Efficacy and safety of vemircopan as monotherapy in patients with paroxysmal nocturnal hemoglobinuria

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, complement-mediated hematologic disease. We present the results of a phase 2, open-label clinical trial of vemircopan monotherapy in patients with PNH to explore the efficacy and safety of inhibiting the complement alternative pathway via factor D. Adults (aged ≥18 years) with PNH who were treatment-naïve and switched from eculizumab with hemoglobin (Hgb) of <10 g/dL or rolled over from danicopan monotherapy (ACH471-103 trial; ClinicalTrials.gov identifier: NCT03181633) were enrolled. The trial comprised a 60-day screening period, 12-week treatment period, and 148-week long-term extension. Participants received vemircopan 120 mg twice daily, with potential escalation to 180 mg twice daily. The primary endpoint was change in Hgb from baseline to week 12. Safety endpoints included treatment-emergent adverse events (TEAEs) and serious AEs. Twenty-nine participants were enrolled (treatment-naïve, n = 12; eculizumab-switch, n = 11; and danicopan-rollover, n = 6); all completed the 12-week treatment period, and 1 danicopan-rollover participant completed the long-term extension. Clinically meaningful improvements from baseline to week 12 in Hgb (change of ≥2 g/dL) were reported in the treatment-naïve (mean, 3.6 [standard deviation [SD], 1.5]) and eculizumab-switch (mean, 3.3 [SD, 2.0]) cohorts and maintained through the end of the trial. Eighty-two breakthrough intravascular hemolysis (BT-IVH) events in 25 participants were reported. Twenty-eight participants reported TEAEs, and 14 reported serious AEs; most were unrelated to vemircopan. No deaths occurred. This trial evaluating vemircopan monotherapy met its primary efficacy endpoint; however, concerns regarding BT-IVH risk and suboptimal, inconsistent control of IVH emerged, leading to early trial termination. This trial was registered at www.clinicaltrials.gov as #NCT04170023, and EudraCT as #2019-003830-17.