Verzenio (abemaciclib) is approved for patients for whom endocrine therapy was not effective.

Breast cancer is the most common form of cancer affecting women on a global basis, according to the World Cancer Research Fund International. There are two forms of advanced breast cancer as defined by the American Cancer Society: metastatic breast cancer in which the cancer has spread from the breast tissue to other parts of the body, and locally or regionally advanced breast cancer in which the cancer has grown outside the organ where it started, but has not yet spread to other parts of the body. In the US, 6-10% of breast cancer patients are initially diagnosed as having metastatic breast cancer, with an additional 30% of early stage breast cancer patients eventually suffering from metastatic cancer, according to the Metastatic Breast Cancer Network.

These patients may have a better chance of survival with the recent approval of a new treatment from Eli Lilly. Verzenio (abemaciclib) is a cell cycle inhibitor designed to block cancer cell growth through inhibition of CDK4 and CDK6 enzymes. FDA approved the drug in combination with Faslodex (fulvestrant) for the treatment of adult patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced/metastatic breast cancer that has progressed after endocrine therapy and as a monotherapy for HR+/HER2- breast cancer patients who have been previously treated with endocrine therapy and chemo after metastasis. Approximately 72 percent of patients with breast cancer have tumors that are HR-positive and HER2-negative, according to the National Cancer Institute at the National Institutes of Health.

Verzenio received priority review and breakthrough therapy designations and was approved by the agency even more rapidly than expected (initially thought to be issues in Q1 of 2018).

CDK4 and CDK6 are cyclin-dependent kinases that they exhibit increased signaling cause a loss of cell-cycle regulation that results in uncontrolled cell growth. Abemaciclib is an oral cell cycle inhibitor that inhibits cyclin, CDK4 and CDK6. In breast cancer, according to Eli Lily, Cyclin D1/CDK4 has been shown to promote phosphorylation of the retinoblastoma protein (Rb), cell proliferation and tumor growth. In hormone receptor-positive breast cancer cell lines, sustained target inhibition by abemaciclib reduced phosphorylation of Rb, inducing cell cycle arrest.

Two other drugs in this same class have been previously approved for certain patients with breast cancer, including palbociclib (Ibrance from Pfizer approved in February 2015) and ribociclib (Kisqali from Novartis, approved in March 2017).

"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, M.D., 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. 

In addition to its current MONARCH clinical trials evaluating abemaciclib in breast cancer, a Phase 3 trial of abemaciclib in lung cancer is also underway.