Puma Biotechnology Presents Positive Results From Phase III Trial Of PB272

(RTTNews) - Puma Biotechnology Inc. (PBYI) announced the presentation of positive results from the Phase III clinical trial of Puma's investigational drug PB272 (neratinib) for the extended adjuvant treatment of breast cancer (ExteNET trial) in patients with centrally confirmed HER2-positive early stage breast cancer.

The ExteNET trial is a double-blind, placebo-controlled, Phase III trial of neratinib versus placebo after adjuvant treatment with trastuzumab (Herceptin) in women with early stage HER2-positive breast cancer.

The data was presented today in an oral presentation at the American Society of Clinical Oncology (ASCO) 2015 Breast Cancer Symposium in San Francisco, California.

The ExteNET trial randomized 2,840 patients in 41 countries with early-stage HER2-positive breast cancer who had undergone surgery and adjuvant treatment with trastuzumab. After completion of adjuvant treatment with trastuzumab, patients were randomized to receive extended adjuvant treatment with either neratinib or placebo for a period of one year. Patients were then followed for recurrent disease, ductal carcinoma in situ (DCIS), or death for a period of two years after randomization in the trial.

The patient characteristics in the trial were well balanced between the neratinib and placebo arms of the trial. For the 1,420 patients in the neratinib arm of the trial, 1,085 (76.4%) were node positive while for the 1,420 patients in the placebo arm of the trial, 1,084 (76.3%) were node positive.

Additionally in the neratinib arm of the trial, 816 (57.5%) patients were hormone receptor positive, and in the placebo arm of the trial, 815 (57.4%) patients were hormone receptor positive. The median time from the last trastuzumab dose to entry into the trial was 4.4 months for the neratinib treated patients and 4.6 months for the placebo-treated patients.

The safety results of the study showed that the most frequently observed adverse event for the neratinib-treated patients was diarrhea, with approximately 39.9% of the neratinib-treated patients experiencing grade 3 or higher diarrhea (1 (0.1%) patient had grade 4 diarrhea). Patients who received neratinib in this trial did not receive any prophylaxis with antidiarrheal agents to prevent the neratinib-related diarrhea.

Puma's recently reported clinical data from several trials have demonstrated that the use of high dose prophylactic loperamide greatly reduces the rate of grade 3 diarrhea with neratinib, with grade 3 diarrhea rates ranging from 0-17% in studies in which high dose loperamide prophylaxis was used. In all of its current ongoing studies Puma is instituting the use of high dose loperamide for the first cycle of treatment in order to continue to reduce the neratinib-related diarrhea.