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EXHIBIT 5.1
[COOLEY GODWARD LLP LETTERHEAD]
September 21, 2000
ONYX Pharmaceuticals, Inc.
3031 Research Drive
Richmond, CA 94806
Ladies and Gentlemen:
You have requested our opinion with respect to certain matters in connection
with the filing by ONYX Pharmaceuticals, Inc. (the "Company") of a Registration
Statement on Form S-3 (the "Registration Statement") with the Securities and
Exchange Commission covering an underwritten public offering of up to 3,450,000
(including 450,000 shares for which the underwriters have been granted an over-
allotment option) shares of the Company's common stock (the "Shares"). Defined
terms used herein shall have the meanings attributed to such terms in the
Registration Statement unless otherwise stated herein.
In connection with this opinion, we have examined and relied upon the
Registration Statement, the Company's Amended and Restated Certificate of
Incorporation and Amended and Restated Bylaws, and such other documents,
records, certificates, memoranda and other instruments as we deem necessary as a
basis for this opinion. We have assumed the genuineness and authenticity of all
documents submitted to us as originals, the conformity to originals of all
documents submitted to us as copies thereof, and the due execution and delivery
of all documents where due execution and delivery are a prerequisite to the
effectiveness thereof. We have assumed that the Shares will be sold by the
Underwriters at a price established by the Pricing Committee of the Board of
Directors of the Company.
On the basis of the foregoing, and in reliance thereon, we are of the opinion
that the Shares, when sold and issued in accordance with the Registration
Statment, will be validly issued, fully paid, and nonassessable.
We consent to the filing of this opinion as an exhibit to the Registration
Statement and to the reference to our firm under the caption "Legal Matters" in
the prospectus included in the Registration Statement.
Very truly yours,
Cooley Godward LLP
By: /s/ Robert L. Jones
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Robert L. Jones
