EXHIBIT 5.1



                        [COOLEY GODWARD LLP LETTERHEAD]



July 29, 2004


MannKind Corporation
28903 North Avenue Paine
Valencia, CA 91355

Ladies and Gentlemen:

You have requested our opinion with respect to certain matters in connection
with the filing by MannKind Corporation, a Delaware Corporation (the "Company"),
of a Registration Statement on Form S-8 (the "Registration Statement") with the
Securities and Exchange Commission covering the offering of an aggregate of up
to 8,592,848 shares of the Company's Common Stock, $0.01 par value (the
"SHARES"), including (a) 5,000,000 shares reserved for issuance under the
Company's 2004 Equity Incentive Plan, 800,000 shares reserved for issuance under
the Company's 2004 Non-Employee Directors' Stock Option Plan, 2,000,000 shares
reserved for future grants under the Company's 2004 Employee Stock Purchase
Plan, 126,099 shares reserved for issuance under the Pharmaceutical Discovery
Corporation 1991 Stock Option Plan, 305,430 shares reserved for issuance under
the Pharmaceutical Discovery Corporation 1999 Stock Plan, 14,366 shares reserved
for issuance under the AlleCure Corp. 2000 Stock Option and Stock Plan, and
105,981 shares reserved for issuance under the CTL ImmunoTherapies Corp. 2000
Stock Option and Stock Plan (collectively, the "PLANS"), and (b) 240,972 shares
reserved for issuance upon exercise of stock options granted outside of the
Plans (the "NON-PLAN OPTION GRANTS").

In connection with this opinion, we have examined the Registration Statement and
related Prospectuses, the Company's Amended and Restated Certificate of
Incorporation and Bylaws, the Plans, 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.

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 Plans or the
Non-Plan Option Grants, the Registration Statement, and related Prospectuses,
will be validly issued, fully paid, and nonassessable (except as to shares
issued pursuant to certain deferred payment arrangements, which will be fully
paid and nonassessable when such deferred payments are made in full).

We consent to the filing of this opinion as an exhibit to the Registration
Statement.

Very truly yours,

COOLEY GODWARD LLP



By: /s/ Jeremy D. Glaser
    -----------------------------
        Jeremy D. Glaser, Esq.