Positive phase III results for inavolisib combination in advanced hormone receptor-positive, HER2-negative breast cancer with a PIK3CA mutation

The study met its primary endpoint of progression-free survival (PFS), demonstrating a statistically significant and clinically meaningful improvement compared to palbociclib and fulvestrant alone. Overall survival data were immature at this time, but a clear positive trend has been observed. Follow-up will continue to the next analysis.

“These pivotal study results for this inavolisib combination represent a transformative medical advance for people with PIK3CA-mutated HR-positive breast cancer,” said Levi Garraway, M.D., Ph.D., Genentech’s chief medical officer and head of Global Product Development. “We are excited about the opportunity to expand our portfolio of breast cancer medicines into the HR-positive space and bring this potentially best-in-class new treatment option to patients as quickly as possible.”

The inavolisib combination was well tolerated and adverse events were consistent with the known safety profiles of the individual study treatments, with no new safety signals observed.

Inavolisib is currently being investigated in three Phase III clinical studies in people with PIK3CA-mutated metastatic breast cancer (INAVO120, INAVO121, INAVO122) in various combinations.

About the INAVO120 Study: The INAVO120 study [NCT04191499] is a Phase III, randomized, double-blind, placebo-controlled study evaluating the efficacy and safety of inavolisib in combination with palbociclib and fulvestrant versus placebo plus palbociclib and fulvestrant in people with PIK3CA-mutated, hormone receptor (HR)-positive, HER2-negative, locally advanced or metastatic breast cancer whose disease progressed during treatment or within 12 months of completing adjuvant endocrine therapy and who have not received prior systemic therapy for metastatic disease. The study included 325 patients, who were randomly assigned to either the investigational or control treatment arm. The primary endpoint is progression-free survival, as assessed by investigators, defined as the time from randomization in the clinical trial to the time when the disease progresses, or a patient dies from any cause. Secondary endpoints include overall survival, objective response rate, and clinical benefit rate.

About Hormone Receptor-Positive Breast Cancer: Hormone receptor (HR)-positive breast cancer is the most prevalent type of all breast cancers. A defining feature of HR-positive breast cancer is that its tumor cells have receptors that attach to one or both hormones – estrogen or progesterone – which can contribute to tumor growth. People diagnosed with HR-positive metastatic breast cancer often face the risk of disease progression and treatment side effects, creating a need for additional treatment options. The PI3K signaling pathway is commonly dysregulated in HR-positive breast cancer, often due to activating PIK3CA mutations, which have been identified as a potential mechanism for resistance to endocrine therapy and CDK4/6 inhibitors.