ANOTHER CDK4/6 INHIBITOR APPROVED FOR HR+/HER2- BREAST CANCER BY FDA

The US Food and Drug Administration (FDA) today approved abemaciclib (Verzenio, Eli Lilly) for the treatment of hormone receptor (HR)–positive, human epidermal growth factor receptor 2 (HER2)–negative advanced or metastatic breast cancer that has progressed after endocrine therapy.

Abemaciclib is approved in combination with the endocrine therapy fulvestrant.

The agent becomes the third approved cyclin-dependent kinase (CDK) 4/6 inhibitor, a new class of drugs for use in breast cancer. Already on the market are palbociclib (Ibrance, Pfizer) and ribociclib (Kisqali, Novartis).

But abemaciclib has a unique feature among the three, explained the FDA in today's announcement.

"Verzenio provides a new targeted treatment option for certain patients with breast cancer who are not responding to treatment, and unlike other drugs in the class, it can be given as a stand-alone treatment to patients who were previously treated with endocrine therapy and chemotherapy," said Richard Pazdur, MD, director of the FDA's Oncology Center of Excellence and acting director of the Office of Hematology and Oncology Products in the FDA's Center for Drug Evaluation and Research.

The new approval is based in part on results from the MONARCH 2 clinical trial. In the trial, abemaciclib in combination with fulvestrant were compared with placebo and fulvestrant in a randomized trial of 669 patients with HR-positive, HER2-negative breast cancer who had progressed on endocrine therapy and had not received chemotherapy since the cancer had metastasized.

The median progression-free survival was 16.4 months for patients receiving abemaciclib and fulvestrant vs 9.3 months for patients receiving placebo and fulvestrant.

In a separate single-group trial, abemaciclib was evaluated as a stand-alone treatment among 132 patients with HR-positive, HER2-negative metastatic breast cancer that had progressed after endocrine therapy and chemotherapy.

In the study, the objective response rate was 19.7% and the median duration of response was 8.6 months.

In terms of adverse events, data from three clinical trials of abemaciclib indicate that patients who receive abemaciclib have more diarrhea and less neutropenia than those receiving the other two CDK 4/6 inhibitors, as reported by Medscape Medical News.

According to the FDA, the most common adverse effects of abemaciclib include diarrhea, neutropenia, leukopenia, nausea, abdominal pain, infections, fatigue, anemia, decreased appetite, vomiting, and headache.

Serious adverse events seen with abemaciclib include diarrhea, neutropenia, elevated liver blood test results, and deep venous thrombosis/pulmonary embolism. Abemaciclib is contraindicated during pregnancy because it is teratogenic.

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