Seres Therapeutics (MCRB) Form 3 Seres Therapeutics / DAVID N COOK ownership change

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^*

COOK DAVID N

(Last) (First) (Middle)

C/O SERES THERAPEUTICS, INC.

215 FIRST STREET

(Street)

CAMBRIDGE MA 02142

(City) (State) (Zip)

2. Date of Event Requiring Statement (Month/Day/Year)
06/25/2015

3. Issuer Name and Ticker or Trading Symbol
Seres Therapeutics, Inc. [ MCRB ]

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director	10% Owner
X	Officer (give title below)	Other (specify below)
CSO and EVP of R&D

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	184,219	D

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
Stock Option (right to buy)	(1)	05/16/2023	Common Stock	143,281	0.48	D
Series B Convertible Preferred Stock	(2)	(2)	Common Stock	45,454	(2)	D

Explanation of Responses:

1. The option vested as to 25% of the shares on October 24, 2013. The remainder of the shares vested or will vest in 12 equal quarterly installments thereafter.

2. The Series B Convertible Preferred Stock is convertible into Common Stock on a one-for-one basis and has no expiration date. Each share of Series B Convertible Preferred Stock will convert into Common Stock upon the listing of the issuer's securities on The NASDAQ Global Select Market.

Remarks:

Exhibit List: Exhibit 24 - Power of Attorney

	/s/ Eric D. Shaff, Attorney-in-Fact	06/25/2015
	** 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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