Ostarine increases muscle mass and strength in postmenopausal women: Study

GTx, Inc. (Nasdaq: GTXI) announced that Ostarine™ (GTx-024, formerly MK-2866) increased lean body mass and leg press strength in a head to head study evaluating Ostarine and another selective androgen receptor modulator (SARM), MK-3984, in postmenopausal women. The data were presented yesterday at the 2010 Annual Meeting of the Endocrine Society. GTx is developing its lead SARM, Ostarine, for the treatment of cancer induced muscle wasting (cancer cachexia).

“This is the third Ostarine clinical study that measured lean body mass and physical performance endpoints, and Ostarine has consistently demonstrated the ability to increase muscle mass and strength”

"This is the third Ostarine clinical study that measured lean body mass and physical performance endpoints, and Ostarine has consistently demonstrated the ability to increase muscle mass and strength," said Mitchell S. Steiner, MD, CEO of GTx. "We also continue to be pleased with Ostarine's safety profile."

The 12 week, randomized clinical trial evaluated Ostarine 3 mg and two doses of MK-3984 compared to placebo in 88 postmenopausal women. Total lean body mass was measured by DEXA at baseline and 12 weeks, and physical performance was evaluated at the same interval by bilateral leg press machine.

After 12 weeks of treatment, Ostarine 3 mg and MK-3984 significantly increased total lean body mass. Compared to placebo, mean differences from baseline for lean body mass were observed with increases of 1.54 kg (p value<0.001) for both Ostarine 3 mg and 50 mg of MK-3984 and an increase of 1.74 kg (p value<0.001) for 125 mg of MK-3984. Increases in thigh muscle volume as measured by MRI for Ostarine and MK-3984 were noted as early as week 4 with the effect persisting through the end of the study. Ostarine 3 mg and MK-3984 treatment resulted in an increase in leg muscle strength. Mean leg muscle strength at 12 weeks for Ostarine 3 mg treated subjects increased by 22 pounds from baseline.

Ostarine 3 mg and MK-3984 were tissue selective. Treatment did not cause virilization in these women, as there was no change in sebaceous gland volume, rate of sebum excretion, or hair follicle gene expression. Moreover, Ostarine 3 mg and MK-3984 did not stimulate endometrial proliferation as measured by endometrial thickness. As for safety, seven subjects treated with MK-3984 were discontinued from the study due to elevations in liver enzymes greater than three times the upper limit of normal, whereas no clinically significant liver enzyme elevations occurred in subjects treated with Ostarine.

In summary, 12 week treatment with Ostarine 3 mg and MK-3984 had comparable efficacy on total lean body mass, muscle strength and tissue selectivity in postmenopausal women. Ostarine 3 mg was well tolerated with no clinically significant liver enzyme elevations.