Clinical characteristics of 512 eculizumab-naive paroxysmal nocturnal hemoglobinuria patients in China: a single-center observational study.

OBJECTIVES: With large patient population and complement inhibitors naïve background, the characteristics patients with paroxysmal nocturnal hemoglobinuria (PNH) in China have not been well studied, especially for different subtypes. METHODS: We retrospectively reviewed patients with complete data who visited Peking Union Medical College Hospital (PUMCH) from 2009 to 2019 and had been followed up for more than 2 years. RESULTS: Five hundred and twelve patients were enrolled including 56.3% males and 43.7% females. The median age at disease onset was 33 (9∼80) years. Most were aged 21∼40 years (50.6%). 52.1%, 46.3% and 1.6% of the patients had classic PNH, bone marrow failure (BMF)/PNH and subclinical PNH, respectively. Symptoms of classic PNH were associated with hemolysis, whereas bleeding was more common in BMF/PNH patients. Classic PNH had higher survival rate, larger PNH clone size, higher lactate dehydrogenase (LDH) level and lower ferritin level than BMF/PNH. Although the rate of thrombosis was similar in the classic PNH and BMF/PNH (P = 0.66), those with BMF/PNH had higher chance of renal impairment (P < 0.05). Immunosuppressive agents was more common use in BMF/PNH (P < 0.05), but glucocorticoids, iron supplements and anticoagulants were more common used in classic PNH (P < 0.05) patients. Less evolution to myeloid malignancies was observed in classic PNH than in BMF/PNH (P = 0.02). The major causes of deaths were thrombosis (29.6%), hemorrhage (18.5%) and infections (18.5%). CONCLUSION: Patients with classic PNH and BMF/PNH have different clinical profiles, and we described a more hemolytic features of PNH in China which might be improved with complement inhibitors.

The complement receptor 2/factor H fusion protein TT30 protects paroxysmal nocturnal hemoglobinuria erythrocytes from complement-mediated hemolysis and C3 fragment.

Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by complement-mediated intravascular hemolysis because of the lack from erythrocyte surface of the complement regulators CD55 and CD59, with subsequent uncontrolled continuous spontaneous activation of the complement alternative pathway (CAP), and at times of the complement classic pathway. Here we investigate in an in vitro model the effect on PNH erythrocytes of a novel therapeutic strategy for membrane-targeted delivery of a CAP inhibitor. TT30 is a 65 kDa recombinant human fusion protein consisting of the iC3b/C3d-binding region of complement receptor 2 (CR2) and the inhibitory domain of the CAP regulator factor H (fH). TT30 completely inhibits in a dose-dependent manner hemolysis of PNH erythrocytes in a modified extended acidified serum assay, and also prevents C3 fragment deposition on surviving PNH erythrocytes. The efficacy of TT30 derives from its direct binding to PNH erythrocytes; if binding to the erythrocytes is disrupted, only partial inhibition of hemolysis is mediated by TT30 in solution, which is similar to that produced by the fH moiety of TT30 alone, or by intact human fH. TT30 is a membrane-targeted selective CAP inhibitor that may prevent both intravascular and C3-mediated extravascular hemolysis of PNH erythrocytes and warrants consideration for the treatment of PNH patients.

Decreased susceptibility of leukemic cells with PIG-A mutation to natural killer cells in vitro.

The cloning of the PIG-A gene has facilitated the unraveling of the complex pathophysiology of paroxysmal nocturnal hemoglobinuria (PNH). Of current major concern is the mechanism by which a PNH clone expands. Many reports have suggested that an immune mechanism operates to cause bone marrow failure in some patients with PNH, aplastic anemia, and myelodysplastic syndromes. Because blood cells of PNH phenotype are often found in patients with these marrow diseases, one hypothesis is that the PNH clone escapes immune attack, producing a survival advantage by immunoselection. To test this hypothesis, we examined the sensitivity of blood cells, with or without PIG-A mutations, to killing by natural killer (NK) cells, using 51Cr-release assay in vitro. To both peripheral blood and cultured NK cells, PIG-A mutant cells prepared from myeloid and lymphoid leukemic cell lines were less susceptible than their control counterparts (reverted from the mutant cells by transfection with a PIG-A cDNA). NK activity was completely abolished with concanamycin A and by calcium chelation, indicating that killing was perforin-dependent. There were no differences in major histocompatibility (MHC) class I expression or sensitivity to either purified perforin or to interleukin-2-activated NK cells between PIG-A mutant and control cells. From these results, we infer that PIG-A mutant cells lack molecules needed for NK activation or to trigger perforin-mediated killing. Our experiments suggest that PIG-A mutations confer a relative survival advantage to a PNH clone, contributing to selective expansion of these cells in the setting of marrow injury by cytotoxic lymphocytes.