A phase III trial of alpelisib + trastuzumab ± fulvestrant versus trastuzumab + chemotherapy in HER2+ PIK3CA-mutated breast cancer.

ABSTRACT

ALPHABET is a randomized phase III trial assessing alpelisib + trastuzumab with or without fulvestrant in previously treated HER2-positive PIK3CA-mutated advanced breast cancer. Patients will be included in two cohorts according to hormone receptor (HR) status. In the experimental arms, patients in the HR-negative cohort will receive trastuzumab + alpelisib, and patients in the HR-positive cohort will receive the same treatment plus fulvestrant. Patients in the control arms will receive trastuzumab + physician's choice chemotherapy (eribuline, capecitabine or vinorelbine). Key eligibility criteria include 1-4 previous lines of anti-HER2 therapy and prior trastuzumab emtansine. The primary end point is investigator-assessed progression-free survival. The study aims to recruit a total of 300 patients.

ALPHABET is a clinical study investigating the potential use of alpelisib for the treatment of certain subtypes of breast cancer. Alpelisib is a novel drug that is given orally. It specifically targets a protein called PI3K. PI3K is hyperactivated in some tumors, allowing uncontrolled growth. This study is enrolling patients with HER2-positive advanced breast cancer whose tumor tests positive for a mutation in the PIK3CA gene, which encodes PI3K. Patients are allocated at random to receive either a combination treatment of trastuzumab (an anti-HER2-targeted therapy) with alpelisib or standard chemotherapy and trastuzumab without alpelisib. The efficacy of each treatment will be determined by comparing how long patients in each group live for without further tumor growth. Additional analyses will also look at the side effects experienced by patients, as well as their quality of life.