GTx of the USA, and European licensee Ipsen, have been boosted by highly promising data from a late-stage trial of prostate cancer agent toremifene.

The Memphis-based group presented results of the first Phase III study evaluating the efficacy and safety of toremifene 80mg daily, on multiple side effects of androgen deprivation therapy in advanced prostate cancer patients. The two-year study involved almost 1,400 ADT patients and revealed that the drug demonstrated a 50% reduction in morphometric vertebral fractures. It also met other key endpoints, including bone mineral density, lipid profiles and gynecomastia.

GTx noted that ADT, using either hormone therapy or surgical castration, is the most common treatment for advanced prostate cancer and has proved effective but they also come with serious side effects. Their impact on testosterone and oestrogen levels could result in a decrease of bone mineral density in men, potentially leading to osteoporotic fractures and other adverse effects such as lipid changes, gynecomastia and hot flashes.

On the basis of these results, GTx plans to file a New Drug Application with the US Food and Drug Administration by the summer of 2008 and Ipsen will do the same in the European Union before year-end 2008.

Stephane Thiroloix, executive vice president of corporate development at the French drugmaker, said that the drug, which Ipsen will sell as Acapodene, has the potential to address a significant unmet medical need. He added that this product “is an excellent fit” with Ipsen’s existing Decapeptyl (triptorelin) prostate cancer franchise, “reinforcing our positioning in the treatment of hormone-dependent diseases.”

GTx licensed the rights to toremifene (except for breast cancer) from Finland’s Orion and signed the European deal with Ipsen in 2006.