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DENVER (EGMN) - GTx-024, the first agent in a new drug class known as selective androgen receptor modulators, brought clinically meaningful gains in lean body mass and muscle function in patients with cancer cachexia in a phase II clinical trial.
The benefits of the investigational oral SARM were not accompanied by unwanted androgenic effects. There was no virilization and no significant changes in serum prostate-specific antigen, testosterone, or luteinizing-hormone levels, Dr. Casey Bohl said at the annual meeting of the American Association for Cancer Research.
The trial involved 159 cachexic patients with colorectal cancer, breast cancer, non-small cell lung cancer, non-Hodgkin's lymphoma, and chronic lymphocytic leukemia. They had lost a mean 8.8% of their body weight during the 6 months preceding study enrollment. Participants were randomized to 1 mg or 3 mg of GTx-024 (Ostarine) daily or placebo for 16 weeks.
The primary study end point was change in total lean body mass as measured by dual-energy x-ray absorptiometry. Patients on 1 mg and 3 mg of GTx-024 daily averaged 1.5- and 1.3-kg gains, respectively, over baseline, both significantly better than the 0.1-kg gain in controls, according to Dr. Bohl, a research scientist at GTx Inc., the Memphis-based biopharmaceutical company developing the SARM.
A key secondary end point was change in muscle function as assessed in a 12-step stair-climb test. Stair-climb power improved by 35.2 and 44.7 watts with 1 mg and 3 mg/day of GTx-024, respectively, but was unimproved over time in the placebo arm. Grip strength and 6-minute walk distance weren't significantly different in the GTx-024 and placebo arms.
Body weight didn't change over time in the GTx-024-treated patients because as their lean body mass increased, fat mass decreased.
No drug-related adverse events were noted.
In an earlier phase II clinical trial that was conducted in a healthy elderly population with sarcopenia - that is, aging-related skeletal muscle loss - GTx-024 also resulted in significant gains in lean body mass and muscle performance as measured by the 12-step stair-climb test. So a phase III trial lies ahead, but the target population remains unclear.
"GTx and Merck are in a collaboration. We're moving forward. The question is, for what indication? We're still figuring out whether it'll be with cachexia, or the healthier population with sarcopenia," Dr. Bohl said in an interview.
It's estimated that roughly one-third of the 1.3 million Americans diagnosed with cancer each year will develop cachexia.
SARMS could potentially be used by athletes to improve performance, much as anabolic steroids are but with far fewer side effects. For this reason, the World Anti-Doping Agency (WADA) has already banned the use of SARMS by athletes, even though none is on the market yet.


Hopeful