An experimental medication safely increases muscle strength and physical functioning among cancer patients with low testosterone levels, a new drug study finds. The results will be presented Sunday at The Endocrine Society's 94th Annual Meeting in Houston.
The medication, called enobosarm, is the first of a new class of drugs known as selective androgen receptor modulators, which are similar to steroids in their growth-enhancing effects but, potentially, have fewer side effects.
Muscle wasting is a significant problem for many cancer patients due to imbalances in body systems caused by the underlying cancer. In addition, this muscle wasting may be related to low testosterone levels, or hypogonadism, which affects approximately 50 percent of men undergoing treatment for late-stage cancer. Muscle wasting can seriously limit mobility, functioning, and quality of life for affected patients.
In this multi-center drug trial, enobosarm significantly improved physical function among patients with low testosterone, as well as normal hormone levels. Among the low testosterone group, physical function improved by 19 percent, while patients with normal hormone measurements increase their functional ability by 13 percent. At the study's start, 60 percent of patients had subnormal testosterone levels, lost more weight, and suffered greater declines in physical functioning than patients with normal hormone concentrations.
"These data provide evidence that enobosarm may play an important role in the management of cancer-related muscle-wasting even in the setting of low testosterone," said study lead author Adrian Dobs, M.D., M.H.S., professor of medicine and oncology, and vice-chair of the Department of Medicine, Faculty Development at Johns Hopkins University Medical School in Baltimore, MD.
The overall study included 159 cancer patients, of which 65 percent were men. Female participants were post-menopausal, and males were >45 years old. Participants had lost on average about 8 percent of their body weight in the six months preceding the study, and had a body mass index, which is a calculation of weight to height, of <35. Additionally, all patients had received a cancer diagnosis, which included one of the following: non-small-cell lung carcinoma, colorectal cancer, non-Hodgkin's lymphoma, chronic lymphocytic leukemia, and breast cancer.
This particular study examined a subset of this population, which comprised 93 male patients. Sixty percent of these men had low testosterone levels at the beginning of the trial. Investigators randomly assigned these participants to receive either 1 or 3 milligrams of oral enobosarm or placebo daily for 16 weeks. Since the trial was double-blinded, neither patients nor researchers knew which group was receiving the study drug versus placebo. At the study's beginning and end, investigators assessed patients' physical functioning using a stair-climbing test.
According to Dobs, this study laid the groundwork for ongoing research examining enobosarm's effects on muscle-wasting specifically among lung-cancer patients.
"Enobosarm has the potential to improve physical performance and increase muscle mass, potentially providing lung-cancer patients with improved strength, or physical function, more independence, increased quality of life, better response to chemotherapy and hopefully longer survival," Dobs said.
Previous findings from the larger study comprising male and female patients have been reported, but these data on the subset of male patients with baseline low testosterone are being presented for the first time.
GTx, Inc. Memphis, TN, funded the study.