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July 6, 2020, 1:00 a.m. EDT

ObsEva Announces Positive Results from two Phase 3 Studies, PRIMROSE 1 and 2, of Yselty(R) (linzagolix) for the Treatment of Uterine Fibroids

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- PRIMROSE 1 achieved statistically significant and clinically meaningful results across primary and key secondary endpoints at week 24

- PRIMROSE 2 results demonstrate sustained efficacy and continued safety of linzagolix at week 52

- Results confirm linzagolix as a potential best-in-class GnRH antagonist, with a pooled responder rate of 84.7% for the 200 mg with Add Back Therapy* (ABT) dose from PRIMROSE 1 and 2

- Linzagolix is the only GnRH antagonist as a potential unique treatment option for up to 50% of US women with uterine fibroids for whom ABT therapy may be contraindicated

- Success of PRIMROSE 1 and 2 studies enables progression towards regulatory submissions, anticipated 4Q 2020 in the EU and 1H 2021 in the US

GENEVA, Switzerland and BOSTON, MA (July 6, 2020) - ObsEva SA /zigman2/quotes/208216166/composite OBSV -0.60% (six:OBSN), a biopharmaceutical company developing and commercializing novel therapies to improve women's reproductive health, today announced top-line results from the PRIMROSE 1 and 2 studies of Yselty(R) (linzagolix) to assess the efficacy and safety in women with heavy menstrual bleeding due to uterine fibroids.

PRIMROSE 1 met the primary endpoint at week 24, and showed that women receiving linzagolix experienced a statistically significant and clinically meaningful reduction in menstrual blood loss (less-than or equal to80 mL and a greater-than or equal to50% reduction from baseline) compared to placebo. Women receiving 200 mg with ABT achieved a 75.5% (P<0.001) responder rate and those receiving 100 mg without ABT achieved a 56.4% (P=0.003) responder rate.

The pooled week 24 data from these two Phase 3 studies support a best-in-class profile, with a responder rate of 84.7% in women receiving linzagolix 200 mg with ABT, and 56.6% in women receiving linzagolix 100 mg without ABT.

In addition, new data from PRIMROSE 2 demonstrate that continued treatment with linzagolix for 52 weeks provides sustained efficacy and is well tolerated. Responder rates of 91.6% and 53.2% were observed in women receiving 200 mg with ABT and 100 mg without ABT, respectively, both of which are similar to the responder rates observed at week 24 of the study.

Across both studies, women receiving linzagolix experienced statistically significant improvements across a number of clinically relevant secondary endpoints, including reduction 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. 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," said Dr. Ernest Loumaye, ObsEva CEO and cofounder. "Yselty's unique and differentiated profile reinforces its potential as a promising, commercially competitive product, designed to offer more women a treatment adapted to their clinical and personal needs. These excellent data move us closer to the potential commercialization of Yselty and our immediate priority is to progress our regulatory filings."

In PRIMROSE 1, the incidence of adverse events was similar between placebo and active treatment. The most frequently observed adverse events, with an incidence >5%, were headache and hot flushes. In addition, a minimal mean percentage change in lumbar spine bone mineral density (BMD) from baseline was observed in both treatment arms at week 24.

In PRIMROSE 2, the most frequently observed adverse events, with an incidence >5%, were headache, hot flushes and anemia. In addition, a small incremental change in BMD was observed at week 52 compared to week 24.

"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 Dr. Hugh Taylor, Professor at Yale School of Medicine, U.S. "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 fibroid related pain and improving anemia. This could provide a long-awaited medical treatment option to address current unmet needs."

ObsEva is now preparing its regulatory submissions to the European Medicines Agency (EMA) and the U.S. Food and Drug Administration (FDA) which it anticipates submitting in 4Q 2020 and 1H 2021, respectively. Data from across the clinical trial program will be submitted for presentation at upcoming scientific conferences.

Yselty(R) is a registered trademark owned by Kissei for use by ObsEva. Yselty(R) is not yet approved for use anywhere in the world.

* Add Back Therapy = 1 mg estradiol and 0.5 mg norethindrone acetate daily

Conference Call and Webcast Today

ObsEva will host a conference call and audio webcast today beginning at 8:00 a.m. Eastern Time / 2:00 p.m. Central European Time to discuss Phase 3 PRIMROSE 1 & 2 study results of linzagolix. Investors may participate by dialing (844) 419-1772 for U.S. callers or +1 (213) 660-0921 for international callers, and referring to conference ID 6673575. A live or archived webcast of the conference call can be accessed via the following link: https://www.obseva.com/event-detail/?event=3249 .

About Linzagolix

Yselty(R) (linzagolix) is a novel, once daily, oral GnRH receptor antagonist with a potentially best-in-class profile. Linzagolix is currently in late-stage clinical development for the treatment of heavy menstrual bleeding associated with uterine fibroids and pain associated with endometriosis. ObsEva licensed linzagolix from Kissei in late 2015 and retains worldwide commercial rights, excluding Asia, for the product. Linzagolix is not currently approved anywhere in the world.

About Phase 3 PRIMROSE Program in Uterine Fibroids

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