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Allogeneic bone marrow transplantation (BMT) from an HLA-matched sibling donor is recommended as an initial treatment for young patients. However, immunosuppressive therapy (IST) with cyclosporine and anti-thymocyte globulin may be a viable option even when an HLA-identical sibling donor is available.We constructed a Markov model to simulate the 10-year clinical course of patients aged 21-40 years with newly diagnosed severe aplastic anemia. Immediate BMT and IST were compared as an initial treatment assuming the availability of an HLA-identical sibling donor. Transition probabilities after treatment were determined based on a registry data analysis for BMT and a long-term prospective study for IST.Quality-adjusted life years (QALYs) after treatment selection were 6.77 for BMT and 6.74 for IST. One-way sensitivity analysis revealed that the utility for being alive without GVHD after BMT, that for being alive with partial response after IST, and the response rate after initial IST strongly affected the results.BMT and IST produced similar QALY for young patients with severe aplastic anemia. An estimation of the response rate to the initial IST may enable an individualized comparison between BMT and IST.

Acquired pure red cell aplasia (PRCA) is a rare syndrome characterized by anemia with reticulocytopenia and a marked reduction in erythroid precursors. Given its rarity, the true incidence is largely unknown, and epidemiological data representing the general population, with a description of the full spectrum of etiologies, are scarce. An epidemiological study on PRCA in Japan conducted 30 years ago estimated the annual incidence as 0.3 per million. To update the data and investigate the incidence and demographics of PRCA, we conducted a nationwide epidemiological study using the Japanese Society of Hematology (JSH) Hematologic Disease Registry, a hematologic disease registration database managed by the JSH and the Diagnosis Procedure Combination (DPC) study data available at a website of the Ministry of Health, Labor, and Welfare (MHLW) of Japan. A total of 1055 patients with newly diagnosed acquired PRCA were identified between 2012 and 2019, and the average annual incidence was calculated at 1.06 (95% confidence interval [CI], 0.83-1.28) per million. The median age was 73 (range, 18-99) years. The female-to-male ratio was 1.5:1, and the female predominance was most prominent in the child-bearing age group. Sixty-nine percent of acquired PRCA was idiopathic. The incidence of PRCA was approximately 20% of that of aplastic anemia (AA) during the same period. Approximately 0.98 patients per million per year (95% CI, 0.89-1.07) required hospitalization for the treatment of PRCA. These results are expected to contribute to the discussion of resource allocation for PRCA in the aging population in many countries, including Japan.

Differential diagnosis of pancytopenia with bone marrow (BM) hypoplasia represented by aplastic anemia (AA) is often challenging for physicians, because no laboratory tests have been established, until recently, to distinguish immune-mediated BM failure, which includes acquired AA (aAA) and a subset of low-risk myelodysplastic syndrome (MDS), from non-immune BM failure, which is primarily caused by genetic abnormalities in hematopoietic stem cells (HSCs). HSCs of healthy individuals often undergo somatic mutations, and some acquire phenotypic changes that allow them to escape immune attack against themselves. Once an immune attack against HSCs occurs, HSCs that undergo somatic mutations survive the immune attack and continue to produce their progenies with the same genetic or phenotypic changes. The presence of mature blood cells derived from mutated HSCs in the peripheral blood serves as evidence of the immune-mediated destruction of HSCs. Glycosylphosphatidylinositol-anchored protein-deficient (GPI[-]) blood cells and HLA class I allele-lacking (HLA[-]) leukocytes are two major aberrant cell types that represent the immune mechanism underlying BM failure. This review focuses on the importance of identifying immune mechanisms using laboratory markers, including GPI(-) cells and HLA(-) leukocytes, in the management of BM failure.

In immune aplastic anemia (IAA), severe pancytopenia results from the immune-mediated destruction of hematopoietic stem cells. Several autoantibodies have been reported, but no clinically applicable autoantibody tests are available for IAA. We screened autoantibodies using a microarray containing >9000 proteins and validated the findings in a large international cohort of IAA patients (n = 405) and controls (n = 815). We identified a novel autoantibody that binds to the C-terminal end of cyclooxygenase 2 (COX-2, aCOX-2 Ab). In total, 37% of all adult IAA patients tested positive for aCOX-2 Ab, while only 1.7% of the controls were aCOX-2 Ab positive. Sporadic non-IAA aCOX-2 Ab positive cases were observed among patients with related bone marrow failure diseases, multiple sclerosis, and type I diabetes, whereas no aCOX-2 Ab seropositivity was detected in the healthy controls, in patients with non-autoinflammatory diseases or rheumatoid arthritis. In IAA, anti-COX-2 Ab positivity correlated with age and the HLA-DRB1*15:01 genotype. 83% of the >40 years old IAA patients with HLA-DRB1*15:01 were anti-COX-2 Ab positive, indicating an excellent sensitivity in this group. aCOX-2 Ab positive IAA patients also presented lower platelet counts. Our results suggest that aCOX-2 Ab defines a distinct subgroup of IAA and may serve as a valuable disease biomarker.

Objectives Patients with acquired aplastic anemia (AA) without HLA-matched sibling donors or aged >40 years receive immunosuppressive therapy (IST) with anti-thymocyte globulin (ATG). We investigated the relationship between plasma rabbit ATG (r-ATG) concentration and IST response. Methods From May 2012 to October 2017, 81 patients with severe AA who required initial IST were included. A 1:1 block randomization was employed for 2.5 and 3.5 mg/kg doses of r-ATG. Results No significant difference in response rates was observed between the 2.5 and 3.5 mg/kg groups (63% vs. 58%, P = .894). Median r-ATG concentrations on days 14 and 28 after IST were 15.2 (0.0-97.7) and 1.8 (0.0-74.9 µg/mL), respectively. According to r-ATG concentration, response rates were significantly higher in the group with higher r-ATG concentration than in those with lower r-ATG concentration (day 14, 88% vs. 52%; P = .006 and day 28, 79% vs. 46%; P = .005). In multivariate analysis, higher r-ATG concentrations at day 28 were independent predictors of favorable response to IST at 6 months (odds ratio, 0.29; 95% confidence interval, 0.09-0.93; P = .037). Conclusions The present data indicate that higher r-ATG concentration at day 28 resulted in improved IST response.

Although some studies have suggested the effectiveness of hyperbaric oxygen (HBO) therapy for hemorrhagic cystitis (HC) after allogeneic hematopoietic stem cell transplantation (HSCT), the role of HBO has not been established. We compared the treatment outcomes of 8 patients with viral HC (adenovirus [ADV], n = 2; BK virus [BKV], n = 6) treated with HBO (HBO[+]) and 8 patients (ADV, n = 2; BKV, n = 6) treated with conventional therapy (HBO[−]), such as urinary catheterization and intravenous cidofovir. HBO therapy was performed at 2.1 atmospheres for 90 min/day until clinical improvement was achieved. The median number of HBO treatments was 10 (range 8–12). The median duration of HBO treatment was 19.5 days (range 10–23 days). All 8 HBO(+) patients achieved complete remission (CR) at a median of 14.5 days (range 5–25 days). Of the 8 HBO(−) patients, 5 (62.5%) obtained CR and 3 remained symptomatic for 2–6 months. The cumulative incidence of transplant-related mortality at day 100 after allogeneic HSCT was significantly higher in the HBO(−) patients than in the HBO(+) patients (14.2 vs. 0%, P

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired clonal hematopoietic stem cell disorder caused by a mutation of the X-linked PIGA gene, resulting in a deficient expression of glycosylphosphatidylinositol (GPI)-anchored proteins. While large clonal expansions of GPI(-) cells cause hemolytic symptoms, tiny GPI(-) cell populations can be found in healthy individuals and remain miniscule throughout life. The slight expansion of PNH clones often occurs in patients with acquired aplastic anemia (AA), an autoimmune bone marrow (BM) failure caused by autoreactive cytotoxic T lymphocyte attack on hematopoietic stem and progenitor cells (HSPCs). The presence of PNH clones is thought to represent the immune pathophysiology of BM failure and be derived from GPI(-) HSPCs that evaded immune attack against HSPCs. However, which mechanisms underlie the selection of GPI(-) HSPCs as well as their overwhelming clonal expansion remains unclear. Ancestral or secondary somatic mutations in GPI(-) HSPCs contribute to the clonal expansion of the aberrant HSPCs in certain patients with PNH; however, it remains unclear whether such driver mutations are responsible for clonal expansion of all patients. Increased sensitivity to TGF-β in GPI(-) HSPCs partly explains the predominance of GPI(-) erythrocytes in immune-mediated BM failure. CD4

Small populations of glycosylphosphatidylinositol-anchored protein-deficient (GPI[-]) cells accounting for up to 0.01% of total granulocytes can be accurately detected by a high-sensitivity flow cytometry (FCM) assay established by the Clinical and Laboratory Standards Institute (CLSI method) and have a prognostic value in bone marrow failure (BMF); however, the significance of GPI(-) granulocytes accounting for 0.001-0.009% of granulocytes remains unclear. To clarify this issue, we examined the peripheral blood of 21 BMF patients in whom minor (around 0.01%) populations of GPI(-) granulocytes had been previously detected by a different high-resolution FCM method (OPTIMA method, which defines ≥ 0.003% GPI(-) granulocytes as an abnormal increase) using both the CLSI and OPTIMA methods simultaneously. These two methods detected an "abnormal increase" in GPI(-) granulocytes in 10 patients (48%) and 17 patients (81%), respectively. CLSI detected 0.002-0.005% (median, 0.004%) GPI(-) granulocytes in 7 patients who were deemed positive for PNH-type cells according to the OPTIMA method, which detected 0.003-0.012% (median 0.006%) GPI(-) granulocytes. The clone sizes of GPI(-) cells detected by each assay were positively correlated (r = 0.994, p < 0.001). Of the seven patients who were judged positive for PNH-type cells by OPTIMA alone, five received immunosuppressive therapy, and all of them achieved a partial or complete response. GPI(-) granulocytes detected in BMF patients by the CLSI method should thus be considered significant, even at percentages of < 0.01%.

Leukocytes that lack expression of HLA alleles are frequently detected in patients with acquired aplastic anemia (AA) who respond to immunosuppressive therapy, although the exact mechanisms underlying the HLA loss and HLA allele repertoire likely to acquire loss-of-function mutations are unknown. We identified a common nonsense mutation at codon 19 (c.19C>T, p.R7X) in exon 1 (Exon1mut) of different HLA-A and -B alleles in HLA-lacking granulocytes from AA patients. A droplet digital polymerase chain reaction assay capable of detecting as few as 0.07% Exon1mut HLA alleles in total DNA revealed that the mutation was present in 29% (101/353) of AA patients, with a median allele frequency of 0.42% (range, 0.071% to 21.3%). Exon1mut occurred in only 12 different HLA-A (n=4) and HLA-B (n=8) alleles, including B*40:02 (n=31) and A*02:06 (n=15), which correspond to four HLA class I supertypes (A02, A03, B07, and B44). The percentages of patients who possessed at least one of these 12 HLA alleles were significantly higher in the 353 AA patients (92%, P

To determine whether antigen presentation by HLA-DR on hematopoietic stem progenitor cells (HSPCs) is involved in the development of acquired aplastic anemia (AA), we studied the HLA-DR expression on CD45

Acquired chronic pure red cell aplasia (PRCA) develops idiopathically or in association with other medical conditions, including T cell large granular lymphocytic leukemia (T-LGLL) and thymoma. T cell dysregulation is considered a cardinal pathogenesis of PRCA, but genetic-phenotypic associations in T cell abnormalities are largely unclear. We evaluated an extended cohort of 90 patients with acquired PRCA, including 26 with idiopathic, 36 with T-LGLL-associated and 15 with thymoma-associated PRCA, for their T cell immuno-phenotypes, clonalities and STAT3 mutations. TCR repertoire skewing of CD8

The plasticity of induced pluripotent stem cells (iPSCs) with the potential to differentiate into virtually any type of cells and the feasibility of generating hematopoietic stem progenitor cells (HSPCs) from patient-derived iPSCs (iPSC-HSPCs) has many potential applications in hematology. For example, iPSC-HSPCs are being used for leukemogenesis studies and their application in various cell replacement therapies is being evaluated. The use of iPSC-HSPCs can now provide an invaluable resource for the study of diseases associated with the destruction of HSPCs, such as bone marrow failure syndromes (BMFSs). Recent studies have shown that generating iPSC-HSPCs from patients with acquired aplastic anemia and other BMFSs is not only feasible, but is also a powerful tool for understanding the pathogenesis of these disorders. In this article, we highlight recent advances in the application of iPSCs for disease modeling of BMFSs and discuss the discoveries of these studies that provide new insights in the pathophysiology of these conditions.

We sought to determine the efficacy of a new, inexpensive, single-tube 8-color multiparameter flow cytometry (MFC) method (SRL-Flow), which is based on the EuroFlow next-generation flow (NGF) (tube 2 only), to assess minimal residual disease (MRD)-negative status. MRD-negative status is considered a treatment milestone in multiple myeloma (MM). We used 45 bone marrow samples from patients with MM, including 11 cases treated with anti-CD38 monoclonal antibody. The SRL-Flow sample preparation protocol was identical to that of EuroFlow-NGF. The antibody panel for SRL-Flow was as follows: CD138V450/CD27V500/CD38ME (multiepitope)FITC/CD56PE/CD45PerCP-Cy5.5/CD19PE-Cy7/cytoplasmic (Cy) immunoglobulin (Ig) κAPC/CyIgλAPC-H7. To identify abnormal plasma cells (aPCs) of patients with MM who received anti-CD38 monoclonal antibody, we used a panel of anti-CD45 and anti-CD138 antibodies (Abs) rather than a panel of anti-CD45 and anti-CD38 Abs. We comparatively analyzed the total nucleated cell numbers, total PC levels, and MRD levels between the SRL-Flow and EuroFlow-NGF. High correlations (r > 0.9) in total PC and MRD levels were noted among SRL-Flow, original EuroFlow-NGF (2 tubes), and EuroFlow-NGF (tube 2 only), suggesting that SRL-Flow is an inexpensive (< $200 USD/sample as of January of 2019) alternative to EuroFlow-NGF (< $350 USD/sample) for assessing MRD in MM.

The outcome of immunosuppressive therapy (IST) and prognosis in patients with aplastic anaemia (AA) secondary to chemotherapy or radiotherapy for cancers remains unknown. A total of 43 of 2559 patients with AA referred to our hospital had previously received chemoradiotherapy for various types of solid tumours (n = 25) or haematological malignancies (n = 18). Their cancer status was complete remission (CR) in 27, non-CR in 13, and unknown in three. Small populations of glycosylphosphatidylinositol-anchored protein-deficient [GPI(-)] granulocytes were detected in 16 patients (37·2%). Of 18 patients who were treated with IST, 50% improved regardless of the presence of GPI(-) cells. The overall survival (OS) rate was significantly higher in patients with a history of solid tumours patients than in those of haematological malignancies (median OS, 87 vs. 11 months, P = 0·0003), and in patients treated with IST than in those of untreated patients (median OS, 115 vs. 20 months, P = 0·028). Cancer aggravation occurred in two of four patients who were treated with IST while in non-CR of their original cancers. Progression to myelodysplastic syndromes was observed in two patients not possessing GPI(-) cells. IST should thus be considered for patients with AA secondary to chemoradiotherapy for cancers, particularly when their original solid tumours are in CR.

This nationwide multicentre retrospective study was performed to analyze clinical features that predict the prognosis of central nervous system invasion in multiple myeloma (CNS-MM, approximately 1% of MM). Overall, of the 77 adult patients with CNS-MM identified between 2005 and 2016, those diagnosed at MM diagnosis (n = 3) had longer overall survival (OS) than those diagnosed at relapse (n = 74; median: 48·5 vs 2·7 months). Therefore, we compared the relapsed MM with CNS-MM in patients with any treatment (n = 60). Multivariate analyses revealed that lenalidomide treatment [hazard ratio (HR) 0·27, P = 0·003], intrathecal chemotherapy (IT; HR 0·54, P = 0·05), and radiation therapy (RTx; HR 0·33, P

Background Autologous stem cell transplantation (ASCT) is still a gold standard treatment in multiple myeloma (MM). So far, we have reported the prognostic value of minimal residual disease (MRD) detection in autografts at ASCT setting using EuroFlow next-generation flow (NGF) and next-generation sequencing (NGS) (Takamatsu et al, ASH 2018). The main problem of EuroFlow-NGF is its lower sensitivity (2×10-6) compared with that of NGS ( Methods The study enrolled 9 newly-diagnosed MM patients whose frozen autografts’ cells were preserved. The median age at ASCT was 52 (range 47-61) years and included 4 males and 5 females at ISS I (n=2), II (n=6) and III (n=1). Of there, 4 patients harbored high-risk chromosomal abnormalities including t(4;14) (n=1), t(14;16) (n=1), del17p (n=1), and t(4;14) and del 17p (n=1). All patients received bortezomib-based chemotherapy for induction together with melphalan at 200 mg/m2 for conditioning before ASCT. Two patients received consolidation therapy with carfilzomib-lenalidomide-dexamethasone (KRD) and all patients received lenalidomide maintenance until progressive disease. Frozen autografts (n=9) and primary myeloma cells (n=1) were thawed for MRD assessment by EuroFlow-NGF and NGS. The EuroFlow-NGF method was based on the previous report (Flores-Montero et al., Leukemia 2017). NGS-based MRD assessment was performed using Adaptive’s standardized NGS-MRD Assay (Seattle, WA) (Ching et al., BMC Cancer 2020). The EuroFlow-NGF method was modified to increase the sensitivity of MRD by capturing cells up to 5×107. Results Because frozen autografts were used in this study, we performed the sensitivity test using the dilution of frozen/thawed primary MM cells in an autograft by EuroFlow-NGF. The sensitivity test revealed a strong correlation between 1×10-7 and 1×10-4 of MRD level (r=0.9996, p Conclusions This modified EuroFlow-NGF method can assess MRD of frozen/thawed autografts and its sensitivity can be increased up to 4×10-7 that is comparable to NGS.

To characterize glycosylphosphatidylinositol-anchored protein-deficient (GPI[−]) and HLA-class I allele-lacking (HLA[−]) hematopoietic stem progenitor cells (HSPCs) in acquired aplastic anemia (AA), we studied the peripheral blood (PB) of 56 AA patients in remission who possessed both (n = 13, Group A) or either GPI(−) (n = 34, Group B) and HLA(−) (n = 9, Group C) cell populations. Seventy-seven percent (10/13) of Group A had HLA(−) cells in all lineages of PB cells, including platelets, while only 23% (3/13) had GPI(−) cells in all lineages, and the median percentage of HLA(−) granulocytes in the total granulocytes (21.2%) was significantly higher than that of GPI(−) granulocytes (0.28%, P

A previous dose‐finding study has suggested that romiplostim is effective in patients with refractory aplastic anaemia (AA) and 10 µg/kg once weekly was recommended as a starting dose. In this Phase II/III, multicentre, open‐label study, romiplostim was administered subcutaneously at a fixed dose of 10 µg/kg once weekly for 4 weeks (weeks 1–4) followed by weekly doses (5, 10, 15 and 20 µg/kg) titrated by platelet response for up to 52 weeks (weeks 5–52). A total of 31 patients with AA who were refractory to immunosuppressive therapy (IST) and thrombocytopenia (platelet count of ≤30 × 109/l) were enrolled. The primary efficacy endpoint of the proportion of patients achieving any haematological (platelet, neutrophil and erythrocyte) response at week 27 was 84% [95% confidence interval (CI) 66–95%]. Trilineage response was 39% (95% CI 22–58%) at week 53. The most common treatment‐related adverse events (AEs) were headache and muscle spasms (each 13%). All AEs were mild or moderate except for three patients with Grade 3 hepatic AEs; no AEs necessitated romiplostim discontinuation. Two patients developed cytogenetic abnormalities, of whom one returned to normal karyotype at last follow‐up. High‐dose romiplostim is effective and well tolerated in the treatment of patients with AA refractory to IST.

Epstein–Barr virus-associated hemophagocytic lymphohistiocytosis (EBV-HLH) is a life-threatening disease characterized by the uncontrolled proliferation of EBV-infected T/NK cells with resultant immune system failure against EBV. While a CD5−HLA-DR+CD8+ T-cell population was previously shown to be EBV-infected cells and a useful marker for monitoring the response to treatment of EBV-HLH, changes in other lymphocyte subsets associated with EBV-HLH treatments have not been closely studied. We herein report a 25-year-old woman with EBV-HLH who presented with a fever, liver failure, and pancytopenia. CD8+ T cells harbored EBV. After failing steroid pulse therapy, one course of CHOP therapy immediately improved her fever and laboratory data and reduced the population of EBV-infected cells. Although the number of EBV-infected cells increased on day 20 of CHOP, a sharp increase in NK cells and normal activated T cells ensued, and the infected cells disappeared without an additional CHOP cycle. She has maintained remission without complications. This rapid immune reconstitution has not been observed in two other patients treated with HLH-2004 protocol-like regimens including prolonged immunosuppressants and etoposide. One cycle of CHOP was thought to have induced the resolution of EBV-HLH by eliminating infected cells as well as inducing the reconstruction of anti-EBV immunity.

Ravulizumab demonstrated noninferior efficacy and comparable safety to eculizumab in two open-label, phase 3 studies in patients with paroxysmal nocturnal hemoglobinuria (PNH) who complement inhibitor-naive (Study 301) or were previously treated with eculizumab (Study 302). This subgroup analysis assessed ravulizumab's efficacy and safety in Japanese patients in Studies 301 and 302, who are known to have different clinicopathologic features from white patients. Patients were randomly assigned (1:1) to eculizumab every-two-weeks or weight-based dosing of ravulizumab every-eight-weeks for 26 weeks. Co-primary endpoints were transfusion avoidance and lactate dehydrogenase (LDH) normalization in Study 301 and percentage change in LDH levels from baseline to day 183 in Study 302. Thirty-three Japanese patients (n = 18 ravulizumab; n = 15 eculizumab) enrolled in Study 301; 12 enrolled in Study 302 (n = 5 ravulizumab; n = 7 eculizumab). In the Study 301 ravulizumab group, 83.3% (15/18) of patients avoided transfusion; the adjusted prevalence of LDH normalization was 52.1%. In the Study 302 ravulizumab group, the least-squares-mean percentage change from baseline in LDH was 8.34%. No deaths or meningococcal infections occurred during the 6-month primary evaluation period in either study. In conclusion, ravulizumab's efficacy and safety were consistent in the Japanese and global patient populations with PNH in the phase 3 studies. Clinical Trial Identifier: NCT02946463; NCT03056040.

Dysregulation of T-cell–mediated immunity is responsible for acquired pure red cell aplasia (PRCA). Although STAT3 mutations are frequently detected in patients with T-cell large granular lymphocytic leukemia (T-LGLL), which is often complicated by PRCA and which is also reported to be associated with acquired aplastic anemia (AA) and myelodysplastic syndrome (MDS), whether STAT3-mutated T cells are involved in the pathophysiology of PRCA and other types of bone marrow failure remains unknown. We performed STAT3 mutation analyses of the peripheral blood mononuclear cells from PRCA patients (n = 42), AA (n = 54), AA–paroxysmal nocturnal hemoglobinuria (AA-PNH; n = 7), and MDS (n = 21) using an allele-specific polymerase chain reaction and amplicon sequencing. STAT3 mutations were not detected in any of the 82 patients with AA/PNH/MDS but were detected in 43% of the 42 PRCA patients. In all 7 STAT3-mutation–positive patients who were studied, the STAT3 mutations were restricted to sorted CD8+ T cells. The prevalence of STAT3 mutation in idiopathic, thymoma-associated, autoimmune disorder–associated, and T-LGLL–associated PRCA was 33% (5 of 15), 29% (2 of 7), 20% (1 of 5), and 77% (10 of 13), respectively. The STAT3-mutation–positive patients were younger (median age, 63 vs 73 years; P= .026) and less responsive to cyclosporine (46% [6 of 13] vs 100% [8 of 8]; P= .0092) in comparison with STAT3-mutation–negative patients. The data suggest that STAT3-mutated CD8+ T cells may be closely involved in the selective inhibition of erythroid progenitors in PRCA patients.

Clonal hematopoiesis by hematopoietic stem progenitor cells (HSPCs) that lack an HLA class I allele (HLA − HSPCs) is common in patients with acquired aplastic anemia (AA); however, it remains unknown whether the cytotoxic T lymphocyte (CTL) attack that allows for survival of HLA − HSPCs is directed at nonmutated HSPCs or HSPCs with somatic mutations or how escaped HLA − HSPC clones support sustained hematopoiesis. We investigated the presence of somatic mutations in HLA − granulocytes obtained from 15 AA patients in long-term remission (median, 13 years; range, 2-30 years). Targeted sequencing of HLA − granulocytes revealed somatic mutations ( DNMT3A , n = 2; TET2 , ZRSR2 , and CBL , n = 1) in 3 elderly patients between 79 and 92 years of age, but not in 12 other patients aged 27 to 74 years (median, 51.5 years). The chronological and clonogenic analyses of the 3 cases revealed that ZRSR2 mutation in 1 case, which occurred in an HLA − HSPC with a DNMT3A mutation, was the only mutation associated with expansion of the HSPC clone. Whole-exome sequencing of the sorted HLA − granulocytes confirmed the absence of any driver mutations in 5 patients who had a particularly large loss of heterozygosity in chromosome 6p (6pLOH) clone size. Flow–fluorescence in situ hybridization analyses of sorted HLA + and HLA − granulocytes showed no telomere attrition in HLA − granulocytes. The findings suggest that HLA − HSPC clones that escape CTL attack are essentially free from somatic mutations related to myeloid malignancies and are able to support long-term clonal hematopoiesis without developing driver mutations in AA patients unless HLA loss occurs in HSPCs with somatic mutations.

Hematopoietic stem cells (HSCs) that lack HLA-class I alleles as a result of copy-number neutral loss of heterozygosity of the short arm of chromosome 6 (6pLOH) or HLA allelic mutations often constitute hematopoiesis in patients with acquired aplastic anemia (AA), but the precise mechanisms underlying clonal hematopoiesis induced by these HLA-lacking (HLA-) HSCs remain unknown. To address this issue, we generated induced pluripotent stem cells (iPSCs) from an AA patient who possessed HLA-B4002-lacking (B4002-) leukocytes. Three different iPSC clones (wild-type [WT], 6pLOH+, and B*40:02-mutant) were established from the patient's monocytes. Three-week cultures of the iPSCs in the presence of various growth factors produced hematopoietic cells that make up 50% to 70% of the CD34+ cells of each phenotype. When 106 iPSC-derived CD34+ (iCD34+) cells with the 3 different genotypes were injected into the femoral bone of C57BL/6.Rag2 mice, 2.1% to 7.3% human multilineage CD45+ cells of each HLA phenotype were detected in the bone marrow, spleen, and peripheral blood of the mice at 9 to 12 weeks after the injection, with no significant difference in the human:mouse chimerism ratio among the 3 groups. Stimulation of the patient's CD8+ T cells with the WT iCD34+ cells generated a cytotoxic T lymphocyte (CTL) line capable of killing WT iCD34+ cells but not B4002- iCD34+ cells. These data suggest that B4002- iCD34+ cells show a repopulating ability similar to that of WT iCD34+ cells when autologous T cells are absent and CTL precursors capable of selectively killing WT HSCs are present in the patient's peripheral blood.

Late graft failure (LGF) without evidence of residual recipient cells is a serious complication after allogeneic hematopoietic stem cell transplantation (allo-SCT) and often requires stem cell infusion from the same donor when the patient fails to respond to conventional therapies. We screened the peripheral blood (PB) of 14 patients who developed donor-type LGF at 2 to 132 months after allo-SCT for the presence of the markers for immune-mediated bone marrow (BM) failure. Increased glycosylphosphatidyl inositol-anchored protein-deficient (GPI-AP-) leukocytes, which accounted for .009% to 0.147% of the total granulocytes, were detected in 5 patients (severe aplastic anemia, n = 2; follicular lymphoma, n = 1; acute lymphoblastic leukemia, n = 1; myelodysplastic syndromes; n = 1) and 4.7% to 81.2% HLA-allele–lacking leukocytes (HLA-LLs) were detected in 2 patients (acute myelogenous leukemia, n = 1; and myelodysplastic syndromes, n = 1). Three of the 5 patients with increased GPI-AP- leukocytes were treated with antithymocyte globulin (ATG), and 2 patients achieved transfusion independence. These results suggest that immune mechanisms that are similar to acquired aplastic anemia underlie condition of approximately one-half of the patients with donor-type LGF, and that in patients with increased GPI-AP- cells, donor-derived hematopoiesis may be restored by ATG therapy alone without donor stem cell infusion.

Background: Autologous stem cell transplantation (ASCT) remains the gold-standard treatment for multiple myeloma (MM). To date, we have reported the prognostic value of minimal residual disease (MRD) detection in autografts in an ASCT setting using EuroFlow next-generation flow (NGF) and next-generation sequencing (NGS) (Takamatsu et al., ASH 2018, 2020). The main problem with NGF is its lower sensitivity (2 × 10 -6) compared with that of NGS ( Methods: We reanalyzed 11 autografts in which the MRD were negative on NGF but positive (n = 7) or negative (n = 4) on NGS (Takamatsu et al., ASH 2018, abstract #258) using 5-20 mL of autografts with NGF to increase the sensitivity of MRD detection. Additionally, we enrolled 9 patients with newly diagnosed MM, from whom 5-20 mL of apheresed autografts were cryopreserved. We included 20 patients with newly diagnosed MM. The median age at ASCT was 60 (range, 45-67) years, and the patients included 12 men and 8 women at International Staging System I (n = 3), II (n = 13), and III (n = 4), 6 of whom harbored high-risk chromosomal abnormalities, including t(4;14) (n = 3), t(14;16) (n = 1), del17p (n = 1), and t(4;14) and del 17p (n = 1). All patients received bortezomib-based chemotherapy for induction followed by melphalan at a dose of 200 mg/m 2 for conditioning before ASCT. Three patients received consolidation therapy with carfilzomib-lenalidomide-dexamethasone (n = 2) or bortezomib-lenalidomide-dexamethasone (n = 1), and 18 patients received lenalidomide (n = 16), thalidomide (n = 1), or thalidomide and lenalidomide (n = 1) maintenance. Frozen autografts (n = 20) were thawed for MRD assessment using NGF and NGS. The NGF method was based on a previous report (Flores-Montero et al., Leukemia 2017). NGS-based MRD assessment was performed using Adaptive's standardized NGS-MRD assay (Seattle, WA) (Ching et al., BMC Cancer 2020). The NGF method was modified to increase the sensitivity of MRD detection by capturing up to 6 × 10 7 cells. Results: Frozen autografts were used in this study; therefore, we performed a sensitivity test using a dilution of frozen/thawed primary MM cells in an autograft with NGF. The sensitivity test revealed a strong correlation between 5 × 10 -7 and 1 × 10 -4 MRD levels (Figure 1A; r = 0.999, P Conclusion: The modified EuroFlow-NGF method may be used to assess MRD in frozen/thawed autografts, and its sensitivity may increase up to 5 × 10 -7, which is comparable to that of NGS. Figure 1 Figure 1. Disclosures Yamashita: Janssen: Honoraria; Bristol-Myers Squibb: Honoraria; celgene: Honoraria; Takeda: Honoraria. Nakao: Novartis Pharma: Honoraria; Symbio: Consultancy; Kyowa Kirin: Honoraria; Alexion Pharma: Research Funding. Takamatsu: Adaptive Biotechnologies, Eisai: Honoraria; SRL: Consultancy; Bristol-Myers Squibb: Honoraria, Research Funding; Janssen: Consultancy, Honoraria, Research Funding.

Background: Small populations of paroxysmal nocturnal hemoglobinuria (PNH)-type cells ( Methods: Patients diagnosed with PNH, AA, MDS or indistinguishable BMF without malignant diseases were prospectively recruited to the study between April 1 st, 2016 and December 31 st, 2019 in Japan. Participants were excluded from the study if treated with eculizumab or ravulizumab. Peripheral blood samples were obtained with informed consent and sent to the single laboratory every 12months (mos) for 36 mos. A high-resolution flow cytometry assay known as OPTIMA method (Ann Hematol 97(12):2289-2297) was used to precisely detect a small population of GPI(-) cells, which defines ≥0.003% PNH-type granulocytes (Gran) and ≥0.005% erythrocytes as an abnormal increase. The quality of life (QOL) of the pts was assessed using the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-Fatigue) and European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30) instruments. All other lab data and clinical information were obtained at each participating institute or hospital on sample collection, and were accumulated by the Japan PNH Study Group for analysis. Results: Total 1,985 pts were registered and 1,813 pts were eligible for analysis. Median age was 67 with 50.5% male patients. PNH-type cells were positive in 50.4% (235/466) of AA, 19.7% (70/355) of MDS, 22.3% (61/273) of suspected PNH, and 33.9% (232/685) of undiagnosed BMF. PNH-type cells were increased in nearly 30% of the pts with RCUD, RCMD, MDS-U, and 5q-, but not in RARS, RAEB-1, or RAEB-2. Time-course data of the size of PNH-type cells were available in 651 pts at 12mos and in 210 pts at 36mos. Small ( Conclusion: PNH-type cells were detected exclusively in AA and low-risk MDS, supporting the hypothesis that the increase of PNH-type cells in BMF underpin the benign immune-mediated feature of the disease. The presence of PNH-type cells predicts a better response to IST in BMF, which is consistent with previous reports. Detection of subclinical PNH-type cells was associated with an improvement of QOL scores in multiple items at 36mos. Those small populations of PNH-type cells stayed subclinical in most of the cases, but caution should be exercised in monitoring the sizes as some may evolve into clinical PNH. Figure 1 Figure 1. Disclosures Ueda: Chugai Pharmaceutical: Consultancy, Honoraria, Research Funding; Alexion Pharma: Consultancy, Honoraria; Sanofi: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Yonemura: Alexion Pharma: Honoraria, Research Funding; Chugai Pharmaceutical: Research Funding; Novartis Pharma: Honoraria. Obara: Novartis Pharma: Honoraria; Chugai Pharmaceutical: Honoraria, Research Funding; Alexion Pharma: Honoraria, Research Funding. Ando: Novartis: Honoraria; Kyowa Kirin: Research Funding; Chugai Pharmaceutical: Research Funding; Celgene: Honoraria; Astellas Pharma: Honoraria; Takeda Pharmaceutical: Research Funding. Kawaguchi: Alexion Pharma: Honoraria. Nishimura: Alexion Pharma: Consultancy; Chugai Pharmaceutical: Consultancy; Novartis Pharma: Consultancy; Roche: Consultancy; apellis pharmaceuticals: Consultancy; Biocryst: Consultancy; Sanofi: Consultancy. Nakao: Kyowa Kirin: Honoraria; Novartis Pharma: Honoraria; Symbio: Consultancy; Alexion Pharma: Research Funding.

[Background] Minor populations (0.003%-1.0%) of glycosylphosphatidylinositol-anchored protein-deficient granulocytes (GPI[-] Gs) are often detected in the peripheral blood (PB) of patients with acquired aplastic anemia (AA) and low-risk myelodysplastic syndromes and are thought to represent immune pathophysiology of bone marrow failure. We previously reported that minor GPI(-) G populations were detected in some healthy individuals (HIs) and persisted over several years at similar percentages (Katagiri T, et al. Stem Cells 2013). Several lines of evidence have suggested that small numbers of GPI(-) Gs detected in HIs are polyclonal populations mostly derived from short-lived PIGA-mutated committed progenitor cells. Minor GPI(-) G populations in AA patients may also be derived from multiple committed progenitor cells rather than from a few hematopoietic stem progenitor cells (HSPCs) with PIGA mutations. However, minor GPI(-) G populations usually persist for a long period of time at similar frequencies in AA patients, suggesting that they may instead be derived from a few HSPCs that have undergone PIGA mutations. This issue remains debated due to the inability to sequence the PIGA gene in the very few GPI(-) granulocytes available. We recently developed a sensitive method capable of detecting PIGA mutations in minor GPI(-) Gs using amplicon sequencing of GPI(-) Gs that were enriched with magnetic microbeads followed by FACS sorting. Using this method, we addressed whether minor GPI(-) G populations in AA patients and HIs are oligoclonal or polyclonal as well as which cell population they are derived from HSPCs or committed progenitor cells. [Methods] Five AA patients possessing 0.025%-0.898% GPI(-) Gs, 3 HIs who were found to have ≥0.003% (0.006%, 0.051%, and 0.059%) GPI(-) Gs during a screening of more than 200 HIs for GPI(-) Gs, 30 HIs (median: 37 years old, male/female:17/13) with 0% to 0.002% GPI(-) Gs, and 8 cord blood (CB) samples were subjected to enrichment of GPI(-) Gs for PIGA sequencing. Their leukocytes were treated with PE-labelled anti-CD55 monoclonal antibodies (mAbs) and anti-CD59 mAbs, and CD55 +CD59 + granulocytes were removed using magnetic microbeads labelled with anti-PE mAbs. CD11b +FLAER-negative granulocytes were sorted from the remaining granulocytes using FACSAria Fusion. DNA from sorted GPI(-) Gs was amplified using primers covering all exons of PIGA. Nucleotide sequences of the PIGA gene in GPI(-) Gs were determined using a next-generation sequencer. [Results] This novel enrichment method enabled the detection of only 1-4 different PIGA mutations in all 5 female AA patients (AA 1-5) with the total of different VAFs in each case reaching nearly 50% (Table 1). Limited kinds of PIGA mutations were also detected in three HIs (two males [HI 1 and 3] and one female [HI 2]). For HI 1 and HI 3, the VAFs of predominant PIGA-mutated sequences were longitudinally measurable using whole-blood DNA samples with droplet digital PCR, which showed no apparent changes in the VAF (0.020%-0.027% for HI 1 and 0.012%-0.025% for HI 3 over 4 and 6 years, respectively). The presence of mono or oligoclonal GPI(-) Gs in the 3 HIs prompted us to study 30 HIs who had been judged to be negative for minor GPI(-) G populations by a high-sensitivity flow cytometry method. The enrichment method unexpectedly identified clear CD11b highFLAER - GPI(-) G clusters in granulocytes from 24 of the 30 HIs (Figure 1a). The median number of GPI(-) Gs contained in 7 ml of PB was 31 (range, 1-136 cells). Sufficient amounts of DNA for NGS were obtained from sorted GPI(-) Gs of six subjects, and PIGA amplicon sequencing revealed 1-3 different PIGA mutations in four of the six subjects. The examination of fresh CB also revealed clear GPI(-) G clusters in four of eight samples (Figure 1b). PIGA amplicon sequencing of 79 GPI(-) Gs obtained from 1 male CB sample (CB 1) showed a sole PIGA mutation with VAFs of 95% (Figure 1c). [Conclusion] Minor GPI(-) G populations detectable in patients with AA and HIs are derived from a few PIGA-mutated HSPCs, not from committed myeloid progenitor cells, a finding that negates a hypothesis that a few PIGA-mutated HSPCs are selected from polyclonal PIGA-mutated HSPCs during transition from AA to florid PNH. Very small numbers of GPI(-) Gs are present much more frequently in HIs than previously thought and may also be derived from a few HSPCs with PIGA mutations that occur in HSPCs during the fetal stage. Figure 1 Figure 1. Disclosures Takamatsu: Bristol-Myers Squibb: Honoraria, Research Funding; Adaptive Biotechnologies, Eisai: Honoraria; SRL: Consultancy; Janssen: Consultancy, Honoraria, Research Funding. Yamazaki: Novartis Pharma: Honoraria; Kyowa Kirin: Research Funding; Kyowa Kirin: Honoraria. Nakao: Symbio: Consultancy; Kyowa Kirin: Honoraria; Novartis Pharma: Honoraria; Alexion Pharma: Research Funding.

Background: Novel agents capable of inducing deeper responses dramatically improve the prognosis of patients with multiple myeloma (MM). Innovative technologies such as multiparameter flow cytometry (MFC) and next-generation sequencing (NGS) are utilized to assess minimal residual disease (MRD) for further stratification of patients who achieve a complete response (CR). EuroFlow-next-generation flow (EuroFlow-NGF) is one of the gold standard MFC methods. Recently, both NGF and NGS have been used in many clinical trials to assess MRD levels associated with progression-free survival (PFS) and overall survival (OS). The present study prospectively assessed MRD levels by both NGF and NGS to elucidate the prognostic impact of both methods and clarify their characteristics in MM patients in an autologous stem cell transplantation (ASCT) setting. Methods: We prospectively assessed the response in Japanese patients with newly diagnosed MM who underwent ASCT and lenalidomide-based maintenance therapy at multiple Japanese medical centers between September 2016 and July 2021. The diagnosis of MM and patients' responses to therapy were assessed using the IMWG criteria. Only patients with CR or stringent CR on days 100-365 post-ASCT were included, and bone marrow (BM) samples were obtained to assess MRD. Four milliliters of BM was divided equally. Cells derived from 2 mL BM were analyzed by the NGF method (Flores-Montero et al., Leukemia 2017) at Kanazawa University, and DNA extracted from the remaining 2 mL BM cells was processed by Adaptive Biotechnologies' standardized NGS-MRD assay (Seattle, WA) (Ching et al., BMC Cancer 2020) to assess MRD levels. MRD levels in BM were also monitored at 1-year (± 20 days) and 2-year (± 20 days) post-ASCT. The prognostic value of MRD levels in BM was assessed, and their correlation between NGF and NGS was compared at a cut-off value of 1×10 -5. Sustained MRD negativity was defined as the maintenance of MRD negativity in the BM for more than 6 months. BM cells were analyzed for high-risk cytogenetics (del(17p), t(4;14), and t(14;16)) by FISH. Results: A total of 60 patients (male = 29, female = 31) underwent bortezomib-based induction therapy, ASCT conditioned with high-dose melphalan, and lenalidomide-based maintenance. The median age was 62 years at the ASCT (range 36-71; ISS 1 [n = 13], 2 [n = 24], and 3 [n = 23]). Thirty-three percent of patients showed high-risk chromosomal abnormalities (del17p (n=11), t(4;14) (n=10), t(14;16) (n=2)), 3 patients had double hit diseases, and five patients had extramedullary diseases. With a median follow-up of 3 years, the 3-year progression-free survival (PFS) and 3-year overall survival (OS) rates were 69.2% and 94.2%, respectively. In total, 148 samples were analyzed using NGF and 138 were analyzed using NGS. The rates of MRD negativity at least once using NGF and NGS were 80% and 61%, respectively. The patients who achieved at least one MRD negativity exhibited significantly better 3-year PFS (82.9% by NGF; 84.8% by NGS) than those who did not (P < 0.0001, 0% by NGF; P = 0.005, 49.1% by NGS). Patients who sustained MRD negativity for more than 6 months also showed significantly better 3-year PFS (96.7% by NGF; 92.3% by NGS) compared with those without sustained MRD negativity (Figure; P < 0.0001, 37.1% by NGF; P < 0.01, 50.9% by NGS). The MRD levels between the NGF and NGS methods were significantly correlated with each other (r = 0.9295, P < 0.0001). Among the 17 patients who developed PD after ASCT, seven cases showed discrepancies in the MRD results and two cases in which one case was MRD-positive and the other was MRD-negative by both methods progressed with extramedullary diseases. Five of the seven cases were MRD-positive by NGS and MRD-negative by NGF. Conclusions: In this prospective comparison study of MRD assessment in BM cells using EuroFlow-NGF and NGS approaches, MRD levels highly correlated with each other, and MRD negativity and sustained MRD negativity were significantly associated with prolonged PFS. Multiple MRD assessments by NGF or NGS are essential for predicting durable remission and prolonged clinical outcomes. Figure 1 Figure 1. Disclosures Takamatsu: Bristol-Myers Squibb: Honoraria, Research Funding; Adaptive Biotechnologies, Eisai: Honoraria; SRL: Consultancy; Janssen: Consultancy, Honoraria, Research Funding. Yoshihara: Bristol-Myers Squibb: Honoraria; Janssen: Honoraria; Novartis: Honoraria. Matsumoto: Sanofi: Honoraria; Janssen: Honoraria; Ono: Honoraria; Bristol-Myers Squibb: Honoraria. Yamashita: Janssen: Honoraria; Bristol-Myers Squibb: Honoraria; celgene: Honoraria; Takeda: Honoraria. Fuchida: Takeda Pharmaceutical Co., Ltd.: Honoraria; Ono Pharmaceutical Co., Ltd.: Honoraria; Janssen Pharmaceutical K.K.: Honoraria; Sanofi: Honoraria; Bristol-Myers Squibb Co., Ltd.: Honoraria; Celgene Co., Ltd.: Honoraria. Hiragori: BML: Current Employment. Suzuki: Amgen: Consultancy, Honoraria, Research Funding; Takeda: Consultancy, Honoraria; ONO: Honoraria; Novartis: Honoraria; Sanofi: Honoraria; Abie: Honoraria; Janssen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding. Nakao: Symbio: Consultancy; Kyowa Kirin: Honoraria; Novartis Pharma: Honoraria; Alexion Pharma: Research Funding. Durie: Amgen: Other: fees from non-CME/CE services ; Amgen, Celgene/Bristol-Myers Squibb, Janssen, and Takeda: Consultancy.

In immune-mediated acquired aplastic anemia (AA), the presence of an HLA allele, which is highly overrepresented or lost due to somatic mutations, may represent a specific immune pathophysiology and a clinical manifestation. HLA-B*14:02 is one of the most overrepresented class I alleles in AA and is also frequently affected by a somatic loss of expression; the inherited B*14:02 genotype was correlated with high-risk clonal evolution in two independent cohorts in the U.S. (Babushok DV et al. Blood Adv 2017; Zaimoku Y et al. manuscript in preparation). In contrast, HLA-B*14:02 is virtually absent in Japanese, in whom somatic mutations of AA have frequently been detected in HLA-B*40:02, B*54:01, and A*02:06, and occasionally in A*02:01, A*02:07, A*31:01, B*13:01, B*40:01, B*40:03, B*44:03, B*55:02, and B*56:01 (Mizumaki H et al. Haematologica 2021). A class II allele HLA-DRB1*15 is highly overrepresented in AA across various ethnic groups, including those in the U.S. and Japanese. This retrospective study in the Japanese population aimed to explore the clinical significance of disease-associated non-B*14:02 HLA class I and II alleles in AA. A total of 423 enrolled patients with AA (very severe [n = 81], severe [n = 266], transfusion dependent non-severe [n = 76]; median age 60 [range, 1-86] years) had undergone genotyping for HLA-A, HLA-B, HLA-C, and HLA-DRB1 at 2-field resolution. The HLA allele frequencies in these patients were compared to those in a Japanese HLA haplotype dataset (n = 19183; Ikeda N et al. Tissue Antigens 2016). The most overrepresented allele in AA was HLA-DRB1*15:02, followed by DRB1*15:01, B*40:02, and A*02:06 (Table); DRB1*13:02 and B*44:03, which are in linkage disequilibrium, were markedly underrepresented, consistent with a well-known protective role of DRB1*13 against autoimmune diseases. HLA-DRB1*15:02 was also significantly correlated with age and its frequency among patients aged The overall response rate to anti-thymocyte globulin-based immunosuppressive therapy at 6 months was 63% (139 of 220 treated and evaluable patients). A trend for a higher response was observed in patients harboring mutation-related HLA-B alleles (except for minor alleles B*13:01, B*40:03, and B*55:02) and the highly overrepresented or protective HLA-DRB1 alleles, but not in the HLA-A alleles (Figure D). A multivariate logistic regression revealed that the combination of the presence of any favorable alleles in HLA-B (odds ratio 3.6, P < 0.0001) or in HLA-DRB1 (odds ratio 2.3, P = 0.00085) was significantly and independently associated with a hematologic response; the tendencies for a lower or higher response in very severe disease and the presence of paroxysmal nocturnal hemoglobinuria clone did not reach statistical significance. Further, there was likely an additive effect when two favorable alleles coexisted in HLA-B or HLA-DRB1 (Figure E); the copy number of the favorable HLA-B and HLA-DRB1 alleles stratified the response rate to four groups: three or four copies, 95% (19 of 20); two copies, 72% (61 of 85); one copy, 59% (50 of 85); and zero copy, 30% (9 of 30). Only eight patients displayed clonal evolution to monosomy 7, myelodysplastic syndrome, or acute myeloid leukemia after immunosuppression without significant overrepresentation or underrepresentation of the pathogenic HLA alleles. Using a large dataset of homogeneous Japanese population with high-resolution HLA typing, we revealed, for the first time, a strong relationship between disease-associated (overrepresented, inactivated, or protecting) HLA alleles and the responsiveness to immunosuppressive therapy. Figure 1 Figure 1. Disclosures Takamatsu: Bristol-Myers Squibb: Honoraria, Research Funding; SRL: Consultancy; Adaptive Biotechnologies, Eisai: Honoraria; Janssen: Consultancy, Honoraria, Research Funding. Yamazaki: Novartis Pharma: Honoraria; Kyowa Kirin: Honoraria; Kyowa Kirin: Research Funding. Nakao: Symbio: Consultancy; Kyowa Kirin: Honoraria; Novartis Pharma: Honoraria; Alexion Pharma: Research Funding.

Graft failure (GF) is the most critical life-threatening complication of allogeneic hematopoietic stem cell transplantation (HSCT) for aplastic anemia, for which a second transplantation is the only effective treatment. Optimal procedures have not been established for the second transplantation in this setting, however. Here we retrospectively analyzed the outcomes of 22 patients with aplastic anemia, age ≥16 years, who underwent umbilical cord blood transplantation for GF after the first HSCT using the registry database of the Japan Society for Hematopoietic Cell Transplantation. The median age of patients was 36 years (range, 16 to 72 years), and the median time from the first to the second transplant was 77 days (range, 29 to 1061 days). The cumulative incidence of neutrophil engraftment at day 60 post-transplantation was 45.5% (95% confidence interval [CI], 23.6% to 65.0%). With a median follow-up of 50 months, the 4-year overall survival (OS) was 38.5% (95% CI, 18.4% to 58.5%). Mycofenolate mofetil–based graft-versus-host disease prophylaxis demonstrated greater neutrophil recovery than prophylaxis with calcineurin inhibitor alone or methotrexate-based prophylaxis (66.7% versus 37.5%; P = .04). The use of such conditioning regimens as fludarabine + melphalan or cyclophosphamide + low-dose total body irradiation was associated with better engraftment (58.3% versus 30%; P = .05) and better 4-year OS (55.6% versus 20%; P = .05) than other regimens. Although further investigation is needed, umbilical cord blood could be an effective and promising option for stem cell source for urgent second transplantation in patients with aplastic anemia who develop GF after the first HSCT.

Background Most patients with multiple myeloma (MM) are considered to be incurable, and relapse owing to minimal residual disease (MRD) is the main cause of death among these patients. Therefore, new technologies to assess deeper response are required. Patients and methods We retrospectively analyzed 125 patients with MM who underwent high-dose melphalan plus autologous stem-cell transplantation (ASCT) to detect MRD in autograft/bone marrow (BM) cells using a next-generation sequencing (NGS)-based method and allele-specific oligonucleotide-polymerase chain reaction (ASO-PCR). Results NGS-based method was applicable to 90% and this method had at least one to two logs greater sensitivity compared to ASO-PCR. MRD negative by NGS [MRDNGS(−)] (defined as

To the editor: In idiopathic aplastic anemia (IAA), bone marrow failure (BMF) is caused by depletion of hematopoietic stem cells (HSCs), thought to result from a T-cell-mediated autoimmune process.[1][1] Paroxysmal nocturnal hemoglobinuria (PNH) is a clonal hematopoietic disorder characterized by a

[Background] HLA-DR15 (DR15) has been implicated in the susceptibility to immune-mediated bone marrow (BM) failure, such as acquired aplastic anemia (AA), wherein the hematopoietic function depends on cyclosporine (CsA), paroxysmal nocturnal hemoglobinuria (PNH) with BM failure, and low-risk myelodysplastic syndrome responsive to immunosuppressive therapy. However, how DR15 contributes to the development of such immune-mediated BM failure remains unclear. Although the copy-number neutral loss of heterozygosity in chromosome 6p (6pLOH) of hematopoietic stem progenitor cells (HSPCs) in AA patients sometimes involves the HLA-DRB1 region, the frequency of the resultant DR15 loss is low, suggesting little involvement of this DR allele in the escape of HSPCs from cytotoxic T-cell attack. Several studies have recently reported that acute myeloid leukemia cells that relapse after allogeneic hematopoietic stem cell transplantation often lack HLA class II expression through an epigenetic mechanism and thereby escape the graft-versus-leukemia effect. The epigenetic loss of HLA class II expression may also occur in HSPCs that survive the immune attack in AA patients in remission. [Objectives/Methods] To test this hypothesis, we determined the HLA-DR expression on HSPCs defined by lineage-CD45dimCD34+CD38+ cells as well as their subpopulations, including common myeloid progenitors (CMPs), megakaryocyte-erythroid progenitors (MEPs), and granulocyte-monocyte progenitors (GMPs), in the peripheral blood of 52 AA patients (34 with DR15 and 18 without DR15) and 20 healthy individuals using flow cytometry (FCM) with anti-pan-HLA-DR antibodies. All patients were in remission after ATG-based therapy (ATG+CsA±thrombopoietin receptor agonists [TPO-RA] or anabolic steroids [AS], n=19), CsA-based therapy (CsA±TPO-RA or AS, n=27), and others (n=6), and 18 required low-dose CsA to maintain remission. Eighteen (35%) had HLA-class I allele-lacking (HLA-class I[-]) leukocytes due to 6pLOH and/or allelic mutations while 33 (63%) had 0.003-83.8% (median 0.194%) GPI-anchored protein-deficient (GPI[-]) granulocytes. HLA-DR(-) HSPCs detected in some patients were sorted together with their HLA-DR(+) counterparts and subjected to incubation in the presence of interferon gamma (IFN-γ) to see whether or not the DR expression was restored; in addition, they were subjected to RNA sequencing to compare the gene expression profiles between DR(-) and DR(+) HSPCs. [Results] Five (9.6%) of the 52 AA patients had 28.6% to 42.3% (median 34.0%) DR(-) cell populations in HSPCs, which were not detected in either monocytes or B lymphocytes of the same patients or in HSPCs of any healthy individuals (Figure 1a). All 5 patients possessed either HLA-DRB1*15:01 (n=3), DRB1*15:02 (n=1), or DRB1*15:01/15:02 (n=1), with the other DRB1 alleles differing among individuals, and their hematopoietic function depended on CsA, except for 1 patient (Case 5) whose HSPCs consisted of 69% GPI(+) and 31% GPI(-) cells. Of particular interest, Case 5's DR(-) cells were detected in GPI(+) HSPCs but not in GPI(-) HSPCs (Figure 1b). None of the 5 patients possessed HLA-class I(-) leukocytes, which were detected in 18 (38%) of 47 patients not possessing DR(-) HSPCs. In contrast to the patients possessing DR(-) HSPCs, CsA dependency was only observed in 13 (28%) of the 47 AA patients without DR(-) HSPCs. Incubation of sorted DR(-) HSPCs in the presence of IFN-γ for 72 h resulted in full restoration of the DR expression in all HSPC subpopulations (Figure 2). A comparison of the transcriptome profile between DR(-) and DR(+) HSPCs revealed that the signature of differentially expressed genes was enriched in immune response-related genes. [Conclusions] HSPCs that lacked DR due to an epigenetic mechanism were frequently detected in AA patients with DR15 characterized by CsA dependency. Although the loss of expression occurred in both DR alleles, the fact that only DRB1*15:01 or 15:02 was an allele shared by the five patients indicates that the DR loss phenomenon targeted DR15. The DR15(-) HSPCs may escape from antigen-specific CD4+ T-cell attack, which cannot be completely abolished by CsA. As demonstrated by findings of Case 5 showing the presence of a DR(-) cell population only in GPI(+) HSPCs, the lack of GPI may be a mechanism underlying substitution for the DR15 loss. Disclosures Takamatsu: Ono pharmaceutical: Honoraria, Research Funding; SRL: Consultancy, Research Funding; Janssen Pharmaceutical: Consultancy, Honoraria, Research Funding; Bristol-Myers Squibb: Honoraria, Research Funding; Adaptive Biotechnologies: Honoraria. Ishiyama:Alexion: Research Funding; Novartis: Honoraria. Yamazaki:Kyowa Kirin: Honoraria, Research Funding; Novartis: Honoraria. Nakao:Alexion: Research Funding; Novartis: Honoraria; Kyowa Kirin: Honoraria; Symbio: Consultancy.

Background: Autologous stem cell transplantation (ASCT) in conjunction with novel therapeutic drugs can dramatically improve response rates and the prognoses of patients with multiple myeloma (MM). However, most patients with MM ultimately relapse due to minimal residual disease (MRD). Next-generation multiparameter flow cytometry (MFC) (EuroFlow-NGF) and next-generation sequencing (NGS) are currently the standard methods to assess MRD. Aims: To compare the prognostic value of MRD detection in autografts and bone marrow (BM) cells using 8-color MFC (EuroFlow-NGF) and NGS (Adaptive Biotechnologies), and also MRD levels between fresh and cryopreserved autografts using NGF. Methods: The study enrolled 52 newly-diagnosed MM patients who underwent ASCT. The median age ASCT was 61 (range 41-69) years and included 29 males and 23 females at ISS I (n = 17), II (n = 23), and III (n = 12). Of these, 18 patients harbored high-risk chromosomal abnormalities including t(4;14) (n = 15), del17p and t(4;14) (n = 2), and complex (n = 1). Bortezomib-based chemotherapy was used for induction together with melphalan at 140 mg/m2 (n = 1) and 200 mg/m2 (n = 51) for conditioning before ASCT. 39 of 52 (75%) patients received maintenance therapy until progressive disease. The best responses achieved post-ASCT included 30 sCR, 4 CR, 15 VGPR, and 3 PR. Forty autografts, one from each MM patient, were analyzed using NGF and NGS protocols, and BM cells at pre/post-ASCT and autografts derived from 16 patients were analyzed using NGS. The EuroFlow-NGF method uses standard sample preparation; large numbers of cells are evaluated using an optimized 8-color antibody panel that facilitates accurate identification of discrimination between phenotypically aberrant plasma cells (aPCs) and their normal counterparts (Flores-Montero et al., Leukemia 2017). NGS-based MRD assessment was performed using Adaptive's standardized NGS-MRD Assay (Seattle, WA) (Martinez-Lopez et al., Blood 2014). Eight additional autografts were used to assess MRD in both fresh and cryopreserved samples by NGF. Results: MRD was evaluated in 48 of 52 autografts (92%) using NGF and in 44 of 52 autografts (85%) using NGS. We identified aPCs in autografts based on multivariate analysis of individual cell populations (e.g., CD56+, CD19−, CyIgκ+, and CD117+). As the results of NGF revealed a strong correlation with respect to MRD in fresh vs. thawed autografts (r = 0.999, P < 0.0001), MRD was subsequently evaluated in thawed autografts. The sensitivity of NGF was 1 × 10−5-2 × 10−6; the sensitivity of NGS was 1 × 10−6. 28 of 48 (58%) of the autografts were MRD-positive by NGF; 30 of 44 (68%) of the autografts were MRD-positive by NGS. MRD levels in autografts using NGF and NGS correlated with one another (r = 0.69, P < 0.0001; Fig. 1A). MRD negative in autografts by NGF cases (MRDNGF (-)) and MRDNGS (-) tended to show better progression-free survival (PFS) than MRDNGF (+) (P = 0.195) and MRDNGS (+) (P = 0.156), respectively. Furthermore, MRDNGS (-) showed significantly better overall survival (OS) than MRDNGS (+) (P = 0.03) (Fig. 1C) while MRDNGF (-) showed better OS than MRDNGF (+) (P = 0.09) (Fig. 1B). Our data revealed only a minimal correlation between MRD in the autografts (median 1.1 × 10−5,range 0-7.29 × 10−4) and in the BM cells at pre-ASCT (median 5.05 × 10−3,range 6 × 10−6-2.64 × 10−1; r = 0.09, P = 0.7) or at post-ASCT (median 2.11 × 10−4,range 0-9.09 × 10−3; r = 0.14, P = 0.6); MRD detected in the autografts was > 27 times lower than that detected in pre-ASCT BM cells, and MRD detected in the post-ASCT BM cells was > 3 times lower than that detected in pre-ASCT BM cells except for one case in which the ratio was increased by two times. Interestingly, while MRD was detected in all BM cells at pre-ASCT (n = 16), 4 of 16 (25%) of these autografts were MRDNGS-negative. The median of MRD levels of the 4 cases in pre-ASCT and post-ASCT BM cells were 4.14 × 10−4 (range 6-583 × 10−6)and 1.8 × 10−5 (range 0-27 × 10−6), respectively. Conclusion: Although EuroFlow-NGF is a rapid and accurate method for detecting MRD, NGS was more sensitive and provided greater prognostic value than EuroFlow-NGF. Disclosures Takamatsu: Adaptive Biotechnologies: Honoraria; Bristol-Myers Squibb: Honoraria, Research Funding; Janssen Pharmaceutical: Consultancy, Honoraria, Research Funding; Ono pharmaceutical: Honoraria, Research Funding; SRL: Consultancy, Research Funding. Takezako:Bristol-Myers Squibb: Honoraria, Research Funding; Takeda: Honoraria, Research Funding; Janssen: Research Funding; Abbvie: Research Funding. Nakao:Symbio: Consultancy; Kyowa Kirin: Honoraria; Alexion: Research Funding; Novartis: Honoraria.

[Background] HLA-class I allele-lacking (HLA[-]) leukocytes are detected in approximately 30% of patients with acquired aplastic anemia (AA), and are thought to represent the involvement of cytotoxic T lymphocyte attack against hematopoietic stem cells (HSCs) in the development of AA, based on the high response rate to immunosuppressive therapy (IST) in patients with such aberrant leukocytes. Similar to glycosylphosphatidylinositol-anchored protein (GPI-AP)-deficient (GPI[-]) leukocytes in patients with paroxysmal nocturnal hemoglobinuria (PNH), HLA(-) leukocytes in AA patients are often clonal or oligoclonal and expand to account for more than 50% of the total leukocytes. Despite such overwhelming proliferation, somatic mutations in driver genes as well as telomere shortening that portend clonal evolution are rarely detected in HLA(-) granulocytes, suggesting the genetic stability of HLA(-) HSCs and the persistence of the immune pressure on HSCs that favors expansion of HLA(-) HSCs (Imi, et al. Blood Adv). However, recent studies from the United States have shown a higher incidence of clonal evolution to secondary myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML) in AA patients with HLA(-) leukocytes than in those without such leukocytes, a finding inconsistent with the results of our previous study. Given the high prevalence of HLA(-) leukocytes in AA patients, it is critical to determine whether or not the presence of the aberrant leukocytes is associated with clonal evolution. We therefore addressed this issue by studying the prognosis of a large number of AA patients with or without HLA(-) leukocytes who had been followed for a long term period. We also studied the clonal composition of granulocytes in AA patients with HLA(-) cells, wherein aberrant clones other than HLA(-) cells might be responsible for clonal evolution to MDS/AML. [Methods] We retrospectively analyzed the clinical characteristics of 633 AA patients and peripheral blood samples were examined for the presence of HLA(-) leukocytes using a high-sensitivity flow cytometry (FCM) assay, droplet digital PCR, single-nucleotide polymorphism arrays, or next generation sequencing (NGS) between 2010 and 2020. GPI(-) cells were detected using a high-sensitivity FCM assay as previously described. [Results] HLA(-) granulocytes were detected in 127 (20.1%) of the 633 patients with a median clone size of 16.9% (range, 0.04%-100%); the aberrant granulocytes accounted for greater than 50% of the total granulocytes in 29 (22.8%) of 127 patients. Eighty-nine (70.0%) of the 127 patients possessed aberrant clones other than HLA(-) clones, which included 0.005% to 91.6% GPI(-) cells (n=86), del(13q) cells (n=3), t(1;10) cells (n=1), t(9;13) cells (n=1), inv12 cells (n=1), and trisomy 8 cells (n=1). The prevalence of GPI(-) cells was not significantly different between patients with and without HLA(-) cells (67.7% vs 65.4%). Eighty-five of 102 (83.3%) patients with HLA(-) cells responded to IST, whereas 231 of 318 (72.6%) without HLA(-) cells responded (p90% of granulocytes, suggesting that these few escape clones were enough to sustain the hematopoietic function of the patients. The prognosis survey revealed no clonal evolution to MDS/AML in any of the 127 AA patients with HLA(-) leukocytes after a follow-up period of the median 5 years. In contrast, 15 of 234 (6.4%) patients without HLA(-) cells who were trackable evolved to MDS/AML during a median 5 year follow-up. [ Conclusions] The presence of HLA(-) leukocytes and concomitant aberrant clones was not associated with clonal evolution to MDS/AML in Japanese AA patients, even in those possessing a large (>50% of the total granulocyte) HLA(-) cell population. The discrepancy between our results and the data from the United States may be due to the difference in the race and mechanism underlying HLA loss. These data suggest that HSC clones that escape immune attack, such as HLA(-) and GPI(-) clones, are healthy enough to support hematopoiesis for a long term in AA patients. Disclosures Ishiyama: Novartis: Honoraria; Alexion: Research Funding. Yamazaki:Novartis: Honoraria; Kyowa Kirin: Honoraria, Research Funding. Ogawa:Eisai Co., Ltd.: Research Funding; Sumitomo Dainippon Pharma Co., Ltd.: Research Funding; Chordia Therapeutics, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding; Asahi Genomics Co., Ltd.: Current equity holder in private company; Otsuka Pharmaceutical Co., Ltd.: Research Funding; KAN Research Institute, Inc.: Membership on an entity's Board of Directors or advisory committees, Research Funding. Nakao:Alexion: Research Funding; Kyowa Kirin: Honoraria; Novartis: Honoraria; Symbio: Consultancy.

A “biosimilar” is a biotechnological product with a lower cost profile and equivalent efficacy and safety to the originator, but post-marketing clinical evaluation of biosimilar products has not been adequately conducted. We prospectively investigated the utility of biosimilar filgrastim in 13 peripheral blood stem cell (PBSC) donors from June 2014 to January 2017. In addition, we retrospectively compared these to another 13 PBSC donors mobilized with the originator filgrastim in the same period. Donor characteristics were equivalent between the groups. The median number of CD34+ cells per donor body weight (BW) and blood volume processed (BV) were 4.87 × 106/kg and 25.5 × 103/mL in the biosimilar group and 4.93 × 106/kg and 16.6 × 103/mL in the originator group, respectively. There were no significant differences between the groups in the number of CD34+ cells per donor BW or BV. All adverse events associated with G-CSF were permissive. The total G-CSF cost was significantly lower in the biosimilar group than in the originator group. These findings suggest that biosimilar filgrastim has the same efficacy and short-term safety as originator filgrastim for PBSC mobilization in healthy donors, with economic superiority. Longer follow-up studies are needed to evaluate the incidence of long-term adverse events.