Christophe Arbet-Engels - 01 Oct 2025 Form 4 Insider Report for Altimmune, Inc. (ALT)

Role: Chief Medical Officer
Signature: /s/ Gregory Weaver, as Attorney-in-Fact
Issuer symbol: ALT
Transactions as of: 01 Oct 2025
Net transactions value: $0
Form type: 4
Filing time: 03 Oct 2025, 16:23:25 UTC
Previous filing: 14 Feb 2025
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Arbet-Engels Christophe	Chief Medical Officer	C/O ALTIMMUNE, INC., 910 CLOPPER ROAD, SUITE 201S, GAITHERSBURG	/s/ Gregory Weaver, as Attorney-in-Fact	03 Oct 2025	0001802615

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
transaction	ALT	Stock Options (option to buy)	Award	$0	+450,000		$0.000000	450,000	01 Oct 2025	Common Stock, par value $0.0001	450,000	$3.87	Direct	F1
transaction	ALT	Restricted Stock Units	Award	$0	+150,000		$0.000000	150,000	01 Oct 2025	Common Stock, par value $0.0001	150,000		Direct	F2, F3

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	The shares underlying the option become vested and exercisable over four (4) years with 25% of the shares vesting on October 1, 2026, with the remainder vesting in equal monthly installments for the following thirty-six (36) months, subject to the reporting person's continued service on each applicable vesting date.
F2	Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested
F3	The RSUs become vested over four (4) years with 25% of the shares vesting October 1, 2026, with the remainder vesting in equal annual installments for the following three (3) years, subject to the reporting person's continued service through the applicable vesting date, and have no expiration date.