SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person* Barrett Peter (Last) (First) (Middle) C/O SYNLOGIC, INC. 200 SIDNEY STREET, SUITE 320 (Street) CAMBRIDGE MA 02139 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 08/28/2017	3. Issuer Name and Ticker or Trading Symbol SYNLOGIC, INC. [ SYBX ]
		4. Relationship of Reporting Person(s) to Issuer (Check all applicable) X Director 10% Owner Officer (give title below) Other (specify below)	5. If Amendment, Date of Original Filed (Month/Day/Year)
			6. Individual or Joint/Group Filing (Check Applicable Line) X Form filed by One Reporting Person Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock	2,651,963(1)	I	By Atlas Venture Fund IX, L.P.(1)(2)(3)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Shares of capital stock of the corporation then known as Synlogic, Inc. ("Old Synlogic") were converted into shares of the Issuer pursuant to that certain Agreement and Plan of Merger and Reorganization, dated as of May 15, 2017, by and among the Issuer, Meerkat Merger Sub, Inc. and Old Synlogic (the "Merger Agreement"). Pursuant to the terms of the Merger Agreement, each share of capital stock was exchanged for 0.5532 shares of the Issuer's common stock, after giving effect to a reverse split of the Issuer's common stock of 7-to-1.

2. Represents (i) 500,000 shares of common stock of Old Synlogic, (ii) 559,770 shares of Series A-1 preferred stock of Old Synlogic, (iii) 790,476 shares of Series A-2 preferred stock of Old Synlogic, (iv) 1,474,998 shares of Series A-3 preferred stock of Old Synlogic, (v) 1,096,408 shares of Series B preferred stock of Old Synlogic and (vi) 372,209 shares of Series C preferred stock of Old Synlogic, in each case prior to conversion pursuant to the Merger Agreement.

3. The reportable securities are owned by Atlas Venture Fund IX, L.P. ("Atlas IX"). Atlas Venture Associates IX, L.P. ("AVA IX LP"), is the general partner of Atlas IX, and Atlas Venture Associates IX, LLC ("AVA IX LLC"), is the general partner of AVA IX LP. The Reporting Person disclaims Section 16 beneficial ownership of the securities held by Atlas IX, except to the extent of his pecuniary interest therein, if any.

Remarks:

	/s/ Peter Barrett	08/30/2017
	** 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 5 (b)(v).
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