Long-Term Clinical Outcomes and B Cell Immune Reconstitution Following Allo-HCT With Prophylactic, Post-Transplant Rituximab.

Chronic graft-versus-host disease (cGVHD) remains a significant source of morbidity and mortality following allogeneic hematopoietic cell transplantation (HCT). Post-transplant, prophylactic rituximab has successfully decreased cGHVD rates in clinical trials, but the durability of this strategy is uncertain. The long-terms effect of post-HCT B cell depletion on immune reconstitution, B cell function, and infectious complications are also unknown. In this study, we provide 10 yr follow-up and correlative analyses on patients given post-HCT, prophylactic rituximab. The objective of the study is to examine the durability of cGVHD protection as well as the long-term effect of rituximab prophylaxis on protective immune reconstitution, B cell function, and alloantibody formation. We analyzed 35 patients given prophylactic rituximab on phase II clinical trial. Clinical outcomes included cGVHD development, relapse and survival outcomes, and infectious outcomes. Correlative analyses included B cell subset analysis, development of antibodies to infectious antigens, and, for male patients receiving female donor grafts, development of antibodies to HY antigens. To further investigate the effect of rituximab on immune reconstitution and function, we also analyzed 43 similarly transplanted patients who did not receive post- or peri-HCT rituximab as a comparator group. For patients who received rituximab, the 8-yr cumulative incidence of cGHVD and freedom from immunosuppression were 20.0% and 76.2%, respectively. Importantly, no late incidences of cGVHD developed beyond 14 mo post-HCT. Relative to patients who did not receive rituximab, post-HCT rituximab was associated with increased B cell aplasia at 1 yr post-HCT (42.9% versus 11% of patients, P = .037); by 3 yr post-HCT, this aplasia resolved. Patients who received rituximab also had a significantly lower proportion of IgD+/CD38+ transitional B cells at 3 yr post-HCT (78.8% versus 89.9%, P = .039); at 10 yr post-HCT, this percentage remained markedly decreased at 50.7%. Rituximab prophylaxis altered B cell function. In male patients receiving female donor grafts, fewer patients developed HY antibodies at 3 yr post-HCT (20% versus 78%, P = .04). At 10 yr post-HCT, HY antibody production remained decreased at 33%. Rituximab prophylaxis was also associated with significantly lower antibody response to tetanus and EBV infectious antigens as well as lower IgG levels. Despite these changes, post-HCT was not associated with increased infections, although patients who received rituximab required intravenous immunoglobulin (IVIG) supplementation more frequently than those who did not (62.9% versus 32.6% of patients, P = .01). Prior data on the efficacy and feasibility of rituximab prophylaxis are durable, with persistent reduction in cGVHD. Rituximab prophylaxis also results in lasting B cell immunologic changes, with altered B cell subset composition and decreased alloantibody formation. Associated infectious risks were not increased, perhaps mitigated by high IVIG use.

Measurable residual disease conversion rate with consolidation chemotherapy in acute myeloid leukemia.

The rate of MRD clearance in AML with standard consolidation chemotherapy is not well defined. A multi-institution retrospective analysis was performed on 107 consecutively treated AML patients in morphologic complete remission with detectable MRD post-induction therapy who received standard chemotherapy consolidation. In response to standard intermediate/high-dose cytarabine consolidation therapy, 26 of 60 patients (43.3%) with MRD threshold of detection of at least 0.1% converted to MRD-negative status (undetectable with assay used), and 6 of 47 patients (12.8%) with MRD threshold of detection > 0.1% converted to MRD-negative status. Multivariable logistic regression for patients with MRD threshold of detection of at least 0.1% showed that, when controlling for age, ELN risk category, dose of cytarabine, and use of a combination agent, treatment with 1 cycle of consolidation cytarabine versus ≥2 cycles decreased the odds of conversion of AML to MRD-negative (OR = 0.24, 95% CI 0.07-0.85, p = 0.03).

LNK/SH2B3 as a novel driver in juvenile myelomonocytic leukemia.

Mutations in five canonical Ras pathway genes (NF1, NRAS, KRAS, PTPN11 and CBL) are detected in nearly 90% of patients with juvenile myelomonocytic leukemia (JMML), a frequently fatal malignant neoplasm of early childhood. In this report, we describe seven patients diagnosed with SH2B3-mutated JMML, including five patients who were found to have initiating, loss of function mutations in the gene. SH2B3 encodes the adaptor protein LNK, a negative regulator of normal hematopoiesis upstream of the Ras pathway. These mutations were identified to be germline, somatic or a combination of both. Loss of function of LNK, which has been observed in other myeloid malignancies, results in abnormal proliferation of hematopoietic cells due to cytokine hypersensitivity and activation of the JAK/STAT signaling pathway. In vitro studies of induced pluripotent stem cell-derived JMML-like hematopoietic progenitor cells (HPCs) also demonstrated sensitivity of SH2B3- mutated HPCs to JAK inhibition. Lastly, we describe two patients with JMML and SH2B3 mutations who were treated with the JAK1/2 inhibitor ruxolitinib. This report expands the spectrum of initiating mutations in JMML and raises the possibility of targeting the JAK/STAT pathway in patients with SH2B3 mutations.

FLT3 targeting in the modern era: from clonal selection to combination therapies.

Fms-like tyrosine kinase 3 (FLT3) is the most frequently mutated gene in acute myeloid leukemia (AML). Modern targeting of FLT3 with inhibitors has improved clinical outcomes and FLT3 inhibitors have been incorporated into the treatment of AML in all phases of the disease, including the upfront, relapsed/refractory and maintenance settings. This review will discuss the current understanding of FLT3 biology, the clinical use of FLT3 inhibitors, resistance mechanisms and emerging combination treatment strategies.

Multiomic Single Cell Sequencing Identifies Stemlike Nature of Mixed Phenotype Acute Leukemia and Provides Novel Risk Stratification.

Mixed phenotype acute leukemia (MPAL) is a leukemia whose biologic drivers are poorly understood, therapeutic strategy remains unclear, and prognosis is poor. We performed multiomic single cell (SC) profiling of 14 newly diagnosed adult MPAL patients to characterize the immunophenotypic, genetic, and transcriptional landscapes of MPAL. We show that neither genetic profile nor transcriptome reliably correlate with specific MPAL immunophenotypes. However, progressive acquisition of mutations is associated with increased expression of immunophenotypic markers of immaturity. Using SC transcriptional profiling, we find that MPAL blasts express a stem cell-like transcriptional profile distinct from other acute leukemias and indicative of high differentiation potential. Further, patients with the highest differentiation potential demonstrated inferior survival in our dataset. A gene set score, MPAL95, derived from genes highly enriched in this cohort, is applicable to bulk RNA sequencing data and was predictive of survival in an independent patient cohort, suggesting utility for clinical risk stratification.

Microfluidics-free single-cell genomics with templated emulsification.

Current single-cell RNA-sequencing approaches have limitations that stem from the microfluidic devices or fluid handling steps required for sample processing. We develop a method that does not require specialized microfluidic devices, expertise or hardware. Our approach is based on particle-templated emulsification, which allows single-cell encapsulation and barcoding of cDNA in uniform droplet emulsions with only a vortexer. Particle-templated instant partition sequencing (PIP-seq) accommodates a wide range of emulsification formats, including microwell plates and large-volume conical tubes, enabling thousands of samples or millions of cells to be processed in minutes. We demonstrate that PIP-seq produces high-purity transcriptomes in mouse-human mixing studies, is compatible with multiomics measurements and can accurately characterize cell types in human breast tissue compared to a commercial microfluidic platform. Single-cell transcriptional profiling of mixed phenotype acute leukemia using PIP-seq reveals the emergence of heterogeneity within chemotherapy-resistant cell subsets that were hidden by standard immunophenotyping. PIP-seq is a simple, flexible and scalable next-generation workflow that extends single-cell sequencing to new applications.

Daratumumab Plus Bortezomib and Dexamethasone in Newly Diagnosed Systemic Light Chain Amyloidosis.

Light chain amyloidosis (AL) is a plasma cell dyscrasia characterized by organ dysfunction, morbidity, and early mortality. Daratumumab in combination with cyclophosphamide, bortezomib, and dexamethasone is now standard frontline AL therapy; however, not all patients are candidates for this intensive regimen. Given the potency of Daratumumab, we evaluated an alternative frontline regimen: daratumumab, bortezomib, and limited-duration dexamethasone (Dara-Vd). Over a 3 year period, we treated 21 patients with Dara-Vd. At baseline, all patients had cardiac and/or renal dysfunction, including 30% of patients with Mayo stage IIIB cardiac disease. Nineteen of 21 patients (90%) achieved a hematologic response with 38% achieving a complete response. The median time to response was 11 days. Ten of 15 (67%) evaluable patients achieved a cardiac response and 7 of 9 (78%) achieved a renal response. The 1-year overall survival was 76%. In untreated systemic AL amyloidosis, Dara-Vd produces rapid and deep hematologic and organ responses. Dara-Vd was well-tolerated and efficacious, even among patients with extensive cardiac dysfunction.

Mast cell leukemia: clinical and molecular features and survival outcomes of patients in the ECNM Registry.

Mast cell leukemia (MCL) is a rare subtype of systemic mastocytosis defined by ≥20% mast cells (MC) on a bone marrow aspirate. We evaluated 92 patients with MCL from the European Competence Network on Mastocytosis registry. Thirty-one (34%) patients had a diagnosis of MCL with an associated hematologic neoplasm (MCL-AHN). Chronic MCL (lack of C-findings) comprised 14% of patients, and only 4.5% had "leukemic MCL" (≥10% circulating MCs). KIT D816V was found in 62/85 (73%) evaluable patients; 9 (11%) individuals exhibited alternative KIT mutations, and no KIT variants were detected in 14 (17%) subjects. Ten evaluable patients (17%) had an abnormal karyotype and the poor-risk SRSF2, ASXL1, and RUNX1 (S/A/R) mutations were identified in 16/36 (44%) patients who underwent next-generation sequencing. Midostaurin was the most common therapy administered to 65% of patients and 45% as first-line therapy. The median overall survival (OS) was 1.6 years. In multivariate analysis (S/A/R mutations excluded owing to low event rates), a diagnosis of MCL-AHN (hazard ratio [HR], 4.7; 95% confidence interval [CI], 1.7-13.0; P = .001) and abnormal karyotype (HR, 5.6; 95% CI, 1.4-13.3; P = .02) were associated with inferior OS; KIT D816V positivity (HR, 0.33; 95% CI, 0.11-0.98; P = .04) and midostaurin treatment (HR, 0.32; 95% CI, 0.08-0.72; P = .008) were associated with superior OS. These data provide the most comprehensive snapshot of the clinicopathologic, molecular, and treatment landscape of MCL to date, and should help further inform subtyping and prognostication of MCL.

Frontline treatment patterns and outcomes among older adults with acute myeloid leukemia: A population-based analysis in the modern era.

BACKGROUND: Traditionally, conventional induction chemotherapy has been the primary frontline treatment for acute myeloid leukemia (AML); however, older adults are often poor chemotherapy candidates. Recently, several nonconventional frontline AML regimens, including hypomethylating agents, the BCL-2 inhibitor venetoclax, and targeted therapies, have emerged, and they may offer new options for older adults. This study was aimed at describing treatment patterns and outcomes of older adult AML in a modern population-based cohort. METHODS: This study evaluated patients aged ≥60 years with a first primary diagnosis of AML (2014-2017) in the California Cancer Registry linked to inpatient hospitalizations. Multivariable regression examined factors associated with the frontline treatment regimen and survival. RESULTS: In all, 3068 patients were included; 36% received frontline therapy with a conventional chemotherapy backbone, 42% received nonconventional therapy, and 22% received no treatment. The use of nonconventional therapy increased over time from 38% of patients in 2014 to 47% in 2017 (P < .001). In multivariable analyses, receipt of treatment was associated with an age younger than 80 years, fewer than 2 comorbidities, and care at a National Cancer Institute-designated cancer center (NCI-CC). Compared with conventional chemotherapy, nonconventional therapy was associated with Black race/ethnicity, public health insurance, fewer hospital admissions, and fewer inpatient days. Receiving frontline therapy at an NCI-CC was independently associated with superior overall survival. CONCLUSIONS: Using a population-based approach, this study has demonstrated that patterns of care for frontline AML treatment in older adults are changing, with increasing use of nonconventional therapies. A significant proportion of older adults remain untreated. At the population level, there remain opportunities to increase therapy access for older adults with AML.

Haematopoietic stem-cell transplantation in older adults: geriatric assessment, donor considerations, and optimisation of care.

Haematopoietic stem-cell transplantation (HSCT) has seen substantial growth among older adults. Chronological age is no longer viewed as an absolute barrier to HSCT, and alternative methods for assessing pre-transplantation fitness are increasingly used. In this Series paper, we summarise the metrics for pre-transplantation risk assessment in older adults, including both traditional metrics and geriatric assessment, and the ability of these metrics to predict post-transplantation outcomes. We also discuss strategies to broaden the utility of geriatric assessment, including in chronologically younger HSCT candidates and to guide individualised pre-transplantation interventions. Finally, we discuss donor considerations in older adults, including use of older sibling donors, haploidentical donors, and emerging data for donor-associated clonal haematopoiesis of indeterminate potential.

VITT following Ad26.COV2.S vaccination presenting without radiographically demonstrable thrombosis.

We report a case of vaccine-induced immune thrombotic thrombocytopenia (VITT) in a young man diagnosed 13 days after Ad26.COV2.S COVID-19 (Johnson & Johnson/Janssen) vaccination. He presented to us with 5 days of progressive left leg pain, thrombocytopenia, hypofibrinogenemia, and markedly elevated d-dimers, but without radiographically demonstrable thrombosis. Despite negative imaging, we initiated treatment of presumptive VITT given the striking clinical picture that included the timing of his recent adenovirus-based COVID-19 vaccine, leg symptoms, marked thrombocytopenia, and consumptive coagulopathy. He received intravenous immune globulin, prednisone, and argatroban and was discharged 7 days later much improved. His positive platelet factor 4 enzyme-linked immunosorbent assay antibody test returned after treatment was initiated. To our knowledge, this is the first reported case of VITT following Ad26.COV2.S vaccination presenting without radiographically demonstrable thrombosis. Our patient highlights the importance of knowing vaccine status and initiating treatment as soon as possible in the right clinical setting, even in the absence of radiographic evidence of thrombus. Early VITT recognition and treatment provide an opportunity to prevent serious thrombotic complications.

Early Time-to-Tocilizumab after B Cell Maturation Antigen-Directed Chimeric Antigen Receptor T Cell Therapy in Myeloma.

Preemptive administration of tocilizumab (toci) to manage cytokine release syndrome (CRS) after chimeric antigen receptor T cell (CAR-T) therapy may reduce rates of serious CRS but conversely may worsen neurotoxicity or risk of infections. Optimal toci administration strategies for patients with relapsed/refractory multiple myeloma (RRMM) receiving B cell maturation antigen (BCMA)-directed CAR-T therapies have not been evaluated. The objective of this study was to identify whether shorter time-to-toci intervals (hours between first fever attributed to CRS and first dose of toci) have any impact on therapy-related toxicities or clinical outcomes among patients with RRMM receiving BCMA-directed CAR-T therapies. We retrospectively analyzed our institution's experience with 4 BCMA-directed CAR-T therapies (idecabtagene vicleucel, bb21217, ciltacabtagene autoleucel, and orvacabtagene autoceucel) for RRMM over a 3-year period ending in June 2020. We divided patients based on the administration of toci and median time-to-toci interval into early-toci (time-to-toci ≤50th percentile), late-toci (time-to-toci >50th percentile), and no-toci (no toci received) groups. We compared the early-toci and late-toci groups with regard to patient characteristics, weight-based CAR-T toxicities, selected toxicities (CRS, neurotoxicity, macrophage activation syndrome, or infections), and clinical outcomes. Of 50 analyzed patients with a median follow-up of 15.3 months, 76% (n = 38) received ≥1 dose of toci (range, 1 to 3) and were classified into early-toci (time-to-toci ≤12 hours) or late-toci (time-to-toci >12 hours) groups. The 2 groups (n = 19 each) had similar CRS grade distributions, hours to CRS onset, CRS-related biomarkers, and incidences of neurotoxicity or severe infections; however, weight-adjusted CAR-T cell doses were higher in the early-toci group (median 5.99 versus 3.80 × 106 cells/kg, P < 0.01). Peak CRS grades (range, 0 to 2) using American Society for Transplantation and Cellular Therapy consensus criteria, neurotoxicity rates, and rates of severe infections were similar between groups; however, the median CRS duration was 18.6 hours for the early-toci group versus 84.7 hours for the late-toci group. The median progression-free survival was 35.7 months in the early-toci group and 13.2 months in the late-toci group. While limited by small sample size and known confounders such as CAR-T cell dose, our analysis suggests that preemptive toci strategies for CRS management with BCMA-directed CAR-T therapy-specifically, toci administration within 12 hours of the first fever attributed to CRS-do not appear to increase rates of therapy-related toxicities or compromise efficacy. However, total CRS duration may be shorter with early-toci workflows. Prospective validation of our findings may lead to improved safety and cost-effectiveness profiles for CAR-T therapy in RRMM.