Why Puma Biotechnology (PBYI) Stock Is Plunging Today

NEW YORK (TheStreet) -- Puma Biotechnology  (PBYI) plunged Monday after GlaxoSmithKline  (GSK) announced its drug Tykerb, designed to treat adjuvant breast cancer, missed its primary endpoint in a Phase III trial. 

Puma is also trying to develop a breast cancer drug, PB272, for the treatment of HER2 positive metastatic breast cancer. The company actually reported positive results from its ongoing Phase II clinical trial of its experimental drug to treat breast cancer that has metastasized to the brain, but the GlaxoSmithKline news sent the stock plummeting.

The stock was down 21.14% to $60.27 at 11:22 a.m.

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