US Food and Drug Administration Approval Summary: Inavolisib With Palbociclib and Fulvestrant for Endocrine-Resistant, -Mutated, Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2-Negative, Locally Advanced or Metastatic Breast Cancer.

Purpose: The US Food and Drug Administration (FDA) approved inavolisib with palbociclib and fulvestrant for adults with endocrine-resistant, -mutated, hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative, locally advanced or metastatic breast cancer (MBC), as detected by an FDA-approved test, FoundationOne Liquid CDx assay, after recurrence on or after completing adjuvant endocrine therapy.

Patients And Methods: Approval was based on INAVO120, a randomized, double-blind, placebo-controlled trial in 325 patients with endocrine-resistant, -mutated, hormone receptor-positive, HER2-negative, locally advanced or MBC. Patients were randomly assigned (1:1) to either inavolisib (n = 161) or placebo (n = 164) in combination with palbociclib and fulvestrant.

Results: INAVO120 met its primary end point of progression-free survival (PFS) by investigator assessment, with a median PFS of 15.0 months for inavolisib + palbociclib + fulvestrant versus 7.3 months for placebo + palbociclib + fulvestrant (hazard ratio [HR], 0.43 [95% CI, 0.32 to 0.59]; < .0001). The objective response rate was 58% (95% CI, 50 to 66) versus 25% (95% CI, 19 to 32). The median duration of response was 18.4 months (95% CI, 10.4 to 22.2) versus 9.6 months (95% CI, 7.4 to 16.6). Interim analysis of overall survival did not reach statistical significance but was supportive of the overall benefit-risk assessment with a HR of 0.64 (95% CI, 0.43 to 0.97). Consistent with the PI3Kα inhibitor class, common adverse reactions noted with inavolisib included hyperglycemia, stomatitis, diarrhea, and rash.

Conclusion: The approval of inavolisib with palbociclib plus fulvestrant was based on a statistically significant and clinically meaningful improvement in PFS observed in the INAVO120 trial. Before this approval, there were no specific therapies approved by the FDA for the first-line treatment of patients with endocrine-resistant, hormone receptor-positive advanced or MBC.