SEC Form SC 13G/A filed by Amylyx Pharmaceuticals Inc. (Amendment)

1	NAMES OF REPORTING PERSONS
	Viking Global Investors LP
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(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
		6	SHARED VOTING POWER
			2,962,555*
		7	SOLE DISPOSITIVE POWER
			0
		8	SHARED DISPOSITIVE POWER
			2,962,555*
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	2,962,555*
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	4.4%*
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	PN

*	See Item 4

1	NAMES OF REPORTING PERSONS
	Viking Global Opportunities Parent GP LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(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
		6	SHARED VOTING POWER
			2,962,555*
		7	SOLE DISPOSITIVE POWER
			0
		8	SHARED DISPOSITIVE POWER
			2,962,555*
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	2,962,555*
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	4.4%*
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	OO

*	See Item 4

1	NAMES OF REPORTING PERSONS
	Viking Global Opportunities GP LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(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
		6	SHARED VOTING POWER
			2,962,555*
		7	SOLE DISPOSITIVE POWER
			0
		8	SHARED DISPOSITIVE POWER
			2,962,555*
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	2,962,555*
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	4.4%*
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	OO

*	See Item 4

1	NAMES OF REPORTING PERSONS
	Viking Global Opportunities Portfolio GP LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(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
		6	SHARED VOTING POWER
			2,012,293*
		7	SOLE DISPOSITIVE POWER
			0
		8	SHARED DISPOSITIVE POWER
			2,012,293*
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	2,012,293*
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	3.0%*
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	OO

*	See Item 4

1	NAMES OF REPORTING PERSONS
	Viking Global Opportunities Illiquid Investments Sub-Master LP
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(a)☐
	(b)☒
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION
	Cayman Islands
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER
			0
		6	SHARED VOTING POWER
			2,012,293*
		7	SOLE DISPOSITIVE POWER
			0
		8	SHARED DISPOSITIVE POWER
			2,012,293*
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	2,012,293*
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	3.0%*
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	PN

*	See Item 4

1	NAMES OF REPORTING PERSONS
	O. Andreas Halvorsen
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(a)☐
	(b)☒
3	SEC USE ONLY
4	CITIZENSHIP OR PLACE OF ORGANIZATION
	Norway
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH		5	SOLE VOTING POWER
			0
		6	SHARED VOTING POWER
			2,962,555*
		7	SOLE DISPOSITIVE POWER
			0
		8	SHARED DISPOSITIVE POWER
			2,962,555*
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	2,962,555*
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	4.4%*
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

*	See Item 4

1	NAMES OF REPORTING PERSONS
	David C. Ott
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(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
		6	SHARED VOTING POWER
			2,962,555*
		7	SOLE DISPOSITIVE POWER
			0
		8	SHARED DISPOSITIVE POWER
			2,962,555*
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	2,962,555*
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	4.4%*
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

*	See Item 4

1	NAMES OF REPORTING PERSONS
	Rose S. Shabet
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(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
		6	SHARED VOTING POWER
			2,962,555*
		7	SOLE DISPOSITIVE POWER
			0
		8	SHARED DISPOSITIVE POWER
			2,962,555*
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	2,962,555*
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	4.4%*
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	IN

*	See Item 4

1	NAMES OF REPORTING PERSONS
	DRAGSA 96 LLC
2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP
	(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
		6	SHARED VOTING POWER
			950,262*
		7	SOLE DISPOSITIVE POWER
			0
		8	SHARED DISPOSITIVE POWER
			950,262*
9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
	950,262*
10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
	☐
11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
	1.4%*
12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
	OO

*	See Item 4

Item 1(a).

Name of Issuer:

Item 1(b).

Address of Issuer’s Principal Executive Offices:

Item 2(a).

Name of Person Filing:

Item 2(b).

Address of Principal Business Office or, if none, Residence:

Item 2(c).

Citizenship:

Item 2(d).

Titles of Classes of Securities:

Item 2(e).

CUSIP NUMBER: 03237H101

Item 3.

If This Statement is Filed Pursuant to Rule 13d-1(b), or 13d-2(b) or (c), Check Whether the Person Filing is a:

	(a)	☐ Broker or dealer registered under Section 15 of the Exchange Act
	(b)	☐ Bank as defined in Section 3(a)(6) of the Exchange Act
	(c)	☐ Insurance company as defined in Section 3(a)(19) of the Exchange Act
	(d)	☐ Investment company registered under Section 8 of the Investment Company Act of 1940
	(e)	☐ Investment Adviser registered under Section 203 of the Investment Advisers Act of 1940: see Rule 13d-1(b)(1)(ii)(E)
	(f)	☐ Employee Benefit Plan, Pension Fund which is subject to the provisions of the Employee Retirement Income Security Act of 1974 or Endowment Fund; see Rule 13d-1(b)(1)(ii)(F)
	(g)	☐ Parent holding company, in accordance with Rule 13d-1(b)(1)(ii)(G).
	(h)	☐ Savings Association as defined in Section 3(b) of the Federal Deposit Insurance Act.
	(i)	☐ Church Plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act of 1940.
	(j)	☐ Non-U.S. institution in accordance with Rule 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with Rule 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: 2,962,555

(b)

Percent of Class: 4.4%

(c)

Number of shares as to which such person has:

(i)

Sole power to vote or to direct the vote: 0

(ii)

Shared power to vote or to direct the vote: 2,962,555

(iii)

Sole power to dispose or to direct the disposition of: 0

(iv)

Shared power to dispose or to direct the disposition of: 2,962,555

B.

Opportunities Parent

(a)

Amount beneficially owned: 2,962,555

(b)

Percent of Class: 4.4%

(c)

Number of shares as to which such person has:

(i)

Sole power to vote or to direct the vote: 0

(ii)

Shared power to vote or to direct the vote: 2,962,555

(iii)

Sole power to dispose or to direct the disposition of: 0

(iv)

Shared power to dispose or to direct the disposition of: 2,962,555

C.

Opportunities GP

(a)

Amount beneficially owned: 2,962,555

(b)

Percent of Class: 4.4%

(c)

Number of shares as to which such person has:

(i)

Sole power to vote or to direct the vote: 0

(ii)

Shared power to vote or to direct the vote: 2,962,555

(iii)

Sole power to dispose or to direct the disposition of: 0

(iv)

Shared power to dispose or to direct the disposition of: 2,962,555

D.

Opportunities Portfolio GP

(a)

Amount beneficially owned: 2,012,293

(b)

Percent of Class: 3.0%

(c)

Number of shares as to which such person has:

(i)

Sole power to vote or to direct the vote: 0

(ii)

Shared power to vote or to direct the vote: 2,012,293

(iii)

Sole power to dispose or to direct the disposition of: 0

(iv)

Shared power to dispose or to direct the disposition of: 2,012,293

E.

VGOP

(a)

Amount beneficially owned: 2,012,293

(b)

Percent of Class: 3.0%

(c)

Number of shares as to which such person has:

(i)

Sole power to vote or to direct the vote: 0

(ii)

Shared power to vote or to direct the vote: 2,012,293

(iii)

Sole power to dispose or to direct the disposition of: 0

(iv)

Shared power to dispose or to direct the disposition of: 2,012,293

F.

DRAGSA 96

(a)

Amount beneficially owned: 950,262

(b)

Percent of Class: 1.4%

(c)

Number of shares as to which such person has:

(i)

Sole power to vote or to direct the vote: 0

(ii)

Shared power to vote or to direct the vote: 950,262

(iii)

Sole power to dispose or to direct the disposition of: 0

(iv)

Shared power to dispose or to direct the disposition of: 950,262

G.

O. Andreas Halvorsen, David C. Ott and Rose S. Shabet

(a)

Amount beneficially owned: 2,962,555

(b)

Percent of Class: 4.4%

(c)

Number of shares as to which such person has:

(i)

Sole power to vote or to direct the vote: 0

(ii)

Shared power to vote or to direct the vote: 2,962,555

(iii)

Sole power to dispose or to direct the disposition of: 0

(iv)

Shared power to dispose or to direct the disposition of: 2,962,555

Item 5.

Ownership of Five Percent or Less of a Class.

Item 6.

Ownership of More than Five Percent on Behalf of Another Person.

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company.

Item 8.

Identification and Classification of Members of the Group.

Item 9.

Notice of Dissolution of Group.

Item 10.

Certification. (if filing pursuant to Rule 13d-1(c))

	By:	/s/ Scott M. Hendler
	Name:	Scott M. Hendler on behalf of O. Andreas Halvorsen (1)
	By:	/s/ Scott M. Hendler
	Name:	Scott M. Hendler on behalf of David C. Ott (2)
	By:	/s/ Scott M. Hendler
	Name:	Scott M. Hendler on behalf of Rose S. Shabet (3)

	By:	/s/ Scott M. Hendler
	Name:	Scott M. Hendler on behalf of O. Andreas Halvorsen (1)
	By:	/s/ Scott M. Hendler
	Name:	Scott M. Hendler on behalf of David C. Ott (2)
	By:	/s/ Scott M. Hendler
	Name:	Scott M. Hendler on behalf of Rose S. Shabet (3)