Sec Form 3 Filing - Flagship Pioneering Inc. @ Axcella Health Inc. - 2022-10-13

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 Flagship Pioneering Inc. 2. Issuer Name and Ticker or Trading Symbol Axcella Health Inc. [ AXLA] 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 CAMBRIDGE PARKWAY, SUITE 800E 3. Date of Earliest Transaction (MM/DD/YY) 10/13/2022 (Street) CAMBRIDGE, MA02142 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 Common Stock 3,048,780( 1 ) I By FPA, L.P.( 2 )

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

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other Flagship Pioneering Inc. 55 CAMBRIDGE PARKWAY, SUITE 800 E CAMBRIDGE, MA02142 X FPA General Partner LLC 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE, MA02142 X FPA, L.P. 55 CAMBRIDGE PARKWAY, SUITE 800E CAMBRIDGE, MA02142 X Signatures Flagship Pioneering, Inc., By: /s/ Noubar B. Afeyan, PhD., Name: Noubar B. Afeyan, Ph.D., Title: Chief Executive Officer 10/17/2022 Signature of Reporting Person Date FPA General Partner LLC, By: Flagship Pioneering, Inc., its manager, By: /s/ Noubar B. Afeyan, PhD., Name: Noubar B. Afeyan, Ph.D., Title: Chief Executive Officer 10/17/2022 Signature of Reporting Person Date FPA, L.P., By: FPA General Partner LLC, its general partner, By: Flagship Pioneering, Inc., its manager, By: /s/ Noubar B. Afeyan, PhD., Name: Noubar B. Afeyan, Ph.D., Title: Chief Executive Officer 10/17/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On October 13, 2022, FPA, L.P. ("FPA Fund") purchased 3,048,780 shares of the Issuer's Common Stock in a registered direct offering at a price of $1.64 per share pursuant to a Securities Purchase Agreement dated October 13, 2022 ( 2 )Shares held by FPA Fund. FPA General Partner LLC ("FPA Fund GP") is the general partner of FPA Fund. Flagship Pioneering, Inc. ("Flagship Pioneering") is the manager of FPA Fund GP. Noubar B. Afeyan, Ph.D. is the CEO and sole stockholder of Flagship Pioneering. Each of the reporting persons except for FPA Fund disclaims beneficial ownership of such shares except to the extent of his or its pecuniary interest therein.

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).

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