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.

UNIF GIFT MIN ACT – Custodian (Cust) (Minor) under Uniform Gifts to Minors Act (State) The following abbreviations, when used in the inscription on the face of this certificate, shall be construed as though they were written out in full according to applicable laws or regulations: THE COMPANY WILL FURNISH WITHOUT CHARGE TO EACH STOCKHOLDER WHO SO REQUESTS, A SUMMARY OF THE POWERS, DESIGNATIONS, PREFERENCES AND RELATIVE, PARTICIPATING, OPTIONAL OR OTHER SPECIAL RIGHTS OF EACH CLASS OF STOCK OF THE COMPANY AND THE QUALIFICATIONS, LIMITATIONS OR RESTRICTIONS OF SUCH PREFERENCES AND RIGHTS, AND THE VARIATIONS IN RIGHTS, PREFERENCES AND LIMITATIONS DETERMINED FOR EACH SERIES, WHICH ARE FIXED BY THE CERTIFICATE OF INCORPORATION OF THE COMPANY, AS AMENDED, AND THE RESOLUTIONS OF THE BOARD OF DIRECTORS OF THE COMPANY, AND THE AUTHORITY OF THE BOARD OF DIRECTORS TO DETERMINE THE VARIATIONS FOR FUTURE SERIES. SUCH REQUEST MAY BE MADE TO THE OFFICE OF THE SECRETARY OF THE COMPANY OR TO THE TRANSFER AGENT. THE BOARD OF DIRECTORS MAY REQUIRE THE OWNER OF A LOST OR DESTROYED STOCK CERTIFICATE, OR HIS OR HER LEGAL REPRESENTATIVES, TO GIVE THE COMPANY A BOND TO INDEMNIFY IT AND ITS TRANSFER AGENTS AND REGISTRARS AGAINST ANY CLAIM THAT MAY BE MADE AGAINST THEM ON ACCOUNT OF THE ALLEGED LOSS OR DESTRUCTION OF ANY SUCH CERTIFICATE. TEN COM TEN ENT JT TEN as tenants in common as tenants by the entireties as joint tenants with right of survivorship and not as tenants in common Additional abbreviations may also be used though not in the above list. of the common stock represented by the within Certificate, and do hereby irrevocably constitute and appoint Attorney to transfer the said stock on the books of the within-named Corporation with full power of substitution in the premises. Dated, For value received, hereby sell, assign and transfer unto PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING NUMBER OF ASSIGNEE Shares PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS INCLUDING POSTAL ZIP CODE OF ASSIGNEE SIGNATURE(S) GUARANTEED: THE SIGNATURE(S) MUST BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM), PURSUANT TO SEC RULE 17Ad-15. THE SIGNATURE TO THIS ASSIGNMENT MUST CORRESPOND WITH THE NAME AS WRITTEN UPON THE FACE OF THE CERTIFICATE, IN EVERY PARTICULAR, WITHOUT ALTERATION OR ENLARGEMENT, OR ANY CHANGE WHATEVER. NOTICE: