Ravulizumab (ALXN1210), a new complement C5 inhibitor, provides immediate, complete, and sustained C5 inhibition. This phase 3, open-label study assessed the noninferiority of ravulizumab to eculizumab in complement inhibitor–naive adults with paroxysmal nocturnal hemoglobinuria (PNH). Patients with lactate dehydrogenase (LDH) ≥1.5 times the upper limit of normal and at least 1 PNH symptom were randomized 1:1 to receive ravulizumab or eculizumab for 183 days (N = 246). Coprimary efficacy end points were proportion of patients remaining transfusion-free and LDH normalization. Secondary end points were percent change from baseline in LDH, change from baseline in Functional Assessment of Chronic Illness Therapy (FACIT)–Fatigue score, proportion of patients with breakthrough hemolysis, stabilized hemoglobin, and change in serum free C5. Ravulizumab was noninferior to eculizumab for both coprimary and all key secondary end points (Pinf < .0001): transfusion avoidance (73.6% vs 66.1%; difference of 6.8% [95% confidence interval (CI), −4.66, 18.14]), LDH normalization (53.6% vs 49.4%; odds ratio, 1.19 [0.80, 1.77]), percent reduction in LDH (−76.8% vs −76.0%; difference [95% CI], −0.83% [−5.21, 3.56]), change in FACIT-Fatigue score (7.07 vs 6.40; difference [95% CI], 0.67 [−1.21, 2.55]), breakthrough hemolysis (4.0% vs 10.7%; difference [95% CI], −6.7% [−14.21, 0.18]), and stabilized hemoglobin (68.0% vs 64.5%; difference [95% CI], 2.9 [−8.80, 14.64]). The safety and tolerability of ravulizumab and eculizumab were similar; no meningococcal infections occurred. In conclusion, ravulizumab given every 8 weeks achieved noninferiority compared with eculizumab given every 2 weeks for all efficacy end points, with a similar safety profile. This trial was registered at www.clinicaltrials.gov as #NCT02946463.

There is a Blood Commentary on this article in this issue.

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by chronic, complement-mediated hemolysis, frequently leading to debilitating clinical symptoms and life-threatening complications such as thromboembolism (TE). A retrospective analysis was performed on 301 patients from the South Korean National PNH Registry to describe disease burden and identify TE-associated risk factors. TE was identified in 18 % of patients and was associated with increased risk for mortality [odds ratio (OR), 6.85; P < 0.001]. A multivariate analysis showed that PNH patients with elevated hemolysis [lactate dehydrogenase (LDH) levels ≥1.5 times the upper limit of normal (ULN)] at diagnosis were at significantly higher risk for TE than patients with LDH <1.5 × ULN (OR 7.0; P = 0.013). The combination of LDH ≥1.5 × ULN with the clinical symptoms of abdominal pain, chest pain, dyspnea, or hemoglobinuria was associated with a greater increased risk for TE than elevated hemolysis or clinical symptoms alone. Continuous monitoring of these risk factors is critical for identifying PNH patients at risk for morbidities and mortality and allowing early intervention.