Shares of Puma Biotechnology plummeted Thursday on disappointing results from a study of the company's breast cancer drug.
The study involved treatment through the use of Puma's neratinib in combination with the breast cancer drug Herceptin as well as chemotherapy. While 93.9 percent of the patients taking the drug combination were still alive two years later, it wasn't substantially better than the 91.6 percent of patients who were treated with only Herceptin and chemotherapy.
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The drug's backers had been hoping to see better results within the range of a 3 percent improvement.
Shares fell $36.92, or 17.6 percent, to $172.80 in afternoon trading.
Puma shares have been extremely volatile on news stemming from the drug, yet a number of industry analysts were not so quick to discredit neratinib following the study.
Citgroup analyst Dr. Yaron Werber said that the data has several positive points, despite falling just shy of initial expectations. He pointed out that primary and secondary endpoint rates actually topped expectations when it includes only women confirmed with the HER2 protein, which is about 80 percent of all women.
The company said in December that it would hold off on filing for marketing approval of neratinib because it decided to ask the Food and Drug Administration to approve the drug as a treatment for cancer that has metastasized instead of early-stage cancer. It now intends to file for approval in the first quarter of 2016 instead of its previous date of the first half of 2015.