Somatic mutation of PIGA in hematopoietic stem cells causes deficiency of glycosyl phosphatidylinositol-anchored proteins in paroxysmal nocturnal hemoglobinuria (PNH) that underlies the intravascular hemolysis but does not account for expansion of the PNH clone. Immune mechanisms may mediate clonal selection but appear insufficient to account for the clonal dominance necessary for PNH to become clinically apparent. Herein, we report 2 patients with PNH whose PIGAmutant cells had a concurrent, acquired rearrangement of chromosome 12. In both cases, der(12) had a break within the 3 untranslated region of HMGA2, the architectural transcription factor gene deregulated in many benign mesenchymal tumors, that caused ectopic expression of HMGA2 in the bone marrow. These observations suggest that aberrant HMGA2 expression, in concert with mutant PIGA, accounts for clonal hematopoiesis in these 2 patients and suggest the concept of PNH as a benign tumor of the bone marrow. ( IntroductionParoxysmal nocturnal hemoglobinuria (PNH) is a consequence of nonmalignant clonal expansion of hematopoietic stem cells with somatic mutation of PIGA. 1 Mutant PIGA 2 explains the deficiency of glycosyl phosphatidylinositol-anchored proteins (GPI-APs) that underlies the intravascular hemolysis of PNH. 3 However, PIGAmutant stem cells have no intrinsic proliferative advantage, 4,5 suggesting a 2-step model of pathogenesis.Step 1 of this model, clonal selection, 6,7 is envisioned as a conditional survival advantage that depends on deficiency of 1 or more GPI-APs. The close association of PNH with aplastic anemia, suggests that the selection pressure is immune mediated. 6,7 But, although 60% to 70% of patients with aplastic anemia have small, subclinical populations of GPI-AP Ϫ hematopoietic cells at diagnosis, 8 only 10% to 15% subsequently develop clinically apparent PNH. 9 In the remainder, GPI-AP Ϫ cells persist subclinically or disappear, 8 suggesting that mutant PIGA (and the consequent deficiency of GPI-APs) is necessary for clonal selection but is insufficient to account for the clonal expansion required for clinical manifestations of PNH to become apparent.Clonal expansion, step 2 of the PNH pathogenesis model, is envisioned as a consequence of clonal evolution in which a second somatic mutation bestows on the PIGA-mutant stem cell a proliferative advantage. 10 Herein, we present evidence supporting this 2-step model by showing a concurrent, acquired genetic abnormality in the PIGAmutant cells of 2 patients that establishes a novel mechanism for the nonmalignant clonal hematopoieis characteristic of PNH. Patients, materials, and methods PatientsInformed consent was obtained from patients J20 and US1 according to protocols approved by the Institutional Review Boards of Osaka University Hospital (Osaka, Japan) and the University of Utah School of Medicine (Salt Lake City, UT), respectively. Hybrid cell linesMonocytes derived from J20 or US1 were fused with the hypoxanthine phosphoribosyltransferase-negative mouse myeloma cell line, P...

Acute graft-versus-host disease (aGVHD) following allogeneic hematopoietic cell transplantation (HCT) is a primary cause of nonrelapse mortality and a major barrier to successful transplant outcomes. Itacitinib is a Janus kinase (JAK)1–selective inhibitor that has demonstrated efficacy in preclinical models of aGVHD. We report results from the first registered study of a JAK inhibitor in patients with aGVHD. This was an open-label phase 1 study enrolling patients aged ≥18 years with first HCT from any source who developed grade IIB to IVD aGVHD. Patients with steroid-naive or steroid-refractory aGVHD were randomized 1:1 to itacitinib 200 mg or 300 mg once daily plus corticosteroids. The primary endpoint was safety and tolerability; day 28 overall response rate (ORR) was the main secondary endpoint. Twenty-nine patients (200 mg, n = 14; 300 mg, n = 15) received ≥1 dose of itacitinib and were included in safety and efficacy assessments. One dose-limiting toxicity was reported (grade 3 thrombocytopenia attributed to GVHD progression in a patient receiving 300 mg itacitinib with preexisting thrombocytopenia). The most common nonhematologic treatment-emergent adverse event was diarrhea (48.3%, n = 14); anemia occurred in 11 patients (38%). ORR on day 28 for all patients in the 200-mg and 300-mg groups was 78.6% and 66.7%, respectively. Day 28 ORR was 75.0% for patients with treatment-naive aGVHD and 70.6% in those with steroid-refractory aGVHD. All patients receiving itacitinib decreased corticosteroid use over time. In summary, itacitinib was well tolerated and demonstrated encouraging efficacy in patients with steroid-naive or steroid-refractory aGVHD, warranting continued clinical investigations. This trial was registered at www.clinicaltrials.gov as #NCT02614612.

We conducted a multicenter, phase 1 dose escalation study evaluating the safety of the allogeneic multipotent adult progenitor cell (MAPC, MultiStem, Athersys, Inc., Cleveland, OH) stromal product administered as an adjunct therapy to 36 patients after myeloablative allogeneic hematopoietic cell transplantation (HCT). Patients received increasing doses of MAPC (1, 5, or 10 million cells per kilogram recipient weight) as a single i.v. dose on day +2 after HCT (n = 18), or once weekly for up to 5 doses (1 or 5 million cells per kilogram; n = 18). Infusional and regimen-related toxicities were assessed for 30 days after the last MAPC dose. Of 36 allogeneic HCT donors (17 related and 19 unrelated), 35 were 6/6 HLA matched. MAPC infusions were well tolerated without associated infusional toxicity, graft failure, or increased incidence of infection. Median times to neutrophil (n = 36) and platelet (n = 31) engraftment were 15 (range, 11 to 25) and 16 (range, 11 to 41) days, respectively. The overall cumulative incidences of grades II to IV and III and IV acute graft-versus-host disease (GVHD) at day 100 were 37% and 14%, respectively (n = 36). In the group that received the highest single MAPC dose (10 million cells/kg), day 100 incidence of grade II to IV GVHD was 11.1% (1 of 9) with no observed cases of grade III and IV GVHD. We found no evidence for MHC class II allogeneic antibody induction, although some patients showed an increase in serum anticlass I titers compared with baseline. MAPC contribution to blood chimerism was negligible. These phase I data support the safety of stromal stem cell therapy and suggest that MAPC should be tested prospectively as a novel therapeutic option for GVHD prophylaxis after HCT.

Circulating angiogenic factors (AF) reflect tissue healing capacity, although some AF can also contribute to inflammation and are indicative of endothelial dysfunction. The AF milieu in acute graft-versus-host disease (aGVHD) has not been broadly characterized. We hypothesized that patients with abundant AF involved in repair/regeneration vs. those mediating damage/inflammation would have improved outcomes. Circulating AF known predominantly for repair/regeneration (epidermal growth factor [EGF], fibroblast growth factor-1 and -2, heparin binding-EGF-like growth factor, vascular endothelial growth factor-A, -C, and -D) and for damage/inflammation (angiopoietin-2, endothelin-1, soluble endoglin [sEng], follistatin [FS], leptin, placental growth factor [PlGF]) were measured in a discovery set of HCT recipients with grade III/IV aGVHD versus controls, then validated in two aGVHD cohorts enrolled in Blood and Marrow Transplant Clinical Trials Network (BMT CTN) trials 0302 (N=105, serum) and 0802 (N=158, plasma) versus controls without aGVHD (N=53, serum). Levels of EGF and VEGF-A were lower than controls at the onset of aGVHD in both trials and higher with complete response to first-line aGVHD therapy in CTN 0802. FS and PlGF were elevated in aGVHD measured in either serum or plasma. At day 28 after initial aGVHD therapy, elevated FS was an independent negative prognostic factor for survival in both cohorts (hazard ratio 9.3 in CTN 0302, 2.8 in CTN 0802). These data suggest that circulating AF are associated with clinical outcomes after aGVHD and thus may contribute to both pathogenesis and recovery.

In acute myeloid leukemia (AML), the assessment of post‐treatment minimal residual disease (MRD) may inform a more effective management approach. We investigated the prognostic utility of next‐generation sequencing (NGS)‐based MRD detection undertaken before hematopoietic stem cell transplantation (HSCT). Forty‐two AML subjects underwent serial disease monitoring both by standard methods, and a targeted 42‐gene NGS assay, able to detect leukemia‐specific mutant alleles (with >0.5% VAF) (mean 5.1 samples per subject). The prognostic relevance of any persisting diagnostic mutation before transplant (≤27 days) was assessed during 22.1 months (median) of post‐transplant follow‐up. The sensitivity of the NGS assay (27 MRD‐positive subjects) exceeded that of the non‐molecular methods (morphology, FISH, and flow cytometry) (11 positive subjects). Only one of the 13 subjects who relapsed after HSCT was NGS MRD‐negative (92% assay sensitivity). The cumulative incidence of post‐transplant leukemic relapse was significantly higher in the pre‐transplant NGS MRD‐positive (vs MRD‐negative) subjects (P = .014). After adjusting for TP53 mutation and transplant conditioning regimen, NGS MRD‐positivity retained independent prognostic significance for leukemic relapse (subdistribution hazard ratio = 7.3; P = .05). The pre‐transplant NGS MRD‐positive subjects also had significantly shortened progression‐free survival (P = .038), and marginally shortened overall survival (P = .068). In patients with AML undergoing HSCT, the pre‐transplant persistence of NGS‐defined MRD imparts a significant, sensitive, strong, and independent increased risk for subsequent leukemic relapse and death. Given that NGS can simultaneously detect multiple leukemia‐associated mutations, it can be used in the majority of AML patients to monitor disease burdens and inform treatment decisions.