Testosterone level should be used as a surrogate endpoint in phase 3 trials of gonadotropin-releasing hormone (GnRH) analogues for treating advanced prostate cancer, the FDA says in a new draft guidance.
Sponsors should conduct single-arm trials that measure attainment and maintenance of castrate testosterone (T) levels, according to the draft guidance released Wednesday. Trials should look at T levels maintained until the end of a dosing interval as well as immediately after later doses – not the first dose — of the study drug.
“To demonstrate these effects of the study drug on T levels, the treatment period should be at least twice as long as the dosing interval,” the agency advises. Products that act over shorter periods, such as one month, should have treatment periods extending over three to four dosing intervals.