Dated February 2, 2012

Filed Pursuant to Rule 433

Registration No. 333-166404

Issuer Free Writing Prospectus

(Relating to the Preliminary Prospectus

Supplement dated January 31, 2012 and the

Prospectus dated May 11, 2010)

Gross proceeds:

JMP Securities LLC

162,587,279 shares of common stock, or 181,337,279 shares if the warrants offered in this offering are issued and exercised in full, based upon 131,337,279 shares of our common stock outstanding as of September 30, 2011 and excluding, as of that date:

•        9,937,284 shares of common stock issuable upon the exercise of outstanding stock options with a weighted average exercise price of $5.73 per share;

•        4,132,083 shares of common stock issuable upon the settlement of outstanding restricted stock units;

•        14,708,590 shares of common stock issuable upon the conversion of our outstanding 5.75% senior convertible notes due 2015 at a conversion price of approximately $6.80 per share and up to 2,041,820 shares issuable as make-whole premiums if the notes are converted in connection with certain fundamental changes;

•        5,117,523 shares of common stock issuable upon the conversion of our outstanding 3.75% senior convertible notes due 2013 at a conversion price of approximately $22.47 per share and up to 1,484,064 shares issuable as make-whole premiums if the notes are converted in connection with certain fundamental changes; and

•       8,497,236 shares of common stock available for future grant under our 2004 equity incentive plan, 2004 non-employee directors’ stock option plan and 2004 employee stock purchase plan.

The number of shares of common stock to be outstanding immediately after this offering also does not give effect to the shares and/or warrants issuable pursuant to the underwriters’ over-allotment option or the 31,250,000 restricted shares we may issue to The Mann Group LLC pursuant to the concurrent private placement described below.

Concurrent private placement of

common stock to The Mann Group, LLC:

Concurrently with this offering of shares of common stock and warrants, we are entering into an agreement to issue and sell to The Mann Group LLC, an entity controlled by our chief executive officer and principal stockholder, Alfred E. Mann, 31,250,000 restricted shares of our common stock, subject to the expiration or termination of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended (HSR) and receipt of stockholder approval to increase the number of MannKind’s authorized shares, as necessary. The price of the shares to be sold to The Mann Group will be $2.47 per share (the consolidated closing bid price for our common stock as reported by The NASDAQ Global Market on February 2, 2012), which will be paid by cancellation of principal indebtedness under our existing revolving loan arrangement with The Mann Group following receipt of applicable HSR clearance and stockholder approval, as necessary.

The delivery of the shares of common stock and warrants in this offering is not contingent upon the completion of the concurrent private placement, and the concurrent private placement is not contingent upon the completion of this offering.

Concurrent private offering of

convertible notes:

We are not pursuing the concurrent convertible note transaction previously described in the Preliminary Prospectus Supplement at this time.