In an early trial, an experimental breast cancer drug, bemaciclib, demonstrated its ability to stop disease growth and reduce tumor size by more than 30 percent in some patients. A phase 1 trial found bemaciclib to be safe and well-tolerated by women with breast cancer that had spread, or metastasized to other parts of the body.
According to Dr. Amita Patnaik, lead researcher and associate director of clinical research of South Texas Accelerated Research Therapeutics in San Antonio, “This is a novel oral treatment for patients with metastatic breast cancer.”
The researchers report that bemaciclib was effective for the most common form of breast cancer known as hormone receptor-positive breast cancer. These cancer cells grow in response to signals from the hormones estrogen and/or progesterone.
The phase 1 trial included more than 130 women. Patnaik reports that half of them had cancer growth controlled and 25 percent had shrinkage of their tumors. Patnaik notes, unlike standard cancer drugs, bemaciclib is a twice-daily pill that allows women to go on with their daily lives. Standard cancer drugs are given intravenously at a hospital or doctor’s office. Moreover, bemaciclib is a target therapy, a newer type of drug that is better able to identify and attack specific cells. Patnaik does report side effects that include diarrhea, nausea and vomiting, however for study participants, most of these problems were mild or moderate.
Patnaik cautions, this is a first-time examination of bemaciclib, and the results will have to be confirmed in later trials. More trials are currently being planned.
According to Dr. Neelima Denduluri, a medical oncologist at Virginia Cancer Specialists in Arlington and not involved in the study, metastatic breast cancer is generally incurable. “Goals of therapy include maintaining quality of life while administering effective therapy.” She hopes that bemaciclib and other new drugs will make a difference in the therapy of breast cancer. Denduluri notes, doctors often use anti-estrogen treatments for hormone receptor-positive breast cancer, however, tumor cells stop responding to these drugs, so alternative drugs are often needed.
The phase 1 trial tested bemaciclib on 132 women with breast cancer. Forty-seven of these patients had metastatic cancer who had taken as many as 7 drugs before bemaciclib. The patients were administered bemaciclib pills twice daily for 28 days. Thirty-six of the 47 patients with metastatic breast cancer had hormone receptor-positive disease. Nine of the 47 patients had a partial response, and 24 of the 47 patients saw the growth of their cancer stopped. Researchers also note, among the metastatic breast cancer group, 11 patients had their cancer progress despite treatment.
Of the women who had hormone receptor-positive breast cancer, 81% had a complete response, partial response, or stable disease, and their cancer didn’t progress for an average of nine months. Overall, study participants were progression-free for almost 6 months. The phase 1 trial ran for 28 days, but women who benefited from bemaciclib could continue on the drug in 28 day cycles as long as they continued to benefit. Patnaik notes, eighteen of the hormone receptor-positive breast cancer patients are still being treated with the drug.
Dr. Myra Barginear, an oncologist at North Shore-LIJ Cancer Institute in Lake Success, N.Y., notes, “As a breast cancer doctor, I am thrilled to potentially have a new agent for my patients with advanced hormone receptor-positive breast cancer. This is the most common type of breast cancer — representing approximately 80 percent of all cases.”