ObsEva’s Yselty Positive in Two Phase III Trials for Uterine Fibroids


ObsEva, based in Geneva, Switzerland and Boston, Massachusetts, announced topline data from the PRIMROSE 1 and 2 Phase III trials of Yselty (linzagolix) for uterine fibroids.

In PRIMROSE 1, the trial met the primary endpoint at week 24. Women that received the drug showed a statistically significant and clinically meaningful decrease in menstrual blood loss compared to placebo. In women receiving 200 mg Yselty with Add Back Therapy (ABT), which is 1 mg estradiol and 0.5 mg norethindrone acetate daily, had a 75.5% responder rate and patients receiving 100 mg of Yselty without ABT had a 56.4% responder rate.

The pooled data from both trials at week 24 support a “best-in-class profile,” the company indicates, with a responder rate of 84.7% in women receiving 200 mg Yselty with ABT and in women receiving 100 mg without ABT, having a 56.4% responder rate.

Also, new data from PRIMROSE 2 demonstrated that continued treatment with the drug for 52 weeks offered sustained efficacy and was well tolerated. In the women receiving 200 mg with ABT, the responder rates were 91.6% and in women receiving 100 mg without ABT, the responder rate was 53.2%.

In addition, in both trials, the women receiving Yselty showed statistically significant improvements in a number of secondary endpoints, including a decrease in pain, improvement in anemia and quality of life.

“We are extremely pleased by the overall performance of Yselty in addressing heavy menstrual bleeding, a major symptom of uterine fibroids,” said Ernest Loumaye, cofounder and chief executive officer of ObsEva. “These data definitively confirm our belief that Yselty, with and without add-back therapy, has the potential to be an effective treatment for addressing the broad needs of women suffering from uterine fibroids.”

Yselty is a novel, once-a-day, oral GnRH receptor antagonist. It is being developed for heavy menstrual bleeding associated with uterine fibroids and pain associated with endometriosis. Uterine fibroids are a common disorder made up of the growth of benign tumors of the muscular tissue of the uterus. It affects women of childbearing age and can vary in size from undetectable to a large mass. Symptoms can include heavy menstrual bleeding, anemia, pelvic pressure and bloating, urinary frequency and pain that can be debilitating.

ObsEva licensed the drug from Kissei in late 2015 and holds global commercial rights, excluding Asia. The drug is not currently approved anywhere. The company says it is planning regulatory submissions to the U.S. Food and Drug Administration (FDA) in the first half of 2021 and to the European medicines Agency (EMA) in the fourth quarter of 2020.

“Women with symptomatic uterine fibroids experience debilitating pain and discomfort from heavy menstrual bleeding, which often becomes progressively worse, impacting work, home life, and importantly, a woman’s overall health and well-being,” said Hugh Taylor, professor at Yale School of Medicine. “New and effective treatment options that provide long lasting symptom relief are needed for women with uterine fibroids, including for the significant number of women who cannot receive, or wish to avoid, hormone replacement therapy. I am very pleased to see these results, which demonstrate that both regimens of linzagolix are effective in controlling bleeding, reducing fibroids related pain and improving anemia. This could provide a long-awaited medical treatment option to address current unmet needs.”

Company shares climbed 12% in premarket trading at the news.

ObsEva was founded in Switzerland in November 2012. In addition to linzagolix, it is developing OBE022, an oral PGF2alpha receptor antagonist, for preterm labor, and nolasiban, an oral oxytocin receptor antagonist for in vitro fertilization.

On July 1, the company’s partner, Yuyuan Bioscience Technology, submitted a pre-IND meeting request for nolasiban to the Center for Drug Evaluation at the Chinese National Medical Products Administration (NMPA). Two Phase III trials have been completed in Europe and the company plans to initiate a Phase I and Phase II proof-of-concept trial in China.


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