Positive topline data were announced from two phase 3 studies evaluating the efficacy and safety of linzagolix (Yselty®; ObsEva) for the treatment of heavy menstrual bleeding due to uterine fibroids.

Linzagolix is a novel, oral gonadotropin-releasing hormone (GnRH) receptor antagonist. The 52-week, double-blind, placebo-controlled PRIMROSE 1 and PRIMROSE 2 studies included 1061 women with heavy menstrual bleeding associated with uterine fibroids. Patients were randomized to receive linzagolix 100mg or 200mg once daily or placebo, with and without hormonal add-back therapy (ABT) (estradiol 1mg and norethindrone acetate 0.5mg daily). 

The primary end point for both studies was the percentage of responders, defined as menstrual blood loss volume of ≤80mL and a ≥50% reduction from baseline (assessed using the alkaline hematin method).

Findings from PRIMROSE 1 showed that the study met its primary end point at week 24, with a responder rate of 75.5% (P <.001) among patients receiving linzagolix 200mg with ABT and 56.4% (P =.003) among those receiving linzagolix 100mg without ABT. When pooled with 24 week data from PRIMROSE 2, the responder rates were 84.7% and 56.6% among women receiving linzagolix 200mg with ABT and linzagolix 100mg without ABT, respectively.

Additionally, new data from PRIMROSE 2 demonstrated the sustained efficacy of linzagolix through 52 weeks with responder rates of 91.6% and 53.2% among women receiving 200mg with ABT and 100mg without ABT, respectively.

Both studies also showed that linzagolix was associated with statistically significant improvements in several secondary end points, including reduction in pain, improvement in anemia and quality of life. 

With regard to safety, the most frequently observed adverse events with linzagolix were headache, hot flushes and anemia. Both studies also reported a small incremental change in bone mineral density from baseline.

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Data from the clinical trial program will be submitted for presentation at upcoming scientific conferences. The Company expects to submit a New Drug Application to the Food and Drug Administration (FDA) in the first half of 2021.

For more information visit obseva.com.