<PAGE> 1
EXHIBIT 5.1
Letterhead of Morgan, Lewis & Bockius LLC
July 25, 2000
Arena Pharmaceuticals, Inc.
6166 Nancy Ridge Drive
San Diego, California 92121
Re: Public Offering of 6,900,000 Shares of Common Stock,
$0.0001 Par Value Per Share, of Arena Pharmaceuticals, Inc.
Ladies and Gentlemen:
We have acted as counsel to Arena Pharmaceuticals, Inc., a Delaware corporation
(the "Company"), in connection with the preparation of the subject Registration
Statement on Form S-1, File No. 333-35944, including the amendments thereto (the
"Registration Statement") filed with the Securities and Exchange Commission
pursuant to the Securities Act of 1933, as amended (the "Act"), to register up
to 6,900,000 shares (the "Shares") of Common Stock, par value $0.0001 per share
(the "Common Stock") to be sold in a public offering (the "Offering"), including
900,000 shares of Common Stock subject to an over-allotment option, all of which
shares are authorized but heretofore unissued.
In rendering the opinion set forth below, we have reviewed (a) the Registration
Statement; (b) the Company's Fourth Amended and Restated Certificate of
Incorporation to be filed with the Secretary of the State of Delaware prior to
the issuance and sale of the Shares; (c) the Company's By-Laws; (d) certain
records of the Company's corporate proceedings as reflected in its minute and
stock books; (e) the form of Underwriting Agreement filed as Exhibit 1.1 to the
Registration Statement (the "Underwriting Agreement"), to be executed by the
Company and ING Barings LLC for itself and the several underwriters named in
Schedule I thereto (the "Underwriters"); and (f) such records, documents,
statutes and decisions as we have deemed relevant. In our examination, we have
assumed the genuineness of all signatures, the authenticity of all documents
submitted to us as originals and the conformity with the original of all
documents submitted to us as copies thereof.
Based upon the foregoing, we are of the opinion that the Shares to be sold by
the Company as described in the Registration Statement, when and to the extent
purchased by the Underwriters in accordance with the Underwriting Agreement,
will be validly issued, fully paid and nonassessable. We hereby consent to the
use of this opinion as
<PAGE> 2
Exhibit 5.1 to the Registration Statement and to the reference to this firm
under the caption "Legal Matters." In giving such opinion, we do not thereby
admit that we are acting within the category of persons whose consent is
required under Section 7 of the Act or the rules or regulations of the
Securities and Exchange Commission promulgated thereunder.
Very truly yours,
/s/ Morgan, Lewis & Bockius LLP
