Yuan Xuan, Gavriilaki Eleni, Thanassi Jane A, Yang Guangwei, Baines Andrea C, Podos Steven D, Huang Yongqing, Huang Mingjun, Brodsky Robert A
Division of Hematology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Achillion Pharmaceuticals, New Haven, CT, USA.
Haematologica. 2017 Mar;102(3):466-475. doi: 10.3324/haematol.2016.153312. Epub 2016 Nov 3.
Paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome are diseases of excess activation of the alternative pathway of complement that are treated with eculizumab, a humanized monoclonal antibody against the terminal complement component C5. Eculizumab must be administered intravenously, and moreover some patients with paroxysmal nocturnal hemoglobinuria on eculizumab have symptomatic extravascular hemolysis, indicating an unmet need for additional therapeutic approaches. We report the activity of two novel small-molecule inhibitors of the alternative pathway component Factor D using correlates of both paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. Both compounds bind human Factor D with high affinity and effectively inhibit its proteolytic activity against purified Factor B in complex with C3b. When tested using the traditional Ham test with cells from paroxysmal nocturnal hemoglobinuria patients, the Factor D inhibitors significantly reduced complement-mediated hemolysis at concentrations as low as 0.01 μM. Additionally the compound ACH-4471 significantly decreased C3 fragment deposition on paroxysmal nocturnal hemoglobinuria erythrocytes, indicating a reduced potential relative to eculizumab for extravascular hemolysis. Using the recently described modified Ham test with serum from patients with atypical hemolytic uremic syndrome, the compounds reduced the alternative pathway-mediated killing of -null reagent cells, thus establishing their potential utility for this disease of alternative pathway of complement dysregulation and validating the modified Ham test as a system for pre-clinical drug development for atypical hemolytic uremic syndrome. Finally, ACH-4471 blocked alternative pathway activity when administered orally to cynomolgus monkeys. In conclusion, the small-molecule Factor D inhibitors show potential as oral therapeutics for human diseases driven by the alternative pathway of complement, including paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome.
阵发性睡眠性血红蛋白尿症和非典型溶血性尿毒症综合征是补体替代途径过度激活所致的疾病，可使用依库珠单抗进行治疗，依库珠单抗是一种针对终末补体成分C5的人源化单克隆抗体。依库珠单抗必须静脉给药，此外，一些接受依库珠单抗治疗的阵发性睡眠性血红蛋白尿症患者会出现症状性血管外溶血，这表明对其他治疗方法仍有未满足的需求。我们报告了两种新型小分子替代途径成分D因子抑制剂的活性，其使用了阵发性睡眠性血红蛋白尿症和非典型溶血性尿毒症综合征的相关指标。这两种化合物都以高亲和力结合人D因子，并有效抑制其对与C3b结合的纯化B因子的蛋白水解活性。当使用来自阵发性睡眠性血红蛋白尿症患者的细胞进行传统的Ham试验时，D因子抑制剂在低至0.01μM的浓度下就能显著降低补体介导的溶血。此外，化合物ACH-4471显著减少了阵发性睡眠性血红蛋白尿症红细胞上C3片段的沉积，这表明相对于依库珠单抗，其发生血管外溶血的可能性降低。使用最近描述的针对非典型溶血性尿毒症综合征患者血清的改良Ham试验，这些化合物减少了替代途径介导的 - 无效试剂细胞的杀伤，从而确立了它们在这种补体替代途径失调疾病中的潜在效用，并验证了改良Ham试验作为非典型溶血性尿毒症综合征临床前药物开发系统的有效性。最后，ACH-4471经口给予食蟹猴时可阻断替代途径活性。总之，小分子D因子抑制剂显示出作为口服治疗药物用于治疗由补体替代途径驱动的人类疾病的潜力，包括阵发性睡眠性血红蛋白尿症和非典型溶血性尿毒症综合征。
