Neurocrine's Elagolix Misses Main Study Goal

The primary endpoint of the study was a reduction in pelvic pain measured using a daily numeric rating scale. Neurocrine considered this endpoint -- suggested by the National Institutes of Health -- to be "exploratory" because the company had never used it before in a clinical trial of endometriosis patients.

Patients treated with elagolix reported improved daily pelvic pain scores compared with placebo, but the difference wasn't statistically significant, Neurocrine reported Wednesday.

Elagolix also failed to demonstrate benefit over placebo using a daily measure of non-menstrual pelvic pain. The FDA asked the company to include this experimental endpoint in the study.

Elagolix did show strong, statistically significant efficacy when the drug was evaluated using monthly scores of pain reduction and other endometriosis symptoms that have been well validated in previous studies. Treatment with elagolix significantly reduced severe abdominal pain during menstruation compared to treatment with placebo, the company said.

"It is clear from this study and all of our previous studies that elagolix is a safe and effective treatment for endometriosis sufferers," said Kevin Gorman, Neurocrine's president and CEO. "This Phase II study provides the information we need to continue to move this program forward. While limitations were discovered in some of the new exploratory efficacy measures, elagolix again showed strong efficacy in the historical validated endometriosis measures, with an excellent safety profile."

Neurocrine said it would consult with the FDA about how to reconcile the differences seen when pain reduction was measured using daily and monthly scales.

Neurocrine shares closed Wednesday at $3.97, ahead of the elagolix data release, and were recently falling 7.3% to $3.68.

Know what you own: Other companies with endometriosis drugs in development include Abbott Labs(ABT Quote), Repros Therapeutics(RPRX Quote) and Aeterna Zentaris(AEZS Quote).