Estetrol-drospirenone combination oral contraceptive: North American phase 3 efficacy and safety results

Objective: To assess efficacy, cycle control, and safety of an oral contraceptive containing estetrol (E4) 15 mg and drospirenone (DRSP) 3 mg. Study design: Women aged 16 to 50 years with a body mass index ≤35 kg/m² enrolled in this multicenter, open-label, 13-cycle, phase 3 trial evaluating E4/DRSP in a 24-active/4-placebo regimen. Follow-up was scheduled at Cycles 2, 4, 7, and 10 and within 3 weeks of completing Cycle 13. Participants used daily diaries to record pill use and vaginal bleeding. We evaluated efficacy outcomes in women 16 to 35 years and bleeding patterns and safety (adverse events [AEs]) in all participants. We assessed overall and method-failure pregnancy rates using the Pearl index (PI) and life-table analysis. Scheduled bleeding included spotting or bleeding starting during the 4-day placebo period or first 3 days of the next cycle. Results: We enrolled 1864 women of whom 1674 were 16 to 35 years. Women 16 to 35 years had a PI of 2.65 (95% CI 1.73–3.88), method-failure PI of 1.43 (95% CI 0.7–2.39) and 13-cycle life-table pregnancy rate of 2.1%. Scheduled bleeding occurred in 82.9% to 87.0% of women per cycle; median duration was 4.5 days. Unscheduled bleeding decreased from 30.3% in Cycle 1 to 21.3% to 22.1% during Cycles 2 to 4 and remained stable (15.5% to 19.2%) thereafter. The most frequently reported AEs were headache (5.0%) and metrorrhagia (4.6%). One-hundred thirty-two (7.1%) women discontinued the study early for an AE, most commonly for metrorrhagia (0.9%) and menorrhagia (0.8%). No thromboembolic events occurred. Conclusion: E4/DRSP is an effective oral contraceptive with a predictable bleeding pattern for most women and low AE rates. Implications statement: A new oral contraceptive with a novel estrogen, estetrol, combined with drospirenone has efficacy and safety within the range of other available oral contraceptives. Large phase 4 studies will be needed to confirm if this combination is associated with an improved adverse event profile or lower thrombosis risk.