PI3K Inhibitor Wins FDA Approval for Advanced Breast Cancer

The FDA approved the PI3K-pathway inhibitor inavolisib (Itovebi) for use in combination with palbociclib (Ibrance) and fulvestrant to treat locally advanced, PIK3CA-mutated, hormone receptor (HR)-positive/HER2-negative breast cancer that recurred during or after adjuvant endocrine therapy.

Support for the approval came from the multicenter randomized INAVO120 trial, which showed that the addition of inavolisib to palbociclib and fulvestrant more than doubled median progression-free survival (PFS).

“The PI3K pathway plays a pivotal role in disease progression and has been challenging to target,” study investigator Komal Jhaveri, MD, of Memorial Sloan Kettering Cancer Center in New York City, said in a statement from drugmaker Genentech. “The Itovebi-based regimen more than doubled progression-free survival and maintained a manageable safety and tolerability profile, adding a new standard in how PIK3CA-mutated breast cancers are treated.”

INAVO120 involved 325 patients with locally advanced/metastatic endocrine-resistant, HR-positive/HER2-negative breast cancer. Primary resistance was defined as relapse within the first 2 years of adjuvant endocrine therapy, and secondary resistance as relapse on adjuvant therapy after at least 2 years or within 12 months after completing therapy. The patients were randomized to palbociclib and fulvestrant plus either inavolisib or placebo, and the primary endpoint was investigator-assessed PFS.

The primary analysis showed a median PFS of 15 months with inavolisib and 7.3 months without, representing a 57% reduction in the hazard for disease progression or death (P

According to the prescribing information, the most common adverse events (≥20% of patients) associated with inavolisib were decreases in neutrophils, hemoglobin, platelets, lymphocytes, calcium, potassium, sodium, magnesium, and appetite; increases in fasting glucose, alanine aminotransferase, and creatinine; and stomatitis; diarrhea; fatigue; rash; COVID; and headache.

The FDA also approved the FoundationOne Liquid CDx assay as a companion diagnostic to identify patients appropriate for treatment with inavolisib in combination with palbociclib and fulvestrant.