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.

Must Read: Warren Buffett's 25 Favorite Stocks

STOCKS TO BUY: TheStreet Quant Ratings has identified a handful of stocks that can potentially TRIPLE in the next 12 months. Learn more.

PBYI Price Chart

PBYI Price data by YCharts

STOCKS TO BUY: TheStreet Quant Ratings has identified a handful of stocks that can potentially TRIPLE in the next 12 months. Learn more.

Editor's Note: Any reference to TheStreet Ratings and its underlying recommendation does not reflect the opinion of TheStreet, Inc. or any of its contributors including Jim Cramer or Stephanie Link.

More from Markets

Apple and GE Switch Roles; Musk's Super Control of Tesla Explained -- ICYMI

Apple and GE Switch Roles; Musk's Super Control of Tesla Explained -- ICYMI

Trump May Be More to Blame For Higher Oil Prices Than OPEC

Trump May Be More to Blame For Higher Oil Prices Than OPEC

Dow Falls Over 200 Points as Apple's Slump Offsets Gains in General Electric

Dow Falls Over 200 Points as Apple's Slump Offsets Gains in General Electric

Week Ahead: Major Earnings on Tap as Wall Street Readies for Geopolitical Moves

Week Ahead: Major Earnings on Tap as Wall Street Readies for Geopolitical Moves

3 Hot Reads From TheStreet's Top Premium Columnists

3 Hot Reads From TheStreet's Top Premium Columnists