Pill-Based Complement Blocker Brings Near-Normal Blood Counts to Chinese PNH Patients

Paroxysmal nocturnal hemoglobinuria has long been one of hematology’s cruelest puzzles: a rare, acquired stem-cell mutation that leaves red blood cells defenseless against the body’s own complement system, so that they are destroyed overnight and patients wake to dark, hemoglobin-laden urine, profound fatigue, and a lifetime of transfusions. Now a large real-world study from China suggests that a twice-daily pill can quiet that destruction with remarkable consistency. In a multicenter retrospective analysis published in Annals of Hematology, researchers led by Leyu Wang and Bing Han of Peking Union Medical College Hospital report that iptacopan, an oral inhibitor of the complement pathway’s alternative arm, produced sustained control of hemolysis and near-normal hemoglobin levels in the overwhelming majority of Chinese patients who had never previously received a complement inhibitor.

The numbers are striking. Among 54 patients followed for a median of 10 months, 98.1 percent achieved at least one lactate dehydrogenase value at or below 1.5 times the upper limit of normal, the standard biochemical signature that red-cell destruction has been brought to heel. Even more consequential for daily life, 85.2 percent reached hemoglobin concentrations of 120 grams per liter or higher, a threshold that generally marks the boundary between anemia and normal oxygen-carrying capacity. And in a finding that will resonate with every patient who has scheduled life around transfusion appointments, all 20 patients who were transfusion-dependent at the start of treatment became transfusion-independent.

To understand why those results matter, it helps to look at the molecular machinery involved. In PNH, a somatic mutation in the PIGA gene eliminates the glycosylphosphatidylinositol anchors that hold protective proteins such as CD55 and CD59 to the surface of blood cells. Without CD59, the membrane attack complex, a barrel-shaped assembly of complement proteins that punches lethal holes in cell membranes, forms freely on red cells, and chronic intravascular hemolysis follows. Free hemoglobin spills into the plasma, scavenges nitric oxide, and drives the smooth-muscle spasms, abdominal pain, erectile dysfunction, and pulmonary hypertension that make the disease so debilitating. The same uncontrolled complement activation consumes platelets’ protection and fuels the thromboses that historically made PNH one of the deadliest benign hematologic conditions.

The first generation of targeted therapy, the anti-C5 antibodies eculizumab and ravulizumab, transformed that prognosis by blocking the terminal step of the complement cascade. But C5 inhibition has a structural limitation: it stops the membrane attack complex while leaving the upstream alternative pathway running. Red cells coated with C3 fragments survive destruction in the bloodstream only to be cleared by macrophages in the spleen and liver, a process called extravascular hemolysis that keeps many patients anemic and transfusion-dependent. Roughly a quarter of patients on C5 inhibitors continue to require transfusions, and some experience breakthrough hemolysis when complement activation overwhelms the drug.

Iptacopan takes a different route. As a small-molecule inhibitor of factor B, it shuts down the alternative pathway at its point of amplification, upstream of both C3 opsonization and terminal complex formation. In theory, that should prevent intravascular hemolysis and the C3-coated red cells that fuel extravascular hemolysis, addressing the disease at a more fundamental level. The pivotal phase three APPOINT-PNH trial, which enrolled complement inhibitor-naive patients internationally, demonstrated exactly that, with most participants achieving hemoglobin normalization without transfusions and earning the drug regulatory approvals in the United States, Europe, and elsewhere as the first oral monotherapy for PNH.

What the new Chinese study adds is evidence from a real-world population outside the tightly controlled boundaries of a registration trial. The 54 patients, 17 of them women, had a median age of 38 years and ranged from 21 to 82, drawn from a network of hospitals spanning Beijing, Wuhan, Chengdu, Zhengzhou, Taiyuan, Kunming, and other cities. The investigators tracked clinical and laboratory indicators at one, three, and six months after starting iptacopan and through subsequent follow-up. Notably, the benefits held across disease subtypes: patients with classic hemolytic PNH and those with an aplastic anemia-PNH overlap syndrome, in which bone marrow failure compounds the hemolysis, showed no significant differences in their hemolytic parameters on treatment.

Safety, always the second half of the efficacy equation, was equally reassuring. The most common adverse events were headache and upper respiratory tract infection, each affecting 13 percent of patients. Breakthrough hemolysis, the feared scenario in which hemolysis resumes despite therapy, occurred in only 7.4 percent of the cohort. The study recorded no new thrombotic or microvascular events, no extravascular hemolysis, and, critically, no breakthrough infections with Neisseria meningitidis or Streptococcus pneumoniae, the encapsulated bacteria against which complement pathway blockade raises a well-known shield. Meningococcal infection is the reason all complement inhibitor users require vaccination and vigilance, and its complete absence in this cohort, while reassuring, underscores that the follow-up window remains relatively short.

The retrospective design carries inherent caveats that the authors and independent observers alike will emphasize. Without randomization or a control group, the study cannot exclude the influence of selection bias, and the median follow-up of 10 months, with a range of 6 to 18, leaves long-term durability, cumulative toxicity, and pregnancy outcomes open questions. Laboratory monitoring schedules varied across the many participating centers, and the analysis of patients who discontinued treatment or required dose adjustments will be scrutinized as the full paper circulates. Still, the consistency of the findings with the phase three data, in a health system and genetic background not represented in the original trials, strengthens the case that the drug’s benefits generalize.

For Chinese patients, the practical implications are immediate. Before factor B inhibitors, the standard of care in much of China, as in many middle-income countries, was limited by the cost and intravenous infrastructure demands of C5 monoclonal antibodies, leaving many patients managed with transfusions, iron supplementation, and anticoagulation alone. An oral agent that can be prescribed across a network of provincial hospitals, and that returned every transfusion-dependent patient in this cohort to transfusion independence, represents a meaningful shift in what standard care can look like outside major academic centers.

The broader scientific story is equally compelling. PNH was the first disease in which a clonal hematopoiesis was shown to be rescued not by eliminating the mutant clone but by pharmacologically disarming the selective pressure it exploited, a conceptual template now being applied across complement-mediated disorders, from IgA nephropathy to C3 glomerulopathy. Iptacopan’s real-world performance in China, with sustained hemolytic control, significant hemoglobin improvement, and a favorable safety profile, confirms that the alternative pathway is a druggable Achilles’ heel of this disease. As longer follow-up accumulates and prospective studies in additional populations mature, the question is shifting from whether oral factor B inhibition works to how best to sequence, monitor, and eventually tailor complement blockade to each patient’s biology, a question that the next decade of PNH research is now well positioned to answer.

Subject of Research: Real-world efficacy and safety of the oral complement factor B inhibitor iptacopan in Chinese patients with paroxysmal nocturnal hemoglobinuria

Article Title: Iptacopan treatment for chinese patients with hemolytic paroxysmal nocturnal hemoglobinuria (PNH): a multicenter retrospective study

Article References: Wang, L., Zhang, M., Chang, H., Zhou, H., Ma, S., Ma, Y., Miao, D., Zhou, Z., Jia, J., Zhang, R., Zhang, G., Liu, J., Zhu, Q., Yu, B., Wang, H., Hou, R., Ge, W., Wang, L., Lang, J., … Han, B. (2026). Iptacopan treatment for chinese patients with hemolytic paroxysmal nocturnal hemoglobinuria (PNH): a multicenter retrospective study. Annals of Hematology. https://doi.org/10.1007/s00277-026-07230-7

Image Credits: AI Generated

DOI: 10.1007/s00277-026-07230-7

Keywords: paroxysmal nocturnal hemoglobinuria, iptacopan, complement inhibitor, factor B, hemolysis, hemoglobin, transfusion independence, alternative pathway, breakthrough hemolysis, retrospective study, Annals of Hematology, China