Onset and resolution of ovarian toxicity with nirogacestat treatment in females with desmoid tumors: Updated safety analyses from the DeFi phase 3 study

Introduction: Nirogacestat is a targeted gamma secretase inhibitor approved in the United States for adults with progressing desmoid tumors. In the phase 3 DeFi study (NCT03785964) of nirogacestat, ovarian toxicity (OT) was identified as a safety signal among females of reproductive potential (FORP). This analysis further describes the incidence, presentation, and resolution of OT.

Methods: Patients were randomized to twice-daily oral nirogacestat (150 mg) or placebo, taken in continuous 28-day cycles. Investigator-identified OT in FORP was based on abnormal reproductive hormone values or perimenopausal symptoms (or both). Adverse event follow-up was conducted to assess OT resolution. Post hoc analyses included return of menstruation and return of follicle-stimulating hormone (FSH) to within normal limits (WNL) (≤20.4 mIU/mL).

Results: Of 92 randomized females, 73 in the safety population were FORP (n = 36 nirogacestat, n = 37 placebo). OT was identified in 75% (27 of 36) receiving nirogacestat and 0% (0 of 37) receiving placebo. As of October 24, 2022, investigators reported OT resolution in 78% (21 of 27) of patients, with median OT duration of 19.1 weeks. Off-treatment resolution was reported in all 11 patients (100%) who stopped nirogacestat treatment; of these, all nine with available menstruation information experienced return of menstruation and eight had FSH WNL at last reported assessment. Resolution was reported in 10 of 14 (71%) while on nirogacestat; of these, all 10 experienced return of menstruation and seven had FSH WNL. Two patients were lost to follow-up.

Conclusion: Most FORP treated with nirogacestat experienced OT, with the majority resolving, including all who stopped treatment, suggesting that OT is transient.