MannKind Trades Heavily on Insulin Scare

"Given current market sentiment, we have decided to suspend partnership discussions," MannKind said Thursday. MannKind also said it will not be able to get a fair price for the product until late stage clinical data is available.

Shares of Valencia, Calif.-based MannKind Corp. plunged 60 percent Wednesday, setting an all-time low after Pfizer Inc. said a few patients who used Nektar Therapeutics' inhaled insulin Exubera in clinical trials developed lung cancer.

MannKind said that Technosphere Insulin has never been linked to lung cancer in preclinical trials, but noted that it would be difficult to find a partner at present.

Pfizer, which has a partnership with Nektar to develop and market Exubera, said there were too few cases to prove that Exubera was linked to cancer.

Piper Jaffray analyst Thomas Wei downgraded MannKind to "Neutral" from "Buy" Thursday, and UBS analyst Annabel Samimy lowered her rating to "Sell" from "Buy."

MannKind Corp. shares added 18 cents, or 7.7 percent, to $2.53 at more than double their average daily trading volume Thursday.