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Genentech Taking Positive Phase III Results on PI3kα Inhibitor to Health Authorities

NEW YORK – Genentech on Tuesday said it will share with health authorities positive results from a Phase III trial evaluating its PI3kα inhibitor inavolisib with Pfizer's CDK 4/6 inhibitor Ibrance (palbociclib) in patients with PIK3CA-mutated hormone receptor (HR)-positive, HER2-negative advanced breast cancer.

In the INAVO120 trial, investigators enrolled 325 patients with PIK3CA-mutated, HR-positive, HER2-negative, locally advanced or metastatic breast cancer, who had progressed while on treatment or within a year of completing adjuvant endocrine therapy and who had not received prior systemic therapy for metastatic disease. According to Roche subsidiary Genentech, the trial has met its primary endpoint by showing that patients treated with inavolisib, Ibrance, and fulvestrant had statistically significant and clinically meaningful improvements in progression-free survival, compared to those receiving placebo, Ibrance, and fulvestrant. 

The secondary endpoints in the study are objective response rate, duration of response, and overall survival. Although the overall survival results were immature at the time of this analysis, there was a "clear positive trend," Genentech said in a statement. The inavolisib combination was well tolerated, and its safety profile was consistent with what researchers had seen in previous studies, it added.

The company plans to share detailed results from this study at an upcoming medical meeting. Genentech is also studying inavolisib in PIK3CA-mutated metastatic breast cancer in two other clinical trials, INAVO121 and INAVO122.

If inavolisib passes muster with healthcare authorities and reaches the market for treating advanced PIK3CA-mutated breast cancer, it will compete with Novartis' PI3kα inhibitor Piqray (alpelisib).