Sec Form 3 Filing - VIKING GLOBAL INVESTORS LP @ Amylyx Pharmaceuticals, Inc. - 2022-01-06

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

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, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person VIKING GLOBAL INVESTORS LP 2. Issuer Name and Ticker or Trading Symbol Amylyx Pharmaceuticals, Inc. [ AMLX] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 55 RAILROAD AVENUE, 3. Date of Earliest Transaction (MM/DD/YY) 01/06/2022 (Street) GREENWICH, CT06830 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 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

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 (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 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 (MM/DD/YY) 7. Title and Amount of Underlying Securities (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 of Derivative Security: 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 Series C-1 Preferred Stock ( 1 ) ( 1 ) ( 1 ) Common Stock 4,870,536 I See Explanation of Responses( 2 )( 3 )( 4 )

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other VIKING GLOBAL INVESTORS LP 55 RAILROAD AVENUE GREENWICH, CT06830 X Ott David C. 55 RAILROAD AVENUE GREENWICH, CT06830 X HALVORSEN OLE ANDREAS 55 RAILROAD AVENUE GREENWICH, CT06830 X Shabet Rose Sharon 55 RAILROAD AVENUE GREENWICH, CT06830 X Viking Global Opportunities Illiquid Investments Sub-Master LP MAPLES CORPORATE SERVICES LIMITED PO BOX 309, UGLAND HOUSE GRAND CAYMAN, E9KY1-1104 X Viking Global Opportunities GP LLC 55 RAILROAD AVENUE GREENWICH, CT06830 X Viking Global Opportunities Portfolio GP LLC 55 RAILROAD AVENUE GREENWICH, CT06830 X Viking Global Opportunities Parent GP LLC 55 RAILROAD AVENUE GREENWICH, CT06830 X Signatures /s/ Scott M. Hendler signing on behalf of O. Andreas Halvorsen (5)(6) 01/11/2022 Signature of Reporting Person Date /s/ Scott M. Hendler signing on behalf of David C. Ott (5)(6) 01/11/2022 Signature of Reporting Person Date /s/ Scott M. Hendler signing on behalf of Rose S. Shabet (5)(6) 01/11/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )Each share of Series C-1 preferred stock is convertible on a one-for-one basis into Common Stock at any time at the election of the Reporting Persons (defined in footnote 4 below) and will automatically convert upon the closing of the Issuer's initial public offering into the number of shares of the Issuer's Common Stock shown in column 3 without payment or further consideration. The Series C-1 Preferred stock has no expiration date. ( 2 )Andreas Halvorsen, David C. Ott and Rose S. Shabet are Executive Committee members of certain management entities, including Viking Global Partners LLC, the general partner of Viking Global Investors LP ("VGI"), and Viking Global Opportunities Parent GP LLC ("Parent"), which is the sole member of Viking Global Opportunities GP LLC ("Opportunities GP"), which is the sole member of Viking Global Opportunities Portfolio GP LLC ("Opportunities Portfolio GP"). VGI provides managerial services to various investment funds and vehicles, including Viking Global Opportunities Illiquid Investments Sub-Master LP ("Opportunities Fund"). Opportunities Portfolio GP is the general partner of Opportunities Fund. ( 3 )These shares are held directly by Opportunities Fund. Because of the relationship between VGI and Opportunities Fund, VGI may be deemed to beneficially own the shares held directly by Opportunities Fund. Because of the relationship between Parent, Opportunities GP, Opportunities Portfolio GP and Opportunities Fund, each of Parent, Opportunities GP and Opportunities Portfolio GP may be deemed to beneficially own the shares held directly by Opportunities Fund. ( 4 )Each of VGI, Parent, Opportunities GP, Opportunities Portfolio GP, Opportunities Fund, Mr. Halvorsen, Mr. Ott and Ms. Shabet (collectively the "Reporting Persons") may be deemed to beneficially own all of the securities reported on this form. The Reporting Persons disclaim beneficial ownership of these securities except to the extent of their pecuniary interest therein, and the inclusion of these securities in this report shall not be deemed an admission of beneficial ownership of the reported securities for purposes of Section 16 of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), or for any other purpose.

Remarks: (5) The Reporting Persons are jointly filing this Form 3 pursuant to Rule 16a-3(j) under the Exchange Act.(6) Scott M. Hendler is signing on behalf of Mr. Halvorsen, Mr. Ott and Ms. Shabet, each individually and as an Executive Committee Member of VIKING GLOBAL PARTNERS LLC, on behalf of VIKING GLOBAL INVESTORS LP, and as an Executive Committee Member of VIKING GLOBAL OPPORTUNITIES PARENT GP LLC, on behalf of itself and VIKING GLOBAL OPPORTUNITIES GP LLC, VIKING GLOBAL OPPORTUNITIES PORTFOLIO GP LLC, and VIKING GLOBAL OPPORTUNITIES ILLIQUID INVESTMENTS SUB-MASTER LP, pursuant to authorization and designation letters dated February 9, 2021, which were filed with the Securities and Exchange Commission on June 7, 2021.

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).

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