Post-treatment Efficacy and Safety Follow-up in Women with Uterine Fibroids Treated for 52 Weeks With Linzagolix

INTRODUCTION: We previously reported safety and efficacy results from the PRIMROSE 1 and 2 trials of linzagolix in the treatment of women with heavy menstrual bleeding associated with uterine fibroids (UFs), which showed maintenance of treatment effect for up to 52 weeks of dosing. Here we report post-treatment follow-up of key efficacy and safety results from weeks 64 and 76. METHODS: PRIMROSE1 and PRIMROSE2 were two randomized, double-blind, placebo-controlled phase 3 trials investigating the efficacy and safety of linzagolix 100 mg and 200 mg once daily, with or without hormonal add-back therapy (ABT) in the treatment of UFs for 52 weeks. Participants were followed for up to 6 months (week 76) after completion of treatment. RESULTS: At week 64, improvements in pain, hemoglobin, health-related quality of life, and uterine and fibroid volumes, observed at 24 and 52 weeks, were diminished but a beneficial difference from baseline was maintained. In patients with amenorrhea at week 52, the median (95% CI) time to first uterine bleeding was 30 (SD 27; SD 32) and 31 (SD 29; SD 32) days in PRIMROSE 1 and 2, respectively. At week 76, participants had full or partial recovery of lumbar spine bone mineral density (BMD): with 53%, 52% and 64% for 100 mg, 100 mg+ABT and 200 mg+ABT, respectively in PRIMROSE1 and 59%, 80% and 67% in PRIMROSE2. CONCLUSION: Linzagolix effects persisted following treatment discontinuation, although there was partial return to baseline for all measured efficacy endpoints. BMD also improved. The return to menstruation was rapid.