The investigative agent abemaciclib, which is still in clinical trials, appears promising in providing anti-cancer activity among patients with metastatic breast cancer that has progressed following several prior therapies. These results were recently presented at the 2016 annual meeting of the American Society of Clinical Oncology.
Metastatic breast cancer (MBC) refers to cancer that has spread from its site of origin to distant sites in the body. New options in the treatment of MBC have recently become FDA approved and integrated into standard treatment guidelines, resulting in improved outcomes for patients with this disease.
The new treatment paradigm typically includes individualized therapy, meaning the treatment is tailored to specific characteristics of the cancer. Abemaciclib is an agent that is being evaluated in hormone-positive (HR-positive) and human epidermal growth factor receptor 2-negative (HER2-negative) breast cancers.
Abemaciclib targets a cellular pathway referred to as the CDK4/6 pathway. This particular pathway has been implicated in cancer progression among HR-positive breast cancer.
The recent phase II trial, referred to as the MONARCH 1 trial, evaluating abemaciclib included 132 patients with HR-positive, HER2-negative MBC. Over half of the patients had over 3 sites of cancer metastases, and had received a median of least 3 prior therapies for advanced breast cancer. All patients were treated with abemaciclib.
- Overall anti-cancer responses were achieved in nearly 20% of patients.
- Approximately 23% of patients had stabilization of their cancer lasting for at least 6 months.
- Among patients who achieved an anti-cancer response, the median duration of the response was nearly 9 months; over 70% of patients experienced a median duration of response for at least 6 months, and 28.2% of patients experienced a median duration of response for 12 months.
- The most common side effects of abemaciclib were diarrhea, nausea, fatigue, and loss of appetite.
Maura Dickler MD, who reported results of the study stated that “MONARCH 1 confirmed single-agent activity of abemaciclib, a CDK4/6 inhibitor, in a heavily pretreated population with HR-positive, HER2-negative metastatic breast cancer.”
Phase III trials are currently underway further evaluating the effectiveness of abemaciclib plus the hormone agent, fulvestrant, among this patient population.
Reference: Dickler M, et al. MONARCH1: Results from a phase II study of abemaciclib, a CDK4 and CDK6 inhibitor, as monotherapy, in patients with HR+/HER2- breast cancer, after chemotherapy for advanced disease. Proceedings from the 2016 annual meeting of the American Society of Clinical Oncology (ASCO). Abstract #510.