Exhibit 5.1

July 31, 2000



Esperion Therapeutics, Inc.
3621 S. State Street, 695 KMS Place
Ann Arbor, MI 48108


Re:  Public Offering of 6,900,000 Shares of Common Stock,
     $0.001 Par Value Per Share, of Esperion Therapeutics, Inc.
     ----------------------------------------------------------

Ladies and Gentlemen:

We have acted as counsel to Esperion Therapeutics, Inc., a Delaware corporation
(the "Company"), in connection with the preparation of the subject registration
statement on Form S-1 (as such may be amended or supplemented, 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 $0.001 per share (the "Common
Stock") to be sold in a public offering (the "Offering"), including 900,000
shares of Common Stock issuable pursuant to an over-allotment option granted to
the Underwriters, 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 Certificate of Incorporation, as amended to date;
(c) the Company's Bylaws, as amended to date; (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
FleetBoston Robertson Stephens Inc., Chase Securities Inc. and U.S. Bancorp
Piper Jaffray Inc. as representatives of the underwriters for the Offering (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, and in reliance thereon, we are of the opinion that
the Shares to be sold by the Company as described in the Registration Statement,
upon approval by the pricing committee duly authorized by the Company's Board of
Directors, 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 Exhibit 5.1 to the Registration
Statement and further consent to the use of our name wherever appearing in the
Registration Statement, including the prospectus constituting a part thereof,
and any amendment thereto.  In giving such opinion and consent, 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