FDA Approves Abemaciclib for HR+, HER2– High-Risk Early Breast Cancer

Abemaciclib is the first and only FDA approved CDK4/6 inhibitor to treat HR-positive, HER2-negative high-risk early breast cancer.

The FDA has approved abemaciclib (Verzenio) as an adjuvant therapy in combination with endocrine therapy (tamoxifen or an aromatase inhibitor) to treat hormone receptor (HR)-positive, human epidermal growth factor receptor2 (HER2)-negative, node-positive, early breast cancer (EBC) at high risk of recurrence and a Ki-67 score of ≥20% as determined by an FDA-approved test, according to a press release issued by Eli Lilly and Company.1

"Women and men living with high-risk HR-positive, HER2-negative early breast cancer want to do all they can to reduce the risk of the disease coming back, with the hope of living free of cancer. The approval of [abemaciclib] provides a new treatment option to help them do just that," said Jean Sachs, chief executive officer, Living Beyond Breast Cancer, in the release. "This approval brings new optimism to the breast cancer community."

The regulatory decision is based on findings from the randomized, open-label, 2-cohort, multicenter, phase 3 monarchE trial, designed to evaluate abemaciclib plus standard endocrine therapy versus standard endocrine therapy alone in adult patients with HR-positive, HER2-negative, node-positive, resected EBC with clinical and pathological features consistent with a high risk of disease recurrence. Patients were treated with either 2 years of abemaciclib 150 mg twice daily plus standard endocrine therapy, or with standard endocrine therapy as a monotherapy. Patients in both cohorts were prescribed adjuvant endocrine therapy for 5 to 10 years.

The primary end point was invasive disease-free survival (IDFS), defined as the length of time before the breast cancer returns, new cancer develops, or death, and has already been met a pre-specified interim analysis in the intent-to-treat population. Patients receiving abemaciclib have demonstrated superior IDFS compared with those treated with endocrine therapy as a monotherapy.

Overall survival data is not yet ready for analysis and investigators are continuing to conduct additional follow-ups.

No new safety signals were detected in the monarchE trial. Safety and tolerability were assessed across 5,591 patients, of which the most common adverse events (AEs) were diarrhea, infections, fatigue, nausea, headache, vomiting, stomatitis, dizziness, rash, and alopecia.

Laboratory abnormalities to monitor for include an increase in creatinine, a decreased white blood cell count, decreased neutrophil count, anemia, lymphocyte count, platelet count, increased ALT, increased AST, and hypokalemia.

Patients should receive blood counts and liver function tests prior to initiating treatment with abemaciclib. These tests should continue every 2 weeks for the first 2 months, monthly for the following 2 months, and so on, as clinically indicated. Patients taking this medication will also require monitoring for thrombosis and pulmonary embolism.

Patients should be taught to immediately initiate antidiarrheal therapy, increase oral fluids, and notify their health care providers at the first sign of loose stools. The labelling for the drug includes precautions for diarrhea, neutropenia, interstitial lung disease hepatotoxicity, venous thromboembolism, and embryo-fetal toxicity.

In addition, patients should understand that this drug poses serious risk to a fetus. The label urges patients to plan accordingly by using effective contraception.

"The design and results of the monarchE study are practice-changing and represent the first advancement in adjuvant treatment of HR-positive, HER2-negative breast cancer in a very long time," said Sara M. Tolaney, MD, MPH, Harvard Medical School, Dana-Farber Cancer Institute, and investigator on the monarchE study. "This FDA approval for Verzenio in combination with endocrine therapy in the early breast cancer setting has the potential to become a new standard of care for this population. We are encouraged by the marked reduction in the risk of recurrence even beyond the two-year treatment period in these patients, and I'm grateful to be able to offer this as a treatment option to my patients."

Reference

Eli Lilly and Company News Release. FDA approves Verzenio® (abemaciclib) as the first and only CDK4/6 inhibitor for certain people with HR+ HER2- high risk early breast cancer. Lilly. Published October 13, 2021. https://investor.lilly.com/news-releases/news-release-details/fda-approves-verzenior-abemaciclib-first-and-only-cdk46. Accessed October 13, 2021.