A Phase 1 Clinical Trial of NKTR-255 with CD19-22 CAR-T Cell Therapy for Refractory B-cell Acute Lymphoblastic Leukemia.

While chimeric antigen receptor T-cell (CAR-T) therapy has revolutionized the treatment of B-cell malignancies, many patients relapse and therefore strategies to improve antitumor immunity are needed. We previously designed a novel autologous bispecific CAR targeting CD19 and CD22 (CAR19-22), which was well tolerated and associated with high response rates but relapse was common. Interleukin-15 (IL15) induces proliferation of diverse immune cells and can augment lymphocyte trafficking. Here, we report the results of a phase 1 clinical trial of the first combination of a novel recombinant polymer-conjugated IL15 receptor agonist (NKTR-255), with CAR19-22, in adults with relapsed / refractory B-cell acute lymphoblastic leukemia. Eleven patients were enrolled, nine of whom successfully received CAR19-22 followed by NKTR-255. There were no dose limiting toxicities, with transient fever and myelosuppression as the most common possibly related toxicities. We observed favorable efficacy with eight out of nine patients (89%) achieving measurable residual disease negative remission. At 12 months, progression-free survival for NKTR-255 was double that of historical controls (67% vs 38%). We performed correlative analyses to investigate the effects of IL15 receptor agonism. Cytokine profiling showed significant increases in IL15 and the chemokines CXCL9 and CXCL10. The increase in chemokines was associated with decreases in absolute lymphocyte counts and CD8+ CAR T-cells in blood and ten-fold increases in CSF CAR-T cells, suggesting lymphocyte trafficking to tissue. Combining NKTR-255 with CAR19-22 was safe, feasible and associated with high rates of durable responses (NCT03233854).

Bendamustine is a safe and effective lymphodepletion agent for axicabtagene ciloleucel in patients with refractory or relapsed large B-cell lymphoma.

BACKGROUND: Fludarabine in combination with cyclophosphamide (FC) is the standard lymphodepletion regimen for CAR T-cell therapy (CAR T). A national fludarabine shortage in 2022 necessitated the exploration of alternative regimens with many centers employing single-agent bendamustine as lymphodepletion despite a lack of clinical safety and efficacy data. To fill this gap in the literature, we evaluated the safety, efficacy, and expansion kinetics of bendamustine as lymphodepletion prior to axicabtagene ciloleucel (axi-cel) therapy. METHODS: 84 consecutive patients with relapsed or refractory large B-cell lymphoma treated with axi-cel and managed with a uniform toxicity management plan at Stanford University were studied. 27 patients received alternative lymphodepletion with bendamustine while 57 received FC. RESULTS: Best complete response rates were similar (73.7% for FC and 74% for bendamustine, p=0.28) and there was no significant difference in 12-month progression-free survival or overall survival estimates (p=0.17 and p=0.62, respectively). The frequency of high-grade cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome was similar in both the cohorts. Bendamustine cohort experienced lower proportions of hematological toxicities and antibiotic use for neutropenic fever. Immune reconstitution, as measured by quantitative assessment of cellular immunity, was better in bendamustine cohort as compared with FC cohort. CAR T expansion as measured by peak expansion and area under the curve for expansion was comparable between cohorts. CONCLUSIONS: Bendamustine is a safe and effective alternative lymphodepletion conditioning for axi-cel with lower early hematological toxicity and favorable immune reconstitution.

Extracellular release of mitochondria induced by pre-hematopoietic stem cell transplant conditioning exacerbates GVHD.

Despite therapeutic advancements, GVHD is a major complication of HSCT. In current models of GVHD, tissue injury induced by cytotoxic conditioning regimens, along with translocation of microbes expressing Pathogen Associated Molecular Patterns (PAMPs), result in activation of host antigen-presenting cells (APC) to stimulate alloreactive donor T lymphocytes. Recent studies have demonstrated that in many pathologic states, tissue injury results in the release of mitochondria from the cytoplasm to the extracellular space. We hypothesized that extracellular mitochondria, which are related to archaebacteria, could also trigger GVHD by stimulation of host APC. We found that clinically relevant doses of radiation or busulfan induced extracellular release of mitochondria by various cell types, including cultured intestinal epithelial cells. Conditioning-mediated mitochondrial release was associated with mitochondrial damage and impaired quality control but did not affect the viability of the cells. Extracellular mitochondria directly stimulated host APCs to express higher levels of MHC-II, co-stimulatory CD86, and pro-inflammatory cytokines, resulting in increased donor T cell activation, and proliferation in mixed lymphocyte reactions. Analyses of plasma from both experimental mice and a cohort of children undergoing HSCT demonstrated that conditioning induced extracellular mitochondrial release in vivo. In mice undergoing MHC mismatched HSCT, administration of purified syngeneic extracellular mitochondria increased host APC activation and exacerbated GVHD. Our data suggests that pre-HSCT conditioning results in extracellular release of damaged mitochondria which increase alloreactivity and exacerbate GVHD. Therefore, decreasing the extracellular release of damaged mitochondria following conditioning could serve as a novel strategy for GVHD prevention.

Management of post-autologous transplant relapse in patients with T-cell lymphomas.

Autologous hematopoietic cell transplantation (AHCT) is often used as a consolidation for patients with peripheral T-cell lymphomas (PTCLs) due to the poor prognosis associated with this heterogenous group of disorders. However, a significant number of patients will experience post-AHCT disease relapse. Here, we report a retrospective study of consecutive 124 patients with PTCLs who underwent AHCT from 2008 to 2020. With a median follow-up of 6.01 years following AHCT, 49 patients (40%) experienced disease relapse. As expected, more patients who were not in first complete remission experienced post-AHCT relapse. Following relapse, majority of the patients (70%) receiving systemic therapies intended as bridging to curative allogeneic HCT. However, only 18 (53%) patients eventually underwent allogeneic HCT. The estimated 3-year OS among patients proceeding to allogeneic HCT was 72% (95% CI 46%-87%). Our report details the pattern of post-AHCT relapse and the management of relapsed disease using different therapeutic modalities.

CD22 CAR T cells demonstrate high response rates and safety in pediatric and adult B-ALL: Phase 1b results.

Chimeric antigen receptor (CAR) T cells targeting CD22 (CD22-CAR) provide a therapeutic option for patients with CD22+ malignancies with progression after CD19-directed therapies. Using on-site, automated, closed-loop manufacturing, we conducted parallel Phase 1b clinical trials investigating a humanized CD22-CAR with 41BB costimulatory domain in children and adults with heavily treated, relapsed/refractory (r/r) B-ALL. Of 19 patients enrolled, 18 had successful CD22-CAR manufacturing, and 16 patients were infused. High grade (3-4) cytokine release syndrome (CRS) and immune effector-cell-associated neurotoxicity syndrome (ICANS) each occurred in only one patient; however, three patients experienced immune-effector-cell-associated hemophagocytic lymphohistiocytosis-like syndrome (IEC-HS). Twelve of 16 patients (75%) achieved CR with an overall 56% MRD-negative CR rate. Duration of response was overall limited (median 77 days), and CD22 expression was downregulated in 4/12 (33%) available samples at relapse. In summary, we demonstrate that closed-loop manufacturing of CD22-CAR T cells is feasible and is associated with a favorable safety profile and high CR rates in pediatric and adult r/r B-ALL, a cohort with limited CD22-CAR reporting.

CAR19 monitoring by peripheral blood immunophenotyping reveals histology-specific expansion and toxicity.

ABSTRACT: Chimeric antigen receptor (CAR) T cells directed against CD19 (CAR19) are a revolutionary treatment for B-cell lymphomas (BCLs). CAR19 cell expansion is necessary for CAR19 function but is also associated with toxicity. To define the impact of CAR19 expansion on patient outcomes, we prospectively followed a cohort of 236 patients treated with CAR19 (brexucabtagene autoleucel or axicabtagene ciloleucel) for mantle cell lymphoma (MCL), follicular lymphoma, and large BCL (LBCL) over the course of 5 years and obtained CAR19 expansion data using peripheral blood immunophenotyping for 188 of these patients. CAR19 expansion was higher in patients with MCL than other lymphoma histologic subtypes. Notably, patients with MCL had increased toxicity and required fourfold higher cumulative steroid doses than patients with LBCL. CAR19 expansion was associated with the development of cytokine release syndrome, immune effector cell-associated neurotoxicity syndrome, and the requirement for granulocyte colony-stimulating factor 14 days after infusion. Younger patients and those with elevated lactate dehydrogenase (LDH) had significantly higher CAR19 expansion. In general, no association between CAR19 expansion and LBCL treatment response was observed. However, when controlling for tumor burden, we found that lower CAR19 expansion in conjunction with low LDH was associated with improved outcomes in LBCL. In sum, this study finds CAR19 expansion principally associates with CAR-related toxicity. Additionally, CAR19 expansion as measured by peripheral blood immunophenotyping may be dispensable to favorable outcomes in LBCL.

Molecular Imaging of Acute Graft-Versus-Host Disease.

Noninvasive molecular imaging of acute graft-versus-host disease (GvHD) after allogeneic hematopoietic stem cell transplantation has great potential to detect GvHD at the early stages, aid in grading of the disease, monitor treatment response, and guide therapeutic decisions. Although the specificity of currently available tracers appears insufficient for clinical GvHD diagnosis, recently, several preclinical studies have identified promising new imaging agents targeting one or more biologic processes involved in GvHD pathogenesis, ranging from T-cell activation to tissue damage. In this review, we summarize the different approaches reported to date for noninvasive detection of GvHD using molecular imaging with a specific focus on the use of PET. We discuss possible applications of molecular imaging for the detection of GvHD in the clinical setting, as well as some of the predictable challenges that are faced during clinical translation of these approaches.

Single-center randomized trial of T-reg graft alone vs T-reg graft plus tacrolimus for the prevention of acute GVHD.

ABSTRACT: Allogeneic hematopoietic cell transplantation (HCT) is a curative therapy for hematological malignancies for which graft-versus-host disease (GVHD) remains a major complication. The use of donor T-regulatory cells (Tregs) to prevent GVHD appears promising, including in our previous evaluation of an engineered graft product (T-reg graft) consisting of the timed, sequential infusion of CD34+ hematopoietic stem cells and high-purity Tregs followed by conventional T cells. However, whether immunosuppressive prophylaxis can be removed from this protocol remains unclear. We report the results of the first stage of an open-label single-center phase 2 study (NCT01660607) investigating T-reg graft in myeloablative HCT of HLA-matched and 9/10-matched recipients. Twenty-four patients were randomized to receive T-reg graft alone (n = 12) or T-reg graft plus single-agent GVHD prophylaxis (n = 12) to determine whether T-reg graft alone was noninferior in preventing acute GVHD. All patients developed full-donor myeloid chimerism. Patients with T-reg graft alone vs with prophylaxis had incidences of grade 3 to 4 acute GVHD of 58% vs 8% (P = .005) and grade 3 to 4 of 17% vs 0% (P = .149), respectively. The incidence of moderate-to-severe chronic GVHD was 28% in the T-reg graft alone arm vs 0% with prophylaxis (P = .056). Among patients with T-reg graft and prophylaxis, CD4+ T-cell-to-Treg ratios were reduced after transplantation, gene expression profiles showed reduced CD4+ proliferation, and the achievement of full-donor T-cell chimerism was delayed. This study indicates that T-reg graft with single-agent tacrolimus is preferred over T-reg graft alone for the prevention of acute GVHD. This trial was registered at www.clinicaltrials.gov as #NCT01660607.

Single-cell transcriptomics reveal different maturation stages and sublineage commitment of human thymic invariant natural killer T cells.

Invariant natural killer T cells are a rare, heterogeneous T-cell subset with cytotoxic and immunomodulatory properties. During thymic development, murine invariant natural killer T cells go through different maturation stages differentiating into distinct sublineages, namely, invariant natural killer T1, 2, and 17 cells. Recent reports indicate that invariant natural killer T2 cells display immature properties and give rise to other subsets, whereas invariant natural killer T1 cells seem to be terminally differentiated. Whether human invariant natural killer T cells follow a similar differentiation model is still unknown. To define the maturation stages and assess the sublineage commitment of human invariant natural killer T cells during thymic development, in this study, we performed single-cell RNA sequencing analysis on human Vα24+Vß11+ invariant natural killer T cells isolated from thymocytes. We show that these invariant natural killer T cells displayed heterogeneity, and our unsupervised analysis identified 5 clusters representing different maturation stages, from an immature profile with high expression of genes important for invariant natural killer T cell development and proliferation to a mature, fully differentiated profile with high levels of cytotoxic effector molecules. Evaluation of expression of sublineage-defining gene sets revealed mainly cells with an invariant natural killer T2 signature in the most immature cluster, whereas the more differentiated ones displayed an invariant natural killer T1 signature. Combined analysis with a publicly available single-cell RNA sequencing data set of human invariant natural killer T cells from peripheral blood suggested that the 2 main subsets exist both in thymus and in the periphery, while a third more immature one was restricted to the thymus. Our data point to the existence of different maturation stages of human thymic invariant natural killer T cells and provide evidence for sublineage commitment of invariant natural killer T cells in the human thymus.

Improved outcomes for relapsed/refractory Hodgkin lymphoma after autologous transplantation in the era of novel agents.

The treatment landscape of relapsed/refractory (R/R) classic Hodgkin lymphoma (cHL) has evolved significantly over the past decade after the approval of brentuximab vedotin (BV) and the programmed death-1 (PD-1) inhibitors. We evaluated how outcomes and practice patterns have changed for patients with R/R cHL who underwent autologous hematopoietic cell transplantation (AHCT) at our institution from 2011 to 2020 (N = 183) compared with those from 2001 to 2010 (N = 159) and evaluated prognostic factors for progression-free survival (PFS) and overall survival (OS) in both eras. OS was superior in the modern era with a trend toward lower nonrelapse mortality beyond 2 years after transplant. Among patients who progressed after AHCT, 4-year postprogression survival increased from 43.3% to 71.4% in the modern era, reflecting increasing use of BV and the PD-1 inhibitors. In multivariable analysis for patients that underwent transplant in the modern era, age ≥45 years, primary refractory disease, and lack of complete remission pre-AHCT were associated with inferior PFS, whereas receipt of a PD-1 inhibitor-based regimen pre-AHCT was associated with superior PFS. Extranodal disease at relapse was associated with inferior OS. Our study demonstrates improved survival for R/R cHL after AHCT in the modern era attributed to more effective salvage regimens allowing for better disease control pre-AHCT and improved outcomes for patients who progressed after AHCT. Excellent outcomes were observed with PD-1 inhibitor-based salvage regimens pre-AHCT and support a randomized trial evaluating immunotherapy in the second line setting.

Analysis of the T-cell repertoire and transcriptome identifies mechanisms of regulatory T-cell suppression of GVHD.

CD4+FOXP3+ regulatory T cells (Tregs) have demonstrated efficacy in the prevention and treatment of graft-versus-host disease (GVHD). Preclinical and clinical studies indicate that Tregs are able to protect from GVHD without interfering with the graft-versus-tumor (GVT) effect of hematopoietic cell transplantation (HCT), although the underlying molecular mechanisms are largely unknown. To elucidate Treg suppressive function during in vivo suppression of acute GVHD, we performed paired T-cell receptor (TCRα and ΤCRß genes) repertoire sequencing and RNA sequencing analysis on conventional T cells (Tcons) and Tregs before and after transplantation in a major histocompatibility complex -mismatched mouse model of HCT. We show that both Tregs and Tcons underwent clonal restriction, and Tregs did not interfere with the activation of alloreactive Tcon clones and the breadth of their TCR repertoire but markedly suppressed their expansion. Transcriptomic analysis revealed that Tregs predominantly affected the transcriptome of CD4 Tcons and, to a lesser extent, that of CD8 Tcons, thus modulating the transcription of genes encoding pro- and anti-inflammatory molecules as well as enzymes involved in metabolic processes, inducing a switch from glycolysis to oxidative phosphorylation. Finally, Tregs did not interfere with the induction of gene sets involved in the GVT effect. Our results shed light onto the mechanisms of acute GVHD suppression by Tregs and will support the clinical translation of this immunoregulatory approach.

Prevention of acute GVHD using an orthogonal IL-2/IL-2Rß system to selectively expand regulatory T cells in vivo.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative option for patients with hematological disorders and bone marrow (BM) failure syndromes. Graft-versus-host disease (GVHD) remains a leading cause of morbidity posttransplant. Regulatory T cell (Treg) therapies are efficacious in ameliorating GVHD but limited by variable suppressive capacities and the need for a high therapeutic dose. Here, we sought to expand Treg in vivo by expressing an orthogonal interleukin 2 receptor ß (oIL-2Rß) that would selectively interact with oIL-2 cytokine and not wild-type (WT) IL-2. To test whether the orthogonal system would preferentially drive donor Treg expansion, we used a murine major histocompatibility complex-disparate GVHD model of lethally irradiated BALB/c mice given T cell-depleted BM from C57BL/6 (B6) mice alone or together with B6Foxp3+GFP+ Treg or oIL-2Rß-transduced Treg at low cell numbers that typically do not control GVHD with WT Treg. On day 2, B6 activated T cells (Tcons) were injected to induce GVHD. Recipients were treated with phosphate-buffered saline (PBS) or oIL-2 daily for 14 days, then 3 times weekly for an additional 14 days. Mice treated with oIL-2Rß Treg and oIL-2 compared with those treated with PBS had enhanced GVHD survival, in vivo selective expansion of Tregs, and greater suppression of Tcon expansion in secondary lymphoid organs and intestines. Importantly, oIL-2Rß Treg maintained graft-versus-tumor (GVT) responses in 2 distinct tumor models (A20 and MLL-AF9). These data demonstrate a novel approach to enhance the efficacy of Treg therapy in allo-HSCT using an oIL-2/oIL-2Rß system that allows for selective in vivo expansion of Treg leading to GVHD protection and GVT maintenance.

IL-2 receptor engineering enhances regulatory T cell function suppressed by calcineurin inhibitor.

Clinical trials utilizing regulatory T cell (Treg) therapy in organ transplantation have shown promising results, however, the choice of a standard immunosuppressive regimen is still controversial. Calcineurin inhibitors (CNIs) are one of the most common immunosuppressants for organ transplantation, although they may negatively affect Tregs by inhibiting IL-2 production by conventional T cells. As a strategy to replace IL-2 signaling selectively in Tregs, we have introduced an engineered orthogonal IL-2 (ortho IL-2) cytokine/cytokine receptor (R) pair that specifically binds with each other but does not bind with their wild-type counterparts. Murine Tregs were isolated from recipients and retrovirally transduced with ortho IL-2Rß during ex vivo expansion. Transduced Tregs (ortho Tregs) were transferred into recipient mice in a mixed hematopoietic chimerism model with tacrolimus administration. Ortho IL-2 treatment significantly increased the ortho IL-2Rß(+) Treg population in the presence of tacrolimus without stimulating other T cell subsets. All the mice treated with tacrolimus plus ortho IL-2 achieved heart allograft tolerance, even after tacrolimus cessation, whereas those receiving tacrolimus treatment alone did not. These data demonstrate that Treg therapy can be adopted into a CNI-based regimen by utilizing cytokine receptor engineering.

ICOS immunoPET enables visualization of activated T cells and early diagnosis of murine acute gastrointestinal GvHD.

Allogeneic hematopoietic cell transplantation (HCT) is a well-established and potentially curative treatment for a broad range of hematological diseases, bone marrow failure states, and genetic disorders. Acute graft-versus-host disease (GvHD), mediated by donor T cells attacking host tissues, still represents a major cause of morbidity and mortality following allogeneic HCT. Current approaches to diagnosis of gastrointestinal acute GvHD rely on clinical and pathological criteria that manifest at late stages of disease. New strategies allowing for GvHD prediction and diagnosis, prior to symptom onset, are urgently needed. Noninvasive antibody-based positron emission tomography (PET) (immunoPET) imaging of T-cell activation post-allogeneic HCT is a promising strategy toward this goal. In this work, we identified inducible T-cell costimulator (ICOS) as a potential immunoPET target for imaging activated T cells during GvHD. We demonstrate that the use of the Zirconium-89-deferoxamine-ICOS monoclonal antibody PET tracer allows in vivo visualization of donor T-cell activation in target tissues, namely the intestinal tract, in a murine model of acute GvHD. Importantly, we demonstrate that the Zirconium-89-deferoxamine-ICOS monoclonal antibody PET tracer does not affect GvHD pathogenesis or the graft-versus-tumor (GvT) effect of the transplant procedure. Our data identify ICOS immunoPET as a promising strategy for early GvHD diagnosis prior to the appearance of clinical symptoms.

Multiparameter Longitudinal Imaging of Immune Cell Activity in Chimeric Antigen Receptor T Cell and Checkpoint Blockade Therapies.

Longitudinal multimodal imaging presents unique opportunities for noninvasive surveillance and prediction of treatment response to cancer immunotherapy. In this work we first designed a novel granzyme B activated self-assembly small molecule, G-SNAT, for the assessment of cytotoxic T lymphocyte mediated cancer cell killing. G-SNAT was found to specifically detect the activity of granzyme B within the cytotoxic granules of activated T cells and engaged cancer cells in vitro. In lymphoma tumor-bearing mice, the retention of cyanine 5 labeled G-SNAT-Cy5 correlated to CAR T cell mediated granzyme B exocytosis and tumor eradication. In colorectal tumor-bearing transgenic mice with hematopoietic cells expressing firefly luciferase, longitudinal bioluminescence and fluorescence imaging revealed that after combination treatment of anti-PD-1 and anti-CTLA-4, the dynamics of immune cell trafficking, tumor infiltration, and cytotoxic activity predicted the therapeutic outcome before tumor shrinkage was evident. These results support further development of G-SNAT for imaging early immune response to checkpoint blockade and CAR T-cell therapy in patients and highlight the utility of multimodality imaging for improved mechanistic insights into cancer immunotherapy.

Allogeneic Hematopoietic Cell Transplantation for Adult Acute Lymphoblastic Leukemia in the Modern Era.

Allogeneic hematopoietic cell transplantation (HCT) remains an important treatment for adults with acute lymphoblastic leukemia (ALL). We hypothesized that advances in ALL and transplantation have resulted in improved HCT outcomes in recent years. In this study, we evaluated the characteristics and outcomes of adult ALL patients undergoing allogeneic HCT over the last decade. Patients with ALL aged 18 years and older who underwent allogeneic HCT at Stanford University between 2008 and 2019 were included in this study. Patients were divided into 2 eras based on year of HCT: 2008 to 2013 (earlier era) and 2014 to 2019 (later era). A total of 285 patients were included: 119 patients underwent HCT in the earlier era and 166 in the later era. Patients who underwent transplantation in the later era were more likely to be Hispanic (38% versus 21%) and to have an HCT-comorbidity index ≥3 (31% versus 18%). Donor source for HCT also differed with an increase in the use of HLA-mismatched donor sources (38% versus 24%), notably umbilical cord blood in the later era (16% versus 0%). Patients in the later era were less likely to undergo transplantation with active disease (4% versus 16%); pre-HCT rates of measurable residual disease were similar across the eras (38% versus 40%). In unadjusted analyses, overall survival (OS) improved across eras, with 2-year estimates for the later and earlier eras of 73% (95% confidence interval [CI], 66%-80%) versus 55% (95% CI, 46%-64%), respectively. Multivariable analysis confirmed the association between later era and OS (hazard ratio = 0.52, 95% CI, 0.34-0.78). Finally, among patients relapsing after HCT (25% in later era and 33% in earlier era), the use of novel immunotherapies increased in the later era (44% versus 3%), as did the median OS after post-HCT relapse (16 months versus 8 months, P< .001). OS after HCT for adult ALL has improved in recent years. This is due, in part, to a significant improvement in the ability to effectively salvage adults with ALL relapsing after HCT.

Real-World Experience of Cryopreserved Allogeneic Hematopoietic Grafts during the COVID-19 Pandemic: A Single-Center Report.

In response to the widespread COVID-19 pandemic, cryopreservation of allogeneic donor apheresis products was implemented to mitigate the challenges of donor availability and product transport. Although logistically beneficial, the impact of cryopreservation on clinical outcomes and graft composition remains unclear. In this study, we compared outcomes and graft composition with cryopreserved versus fresh allografts in the setting of allogeneic hematopoietic cell transplantation (allo-HCT). We retrospectively analyzed the clinical outcomes of 30 consecutive patients who received cryopreserved allografts between March and August 2020 and 60 consecutive patients who received fresh allografts before the COVID-19 pandemic. Primary endpoints were hematopoietic engraftment and graft failure (GF), and secondary outcomes were overall survival (OS), relapse-free survival (RFS) and nonrelapse mortality (NRM). In addition, extended immunophenotype analysis was performed on cryopreserved and prospectively collected fresh apheresis samples. Compared with recipients of fresh allografts, both neutrophil and platelet recovery were delayed in recipients of cryopreserved reduced-intensity conditioning (RIC) allo-HCT, with a median time to engraftment of 24 days versus 18 days (P = .01) for neutrophils and 27 days versus 18 days (P = .069) for platelets. We observed primary GF in 4 of 30 patients in the cryopreserved cohort (13.3%) versus only 1 of 60 patients (1.7 %) in the fresh cohort (P = .03). Cryopreserved RIC allo-HCT was associated with significantly lower median total, myeloid, and T cell donor chimerism at 1 month. OS and RFS were inferior for cryopreserved graft recipients (hazard ratio [HR], 2.16; 95% confidence interval [CI], 1.00 to 4.67) and HR, 1.90; 95% CI, 0.95 to 3.79, respectively. Using an extended immunophenotype analysis, we compared 14 samples from the cryopreserved cohort to 6 prospectively collected fresh apheresis donor samples. These analyses showed both a decrease in total cell viability and a significantly reduced absolute number of natural killer cells (CD3-CD56+) in the cryopreserved apheresis samples. In this single-institution study, we found delayed engraftment and a trend toward clinical inferiority of cryopreserved allografts compared with fresh allografts. Further evaluation of the use of cryopreserved allografts and their impact on clinical and laboratory outcomes is warranted.

Incidence and risk factors associated with bleeding and thrombosis following chimeric antigen receptor T-cell therapy.

Bleeding and thrombotic events are an emerging toxicity associated with chimeric antigen receptor (CAR) therapies. To determine their incidence, we retrospectively analyzed consecutive adult patients (N = 127) with large B-cell lymphoma (LBCL) or B-cell acute lymphoblastic leukemia (B-ALL) treated from 2017 through 2020 with axicabtagene ciloleucel (axi-cel; n = 89) or a bispecific CD19/CD22 CAR (n = 38). Twelve (9.4%) and 8 (6.3%) patients developed bleeding and thrombosis within the first 3 months, respectively. In the axi-cel subgroup, these occurred in 11.2% and 6.7%, respectively. Bleeding occurred between days 8 and 30 (median, 17.5) and thrombosis between days 2 and 91 (median, 29). Bleeding sites included genitourinary, soft tissue, intracranial, gastrointestinal, and pulmonary and were associated with features of consumptive coagulopathy. On univariate analysis, patients with bleeding were older, had lower baseline platelets (86 × 103/µL vs 178 × 103/µL; P < .01), lower platelet and fibrinogen nadirs , and elevated lactate dehydrogenase. Immune effector cell (IEC)-associated neurotoxicity syndrome (ICANS) grade ≥3 was associated with increased bleeding (50% vs 15%; P = .01), thrombosis (50% vs 16%; P = .04), prothrombin time prolongation, hypofibrinogenemia, and elevated D-dimer. Low pretreatment platelet counts were associated with bleeding in a multivariate logistic regression model. Patients with thrombocytopenia or severe ICANS are at increased risk of bleeding and should be closely monitored, particularly within the first month after CAR therapy. Future studies in larger cohorts should assess risk factors for systemic coagulopathies in CAR T therapy, including their association with neurotoxicity.

Concordance of peripheral blood and bone marrow measurable residual disease in adult acute lymphoblastic leukemia.

Monitoring of measurable residual disease (MRD) is essential to the management of acute lymphoblastic leukemia (ALL) and is typically performed through repeated bone marrow (BM) assessments. Using a next-generation sequencing (NGS) MRD platform, we performed a prospective observational study evaluating the correlation between peripheral blood (PB) and BM MRD in adults with ALL receiving cellular therapies (hematopoietic cell transplantation [HCT] and chimeric antigen receptor T-cell [CAR-T] therapies). Among the study cohort (N = 69 patients; 126 paired PB/BM samples), we found strong correlation between PB and BM MRD (r = 0.87; P < .001), with a sensitivity and specificity of MRD detection in the PB of 87% and 90%, respectively, relative to MRD in the BM. MRD became detectable in the PB in 100% of patients who subsequently relapsed following HCT, with median time from MRD+ to clinical relapse of 90 days, and in 85% of patients who relapsed following CAR T, with median time from MRD+ to clinical relapse of 60 days. In adult patients with ALL undergoing cellular therapies, we demonstrate strong concordance between NGS-based MRD detected in the PB and BM. Monitoring of ALL MRD in the PB appears to be an adequate alternative to frequent invasive BM evaluations in this clinical setting.

Allogeneic CAR Invariant Natural Killer T Cells Exert Potent Antitumor Effects through Host CD8 T-Cell Cross-Priming.

PURPOSE: The development of allogeneic chimeric antigen receptor (CAR) T-cell therapies for off-the-shelf use is a major goal that faces two main immunologic challenges, namely the risk of graft-versus-host disease (GvHD) induction by the transferred cells and the rejection by the host immune system limiting their persistence. In this work we assessed the direct and indirect antitumor effect of allogeneic CAR-engineered invariant natural killer T (iNKT) cells, a cell population without GvHD-induction potential that displays immunomodulatory properties. EXPERIMENTAL DESIGN: After assessing murine CAR iNKT cells direct antitumor effects in vitro and in vivo, we employed an immunocompetent mouse model of B-cell lymphoma to assess the interaction between allogeneic CAR iNKT cells and endogenous immune cells. RESULTS: We demonstrate that allogeneic CAR iNKT cells exerted potent direct and indirect antitumor activity when administered across major MHC barriers by inducing tumor-specific antitumor immunity through host CD8 T-cell cross-priming. CONCLUSIONS: In addition to their known direct cytotoxic effect, allogeneic CAR iNKT cells induce host CD8 T-cell antitumor responses, resulting in a potent antitumor effect lasting longer than the physical persistence of the allogeneic cells. The utilization of off-the-shelf allogeneic CAR iNKT cells could meet significant unmet needs in the clinic.