Receptos, Inc. Watch

from S-3ASR 55 pages Receptos, Inc. to [ ] Trustee Indenture Dated as of L Receptos, Inc. Reconciliation and Tie Between Trust Indenture Act of 1939 and Indenture, Dated as of —

from S-3ASR 55 pages Receptos, Inc. to [ ] Trustee Indenture Dated as of L Receptos, Inc. Reconciliation and Tie Between Trust Indenture Act of 1939 and Indenture, Dated as of —

from S-1/A 6 pages Form of Omnibus Acknowledgment and Agreement With Respect to Potential Initial Public Offering

from S-1/A 1 page Common Stock Cusip 756207 10 6 See Reverse for Certain Definitions Countersigned and Registered: American Stock Transfer & Trust Company, LLC (Brooklyn, N.Y.) Transfer Agent and Registrar by Authorized Signature Fully Paid and Non-Assessable Shares of the Common Stock, $0.001 Par Value Per Share, of Vice President, Finance and Administration President and Chief Executive Officer Transferable Only on the Books of the Corporation in Person or by Duly Authorized Attorney Upon Surrender of This Certificate Properly Endorsed. This Certificate and the Shares Represented Hereby Are Subject to the Laws of the State of Delaware, and to the Certificate of Incorporation and Bylaws of the Corporation, as Now or Hereafter Amended. This Certificate Is Not Valid Unless Countersigned by the Transfer Agent and Registered by the Registrar. Witness the Facsimile Seal of the Corporation and the Facsimile Signatures of Its Duly Authorized Officers. Dated This Certifies That Is the Owner of Rec Receptos, Inc. Incorporated Under the Laws of the State of Delaware Receptos, Inc. Delaware Seal 2 0 0 8 Corporate Receptos, Inc

from S-1 42 pages Third Amended and Restated Right of First Refusal and Co-Sale Agreement

from S-1 13 pages Approval With Respect to Series B Preferred Stock Purchase Agreement

from S-1 17 pages Omnibus Approval and Amendment With Respect To: Series B Preferred Stock Purchase Agreement; and Third Amended and Restated Investors’ Rights Agreement

from S-1 18 pages Omnibus Approval and Amendment With Respect To: Series B Preferred Stock Purchase Agreement; and Third Amended and Restated Investors’ Rights Agreement

from S-1 42 pages Third Amended and Restated Investors’ Rights Agreement

from S-1 21 pages Warrant to Purchase Common Stock of Receptos, Inc

from DRS 42 pages Third Amended and Restated Right of First Refusal and Co-Sale Agreement

from DRS 13 pages Approval With Respect to Series B Preferred Stock Purchase Agreement

from DRS 17 pages Omnibus Approval and Amendment With Respect To: Series B Preferred Stock Purchase Agreement; and Third Amended and Restated Investors’ Rights Agreement

from DRS 18 pages Omnibus Approval and Amendment With Respect To: Series B Preferred Stock Purchase Agreement; and Third Amended and Restated Investors’ Rights Agreement

from DRS 42 pages Third Amended and Restated Investors’ Rights Agreement

from DRS 21 pages Warrant to Purchase Common Stock of Receptos, Inc