decreases were partially offset by the increase in expense associated with the start of the AUD and ALD trials.

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

The decrease in non-project costs were primarily due to a $1.3 million initial cost for additional research and discovery projects during 2024 which were not pursued in 2025 and a $0.3 million reduction in overhead costs.

#### General and administrative expenses
General and administrative expenses increased by $1.7 million, or 11%, for the nine months ended September 30, 2025, as compared to the nine months ended September 30, 2024, primarily due to a $1.2 million increase in expenses for professional services and $0.7 million increase in stock compensation and other labor-related expenses.

#### Total other income (expense), net
Total other income (expense), net decreased by $2.2 million, or 35%, for the nine months ended September 30, 2025, as compared to the nine months ended September 30, 2024. The net decrease was primarily due to a $1.4 million decrease in interest income earned on our cash equivalents and short-term investments and a $0.8 million increase in interest expense related to our Term Loan.

*Income tax expense (benefit)*

During the nine months ended September 30, 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 of 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 nine months ended September 30, 2025 and 2024.

***Liquidity and Capital Resources***

#### Overview
Our primary sources of cash during the nine months ended September 30, 2025 were from equity transactions, debt, interest 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 $210.8 million as of September 30, 2025. We believe, based on the operating cash requirements and capital expenditures expected for 2025 and 2026, our cash on hand as of September 30, 2025, together with expected cash receipts from equity transactions, are sufficient to fund operations for at least a twelve-month period from the issuance date of our September 30, 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 September 30, 2025, we had an accumulated deficit of $622.1 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

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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 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 "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 February 27, 2025, we entered an Equity Distribution Agreement (the "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 sale agents from the 2025 Shelf. During the nine months ended September 30, 2025, we have sold 18,524,709 shares of common stock under the 2025 Agreement resulting in approximately $81.9 million in net proceeds, and as of September 30, 2025, $65.4 million remained available to be sold under the 2025 Agreement.

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. During the nine months ended September 30, 2025, we have sold 4,467,866 shares of common stock under the 2023 Agreement, resulting in approximately $30.2 million in net proceeds. Since inception through the expiration of the 2023 Agreement in February 2025, we raised approximately $126.8 million in net proceeds through the issuance of 26,129,903 shares of our common stock. As of September 30, 2025, there were no remaining shares available under the 2023 Agreement as the 2023 Agreement was terminated.

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#### Cash Flows
The following table provides information regarding our cash flows for the nine months ended September 30, 2025 and 2024:

---

| | | | |
|:---|:---|:---|:---|
| | **Nine Months Ended September 30,**  | **Nine Months Ended September 30,**  | **Nine Months Ended September 30,**  |
| <br>*(in thousands)* | **2025** | **2024** | **Increase (Decrease)** |
| Net cash (used in) provided by: |  |  |  |
| &nbsp;&nbsp;Operating activities | $(48087) | $(61583) | $(13496) |
| &nbsp;&nbsp;Investing activities | (53315) | (42018) | (11297) |
| &nbsp;&nbsp;Financing activities | 125712 | (41) | 125753 |
| Net increase (decrease) in cash and cash equivalents and restricted cash | $24310 | $(103642) | $127952 |

---

#### Operating Activities
Net cash used in operating activities was $48.1 million for the nine months ended September 30, 2025 compared to $61.6 million during the nine months ended September 30, 2024. 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 operations of $13.5 million year over year is due to changes in working capital accounts of $1.1 million and a decrease in net loss as adjusted for non-cash items of $12.4 million.

#### Investing Activities
Net cash used in investing activities was $53.3 million for the nine months ended September 30, 2025 compared to $42.0 million net cash used in investing activities during the nine months ended September 30, 2024. The net cash used in investing activities during the nine months ended September 30, 2025 was primarily due to a $196.9 million purchase of short-term investments, partially offset by a $143.6 million in proceeds from sale and maturities of short-term investments. The net cash used in investing activities during the nine months ended September 30, 2024 was primarily due to a $102.5 million purchase of short-term investments, partially offset by a $60.5 million in proceeds from sale and maturities of short-term investments.

#### Financing Activities
Net cash provided by financing activities was $125.7 million during the nine months ended September 30, 2025 compared to a negligible amount of cash used in financing activities during the nine months ended September 30, 2024. The net cash provided by financing activities during the nine months ended September 30, 2025 was primarily the result of the receipt of $111.8 million in net proceeds from the issuance of common stock from our at-the-market offerings program, $14.3 million in net proceeds from the term loan, and $0.3 million in proceeds from the ESPP, partially offset by $0.7 million net payments for tax withholding obligations related to share-based compensation. The net cash used in financing activities during the nine months ended September 30, 2024 was primarily due to $0.8 million net payments for tax withholding obligations related to share-based compensation, partially offset by $0.3 million in proceeds from the ESPP, $0.3 million in proceeds from exercise of stock options and $0.2 million in proceeds from exercise of stock warrants.

***Current Resources***

We have financed our operations to date principally through our equity offerings and proceeds from issuances of our common stock. As of September 30, 2025, we had $210.8 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 September 30, 2025 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.

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***Critical Accounting Estimates***

Management's Discussion and Analysis of Financial Condition and Results of Operations is based upon our unaudited consolidated financial statements, which have been prepared in accordance with U.S. GAAP and the rules and regulations of the SEC for interim financial reporting. The preparation of these financial statements requires us to make estimates and judgments that affect the reported amounts of assets, liabilities, revenues, expenses, and the disclosure of contingent liabilities in our consolidated financial statements. We base our estimates and judgments on historical experience, knowledge of current conditions, and expectations of what could occur in the future given available information.

There have been no changes in our critical accounting policies and significant judgment and estimates as disclosed in our Annual Report on Form 10-K for the year ended December 31, 2024.

#### Item 3. Quantitative and Qualitative Disclosures about Market Risk
As a "smaller reporting company" as defined by Item 10 of Regulation S-K, we are not required to provide the information required by this Item.

#### Item 4. Controls and Procedures

#### Evaluation of Disclosure Controls and Procedures
Our management, with the participation of our principal executive officer and principal financial officer, evaluated the effectiveness of our disclosure controls and procedures pursuant to Rule 13a-15 under the Securities Exchange Act of 1934, as amended (the "Exchange Act") as of the end of the period covered by this Quarterly Report on Form 10-Q.

Based on this evaluation, our principal executive officer and principal financial officer concluded that, as of September 30, 2025, our disclosure controls and procedures were effective to provide reasonable assurance that information we are required to disclose in reports that we file or submit under the Exchange Act is recorded, processed, summarized, and reported within the time periods specified in the SEC's rules and forms, and that such information is accumulated and communicated to our management, including our principal executive officer and principal financial officer, as appropriate, to allow timely decisions regarding required disclosure.

#### Changes in Internal Control Over Financial Reporting
There were no changes in our internal control over financial reporting (as defined in Rule 13a-15(f) and Rule 15d-15(f) under the Exchange Act) during the quarter ended September 30, 2025 identified in connection with the evaluation thereof by our management, including the Chief Executive Officer and Chief Financial Officer, that materially affected, or are reasonably likely to materially affect, our internal control over financial reporting.

#### PART II. OTHER INFORMATION

#### Item 1. Legal Proceedings
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

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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.

From time to time, we may be involved in various legal proceedings or investigations, which could be costly and impose a significant burden on management and employees. The results of any current or future litigation cannot be predicted with certainty, and regardless of the outcome, litigation can have an adverse impact on us because of defense and settlement costs, diversion of management resources and other factors.

#### Item 1A. Risk Factors
There have been no material changes from the risk factors disclosed in our Annual Report on Form 10-K filed with the SEC on February 27, 2025 and the latest Quarterly Report on Form 10-Q filed with the SEC on August 12, 2025.

#### Item 2. Unregistered Sales of Equity Securities and Use of Proceeds
None.

#### Item 3. Default upon Senior Securities
None.

#### Item 4. Mine Safety Disclosures
Not applicable.

#### Item 5. Other Information
During the three months ended September 30, 2025, none of our officers or directors adopted, modified, or terminated a "Rule 10b5-1 trading arrangement" or "non-Rule 10b5-1 trading arrangement" as defined in Item 408(c) of Regulation S-K.

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#### Item 6. Exhibits

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| | |
|:---|:---|
|  | **Exhibit Index** |
| Exhibit No. | Description |
| 3.1 | [Amended and Restated Certificate of Incorporation, dated October 17, 2017 (incorporated by reference to Exhibit 3.1 to the Registrant's Form 8-K filed on October 18, 2017)](https://www.sec.gov/Archives/edgar/data/1326190/000119312517312751/d470504dex31.htm) |
| 3.2 | [Certificate of Amendment to Amended and Restated Certificate of Incorporation regarding a reverse stock split (incorporated by reference to Exhibit 3.1 to the Registrant's Form 8-K filed on September 13, 2018)](https://www.sec.gov/Archives/edgar/data/1326190/000119312518272896/d621454dex31.htm) |
| 3.3 | [Certificate of Amendment to Amended and Restated Certificate of Incorporation regarding an increase in authorized shares (incorporated by reference to Exhibit 3.2 to the Registrant's Form 8-K filed on September 13, 2018)](https://www.sec.gov/Archives/edgar/data/1326190/000119312518272896/d621454dex32.htm) |
| 3.4 | [Amended and Restated Bylaws of Altimmune, Inc. (incorporated by reference to Exhibit 3.2 to the Registrant's Form 8-K filed on October 18, 2017)](https://www.sec.gov/Archives/edgar/data/1326190/000119312517312751/d470504dex32.htm) |
| 10.1 § | [Amendment to Loan and Security Agreement, dated November 5, 2025, by and between Altimmune, Inc. and Hercules Capital, Inc. (incorporated by reference to Exhibit 10.1 to the Registrant's Form 8-K filed on November 6, 2025)](https://www.sec.gov/Archives/edgar/data/1326190/000132619025000055/alt-20251106xex10d1.htm) |
| 10.2\* | [Transitional Services and Release Agreement, dated September 30, 2025, by and between Altimmune, Inc. and M. Scott Harris](alt-20250930xex10d2.htm) |
| 31.1 † | [Certification of Principal Executive Officer Pursuant to SEC Rule 13a-14(a)/15d-14(a)](alt-20250930xex31d1.htm) |
| 31.2 † | [Certification of Principal Financial Officer Pursuant to SEC Rule 13a-14(a)/15d-14(a)](alt-20250930xex31d2.htm) |
| 32.1 † | [Certification Pursuant to Section 1350 of Chapter 63 of Title 18 of the United States Code](alt-20250930xex32d1.htm) |
| 32.2 † | [Certification Pursuant to Section 1350 of Chapter 63 of Title 18 of the United States Code](alt-20250930xex32d2.htm) |
| 101.INS | Inline XBRL Instance Document (the instance document does not appear in the Interactive Data File because its XBRL tags are embedded within the Inline XBRL document) |
| 101.SCH | Inline XBRL Taxonomy Extension Schema Document |
| 101.CAL | Inline XBRL Taxonomy Extension Calculation Linkbase Document |
| 101.DEF | Inline XBRL Taxonomy Extension Definition Linkbase Document |
| 101.LAB | Inline XBRL Taxonomy Extension Label Linkbase Document |
| 101.PRE | Inline XBRL Taxonomy Extension Presentation Linkbase Document |
| 104 | Cover Page Interactive Data File (formatted as Inline XBRL and contained in Exhibit 101) |

---

&nbsp;&nbsp;&nbsp;&nbsp;† This certification will not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), or otherwise subject to the liability of that section. Such certification will not be deemed to be incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except to the extent specifically incorporated by reference into such filing.

\* Filed herewith

§ Certain portions of this exhibit have been omitted in accordance with Item 601(b)(10)(iv) of Regulation S-K.

[**Table of Contents**](#TOC)

#### SIGNATURES
Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused the report to be signed on its behalf by the undersigned, thereunto duly authorized.

---

| | | |
|:---|:---|:---|
|  | ALTIMMUNE, INC. | ALTIMMUNE, INC. |
| Dated: November 6, 2025 | By: | /s/ Vipin K. Garg |
|  | Name: | Vipin K. Garg |
|  | Title: | President and Chief Executive Officer (Principal Executive Officer) |
| Dated: November 6, 2025 | By: | /s/ Gregory Weaver |
|  | Name: | Gregory Weaver |
|  | Title: | Chief Financial Officer (Principal Financial and Accounting Officer) |

---

## Exhibit 10.2

**Exhibit 10.2**

September 30, 2025

M. Scott Harris, MD

**Re: Transitional Services and Release Agreement**

Dear Scott:

This "<u>Agreement</u>" follows our conversations regarding your retirement from employment with Altimmune, Inc. (the "<u>Company</u>"). We appreciate your willingness to provide transitional services to the Company, and in consideration for those services, we offer you the terms described below in this "<u>Agreement</u>."

Regardless of whether you sign the Agreement below, you are subject to continuing obligations under Sections 7, 11 and 12 of your Employment Agreement with the Company dated September 9, 2019) (the "<u>Employment Agreement</u>") (with any other confidentiality, restrictive covenant and other ongoing obligations you have to any of the Releasees (as defined below), the "<u>Ongoing Obligations</u>").

You and the Company further agree as follows:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;**1.** **Transition Period; Separation Date;** 

If you enter into and comply with this Agreement, you will remain employed until February 28, 2026 unless you are terminated by the Company for Cause (as defined in your Employment Agreement) or for breaching this Agreement, or unless you voluntarily terminate your employment. Your last day of employment, whether it is February 28, 2026 or an earlier date, shall be referred to as the "<u>Separation Date</u>." The time period between the date of this letter and the Separation Date shall be referred to as the "<u>Transition Period</u>."

Effective October 1, 2025 (subject to your employment with the Company through such date), your role as Chief Medical Officer will cease and you will immediately become a Senior Strategic Advisor to the Company. To avoid doubt, the Senior Strategic Advisor role will be a W2 employment role.

During the Transition Period, you will (i) assist in transitioning your duties to the new CMO; (ii) attend relevant industry conferences, including with the new CMO; and (iii) provide such other transitional services as the Company reasonably requests.

You shall continue to receive your current salary and benefits (subject to plan terms) as a regular employee during the Transition Period.

Provided you fully comply with this Agreement, are not terminated for Cause or for breaching this Agreement and do not resign, you will eligible for a full 2025 cash annual bonus, subject to bonus criteria achievement as determined by the Board. Any such bonus shall be paid when any 2025 annual bonuses are paid to executives.

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Your equity rights (stock options and RSUs) will continue to vest during the Transition Period, subject to the applicable equity agreements governing your equity rights and the Altimmune, Inc. 2017 Omnibus Incentive Plan (as amended and in effect from time to time) (the "<u>Equity Documents</u>"). Your equity rights will cease vesting as of the Separation Date.

**2.** **Exercise Period Extension**

Provided you fully comply with this Agreement, are not terminated for Cause or for breaching this Agreement and do not resign, subject to the approval of the Compensation Committee of the Company's Board of Directors in its discretion, effective as of the later of the Separation Date and the Effective Date, the time period you have under the Equity Documents to exercise your vested stock options shall be extended until the 12 month anniversary of the Separation Date (but in no event later than the expiration date of the stock options) (the "<u>Exercise Period Extension</u>").

You acknowledge that as a result of the Exercise Period Extension, if your vested stock options were incentive stock options, they will convert to nonqualified stock options, subject to applicable law. You are advised to seek guidance from your personal tax advisors with regard to the tax implications of the Exercise Period Extension.

**3.** **Release of Claims**

In consideration for, among other terms, your eligibility for the consideration described above, for which you acknowledge you would otherwise not be eligible, you (and your affiliates, successors and assigns) voluntarily release and forever discharge the Company, its affiliated and related entities, its and their respective predecessors, successors and assigns, its and their respective employee benefit plans and fiduciaries of such plans, and the current and former officers, directors, shareholders, managers, members, interest holders, investors, insurers, employees, attorneys, accountants and agents of each of the foregoing in their official and personal capacities (collectively referred to as the "<u>Releasees</u>") generally from all claims, demands, debts, damages and liabilities of every name and nature, known or unknown ("<u>Claims</u>") that, as of the date when you sign this Agreement, you have, ever had, now claim to have or ever claimed to have had against any or all of the Releasees. This release includes, without limitation, all Claims:

- relating to your employment by and termination of employment with the Company;

- of wrongful discharge or violation of public policy;

- of breach of contract;

- of defamation or other torts;

- of retaliation or discrimination under federal, state or local law (including, without limitation, Claims of discrimination or retaliation under the Age Discrimination in Employment Act, the Americans with Disabilities Act, and Title VII of the Civil Rights Act of 1964);

- under the Employment Agreement, including without limitation for severance benefits of any kind;

- under any other federal or state statute;

- under Maryland Human Relations Law; Maryland Medical Information Discrimination Law; Maryland Equal Pay For Equal Work Law;

------

- under Virginians with Disabilities Act; Virginia Human Rights Act; Virginia Equal Pay Act; Fairfax Human Rights Ordinance; Human Rights Code of the City of Alexandria; Arlington Human Rights Ordinance; Virginia Genetic Testing Law; Virginia Occupational Safety and Health Act (VAOSHA); Virginia Right-to-Work Law; Virginia Prevention of Employment Law; Virginia Law Regarding Payment of Medical Examination;

- for wages, bonuses, incentive compensation, commissions, stock, stock options, vacation pay or any other compensation or benefits, to the fullest extent waivable under applicable law; and

- for damages or other remedies of any sort, including, without limitation, compensatory damages, punitive damages, injunctive relief and attorney's fees;

*provided*, however, that this release shall not affect your vested rights under the Company's Section 401(k) plan or your rights under this Agreement.

You agree not to accept damages of any nature, other equitable or legal remedies for your own benefit or attorney's fees or costs from any of the Releasees with respect to any Claim released by this Agreement. As a material inducement to the Company to enter into this Agreement, you represent that you have not assigned any Claim to any third party. You agree that you are not eligible for, and will not be paid, any severance benefits under the Employment Agreement.

**4.** **Nondisparagement**

Subject to the Protected Activities section below, you agree not to make any disparaging statements concerning the Company or any of its affiliates or current or former officers, directors, shareholders, employees or agents. These nondisparagement obligations shall not in any way affect your obligation to testify truthfully in any legal proceeding.

**5.** **Confidentiality of Agreement-Related Information; Other Obligations**

Subject to the "Protected Activities" Section below, you agree, to the fullest extent permitted by law, to keep all Agreement-Related Information completely confidential. "<u>Agreement-Related Information</u>" means the negotiations leading to this Agreement and the terms of this Agreement. Notwithstanding the foregoing, you may disclose Agreement-Related Information to your spouse, your attorney and your financial advisors, and to them only; *provided* that they first agree for the benefit of the Company to keep Agreement-Related Information confidential. You represent that during the period since the date of this Agreement, you have not made any disclosures that would have been contrary to the foregoing obligation if it had then been in effect. Nothing in this Section shall be construed to prevent you from disclosing Agreement-Related Information to the extent required by a lawfully issued subpoena or duly issued court order; *provided* that you provide the Company with advance written notice and a reasonable opportunity to contest such subpoena or court order. To the extent you have not assigned any developments or intellectual property rights to the Company that are related to the Company's business activities or were made using the Company's time, equipment or resources, you hereby assign such developments and intellectual property rights to the Company, to the fullest extent permitted by law. You agree to promptly return all Company property to the Company; not to disclose or use any Company confidential information at any time; not to represent yourself as

------

currently employed or engaged by the Company after the Separation Date; subject to the "Protected Activities" Section below, to cooperate with the Company in any future dispute or intellectual property matter; and to notify future employers of your Ongoing Obligations. Subject to the Protected Activities section: (i) you will not encourage, counsel, or assist any attorneys or their clients in the presentation or prosecution of any disputes, differences, grievances, claims, charges, or complaints by any third party against any of the Releasees, unless under a subpoena or other court order to do so; and (ii) if you are approached by anyone for counsel or assistance in the presentation or prosecution of any disputes, differences, grievances, claims, charges, or complaints against any of the Releasees, you shall state only that your cannot provide counsel or assistance.

**6.** **Resignations from Other Positions; Transition of Information and Access**

In connection with the ending of your employment, you hereby (i) agree to execute such documentation as the Company or its applicable affiliate reasonably requires to effectuate your resignation from the CMO position and any officer positions; and (ii) take such steps as the Company (or its applicable affiliate) reasonably requests to ensure the transition of any account access, systems access, password access, customer access, confidential information, Company property, customer information or customer relationships to the Company or its applicable affiliate.

**7.** **Protected Disclosures and Other Protected Actions**

Nothing contained in this Agreement or in any other agreement with the Company limits your ability to: (i) file a charge or complaint with any federal, state or local governmental agency or commission, including without limitation the Equal Employment Opportunity Commission, the National Labor Relations Board or the Securities and Exchange Commission (a "Government Agency"); (ii) communicate with any Government Agency or otherwise participate in any investigation or proceeding that may be conducted by any Government Agency; (iii) exercise any rights you may have under Section 7 of the National Labor Relations Act, including any rights you may have under such provision to assist co-workers with or discuss any employment issue, dispute or term or condition of employment as part of engaging in concerted activities for the purpose of mutual aid or protection; (iv) discuss or disclose information about unlawful acts in the workplace, such as harassment or discrimination or any other conduct that you have reason to believe is unlawful; or (v) testify truthfully in a legal proceeding, in any event with or without notice to or approval of the Company so long as such communications and disclosures are consistent with applicable law and the information disclosure was not obtained through a communication that was subject to the attorney client privilege (unless disclosure of that information would otherwise be permitted consistent with such privilege). If you file any charge or complaint with any Government Agency and if the Government Agency pursues any claim on your behalf, or if any other third party pursues any claim on your behalf, you waive any right to monetary or other individualized relief (either individually or as part of any collective or class action) but the Company will not limit any right you may have to receive an award by an order of a Government Agency pursuant to the whistleblower provisions of any applicable law or regulation for providing information to the Securities and Exchange Commission (the "SEC") or any other Government Agency.

------

**8.** **Other Provisions**

**(a)**<u>Enforceability</u>. If any portion or provision of this Agreement (including, without limitation, any portion or provision of any section of this Agreement) shall to any extent be declared illegal or unenforceable by a court of competent jurisdiction, then the remainder of this Agreement, or the application of such portion or provision in circumstances other than those as to which it is so declared illegal or unenforceable, shall not be affected thereby, and each portion and provision of this Agreement shall be valid and enforceable to the fullest extent permitted by law.

**(b)**<u>Waiver; Absence of Reliance</u>. No waiver of any provision of this Agreement shall be effective unless made in writing and signed by the waiving party. The failure of a party to require the performance of any term or obligation of this Agreement, or the waiver by a party of any breach of this Agreement, shall not prevent any subsequent enforcement of such term or obligation or be deemed a waiver of any subsequent breach. In signing this Agreement, you are not relying upon any promises or representations made by anyone at or on behalf of the Company.

**(c)**<u>Jurisdiction; Governing Law; Interpretation</u>. The jurisdiction, governing law, and jury waiver provisions of the Employment Agreement shall govern any dispute relating to this Agreement.

**(d)**<u>Entire Agreement</u>. This Agreement, the Equity Documents, and the Ongoing Obligations (which are incorporated herein by reference) constitute the entire agreement between you and the Company and supersede any previous agreements or understandings between you and the Company.

**(e)**<u>Time for Consideration; Effective Date</u>. You acknowledge that you have been given the opportunity to consider this Agreement for twenty-one (21) days before signing it (the "<u>Consideration Period</u>") and that you have knowingly and voluntarily entered into this Agreement. You acknowledge that the above release of claims expressly includes without limitation claims under the Age Discrimination in Employment Act. You are advised to consult with an attorney before signing this Agreement. To accept this Agreement, you must return a signed original or a signed PDF copy of this Agreement so that it is received by the undersigned at or before the expiration of the Consideration Period. If you sign this Agreement before the end of the Consideration Period, you acknowledge by signing this Agreement that such decision was entirely voluntary and that you had the opportunity to consider this Agreement for the entire Consideration Period. For the period of seven (7) days from the date when you sign this Agreement, you have the right to revoke this Agreement by written notice to the undersigned. For such a revocation to be effective, it must be delivered so that it is received by the undersigned at or before the expiration of the seven (7) day revocation period (the "<u>Revocation Period</u>"). This Agreement shall not become effective or enforceable during the Revocation Period. It will become effective on the day after the Revocation Period ends (the "<u>Effective Date</u>").

------

**(f)**<u>Counterparts</u>. This Agreement may be executed in separate counterparts. When all counterparts are signed, they shall be treated together as one and the same document.

Please indicate your agreement to the terms of this Agreement by signing and returning to the undersigned the original or a PDF copy of this letter within the time period set forth above.

Very truly yours,

ALTIMMUNE, INC.

---

| | | | |
|:---|:---|:---|:---|
| By: | /s/ Vipin K. Garg | Date | October 1, 2025 |
|  | Vipin K. Garg |  |  |
|  | Chief Executive Officer |  |  |

---

This is a legal document. Your signature will commit you to its terms. By signing below, you acknowledge that you have carefully read and fully understand all of the provisions of this Agreement and that you are knowingly and voluntarily entering into this Agreement.

---

| | | |
|:---|:---|:---|
| /s/ M. Scott Harris | Date | September 30, 2025 |
| M. Scott Harris |  |  |

---

------

## Exhibit 31.1

**Exhibit 31.1**

**Certification of Principal Executive Officer**

**Pursuant to SEC Rule 13a-14(a)/15d-14(a)**

I, Vipin K. Garg, certify that:

&nbsp;&nbsp;&nbsp;&nbsp;1. I have reviewed this report on Form 10-Q of Altimmune, Inc. for the period ended September 30, 2025;

&nbsp;&nbsp;&nbsp;&nbsp;2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

&nbsp;&nbsp;&nbsp;&nbsp;3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

&nbsp;&nbsp;&nbsp;&nbsp;4. The registrant's other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(c) Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(d) Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

&nbsp;&nbsp;&nbsp;&nbsp;5. The registrant's other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

---

| | |
|:---|:---|
| Dated: November 6, 2025 | /s/ Vipin K. Garg |
|  | Name: Vipin K. Garg |
|  | Title: President and Chief Executive Officer<br>(Principal Executive Officer) |

---

------

## Exhibit 31.2

**Exhibit 31.2**

**Certification of Principal Financial Officer**

**Pursuant to SEC Rule 13a-14(a)/15d-14(a)**

I, Greg Weaver, certify that:

&nbsp;&nbsp;&nbsp;&nbsp;1. I have reviewed this report on Form 10-Q of Altimmune, Inc. for the period ended September 30, 2025;

&nbsp;&nbsp;&nbsp;&nbsp;2. Based on my knowledge, this report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements were made, not misleading with respect to the period covered by this report;

&nbsp;&nbsp;&nbsp;&nbsp;3. Based on my knowledge, the financial statements, and other financial information included in this report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in this report;

&nbsp;&nbsp;&nbsp;&nbsp;4. The registrant's other certifying officer(s) and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the registrant and have:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this report is being prepared;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(c) Evaluated the effectiveness of the registrant's disclosure controls and procedures and presented in this report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(d) Disclosed in this report any change in the registrant's internal control over financial reporting that occurred during the registrant's most recent fiscal quarter (the registrant's fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the registrant's internal control over financial reporting; and

&nbsp;&nbsp;&nbsp;&nbsp;5. The registrant's other certifying officer(s) and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrant's auditors and the audit committee of the registrant's board of directors (or persons performing the equivalent functions):

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrant's ability to record, process, summarize and report financial information; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b) Any fraud, whether or not material, that involves management or other employees who have a significant role in the registrant's internal control over financial reporting.

---

| | |
|:---|:---|
| Dated: November 6, 2025 | /s/ Greg Weaver |
|  | Name: Greg Weaver |
|  | Title: Chief Financial Officer<br>(Principal Financial Officer) |

---

------

## Exhibit 32.1

**Exhibit 32.1**

**Certification Pursuant to Section 1350 of Chapter 63**

**of Title 18 of the United States Code**

In connection with the quarterly report on Form 10-Q of Altimmune, Inc. (the "Company") for the period ended September 30, 2025, as filed with the Securities and Exchange Commission (the "Report"), I, Vipin K. Garg, President and Chief Executive Officer of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that to the best of my knowledge:

&nbsp;&nbsp;&nbsp;&nbsp;1. The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934.

&nbsp;&nbsp;&nbsp;&nbsp;2. The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

---

| |
|:---|
| /s/ Vipin K. Garg |
| Vipin K. Garg |
| President and Chief Executive Officer |
| November 6, 2025 |

---

A signed original of this written statement required by Section 906 of the Sarbanes-Oxley Act of 2002 has been provided to the Company and will be retained by the Company and furnished to the Securities and Exchange Commission or its staff upon request.

This certification is being furnished pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, or otherwise subject to the liability of that section. This certification will not be deemed to be incorporated by reference into any filing under the Securities Act of 1933 or the Securities Exchange Act of 1934.

------

## Exhibit 32.2

**Exhibit 32.2**

**Certification Pursuant to Section 1350 of Chapter 63**

**of Title 18 of the United States Code**

In connection with the quarterly report on Form 10-Q of Altimmune, Inc. (the "Company") for the period ended September 30, 2025, as filed with the Securities and Exchange Commission (the "Report"), I, Gregory Weaver, Chief Financial Officer of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that to the best of my knowledge:

&nbsp;&nbsp;&nbsp;&nbsp;1. The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act of 1934.

&nbsp;&nbsp;&nbsp;&nbsp;2. The information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company.

---

| |
|:---|
| /s/ Greg Weaver |
| Gregory Weaver |
| Chief Financial Officer |
| November 6, 2025 |

---

A signed original of this written statement required by Section 906 of the Sarbanes-Oxley Act of 2002 has been provided to the Company and will be retained by the Company and furnished to the Securities and Exchange Commission or its staff upon request.

This certification is being furnished pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 and shall not be deemed "filed" for purposes of Section 18 of the Securities Exchange Act of 1934, or otherwise subject to the liability of that section. This certification will not be deemed to be incorporated by reference into any filing under the Securities Act of 1933 or the Securities Exchange Act of 1934.

------