Exhibit 4.1

COMMON STOCK

PAR VALUE $0.001

COMMON STOCK

THIS CERTIFICATE IS TRANSFERABLE IN CANTON, MA, JERSEY CITY, NJ AND

COLLEGE STATION, TX

OncoMed PHARMACEUTICALS

Certificate Number

ZQ00000000

ONCOMED PHARMACEUTICALS, INC.

INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

Shares

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THIS CERTIFIES THAT

** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. MR. Alexander David SAMPLE Sample **** Mr. Alexander David &Sample MRS. **** Mr. Alexander SAMPLE David Sample **** Mr. Alexander & David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander MR. David Sample SAMPLE **** Mr. Alexander David Sample **** &Mr. Alexander MRS. David Sample SAMPLE **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Alexander David Sample **** Mr. Sample **** Mr. Sample

CUSIP 68234X 10 2

SEE REVERSE FOR CERTAIN DEFINITIONS

is the owner of

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FULLY-PAID AND NON-ASSESSABLE SHARES OF COMMON STOCK OF

OncoMed Pharmaceuticals, Inc. (hereinafter called the “Company”), transferable on the books of the Company in person or by duly authorized attorney, upon surrender of this Certificate properly endorsed. This Certificate and the shares represented hereby, are issued and shall be held subject to all of the provisions of the Certificate of Incorporation, as amended, and the Bylaws, as amended, of the Company (copies of which are on file with the Company and with the Transfer Agent), to all of which each holder, by acceptance hereof, assents. This Certificate is not valid unless countersigned and registered by the Transfer Agent and Registrar.

Witness the facsimile signatures of its duly authorized officers.

President and Chief Executive Officer

DATED DD-MMM-YYYY

COUNTERSIGNED AND REGISTERED:

COMPUTERSHARE TRUST COMPANY, N.A.

TRANSFER AGENT AND REGISTRAR,

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ONCOMED PHARMACEUTICALS, INC.

THE COMPANY IS AUTHORIZED TO ISSUE TWO CLASSES OF STOCK, COMMON STOCK AND PREFERRED STOCK. THE BOARD OF DIRECTORS OF THE COMPANY HAS AUTHORITY TO FIX THE NUMBER OF SHARES AND THE DESIGNATION OF ANY SERIES OF PREFERRED STOCK AND TO DETERMINE OR ALTER THE RIGHTS, PREFERENCES, PRIVILEGES AND RESTRICTIONS GRANTED TO OR IMPOSED UPON ANY UNISSUED SERIES OF PREFERRED STOCK.

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:

TEN COM - as tenants in common

TEN ENT - as tenants by the entireties

JT TEN - as joint tenants with right of survivorship

and not as tenants in common

UNIF GIFT MIN ACT - Custodian

(Cust) (Minor)

under Uniform Gifts to Minors Act

(State)

UNIF TRF MIN ACT - Custodian (until age)

(Cust)

under Uniform Transfers to Minors Act

(Minor) (State)

Additional abbreviations may also be used though not in the above list.

THE COMPANY SHALL FURNISH WITHOUT CHARGE TO EACH STOCKHOLDER WHO SO REQUESTS A STATEMENT OF THE POWERS, DESIGNATIONS, PREFERENCES AND RELATIVE, PARTICIPATING, OPTIONAL OR OTHER SPECIAL RIGHTS OF EACH CLASS OF STOCK OF THE COMPANY OR SERIES THEREOF AND THE QUALIFICATIONS, LIMITATIONS OR RESTRICTIONS OF SUCH PREFERENCES AND/OR RIGHTS. SUCH REQUESTS SHALL BE MADE TO THE COMPANY’S SECRETARY AT THE PRINCIPAL OFFICE OF THE COMPANY.

PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING NUMBER OF ASSIGNEE

For value received, hereby sell, assign and transfer unto

(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING POSTAL ZIP CODE, OF ASSIGNEE)

Shares

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 Company with full power of substitution in the premises.

Dated: 20 Signature(s) Guaranteed: Medallion Guarantee Stamp THE SIGNATURE(S) SHOULD 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 S.E.C. RULE 17Ad-15.

Signature:

Signature:

Notice: 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.

SECURITY INSTRUCTIONS

THIS IS WATERMARKED PAPER, DO NOT ACCEPT WITHOUT NOTING WATERMARK, HOLD TO LIGHT TO VERIFY WATERMARK.

The IRS requires that we report the cost basis of certain shares acquired after January 1, 2011. If your shares were covered by the legislation and you have sold or transferred the shares and requested a specific cost basis calculation method, we have processed as requested. If you did not specify a cost basis calculation method, we have defaulted to the first in, first out (FIFO) method. Please visit our website or consult your tax advisor if you need additional information about cost basis.

If you do not keep in contact with us or do not have any activity in your account for the time periods specified by state law, your property could become subject to state unclaimed property laws and transferred to the appropriate state.

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