Endo testosterone gel approved

The US Food and Drug Administration (FDA) has granted marketing approval to Endo Pharmaceuticals' Fortesta testosterone gel as a treatment for men with hypogonadism.

The product is the first testosterone replacement therapy gel that is approved to be applied to the front and inner thighs, which Endo believes could prove to be a benefit because the thigh area is more often covered by clothing than the upper-body application sites used with other products. This is key because it is important for safety reasons that the gel not be transferred to other people by contact with the uncovered application site.

Hypogonadism, or low testosterone, can lead to erectile dysfunction, fatigue, regression of secondary sexual characteristics and osteoporosis.

The FDA approval was based on Endo's open-label, non-comparative phase III trial, which showed that 78 per cent of hypogonadism patients using the gel had an average serum total testosterone concentration within the normal range at day 90. The most common side-effects associated with the product include skin redness or irritation at the application site, increased prostate specific antigen, and abnormal dreams.

Endo expects to launch its colourless, odourless gel in the US in early 2011. The product is packaged in a metered-dose pump.

The Endo approval closely follows the US approval of Lilly's Axiron testosterone gel, the first approved testosterone replacement therapy that is topically applied to the underarm. That product, which Lilly licensed from the Australian firm Acrux in a deal potentially worth up to $335m, was approved by the FDA in late November.

The US market for testosterone replacement products is estimated to be about $1.1bn and is growing rapidly, according to the market research firm IMS Health.