Reduced-intensity stem cell allografting for PNH patients in the eculizumab era: The Mexican experience

Hematopoietic Stem Cell Transplantation for Patients with Paroxysmal Nocturnal Hemoglobinuria with or without Aplastic Anemia: A Multicenter Turkish Experience

Objective:

Although inhibition of the complement system at different steps is a promising therapy modality in patients with paroxysmal nocturnal hemoglobinuria (PNH), allogeneic hematopoietic stem cell transplantation (HCT) is still the only curative therapy, especially for patients with intractable hemolysis or bone marrow failure. The aim of this study is to evaluate the outcomes of allogeneic HCT in PNH patients with aplastic anemia (PNH-AA) or without.

Materials and Methods:

Thirty-five PNH/PNH-AA patients who were treated with allogeneic HCT in 10 transplantation centers in Turkey were retrospectively analyzed.

Results:

Sixteen (45.7%) and 19 (54.3%) patients were diagnosed with classical PNH and PNH-AA, respectively. The median age of the patients was 32 (18-51) years. The 2-year overall survival (OS) rate and rate of graft-versus-host disease-free, failure-free survival (GFFS) was 81.2% and 78.1%, respectively. The 2-year OS in cases of classical PNH and PNH-AA was 81.3% and 79.9%, respectively (p=0.87), and 2-year GFFS in cases of PNH and PNH-AA was 79% and 76% (p=0.977), without statistical significance. The OS and GFFS rates also did not differ between transplantations with matched sibling donors (MSDs) and matched unrelated donors (MUDs).

Conclusion:

Allogeneic HCT with MSDs or MUDs is a good option for selected patients with classical PNH and PNH-AA. In particular, patients with debilitating and refractory hemolysis and patients with bone marrow failure might form an excellent group of candidates for allogeneic HCT.

Paroxysmal nocturnal hemoglobinuria: role of the complement system, pathogenesis, and pathophysiology

The complement system is part of the innate immune response system, which comprises more than 50 distinct plasma and serum proteins that interact to opsonize pathogens (i.e., mark pathogens for destruction) and induce inflammatory responses to fight infection. The role of the complement system is 2-fold: immune surveillance and host defense. Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, chronic, acquired, hematologic disease caused by somatic mutations in the gene PIGA in the hematopoietic stem cells. These stem cells produce abnormal clone blood cells that lack the complement regulatory proteins CD55 and CD59, causing the body to recognize these otherwise healthy red blood cells as damaged. The complement system destroys cells without these protective proteins, resulting in general hemolysis. PNH is characterized by fatigue; hemolytic anemia that can be severe and debilitating; increased lactic dehydrogenase level, reticulocyte count, and bilirubin level; propensity for thrombotic events; and renal dysfunction. Epidemiologic data, while sparse, suggest that an estimated 5,000-6,000 individuals in the United States are affected by PNH. If left untreated, PNH has a 10-year mortality rate of 29%, although the natural history of this disease has been recently altered by the introduction of complement inhibitors for the treatment of PNH. DISCLOSURES: This research was developed under a research contract between RTI Health Solutions and Apellis Pharmaceuticals and was funded by Apellis Pharmaceuticals. Bektas, Copley-Merriman, and Khan are employees of RTI Health Solutions. Sarda is an employee of Apellis Pharmaceuticals. Shammo consults for Apellis Pharmaceuticals.

Allogeneic Hematopoietic Stem Cell Transplantation for Paroxysmal Nocturnal Hemoglobinuria: Multicenter Analysis by the Polish Adult Leukemia Group

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is the sole potential cure for paroxysmal nocturnal hemoglobinuria (PNH); however, the data on its utility in PNH are limited. This retrospective analysis of patients with PNH who underwent allo-HSCT in 11 Polish centers between 2002 and 2016 comprised 78 patients with PHN, including 27 with classic PNH (cPNH) and 51 with bone marrow failure-associated PNH (BMF/PNH). The cohort was 59% male, with a median age of 29 years (range, 12 to 65 years). There was a history of thrombosis in 12% and a history of hemolysis in 81%, and 92% required erythrocyte transfusions before undergoing allo-HSCT. No patient received eculizumab, and 26% received immunosuppressive treatment. The median time from diagnosis to allo-HSCT was 12 months (range, 1 to 127 months). Almost all patients (94%) received reduced-toxicity conditioning, 66% with treosulfan. The stem cell source was peripheral blood in 72% and an identical sibling donor in 24%. Engraftment occurred in 96% of the patients. With a median follow-up of 5.1 years in patients with cPNH and 3.2 years in patients with BMF/PNH, 3-year overall survival (OS) was 88.9% in the former and 85.1% in the latter (P = not significant [NS]). The 3-year OS for patients with/without thrombosis was 50%/92% (P = NS) in the cPNH group and 83.3%/85.3% (P = NS) in the BMF/PNH group. The 3-year OS for in the BMF/PNH patients with/without hemolysis was 93.9%/62.9% (hazard ratio, .13; P = .016). No other factors impacted OS. After allo-HSCT, the frequency of the PNH clone was reduced to 0%, <1%, and <2.4% in 48%, 48%, and 4% of cPNH patients and in 84%, 11%, and 5% of BMF/PNH patients, respectively. The frequency of acute graft-versus-host disease (GVHD) grade II-IV was 23%, and the cumulative 1-year incidence of extensive chronic GVHD was 10.8% in the BMF/PNH group and 3.7% in the cPNH group. Allo-HSCT is a valid option for PNH patients, effectively eliminating the PNH clone with satisfactory overall survival and acceptable toxicity. Reduced-toxicity conditioning with treosulfan is effective and safe in patients with cPNH and BMF/PNH.

Hematopoietic Cell Transplantation for Paroxysmal Nocturnal Hemoglobinuria in the Age of Eculizumab

Paroxysmal nocturnal hemoglobinuria (PNH) is a rare, acquired clonal hematopoietic cell disease characterized by the destruction of hematopoietic cells through activation of the complement system with manifestations that can be life-threatening including hemolysis, thrombosis, and marrow failure. Allogeneic hematopoietic cell transplantation (HCT) remains the sole cure for PNH, but eculizumab, a terminal complement inhibitor of C5, has been used to prevent complement-mediated hemolysis in patients with PNH since its approval by the Food and Drug Administration in 2007. We examined outcomes of HCT in patients with PNH to evaluate the effects of disease subtype, conditioning intensity, and eculizumab use either pre-HCT or post-HCT. Fifty-five patients with a diagnosis of PNH underwent at least 1 HCT, with 4 patients requiring a second HCT for graft failure. The median age at the time of first HCT was 30.0 years (range, 4.2 to 66.9 years). Seventeen patients (30.9%) had classical PNH, and the remaining 38 patients had PNH associated with another marrow disorder (aplastic anemia in 26 of the 38). Indications for HCT included pancytopenia in 47.3% of the patients, myeloid malignancy (myelodysplastic syndrome, myeloproliferative neoplasm, or acute myelogenous leukemia) in 21.8%, recurrent hemolysis in 20.0%, and thrombosis in 10.9%. Of the 55 first HCTs, 26 were performed with myeloablative conditioning, 27 were performed with reduced-intensity conditioning, and 2 sets of identical twins underwent HCT without any conditioning. Donor types included HLA-matched related in 38.2%, HLA-matched unrelated in 34.5%, single HLA-allele mismatched unrelated in 16.4%, umbilical cord blood in 5.5%, syngeneic in 3.6%, and HLA-haploidentical in 1.8%. The median duration of follow-up in surviving patients was 6.1 years (range, 2.1 to 46.1 years) after first HCT. The median time to neutrophil and platelet engraftment was 17 days and 19 days, respectively; all but 2 patients (96.3%) had sustained engraftment. Overall survival was 70% at 5 years. Neither the choice of conditioning intensity nor PNH subtype affected survival. Nineteen patients died during follow-up, including 12 patients before day +365. Six patients received treatment with eculizumab before HCT, and 2 were treated after HCT. All patients treated with eculizumab were alive at a median follow-up of 2.3 years (range, .2 to 6.9 years). Both patients treated with eculizumab after HCT had minimal to no acute GVHD (aGVHD), with grade I skin aGVHD in 1 patient and no aGVHD in the other patient, and no chronic GVHD at 2.1 and 4.1 years post-HCT, respectively. With the approval of eculizumab, the indications for HCT include persistent hemolysis, persistent thrombosis, and associated marrow failure. Administration of eculizumab before and after HCT warrants further study, particularly considering our observation of minimal to no GVHD in 2 patients who received eculizumab after HCT.