SEC Form 4

FORM 4		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 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* Flagship Ventures Fund 2007, L.P. (Last) (First) (Middle) ONE MEMORIAL DRIVE, 7TH FLOOR (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol Receptos, Inc. [ RCPT ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 05/14/2013
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	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	05/14/2013		C		1,152,039	A	$5.25	1,266,324	D(2)
Common Stock	05/14/2013		C		550,873	A	$7.73	1,817,197	D(2)
Common Stock	05/14/2013		P		107,142	A	$14	1,924,339	D(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 (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	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 (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (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: 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 A Preferred Stock	$5.25	05/14/2013		C(1)			8,640,289	(1)	(1)	Common Stock	1,152,039	$0	0	D(2)
Series B Preferred Stock	$7.73	05/14/2013		C(1)			4,131,552	(1)	(1)	Common Stock	550,873	$0	0	D(2)

1. Name and Address of Reporting Person* Flagship Ventures Fund 2007, L.P. (Last) (First) (Middle) ONE MEMORIAL DRIVE, 7TH FLOOR (Street) CAMBRIDGE MA 02142 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Flagship Ventures 2007 General Partner LLC (Last) (First) (Middle) ONE MEMORIAL DRIVE, 7TH FLOOR (Street) CAMBRIDGE MA 02142 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* KANIA EDWIN M JR (Last) (First) (Middle) ONE MEMORIAL DRIVE, 7TH FLOOR (Street) CAMBRIDGE MA 02142 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* AFEYAN NOUBAR (Last) (First) (Middle) ONE MEMORIAL DRIVE, 7TH FLOOR (Street) CAMBRIDGE MA 02142 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

Explanation of Responses:

1. The Series A preferred stock and Series B preferred stock converted upon the closing of the Issuer's initial public offering at a conversion ratio of 1 share of common stock for every 7.5 shares of Series A preferred stock and Series B preferred stock, for no additional consideration.

2. Beneficial ownership consists of: (i) 221,427 shares of common stock held by Flagship Ventures Fund 2007, L.P. ("Flagship Fund"); and (ii) an aggregate of 1,702,912 shares of common stock issued upon conversion of shares of Series A preferred stock and Series B preferred stock held by Flagship Fund. The general partner of Flagship Fund is Flagship Ventures 2007 General Partner LLC ("Flagship GP"), and the managing members of Flagship GP are Noubar B. Afeyan and Edwin M. Kania, Jr. The General Partner and Messrs. Afeyan and Kania have voting and investment control over the shares held by Flagship Fund and may be deemed to be the beneficial owners of such shares and each of them disclaims beneficial ownership of the shares except to the extent of his or its pecuniary interest therein.

	FLAGSHIP VENTURES FUND 2007, L.P. By: /s/ Noubar B. Afeyan	05/14/2013
	FLAGSHIP VENTURES 2007 GENERAL PARTNER LLC By: /s/ Noubar B. Afeyan	05/14/2013
	/s/ Edwin M. Kania, Jr.	05/14/2013
	/s/ Noubar B. Afeyan	05/14/2013
	** Signature of Reporting Person	Date
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* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
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