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Effects of Enobosarm on Muscle Wasting and Physical Function in Cancer


Muscle wasting is a common cancer related symptom which can begin early in the course of a patient’s malignancy resulting in decline in physical function and other detrimental clinical consequences. Muscle wasting and muscle weakness are also side effects of many chemotherapy drugs. There are no drugs approved for the prevention and treatment of muscle wasting in patients with cancer. At diagnosis, approximately 50% of advanced non-small cell lung cancer (NSCLC) patients have severe muscle loss, and approximately 70% of these patients will lose muscle before death. Muscle weakness and functional limitations are highly prevalent, with 88% of NSCLC patients reporting difficulty climbing stairs, lifting and carrying 10 lbs, walking a quarter mile, or stooping, crouching or kneeling. Muscle loss is a predictor of performance status, tolerability to cancer treatment, progression free survival and overall survival. Limitations in physical function predict the ability of a NSCLC patient to tolerate chemotherapy, and patients with functional limitations are less likely to be offered treatment. Functional status is also a predictor of survival.


The following describes the results of a randomized clinical trial of Enobosarm (Ostarine®; GTx-024), an oral selective androgen receptor modulator that GTx is developing for the prevention and treatment of muscle wasting in patients with non-small cell lung cancer. The study was published online in The Lancet Oncology (14 March 2013).


The study enrolled male (>45 years) and female (postmenopausal) patients with cancer who were not obese and who had at least 2% weight loss in the previous 6 months. Participants were randomly assigned (1:1:1 ratio, by computer generated list, block size three, stratified by cancer type) to receive once-daily oral enobosarm 1 mg, 3 mg, or placebo for up to 113 days. The primary endpoint was change in total lean body mass from baseline, assessed by dual-energy x-ray absorptiometry.


Enrolment started on July 3, 2007, and the last patient completed the trial on Aug 1, 2008. 159 patients were analysed for safety (placebo, n=52; enobosarm 1 mg, n=53; enobosarm 3 mg, n=54). The evaluable efficacy population included 100 participants (placebo, n=34; enobosarm 1 mg, n=32; enobosarm 3 mg, n=34). Compared with baseline, significant increases in total lean body mass by day 113 or end of study were noted in both enobosarm groups (enobosarm 1 mg median 1.5 kg; p=0·0012); enodosarm 3 mg 1.0 kg; p=0·046). Change in total lean body mass within the placebo group (median 0·02 kg) was not significant (p=0.88).


According to the authors, cancer cachexia is an unmet medical need and the data suggest that use of enobosarm might lead to improvements in lean body mass, without the toxic effects associated with androgens and progestational agents.


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