On February 26, 2018, the Food and Drug Administration approved abemaciclib in combination with an aromatase inhibitor as initial endocrine-based therapy for postmenopausal women with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced or metastatic breast cancer.

Approval was based on MONARCH 3, a randomised (2:1), double-blinded, placebo-controlled, multicentre clinical trial in postmenopausal women with HR-positive, HER2-negative advanced or metastatic breast cancer.

A total of 493 patients were randomised 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% of patients receiving abemaciclib in MONARCH 3 and more than 2% higher than the placebo arm were diarrhoea, neutropenia, fatigue, infections, nausea, abdominal pain, anaemia, 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.

Source: FDA