Repros Therapeutics confirmed that FDA has lifted the full clinical hold on its Phase II-stage progesterone receptor blocker, Proellex®. The firm will now be allowed to run a single study to evaluate escalating low doses of the drug under a partial clinical hold status. The trial will investigate the safety and lowest potentially effective dose of Proellex.
Clinical trials of the drug were stopped in August 2009 due to concerns about liver toxicity. Repros had previously dropped the maximum dose of the drug evaluated from 50 mg to 25 mg due to concerns about liver enzyme levels.
Repros says that it hopes to start the new FDA-approved study during 2010 and aims to complete it within 18 months. The new dose-escalating trial will evaluate five doses of Proellex sequentially, starting at 1 mg and moving on to 3, 6, 9, and 12 mg doses only when the safety of the previous dose has been confirmed and reported to FDA. Each dose will be tested in 12 different subjects, who will be treated for 10 weeks.
If a safe and effective dose can be demonstrated and cleared by FDA for further study, the firm says it aims to either re-start large efficacy trials in both uterine fibroids and endometriosis patients or outlicense the drug to a pharmaceutical partner.
Repros specializes in the development of oral small molecule drugs for indications in male and female health. The firm’s lead compound is Androxal® an orally active single isomer of clomiphene citrate. The drug is in development for use in men of reproductive age with low testosterone levels who want to improve or maintain their fertility and/or sperm function while being treated for low testosterone.
A Phase II trial for this indication has already been completed. In February Repros received FDA clearance to start a Phase IIa study with Adroxal in the treatment of hypogonadal men with type II diabetes.