Safety and efficacy of pegcetacoplan in paroxysmal nocturnal hemoglobinuria

Abstract

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired, hematologic disease characterized by complement-mediated hemolysis, thrombosis, and various degrees of bone marrow dysfunction. Until recently, C5 inhibition with eculizumab or ravulizumab represented the only therapies approved for patients with PNH by the United States Food and Drug Administration (US FDA). Although C5-inhibitors reduce PNH-related signs and symptoms, many patients continue to exhibit persistent anemia and require frequent blood transfusions. In May 2021, pegcetacoplan became the third US FDA-approved treatment for adults with PNH, and the first to target C3, a complement component upstream of C5. The novel strategy of inhibiting proximal complement activity with pegcetacoplan controls C5-mediated intravascular hemolysis and prevents C3-mediated extravascular hemolysis. Here, we review the results from multiple pegcetacoplan clinical studies on the efficacy and safety of pegcetacoplan treatment in adults with PNH. This review summarizes findings from three studies in complement-inhibitor-naïve patients with PNH (PADDOCK [phase Ib], PALOMINO [phase IIa], PRINCE [phase III; pegcetacoplan versus standard treatment excluding complement-inhibitors]), and one phase III study (PEGASUS) that compared eculizumab to pegcetacoplan in patients who remained anemic (hemoglobin levels < 10.5 g/dL) despite stable eculizumab treatment (⩾3 months). These studies found that pegcetacoplan contributed to superior improvements in primary and secondary endpoints related to hemoglobin levels and other hematologic parameters and provided effective management of anemia and anemia-related complications (i.e. transfusion burden, reticulocyte production, and fatigue). Furthermore, we summarize results from the 32-week open-label period from the PEGASUS trial, which confirmed the long-term safety and durable efficacy of pegcetacoplan as demonstrated by sustained improvements in clinical and hematologic outcomes in pegcetacoplan-treated patients. Pegcetacoplan is approved for the treatment of adults with PNH in the United States (Empaveli™) and for adult patients who remain anemic after at least 3 months of stable C5-inhibitor therapy in the European Union (Aspaveli^®) and Australia (Empaveli; also approved for patients intolerant to C5-inhibitors).

Keywords: anemia; complement-inhibitor; hemolysis; paroxysmal nocturnal hemoglobinuria; pegcetacoplan; quality-of-life.

Figure 1.

The complement cascade and complement-inhibitors approved by the US FDA, EMA, and Australian Therapeutic Goods Agency for the treatment of PNH [Pegcetacoplan (P); Eculizumab (E); and Ravulizumab (R)]. By inhibiting C3 and C3b, pegcetacoplan exerts broad inhibition of the complement cascade, reduces the risk of thrombosis, and prevents both intravascular hemolysis and extravascular hemolysis. C5-inhibitors eculizumab and ravulizumab can reduce thrombosis and intravascular hemolysis but do not address extravascular hemolysis. EVH, extravascular hemolysis; IVH, intravascular hemolysis; MAC, membrane attack complex; PNH, paroxysmal nocturnal hemoglobinuria; RBCs, red blood cells. *PNH RBCs can become opsonized by C3b and its degradation products, iC3b and C3dg, which target PNH RBCs for the destruction by phagocytosis/extravascular hemolysis in the liver and spleen. The relative role of C3b, iC3b, and C3dg in promoting extravascular clearance of PNH RBCs is still under investigation.