Amylyx Co-CEO Klee sells 30K shares for taxes

Amylyx Co-CEO Justin B. Klee reported automatic sales of 30,464 AMLX shares to satisfy tax withholding from vesting equity awards.

Rhea-AI Filing Summary

Amylyx Pharmaceuticals, Inc. (AMLX) director and Co-Chief Executive Officer Justin B. Klee reported selling a total of 30,464 shares of common stock on September 10, 2026. The filing states the shares were sold to cover tax withholding obligations arising from the vesting of performance stock units, and that these sales were automatic and not at his discretion.

Insider Trade Summary

Net Seller: 30,464 shares

Net Sell 2 txns

Insider Klee Justin B.

Role Co-Chief Executive Officer

Sold 30,464 shs ($980K)

Type	Security	Shares	Price	Value
Sale	Common Stock F1, F2	29,025	$32.1293	$933K
Sale	Common Stock F1, F3	1,439	$33.1552	$48K

Holdings After Transaction: Common Stock — 3,613,056 shares (Direct)

Footnotes (3)

1. F1. Represents shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of performance stock units. Such sales were automatic and not at the discretion of the Reporting Person.
2. F2. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $31.81 to $32.75. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.
3. F3. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $32.87 to $33.39. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

Key Figures

Total shares sold: 30,464 shares First transaction shares: 29,025 shares First transaction weighted average price: $32.1293 per share +3 more

6 metrics

Total shares sold 30,464 shares Aggregate common stock sales reported for September 10, 2026

First transaction shares 29,025 shares Common stock sale on September 10, 2026

First transaction weighted average price $32.1293 per share Sold in multiple trades from $31.81 to $32.75

Second transaction shares 1,439 shares Common stock sale on September 10, 2026

Second transaction weighted average price $33.1552 per share Sold in multiple trades from $32.87 to $33.39

Rule 10b5-1 plan status No Rule 10b5-1 plan affirmed Document-level checkbox not marked affirmative

Key Terms

performance stock units, tax withholding obligations, weighted average price

3 terms

performance stock units financial

"in connection with the vesting of performance stock units"

Performance stock units are a type of company award that grants employees shares of stock only if certain performance goals are met. They motivate employees to work toward specific company achievements, aligning their interests with those of shareholders. For investors, they can influence a company's future stock supply and reflect management’s confidence in reaching key targets.

tax withholding obligations financial

"shares required to be sold ... to cover tax withholding obligations"

weighted average price financial

"The price reported in Column 4 is a weighted average price"

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

FAQ

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

What did AMLX Co-CEO Justin B. Klee report in this Form 4?

He reported selling 30,464 shares of Amylyx Pharmaceuticals, Inc. common stock on September 10, 2026 in open-market or private transactions, as recorded in two separate sale entries.

Why were Amylyx (AMLX) shares sold by Justin B. Klee?

The filing states the shares were sold to cover tax withholding obligations related to the vesting of performance stock units, and that these sales were automatic and not at his discretion.

How many AMLX shares did Justin B. Klee sell in each transaction?

He sold 29,025 shares in one transaction and 1,439 shares in another on September 10, 2026, for a reported total of 30,464 shares sold.

What sale prices were reported for Justin B. Klee’s AMLX stock sales?

One sale reported a weighted average price of $32.1293 per share, with prices ranging from $31.81 to $32.75. The other reported a weighted average price of $33.1552, with prices from $32.87 to $33.39.

Were Justin B. Klee’s AMLX stock sales under a Rule 10b5-1 plan?

The filing’s Rule 10b5-1 checkbox is not marked as affirmative, and no footnote states the sales were under a Rule 10b5-1 trading plan; it does state the sales were automatic for tax withholding.

Does the Form 4 state Justin B. Klee’s AMLX holdings after these sales?

For each reported transaction, the field for shares owned after the transaction is blank in the data provided, so this Form 4 does not state a post-transaction share balance.

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

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Available on EDGAR 09/14/2026 - 04:00 PM Accepted by SEC EDGAR 09/14/2026 - 04:00 PM Learn about SEC filing dates

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^*

Klee Justin B.

(Last) (First) (Middle)

C/O AMYLYX PHARMACEUTICALS, INC.

55 CAMBRIDGE PARKWAY, SUITE 6W

(Street)

CAMBRIDGE MASSACHUSETTS 02142

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Amylyx Pharmaceuticals, Inc. [ AMLX ]

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

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Co-Chief Executive Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
09/10/2026

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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	09/10/2026		S(1)		29,025	D	$32.1293(2)	3,614,495	D
Common Stock	09/10/2026		S(1)		1,439	D	$33.1552(3)	3,613,056	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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Represents shares required to be sold by the Reporting Person to cover tax withholding obligations in connection with the vesting of performance stock units. Such sales were automatic and not at the discretion of the Reporting Person.

2. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $31.81 to $32.75. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

3. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $32.87 to $33.39. Full information regarding the number of shares sold at each separate price can be furnished to the SEC staff upon request.

	/s/ Joshua B. Cohen, as Attorney in Fact	09/14/2026
	** 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)