Pfizer Adds Lung Cancer Warning to Exubera Insulin

Pfizer and Nektar Therapeutics said Wednesday clinical trials of the inhaled insulin Exubera found increased cases of lung cancer, leading Nektar to end talks with potential partners to market the product.

Nektar shares tumbled in early trading, while shares of MannKind , which has been developing its own inhaled insulin, plummeted more than 56 percent. Pfizer was little changed at $21.00.

Over the course of the clinical trials, Pfizer said six of the 4,740 Exubera-treated patients versus one of the 4,292 patients not treated with Exubera developed lung cancer. One lung cancer case was also found after Exubera reached the market.

Pfizer updated the Exubera labeling to include a warning with safety information about lung cancer cases found in patients who used Exubera, which U.S. regulators approved in January 2006.

The warning states all patients who developed lung cancer had a prior history of cigarette smoking, and that there were too few cases to determine whether the development of lung cancer is related to Exubera use.

Pfizer said in October it would stop marketing Exubera, ending its involvement with a product once thought to have the potential to become a $2 billion-a-year blockbuster with the promise of helping diabetics avoid needle sticks. Instead, sales were negligible.

The warning in the label stemmed from an ongoing review of data from the Exubera clinical trial program and post-marketing experience by Pfizer and the U.S. Food and Drug Administration, Pfizer said.

Pfizer said it will be discussing the timing of marketing authorization withdrawals with regulatory agencies.

Since Pfizer's exit last year, Eli Lilly and Novo Nordisk also ended inhaled insulin development programs.

Nektar said it will cease all spending associated with its inhaled insulin programs and will not incur charges related to the event.