The FDA recently approved abemaciclib in combination with an aromatase inhibitor as initial endocrine-based therapy for postmenopausal women with HR-positive, HER2-negative advanced or metastatic breast cancer.
Approval was based on MONARCH 3, a randomized (2:1), double-blinded, placebo-controlled, multicenter clinical trial in postmenopausal women with HR-positive, HER2-negative advanced or metastatic breast cancer. A total of 493 patients were randomized to receive either abemaciclib 150 mg or placebo orally twice daily, plus physician's choice of letrozole or anastrozole. The estimated median progression-free survival (RECIST 1.1) was 28.2 months (95% CI: 23.5, not reached) for patients receiving abemaciclib and 14.8 months (95% CI: 11.2, 19.2) for those receiving placebo (HR 0.540; 95% CI: 0.418, 0.698; p<0.0001).
The most common adverse reactions in at least 20 percent of patients receiving abemaciclib in MONARCH 3 and more than 2 percent higher than the placebo arm were diarrhea, neutropenia, fatigue, infections, nausea, abdominal pain, anemia, vomiting, alopecia, decreased appetite, and leukopenia.
The recommended starting dose of abemaciclib in combination with an aromatase inhibitor is 150 mg twice daily orally with or without food. FDA granted this application priority review.