Recent advances in the sensitivity of testing for bioavailable testosterone have significantly enhanced the physicians' ability to diagnose and treat low testosterone. In addition, the growth of the aging population is driving a significant increase in the number of older male patients with symptoms of low testosterone. Such symptoms are most commonly treated with testosterone replacement therapy, primarily as topical or injectable products. These products are designed to provide exogenous testosterone to supplement low levels of testosterone, but do not address the mechanism which causes low testosterone. Furthermore, topical products have certain cosmetic and practical limitations, such as messiness. Intramuscular injections of testosterone are effective but are painful and inconvenient. Oral testosterone therapy is rarely used because of poor bioavailability or the potential risk of life-threatening liver toxicity.

The therapeutic goal of testosterone replacement therapy is to normalize the blood serum testosterone concentration in men to mid to low young adult serum levels and to avoid elevated testosterone levels. In spite of this goal, elevated testosterone levels do occur with replacement therapy and can lead to problems including prostate enlargement and elevations in blood hemoglobin levels that can increase the risk of vascular problems, including stroke. We believe that an oral therapeutic option that could elevate testosterone levels into the normal physiologic range without increasing the risk of prostate enlargement and elevated blood hemoglobin levels would be an important therapeutic option for the treatment of the symptoms of low testosterone.

Current testosterone therapies

Currently, gel and patch formulations of testosterone are the most commonly prescribed replacement therapies. According to IMS Health, in the U.S. alone, sales for this topical category reached $538 million in 2004, a growth of 40% compared to 2003, and almost doubling since 2002. In the same two-year period, U.S. prescriptions grew 25%, from 1.9 million in 2002 to nearly 2.4 million in 2004. Androgel, marketed by Solvay, is the U.S. market leader with a nearly 60% market share of prescriptions and sales of almost $400 million in 2004.