Specifically, the first-in-class AKT kinase inhibitor approval is for patients with one or more PIK3CA/AKT1/PTEN alterations, as detected by an FDA-approved test, whose metastatic disease progressed on at least one endocrine-based regimen or who experienced recurrence on or within 12 months of completing adjuvant therapy, according to the FDA approval announcement.
The FDA also approved a companion diagnostic device, the FoundationOne CDx assay, to identify patients who are eligible for treatment with capivasertib.
Approval of capivasertib was based on findings from the randomized, placebo-controlled, phase 3 CAPItello-291 trial, which involved 708 patients with locally advanced or metastatic HR-positive, HER2-negative breast cancer, including 289 whose tumors had PIK3CA/AKT1/PTEN alterations. All had progressed on aromatase inhibitor–based treatment and may have received up to two prior lines of endocrine therapy and up to one line of chemotherapy.
Patients were randomized to either 400 mg of oral capivasertib or placebo twice daily for 4 days, followed by 3 days off treatment each week over a 28-day treatment cycle. Patients in both arms received 500 mg intramuscular fulvestrant on cycle 1 days 1 and 15, and then every 28 days thereafter. Treatment continued until disease progression or unacceptable toxicity.
In the 289 patients with PIK3CA/AKT1/PTEN–altered tumors, median progression-free survival (PFS) in the capivasertib arm was 7.3 months versus 3.1 months in the placebo group (hazard ratio, 0.50).
An exploratory analysis of PFS in the 313 (44%) patients whose tumors did not have a PIK3CA/AKT1/PTEN alteration demonstrated a less notable benefit to the combination (HR, 0.79; 95% confidence interval, 0.61-1.02), indicating that “the difference in the overall population was primarily attributed to the results seen in the population of patients whose tumors have PIK3CA/AKT1/PTEN alteration,” the FDA explained.
Adverse reactions occurring in at least 20% of patients included decreased lymphocytes, leukocytes, hemoglobin, and neutrophils; increased fasting glucose, creatinine, and triglycerides; and diarrhea, nausea, fatigue, vomiting, and stomatitis.
The recommended capivasertib dose is 400 mg orally twice daily, given about 12 hours apart with or without food, for 4 days followed by 3 off days until disease progression or unacceptable toxicity, according to the prescribing information.
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