Puma Falls on Disappointing Breast-Cancer Drug Results

Puma Biotechnology Inc. (PBYI) plunged the most ever after a company-sponsored study found only a suggestion of benefit with its experimental drug for breast cancer in one group of women whose tumors are driven by a specific protein.

Puma’s shares dropped 18 percent to $86.94 at the close in New York, the biggest single-day fall since April 23, 2012, about a month after the Los Angeles-based biotechnology company’s initial public offering.

A cocktail of drugs containing Puma’s neratinib given before surgery eliminated evidence of cancer in the breast and lymph nodes in 55.6 percent of women, compared with 32.6 percent of those given standard drug therapy, the company said in a statement. The improvement was seen in women with cancer fueled by the HER-2 protein and wasn’t definitive, particularly in cancers also sensitive to the hormone estrogen.

More than one-third of patients treated with neratinib developed moderate to severe diarrhea, compared with those given the standard therapy including Roche Holding AG (ROG)’s Herceptin. Puma adjusted other studies of neratinib that are already under way to include high doses of medicines designed to help prevent diarrhea.

The study, presented at the American Association for Cancer Research annual meeting in San Diego, was from the second of three phases usually needed to get U.S. regulatory approval. The data suggest the drug “has potent activity” when given with the generic medicine paclitaxel, Puma’s Chief Executive Officer Alan Auerback said in the statement.

The company plans to continue studying the drug in the I-SPY 3 Trial later this year, he said in a statement.

Puma’s shares had more than tripled in the past 12 months through April 4.

To contact the reporter on this story: Michelle Fay Cortez in Minneapolis at mcortez@bloomberg.net

To contact the editors responsible for this story: Reg Gale at rgale5@bloomberg.net Andrew Pollack, Bruce Rule

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