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Puma Biotechnology, Inc. (NYSE: PBYI), a development stage biopharmaceutical company, announced that results from an ongoing Phase II clinical trial of Puma's investigational drug PB272 (neratinib) were presented at the 2012 CTRC-AACR San Antonio Breast Cancer Symposium (SABCS) that is currently taking place in San Antonio, Texas. The presentation is further detailed below.
Tolerability and efficacy of targeting both mTOR and HER2 signaling in trastuzumab-refractory HER2+ metastatic breast cancer
The Phase II clinical trial of PB272 given in combination with the anticancer drug temsirolimus was conducted at Memorial Sloan-Kettering Cancer Center. The trial was supported by the National Comprehensive Cancer Network®, ASCO’s Young Investigator Award, Susan G. Komen for the Cure®, and the Terri Brodeur Breast Cancer Foundation. The initial Phase I/II results of this trial were presented last year. The Phase II portion of the study, presented at the SABCS, enrolled patients with HER2+ metastatic breast cancer and disease progression on trastuzumab. Patients in the study received a median of 3 prior cytotoxic regimens (range 1-12 prior regimens) before entering the trial. Of the 27 patients enrolled in the trial, 14 patients (52%) had either estrogen receptor positive disease or progesterone receptor positive disease. In addition, 20 patients (74%) had visceral metastases and 3 patients (11%) had brain metastases. Patients were administered PB272 at a dose of 240 mg per day in combination with temsirolimus given at a dose of 8 mg weekly.
The results of the study presented showed that the combination of PB272 and temsirolimus had acceptable tolerability. The most frequently observed severe adverse events for the 27 patients evaluable for safety were grade 3 diarrhea (22% of patients), grade 3 mucositis (15%), grade 3 hyperglycemia (4%), grade 3 leukopenia (4%), and grade 3 fatigue (4%). The efficacy results from the trial showed that for the 27 evaluable patients, 12 patients (44%) experienced a partial response (PR) and 1 patient (4%) experienced prolonged stable disease (SD) for greater than 6 months, which translates to a clinical benefit rate of 48%. Patients who experienced a partial response to the combination of neratinib plus temsirolimus demonstrated a maximum change in the size of their target lesions of between 33% and 83%. Clinical benefit was seen in patients previously treated with trastuzumab as well as lapatinib, T-DM1 and pertuzumab. The median progression free survival of the 27 evaluable patients was seen to be 18 weeks (4.2 months). Enrollment in this trial is continuing and is anticipated to reach a total of 34 patients.