Repros Therapeutics has completed patient dosing in its Phase II low-dose trial of oral Proellex, intended for the treatment of symptoms of uterine fibroids and endometriosis.

The study, known as ZP-204, involved the evaluation of induction of amenorrhea (cessation of menses) where doses as low as 3mg were found effective. It is a five-arm dose escalation study in which up to 12 women with diagnosed endometriosis or uterine fibroids were randomised to 1mg, 3mg, 6mg, 9mg and 12mg doses of oral Proellex.

In the trial, a 24-hour pharmacokinetic assessment was made on the first day of dosing, and then women continued to take the drug for the following ten weeks, returning to the clinic weekly to assess liver function and determine trough levels of the drug. Subjects were investigated weekly in a single blind placebo run-in for up to six weeks in order to record their weekly changes in liver enzyme as well as their menstrual bleeding events and intensity. At the follow-up visit, baseline endometrial thickness was assessed, and women were made to maintain vaginal daily bleeding diaries over the course of the study and into the follow-up period.

In earlier Phase II studies in uterine fibroids, doses as low as 12mg of Proellex daily considerably minimised symptoms of excessive menstrual bleeding and all the symptoms evaluated by the uterine fibroid symptom quality of life survey. The studies also demonstrated that daily oral doses of 12.5mg to 50mg resulted in a dose-dependent reduction in fibroid size, and 25mg and 50mg daily oral doses of Proellex showed changes in the pain endpoints of endometriosis. Based on the current data and the efficacy signal in its previous Phase II studies, the company plans to re-enter Phase III with low-dose oral Proellex.

Repros Therapeutics is a development stage biopharmaceutical company focused on the development of oral small molecule drugs for major unmet medical needs in male and female health.