Navigating the complement cascade: A multicenter journey from pegcetacoplan to iptacopan in paroxysmal nocturnal hemoglobinuria

Abstract Introduction: The therapeutic landscape for paroxysmal nocturnal hemoglobinuria (PNH) has rapidly evolved with multiple proximal complement inhibitors now available, including pegcetacoplan (C3 inhibitor) and iptacopan (oral factor B inhibitor). While clinical trials have established individual drug efficacy compared with terminal complement inhibitors, real-world evidence regarding therapeutic transitions between proximal complement inhibitors remains extremely limited. As patients and clinicians increasingly seek to optimize treatment through sequential therapy approaches, understanding the outcomes of transitioning from pegcetacoplan to iptacopan becomes critical for evidence-based treatment sequencing in this rare hematologic disorder. Methods: We conducted a retrospective multicenter analysis across 3 academic medical centers (Cleveland Clinic, Mayo Clinic, Levine Cancer Institute) that evaluated 15 consecutive patients with PNH who were considered for transition from pegcetacoplan to iptacopan. Patients had confirmed PNH by flow cytometry and ≥3 months pegcetacoplan exposure. After switching to iptacopan, we assessed treatment acceptance rates, demographic characteristics, clinical outcomes including hemoglobin and lactate dehydrogenase (LDH) levels, and safety parameters. Responses to iptacopan were classified as optimal (hemoglobin >10.5 g/dL with clinical improvement) or suboptimal. Statistical analysis used paired t tests for continuous variables. Results: Of the 15 patients evaluated (median age [range]: 53 [22-81] years; 73% female), 14 patients (93.3%) elected to transition to iptacopan, demonstrating high treatment acceptance. Disease subtypes included classic PNH (36%) and PNH (64%) in the setting of another bone marrow disorder (n=7), multiple myeloma (n=1), and myelofibrosis (n=1). Median (range) duration of pegcetacoplan treatment pre-switch was 3 months (2-7 months), and median (range) duration of iptacopan treatment was 24 months (6-36 months). Among patients who transitioned, 79% (11/14) achieved hemoglobin improvement, with a mean increase from 9.2±1.8 to 10.8±2.1 g/dL (P=.028). Overall, optimal response was achieved in 64% (9/14) of patients. Response rates varied significantly by disease subtype: 80% in patients with classic PNH vs 56% in patients with PNH and aplastic anemia, with particularly poor outcomes in patients with concurrent hematologic malignancies (0%). LDH levels improved in 86% of patients, decreasing from 400±152 to 310±95 U/L (P=.015). PNH clone sizes remained stable throughout transition (erythrocyte: 75.1%±9.2% vs 75.4%±9.4%, P=.62; granulocyte: 95.0%±3.9% versus 95.2%±4.0%, P=.45). Treatment was well tolerated with no serious adverse events, breakthrough hemolysis, thrombosis, or discontinuations required. Two patients experienced mild self-limited gastrointestinal symptoms. Conclusions: This first multicenter real-world analysis demonstrates that the pegcetacoplan-to-iptacopan transition provides clinical benefit in the majority of this initial set of patients with PNH, with significant improvements in hemoglobin and an excellent safety profile while maintaining clone stability. The high acceptance rate suggests that patients prefer oral therapy over subcutaneous administration. These findings address a critical knowledge gap in proximal complement inhibitor sequencing, suggesting that iptacopan is an effective therapeutic option for patients with inadequate pegcetacoplan response and supporting the development of evidence-based treatment algorithms for optimal PNH care in the era of multiple complement inhibitor options.