TCG Crossover holds 5.7% Amylyx Pharmaceuticals (AMLX) passive stake

Rhea-AI Filing Summary

Amylyx Pharmaceuticals Inc. received an updated ownership filing showing that investment entities affiliated with TCG Crossover hold a significant passive stake in its common stock. TCG Crossover Fund II, L.P., together with its general partner TCG Crossover GP II, LLC and Chen Yu, report beneficial ownership of 6,243,812 shares.

This position represents 5.7% of Amylyx’s outstanding common stock, based on 109,819,659 shares outstanding as of October 27, 2025. The reporting parties state they share voting and dispositive power over these shares and certify the holdings are not for the purpose of changing or influencing control of the company.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

Amylyx Pharmaceuticals Inc.

(Name of Issuer)

Common Stock, $0.0001 par value per share

(Title of Class of Securities)

03237H101

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 03237H101

1

Names of Reporting Persons

TCG Crossover GP II, LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 6,243,812.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 6,243,812.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

6,243,812.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.7 %

12

Type of Reporting Person (See Instructions)

OO

Comment for Type of Reporting Person: These securities are held of record by TCG Crossover II (as defined in Item 2(a) below). TCG Crossover GP II (as defined in Item 2(a) below) is the general partner of TCG Crossover II and may be deemed to have voting, investment, and dispositive power with respect to these securities. Chen Yu is the sole managing member of TCG Crossover GP II and may be deemed to share voting, investment and dispositive power with respect to these securities. Based on 109,819,659 shares of Common Stock outstanding as of October 27, 2025, as reported by the Issuer (as defined in Item 1(a) below) in its quarterly report filed with the Securities and Exchange Commission (the Commission) on November 6, 2025 (the Form 10-Q).

SCHEDULE 13G

CUSIP No. 03237H101

1

Names of Reporting Persons

TCG Crossover Fund II, L.P.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 6,243,812.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 6,243,812.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

6,243,812.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.7 %

12

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person: These securities are held of record by TCG Crossover II. TCG Crossover GP II is the general partner of TCG Crossover II and may be deemed to have voting, investment, and dispositive power with respect to these securities. Chen Yu is the sole managing member of TCG Crossover GP II and may be deemed to share voting, investment and dispositive power with respect to these securities. Based on 109,819,659 shares of Common Stock outstanding as of October 27, 2025, as reported by the Issuer in its Form 10-Q.

SCHEDULE 13G

CUSIP No. 03237H101

1

Names of Reporting Persons

Chen Yu

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 6,243,812.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 6,243,812.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

6,243,812.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.7 %

12

Type of Reporting Person (See Instructions)

IN

Comment for Type of Reporting Person: These securities are held of record by TCG Crossover II. TCG Crossover GP II is the general partner of TCG Crossover II and may be deemed to have voting, investment, and dispositive power with respect to these securities. Chen Yu is the sole managing member of TCG Crossover GP II and may be deemed to share voting, investment and dispositive power with respect to these securities. Based on 109,819,659 shares of Common Stock outstanding as of October 27, 2025, as reported by the Issuer in its Form 10-Q.

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Amylyx Pharmaceuticals Inc.
(b)	Address of issuer's principal executive offices: 55 Cambridge Parkway, Suite 6W, Cambridge, MA 02142
Item 2.
(a)	Name of person filing: This Amendment No. 1 (Amendment No. 1) amends and supplements the Schedule 13G initially filed with the Commission on August 26, 2024 (the Original Schedule 13G) and is being filed by TCG Crossover Fund II, L.P. (TCG Crossover II), TCG Crossover GP II, LLC (TCG Crossover GP II, and together with TCG Crossover II, the Reporting Entities) and Chen Yu (the Reporting Individual). The Reporting Entities and the Reporting Individual are collectively referred to as the Reporting Persons. The Reporting Persons expressly disclaim status as a group for purposes of this Schedule 13G. The agreement among the Reporting Persons to file jointly in accordance with the provisions of Rule 13d-1(k)(1) under the Act is attached as Exhibit 1 to the Original Schedule 13G. Other than those securities reported herein as being held directly by such Reporting Person, each Reporting Person disclaims beneficial ownership of all securities reported in this Statement except to the extent of such Reporting Person's pecuniary interest therein. Capitalized terms not defined in this Amendment No. 1 have the meanings ascribed to them in the Original Schedule 13G.
(b)	Address or principal business office or, if none, residence: The address of the principal business office of each Reporting Person is 245 Lytton Ave., Suite 350, Palo Alto, CA 94301.
(c)	Citizenship: TCG Crossover GP II is a limited liability company organized under the laws of the State of Delaware. TCG Crossover II is a limited partnership organized under the laws of the State of Delaware. The Reporting Individual is a citizen of the United States of America.
(d)	Title of class of securities: Common Stock, $0.0001 par value per share
(e)	CUSIP No.: 03237H101
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: See Row 9 of the cover page for each Reporting Person and the corresponding comments.
(b)	Percent of class: See Row 11 of the cover page for each Reporting Person and the corresponding comments.
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: See Row 5 of the cover page for each Reporting Person and the corresponding comments.
	(ii) Shared power to vote or to direct the vote: See Row 6 of the cover page for each Reporting Person and the corresponding comments.
	(iii) Sole power to dispose or to direct the disposition of: See Row 7 of the cover page for each Reporting Person and the corresponding comments.
	(iv) Shared power to dispose or to direct the disposition of: See Row 8 of the cover page for each Reporting Person and the corresponding comments.
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. Under certain circumstances set forth in the limited partnership agreement of TCG Crossover II and the limited liability company agreement of TCG Crossover GP II, the general and limited partners or members, as the case may be, of each of such entities may be deemed to have the right to receive dividends from, or the proceeds from, the sale of securities of the Issuer owned by each such entity of which they are a partner or member, as the case may be.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

TCG Crossover GP II, LLC

Signature:	/s/ Craig Skaling
Name/Title:	Craig Skaling, Authorized Signatory
Date:	02/17/2026

TCG Crossover Fund II, L.P.

Signature:	/s/ Craig Skaling
Name/Title:	Craig Skaling, Authorized Signatory
Date:	02/17/2026

Chen Yu

Signature:	/s/ Craig Skaling
Name/Title:	Craig Skaling, as Attorney-in-Fact for Chen Yu
Date:	02/17/2026

FAQ

What percentage of Amylyx Pharmaceuticals (AMLX) does TCG Crossover report owning?

TCG Crossover-affiliated entities report beneficial ownership of 5.7% of Amylyx Pharmaceuticals’ common stock. This corresponds to 6,243,812 shares, based on 109,819,659 shares outstanding as of October 27, 2025, as cited from the company’s Form 10-Q.

How many Amylyx (AMLX) shares do the TCG Crossover entities beneficially own?

The filing reports beneficial ownership of 6,243,812 Amylyx common shares by TCG Crossover Fund II, L.P., its general partner TCG Crossover GP II, LLC, and Chen Yu. They indicate shared voting and dispositive power over these shares through the fund structure.

Is the TCG Crossover stake in Amylyx (AMLX) a control or activist position?

The reporting parties certify the shares were not acquired to change or influence control of Amylyx. They file on Schedule 13G/A, which is typically used for passive investments, and explicitly state the holdings are not in connection with transactions aimed at control.

Who are the reporting persons in the Amylyx (AMLX) Schedule 13G/A amendment?

The reporting persons are TCG Crossover Fund II, L.P., its general partner TCG Crossover GP II, LLC, and Chen Yu. The entities are organized in Delaware, and Chen Yu is identified as a U.S. citizen and sole managing member of the general partner.

What does shared voting and dispositive power mean in the Amylyx (AMLX) filing?

The filing states the reporting persons have shared voting and dispositive power over 6,243,812 shares. This means they may collectively direct how these shares are voted and when they are sold, through their roles in TCG Crossover Fund II and its general partner.

Do TCG Crossover and Chen Yu claim group status in their Amylyx (AMLX) filing?

The filing explicitly states the reporting persons disclaim status as a group for Schedule 13G purposes. They also disclaim beneficial ownership of securities not held directly, except to the extent of their pecuniary interest through the fund and general partner structures.