Iptacopan Oral Complement Inhibitor Shows 72% Hemoglobin Improvement in PNH and IgA Nephropathy

What Is Iptacopan and How Does Complement Inhibition Work?

The complement system is a part of the innate immune system that, when dysregulated, can attack the body's own cells. In paroxysmal nocturnal hemoglobinuria (PNH), complement destroys red blood cells causing severe anemia, fatigue, and life-threatening blood clots. In IgA nephropathy, complement activation in the kidneys drives progressive inflammation and scarring that can lead to kidney failure. Iptacopan works by selectively inhibiting factor B, a protein essential for the alternative pathway of complement activation.

Unlike existing complement inhibitors such as eculizumab (Soliris) and ravulizumab (Ultomiris), which are administered as IV infusions and target downstream complement protein C5, iptacopan is an oral capsule taken twice daily that blocks complement activation further upstream. This proximal inhibition prevents both the intravascular hemolysis (addressed by C5 inhibitors) and the extravascular hemolysis (which C5 inhibitors do not fully control), explaining the superior hemoglobin improvements seen in PNH trials. The oral route eliminates the need for infusion center visits, significantly reducing treatment burden.

What Were the Results of the PNH and IgA Nephropathy Trials?

The APPLY-PNH Phase 3 trial enrolled adults with PNH who had persistent anemia despite treatment with a C5 inhibitor (eculizumab or ravulizumab). Patients were randomized to switch to iptacopan 200 mg twice daily or continue their existing C5 inhibitor. At 24 weeks, a significantly higher proportion of iptacopan-treated patients achieved a hemoglobin increase of ≥2 g/dL from baseline compared to the C5 inhibitor group, with mean hemoglobin levels approaching normal ranges. Iptacopan patients also had a substantially higher transfusion-free rate. These results, published in the New England Journal of Medicine, supported the FDA's approval of Fabhalta for PNH in December 2023.

In the APPLAUSE-IgAN Phase 3 trial, adults with IgA nephropathy and significant proteinuria despite maximum renin-angiotensin system blockade received iptacopan 200 mg twice daily or placebo. The iptacopan group showed a clinically meaningful reduction in proteinuria (urine protein-to-creatinine ratio) versus placebo, meeting the primary endpoint. Estimated GFR decline was also slower with iptacopan, suggesting meaningful preservation of kidney function. The safety profile was generally favorable, with upper respiratory tract infections being among the most common adverse events and no disproportionate increase in serious infections reported.

What Does This Mean for Patients With Complement-Mediated Diseases?

The availability of an effective oral complement inhibitor transforms the treatment landscape for patients with PNH, who previously faced a lifetime of IV infusions with annual costs that can exceed several hundred thousand dollars. Iptacopan's oral formulation eliminates infusion-related time burden and healthcare resource utilization, offering significant quality-of-life improvements. For IgA nephropathy, which is the world's most common primary glomerulonephritis and a leading cause of kidney failure in young adults, iptacopan offers a targeted complement therapy addressing a key driver of disease progression.

Novartis is pursuing a broad development program for iptacopan across multiple complement-mediated conditions. Trials are underway or planned in C3 glomerulopathy (APPEAR-C3G), atypical hemolytic uremic syndrome (aHUS), and geographic atrophy — the advanced dry form of age-related macular degeneration. If successful across these indications, iptacopan could become a foundational therapy for complement-driven disease. The FDA granted iptacopan Priority Review for PNH, and regulatory review for the IgA nephropathy indication is anticipated based on APPLAUSE-IgAN results.