Altimmune medical chief receives 37,500 vested shares

Q: How many Altimmune (ALT) shares did Christophe Arbet-Engels acquire and surrender?

37,500 common shares were acquired through RSU vesting on October 1, 2026, and 12,679 common shares were surrendered to the issuer solely to cover taxes associated with vesting, at $2.76 per share.

Q: What are the vesting terms for Christophe Arbet-Engels’s Altimmune RSUs?

The RSUs vest over four years, with 25% vesting on October 1, 2026 and the remainder in equal annual installments over the following three years. Vesting is subject to his continued service through each applicable vesting date.

Each restricted stock unit represents a contingent right to receive one common share when vested.

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Rhea-AI Filing Summary

Altimmune, Inc. Chief Medical Officer Christophe Arbet-Engels had 37,500 restricted stock units vest on October 1, 2026, acquiring 37,500 common shares. He surrendered 12,679 common shares to the issuer solely to cover taxes associated with vesting, at a reported $2.76 per share. The reported position following the RSU transaction was 112,500 RSUs.

Insider Trade Summary

37,500 shares exercised/converted

Exercise 3 txns

Insider Arbet-Engels Christophe

Role Chief Medical Officer

Type	Security	Shares	Price	Value
Exercise	Restricted Stock Units ^{F1, F3}	37,500	$0.00	$0.00
Exercise	Common Stock, par value $0.0001 ^F1	37,500	$0.00	$0.00
Tax Withholding	Common Stock, par value $0.0001 ^F2	12,679	$2.76	$35K

Holdings After Transaction: Restricted Stock Units — 112,500 contracts (Direct); Common Stock, par value $0.0001 — 24,821 shares (Direct)

Footnotes (3)

F1. Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.
F2. Vesting transaction: Shares surrendered to the Issuer solely to cover taxes associated with vesting of RSUs.
F3. The RSUs become vested over four (4) years with 25% of the shares vesting on 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.

Key Figures

Restricted stock units vested: 37,500 RSUs Common shares acquired: 37,500 shares Common shares surrendered for taxes: 12,679 shares +4 more

7 metrics

Restricted stock units vested 37,500 RSUs October 1, 2026

Common shares acquired 37,500 shares Through RSU vesting on October 1, 2026

Common shares surrendered for taxes 12,679 shares Solely to cover taxes associated with RSU vesting

Reported price per share $2.76 per share For the shares surrendered to cover taxes

RSUs following transaction 112,500 RSUs Reported position after the RSU transaction

Vesting period 4 years RSU vesting schedule

Initial vesting installment 25% Vested October 1, 2026

Key Terms

Restricted Stock Units, Vesting transaction, contingent right

3 terms

Restricted Stock Units financial

"Each Restricted Stock Unit ("RSU") represents a contingent right"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

Vesting transaction financial

"Vesting transaction: Shares surrendered to the Issuer"

contingent right financial

"represents a contingent right to receive one share"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many Altimmune (ALT) shares did Christophe Arbet-Engels acquire and surrender?

37,500 common shares were acquired through RSU vesting on October 1, 2026, and 12,679 common shares were surrendered to the issuer solely to cover taxes associated with vesting, at $2.76 per share.

What are the vesting terms for Christophe Arbet-Engels’s Altimmune RSUs?

The RSUs vest over four years, with 25% vesting on October 1, 2026 and the remainder in equal annual installments over the following three years. Vesting is subject to his continued service through each applicable vesting date.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 10/05/2026 - 04:10 PM Accepted by SEC EDGAR 10/05/2026 - 04:10 PM

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Arbet-Engels Christophe

(Last)

(First)

(Middle)

910 CLOPPER ROAD

SUITE 201S

(Street)

GAITHERSBURG

MARYLAND

20878

(City)

(State)

(Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Altimmune, Inc. [ ALT ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director	10% Owner
X	Officer (give title below)	Other (specify below)
	Chief Medical Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/01/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock, par value $0.0001	10/01/2026		M		37,500	A	$0⁽¹⁾	37,500	D
Common Stock, par value $0.0001	10/01/2026		F⁽²⁾		12,679	D	$2.76	24,821	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Restricted Stock Units	⁽¹⁾	10/01/2026		M			37,500	⁽³⁾	⁽³⁾	Common Stock, par value $0.0001	37,500	$0	112,500	D

Explanation of Responses:

1. Each Restricted Stock Unit ("RSU") represents a contingent right to receive one share of Common Stock, par value $0.0001, when vested.

2. Vesting transaction: Shares surrendered to the Issuer solely to cover taxes associated with vesting of RSUs.

3. The RSUs become vested over four (4) years with 25% of the shares vesting on 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.

	/s/ Gregory Weaver, as Attorney-in-Fact	10/05/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

Source: View Original Filing on SEC EDGAR