MannKind Corp. shares dropped nearly 15 percent on Tuesday after the cash-strapped biotech said that it plans to sell $50 million worth of stock and warrants in a public offering. The company also announced plans to issue additional restricted shares and make a private placement of up to $161 million of convertible notes.

The Valencia company founded by medical device billionaire Al Mann said it would sell units consisting of one share of MannKind's common stock and a warrant to purchase 0.6 of a share of common stock at a future date. The $50 million issuance amounts to about 15 percent of its market cap of $330 million as of the end of trading Tuesday.

The company currently has more than 122 million shares outstanding, with a public float of 79.4 million. Mann is the largest single shareholder, controlling 32 percent of shares, and also holds through his Mann Group LLC a $350 million promissory note.

Concurrent with the offering, MannKind said it intends in a separate private placement to issue Mann Group restricted shares of common stock in exchange for cancellation of the debt. But it wasn’t disclosed whether the transaction would cancel all $350 million.

MannKind is raising money to bring its first product to market, an inhaled form of insulin that works faster that the injected form of the drug. In January 2011, the Food and Drug Administration decided to require the company to conduct additional studies to confirm the safety and effectiveness of a new insulin inhaler. MannKind now is enrolling diabetics to participate in more studies, which could be completed by the end of the year.

The company on Tuesday cautioned that there was no assurance as to whether or when these new offerings might be completed. Last September, MannKind announced plans to sell senior secured discount notes to raise about $370 million to help pay for the additional drug trials, but never carried out the sale.

Jefferies & Company Inc., Piper Jaffray & Co. and Cowen and Company LLC will act as joint book-running managers on the public offerings.

Shares closed down 47 cents, or 14.8 percent, to $2.70 on the Nasdaq.