BendaEAM versus BEAM as conditioning regimen for ASCT in patients with relapsed lymphoma (BEB): a multicentre, randomised, phase 2 trial.

Background: Replacement of carmustine (BCNU) in the BEAM regimen (BCNU, etoposide, cytarabine, melphalan) with bendamustine (BendaEAM) before autologous stem cell transplantation (ASCT) is feasible in lymphoma. However, randomised trials are lacking. Here, we present the first trial addressing this topic. Methods: This multicentre, randomised, phase 2 study (BEB-trial) conducted at four haematological centres in Austria and Switzerland compares BEAM with BendaEAM in patients with relapsed lymphoma. Both regimens were administered intravenously before ASCT, in BEAM according to the standard protocol (300 mg/m2 BCNU on day -6), in BendaEAM, BCNU was replaced by 200 mg/m2 bendamustine given on days -7 and -6. Eligible patients were aged 18-75 years and had mantle cell lymphoma, diffuse large B-cell lymphoma, or follicular lymphoma in first or second remission or chemosensitive relapse. The primary endpoint of the study was to evaluate whether replacement of BCNU by bendamustine reduces lung toxicity, defined as a decrease of the diffusion capacity of the lung for carbon monoxide by at least 20% at three months after ASCT. Data analyses were performed on an intention-to-treat basis. This study is registered with ClinicalTrials.gov, number NCT02278796, and is complete. Findings: Between April 20, 2015, and November 28, 2018, 108 patients were enrolled; of whom 53 were randomly assigned to receive BendaEAM (36 male, 17 female) and 55 to receive BEAM (39 male, 16 female). All patients engrafted rapidly. Lung toxicity did not differ between groups (BendaEAM: n = 8, 19.5%; BEAM: n = 11, 25.6%; risk difference = -6.1%: 95% confidence interval: -23.9% to 11.7%). Acute toxicities of at least grade 3 were comparable in both groups (BendaEAM: 35.8%, BEAM: 30.9%). Overall survival (BendaEAM: 92.5%, BEAM: 89.1%) and complete remission (BendaEAM: 76.7%, BEAM: 74.3%) after 1 year (median follow-up: 369 days) were similar. No difference in quality of life was observed. Interpretation: Results were similar for both regimens in terms of survival and response rates. A phase 3 non-inferiority study is required to investigate whether BendaEAM can be considered as an alternative to BEAM. Funding: Mundipharma.

Haploidentical transplant with posttransplant cyclophosphamide vs matched related and unrelated donor transplant in acute myeloid leukemia and myelodysplastic neoplasm.

Hematopoietic cell transplantation from haploidentical donors (haploHCT) has facilitated treatment of AML and MDS by increasing donor availability and became more feasible since the introduction of post-transplant cyclophosphamide (ptCY). In our single-center retrospective analysis including 213 patients with AML or MDS, we compare the outcome of haploHCT (n = 40) with ptCY with HCT from HLA-identical MRD (n = 105) and MUD (n = 68). At 2 years after transplantation, overall survival (OS) after haploHCT was not significantly different (0.59; 95% confidence interval 0.44-0.79) compared to MRD (0.77; 0.67-0.88) and MUD transplantation (0.72; 0.64-0.82, p = 0.51). While progression-free survival (PFS) was also not significantly different (haploHCT: 0.60; 0.46-0.78, MRD: 0.55; 0.44-0.69, MUD: 0.64; 0.55-0.74, p = 0.64), non-relapse mortality (NRM) was significantly higher after haploHCT (0.18; 0.08-0.33) vs. MRD (0.029; 0.005-0.09) and MUD (0.06; 0.02-0.12, p < 0.05). Higher NRM was mainly caused by a higher rate of fatal infections, while deaths related to GvHD or other non-relapse reasons were rare in all groups. As most fatal infections occurred early and were bacterial related, one potential risk factor among many was identified in the significantly longer time to neutrophil engraftment after haploHCT with a median of 16 days (interquartile range; 14.8-20.0) vs. 12 days (10.0-13.0) for MRD and 11 days (10.0-13.0) for MUD (p = 0.01).

Diabetes insipidus and Guillain-Barré-like syndrome following CAR-T cell therapy: a case report.

BACKGROUND: Immune effector cell-associated neurotoxicity syndrome (ICANS) is a common adverse event of CD19-directed chimeric antigen receptor (CAR) T cell therapy. Other neurological adverse events, however, have not methodically been described and studied. Furthermore, safety data on CAR-T cell therapy in patients with central nervous system (CNS) lymphoma remain limited. MAIN BODY: We here report occurrence of a Guillain-Barré-like syndrome (GBS) and central diabetes insipidus (cDI) following tisagenlecleucel therapy for relapsed high-grade lymphoma with CNS involvement. Both complications were refractory to standard treatment of ICANS. Weakness of respiratory muscles required mechanical ventilation and tracheostomy while cDI was treated with desmopressin substitution for several weeks. Muscle-nerve biopsy and nerve conduction studies confirmed an axonal pattern of nerve damage. T cell-rich infiltrates and detection of the CAR transgene in muscle-nerve sections imply a direct or indirect role of CAR-T cell-mediated inflammation. In line with current treatment guidelines for GBS, intravenous immunoglobulin was administered and gradual but incomplete recovery was observed over the course of several months. CONCLUSIONS: This case report highlights the risk of rare but severe neurological adverse events, such as acute GBS or cDI, in patients treated with CAR-T cells. It further underlines the importance of appropriate patient surveillance and systematic reporting of rare complications to eventually improve treatment.

Antibody response to a third SARS-CoV-2 vaccine dose in recipients of an allogeneic haematopoietic cell transplantation.

Allogeneic haematopoietic cell transplantation (allo-HCT) recipients show impaired antibody (Ab) response to a standard two-dose vaccination against severe acute respiratory syndrome coronavirus-2 and currently a third dose is recommended as part of the primary vaccination regimen. By assessing Ab titres 1 month after a third mRNA vaccine dose in 74 allo-HCT recipients we show sufficient neutralisation activity in 77% of the patients. Discontinuation of immunosuppression before the third vaccine led to serological responses in 50% of low responders to two vaccinations. Identifying factors that might contribute to better vaccine responses in allo-HCT recipients is critical to optimise current vaccination strategies.

Dynamics of T cell repertoire renewal following autologous hematopoietic stem cell transplantation in multiple sclerosis.

Autologous hematopoietic stem cell transplantation (aHSCT) is a highly effective treatment of multiple sclerosis (MS). It depletes autoreactive cells and subsequently renews adaptive immune cells. The possible proinflammatory potential of surviving T cells early after aHSCT has not been studied. Here, we examined the dynamics of new and surviving T cells in 27 patients after aHSCT by multidimensional flow cytometry, T cell receptor (TCR) sequencing, specificity testing, telomere length profiling, and HLA genotyping. Early after aHSCT, naïve T cells are barely detectable, whereas effector memory (EM) T cells quickly reconstitute to pre-aHSCT values. EM CD4+ T cells early after aHSCT have shorter telomeres, have higher expression of senescence and exhaustion markers, and proliferate less than those before aHSCT. We find a median TCR repertoire overlap of 26% between the early post-aHSCT EM CD4+ T cells and pre-aHSCT, indicating persistence of EM CD4+ T cells early after transplantation. The EM CD4+ TCR repertoire overlap declines to 15% at 12 months after aHSCT, whereas the naïve TCR repertoire entirely renews. HLA-DR-associated EM CD4+ T cell reactivity toward MS-related antigens decreased after aHSCT, whereas reactivity toward EBV increased. Our data show substantial survival of pre-aHSCT EM CD4+ T cells early after transplantation but complete renewal of the T cell repertoire by nascent T cells later.

Introducing innovative cellular therapies into the clinic: a 2-year retrospective experience of a chimeric antigen receptor T-cell programme at a single centre in Switzerland.

AIM OF THE STUDY: Chimeric antigen receptor T (CAR-T) cells are a powerful form of immune-cell therapy for patients with relapsed/refractory B-cell lymphoma and acute B lymphoblastic leukaemia. CAR-T cells have been commercially available in Switzerland since 2018. Because of the complexity and costs of this treatment it is critical to review patient outcomes in real-world settings, to examine whether the promising results from pivotal trials can be reproduced and to identify clinical parameters that determine their efficacy. METHODS: Here we present results of a retrospective study analysing outcomes of patients treated with CAR-T cells in a single academic centre in Switzerland during the first two years after commercial approval (BASEC-No. 2020-02271). Cytokine release syndrome (CRS), immune-cell associated neurotoxicity syndrome (ICANS), responses to treatment, ancillary laboratory studies and administrative specifics of CAR-T treatment were examined and are discussed. RESULTS: From October 2018 to August 2020 CAR-T cell therapy was evaluated in 34 patients, mostly with relapsed/refractory aggressive B-cell lymphoma (87% had refractory disease). Thirty-one patients underwent leukapheresis. Three of 31 patients (9.6%) died of rapid disease progression before the CAR-T cell product was delivered, two patients were enrolled into a clinical trial, three patients were not given CAR-T cells for other reasons. Ultimately, 23 patients were infused with a commercial CAR-T cell product and included in this analysis. Fourteen (61%) patients received bridging therapy while waiting for a median of 41 days (range 31-62) for delivery of the CAR-T cell product. Toxicity and severe side effects were rare (CRS >3 in 13%, ICANS > grade 3 in 10% of patients), manageable and resolved completely thereafter. The best overall response rate was 65%, with complete responses in 38% of lymphoma patients. At 12 months postinfusion, 61% of patients were alive and 35% progression free. With a median follow-up of 14 months, 13/23 (56%) patients were alive at the time of writing. CONCLUSION: CAR-T cell therapy proved to be safe and manageable under adequate hospital conditions. Outcomes resemble results from pivotal trials. The majority of patients was heavily pretreated and refractory at the time of CAR-T cell infusion. Patient selection, time point of leukapheresis, bridging strategies and timing of CAR-T cell infusion may be critical to further improve outcomes.

Resource utilization for chimeric antigen receptor T cell therapy versus autologous hematopoietic cell transplantation in patients with B cell lymphoma.

CD19-directed chimeric antigen receptor T cells (CAR-T) have emerged as a highly efficacious treatment for patients with relapsed/refractory (r/r) B cell lymphoma (BCL). The value of CAR-T for these patients is indisputable, but one-off production costs are high, and little is known about the ancillary resource consumption associated with CAR-T treatment. Here, we compared the resource use and costs of CAR-T treatment with high-dose chemotherapy followed by autologous stem cell transplantation (ASCT) for patients with r/r BCL. Standard operating procedures were used to develop a process model in ClipMedPPM, which comprises all activities and processes to sustain or generate treatment components that together constitute a treatment path. The software allows a graphic representation and the use of standardized linguistic elements for comparison of different treatment paths. Detailed processes involved in CAR-T treatments (n = 1041 processes) and in ASCT (n = 1535) were analyzed for time consumption of treatment phases and personnel. Process costs were calculated using financial controlling data. CAR-T treatment required ~ 30% less staff time than ASCT (primarily nursing staff) due to fewer chemotherapy cycles, less outpatient visits, and shorter hospital stays. For CAR-T, production costs were ~ 8 × higher, but overall treatment time was shorter compared with ASCT (30 vs 48 days), and direct labor and overhead costs were 40% and 10% lower, respectively. Excluding high product costs, CAR-T uses fewer hospital resources than ASCT for r/r BCL. Fewer hospital days for CAR-T compared to ASCT treatment and the conservation of hospital resources are beneficial to patients and the healthcare system.

Better by design: What to expect from novel CAR-engineered cell therapies?

Chimeric antigen receptor (CAR) technology, and CAR-T cells in particular, have emerged as a new and powerful tool in cancer immunotherapy since demonstrating efficacy against several hematological malignancies. However, despite encouraging clinical results of CAR-T cell therapy products, a significant proportion of patients do not achieve satisfactory responses, or relapse. In addition, CAR-T cell applications to solid tumors is still limited due to the tumor microenvironment and lack of specifically targetable tumor antigens. All current products on the market, as well as most investigational CAR-T cell therapies, are autologous, using the patient's own peripheral blood mononuclear cells as starting material to manufacture a patient-specific batch. Alternative cell sources are, therefore, under investigation (e.g. allogeneic cells from an at least partially human leukocyte antigen (HLA)-matched healthy donor, universal "third-party" cells from a non-HLA-matched donor, cord blood-derived cells, immortalized cell lines or cells differentiated from induced pluripotent stem cells). However, genetic modifications of CAR-engineered cells, bioprocesses used to expand cells, and improved supply chains are still complex and costly. To overcome drawbacks associated with CAR-T technologies, novel CAR designs have been used to genetically engineer cells derived from alpha beta (αß) T cells, other immune cells such as natural killer (NK) cells, gamma delta (γδ) T cells, macrophages or dendritic cells. This review endeavours to trigger ideas on the next generation of CAR-engineered cell therapies beyond CAR-T cells and, thus, will enable effective, safe and affordable therapies for clinical management of cancer. To achieve this, we present a multidisciplinary overview, addressing a wide range of critical aspects: CAR design, development and manufacturing technologies, pharmacological concepts and clinical applications of CAR-engineered cell therapies. Each of these fields employs a large number of ground-breaking scientific advances, where coordinated and complex process and product development occur at their interfaces.

Antibody Response to SARS-CoV-2 Vaccination in Patients following Allogeneic Hematopoietic Cell Transplantation.

Vaccines against SARS-CoV-2 have been rapidly approved. Although pivotal studies were conducted in healthy volunteers, little information is available on the safety and efficacy of mRNA vaccines in immunocompromised patients, including recipients of allogeneic hematopoietic cell transplantation (allo-HCT). Here we used a novel assay to analyze patient- and transplantation-related factors and their influence on immune responses to SARS-CoV-2 vaccination over an extended period (up to 6 months) in a large and homogenous group of allo-HCT recipients at a single center in Switzerland. We examined longitudinal antibody responses to SARS-CoV-2 vaccination with BNT162b2 (BioNTech/Pfizer) and mRNA-1273 (Moderna) in 110 allo-HCT recipients and 86 healthy controls. Seroprofiling recording IgG, IgA, and IgM reactivity against SARS-CoV-2 antigens (receptor-binding domain, spike glycoprotein subunits S1 and S2, and nucleocapsid protein) was performed before vaccination, before the second dose, and at 1, 3, and 6 months after the second dose. Patients were stratified to 3 groups: 3 to 6 months post-allo-HCT, 6 to 12 months post-allo-HCT, and >12 months post-allo-HCT. Patients in the 3 to 6 months and 6 to 12 months post-allo-HCT groups developed significantly lower antibody titers after vaccination compared with patients in the >12 months post-allo-HCT group and healthy controls (P < .001). Within the cohort of allo-HCT recipients, patients age >65 years (P = .030), those receiving immunosuppression for prevention or treatment of graft-versus-host disease (GVHD) (P = .033), and patients with relapsed disease (P = .014) displayed low humoral immune responses to the vaccine. In contrast, the intensity of the conditioning regimen, underlying disease (myeloid/lymphoid/other), and presence of chronic GVHD had no impact on antibody levels. Antibody titers achieved the highest levels at 1 month after the second dose of the vaccine but waned substantially in all transplantation groups and healthy controls over time. This analysis of long-term vaccine antibody response is of critical importance to allo-HCT recipients and transplant physicians to guide treatment decisions regarding revaccination and social behavior during the SARS-CoV-2 pandemic.

Association of Host Factors With Antibody Response to Seasonal Influenza Vaccination in Allogeneic Hematopoietic Stem Cell Transplant Patients.

BACKGROUND: Influenza vaccination efficacy is reduced after hematopoietic stem cell transplantation (HSCT) and patient factors determining vaccination outcomes are still poorly understood. METHODS: We investigated the antibody response to seasonal influenza vaccination in 135 HSCT patients and 69 healthy volunteers (HVs) in a prospective observational multicenter cohort study. We identified patient factors associated with hemagglutination inhibition titers against A/California/2009/H1N1, A/Texas/2012/H3N2, and B/Massachusetts/2012 by multivariable regression on the observed titer levels and on seroconversion/seroprotection categories for comparison. RESULTS: Both regression approaches yielded consistent results but regression on titers estimated associations with higher precision. HSCT patients required 2 vaccine doses to achieve average responses comparable to a single dose in HVs. Prevaccination titers were positively associated with time after transplantation, confirming that HSCT patients can elicit potent antibody responses. However, an unrelated donor, absolute lymphocyte counts below the normal range, and treatment with calcineurin inhibitors lowered the odds of responding. CONCLUSIONS: HSCT patients show a highly heterogeneous vaccine response but, overall, patients benefited from the booster shot and can acquire seroprotective antibodies over the years after transplantation. Several common patient factors lower the odds of responding, urging identification of additional preventive strategies in the poorly responding groups. CLINICAL TRIALS REGISTRATION: NCT03467074.

Second-Line Tisagenlecleucel or Standard Care in Aggressive B-Cell Lymphoma.

BACKGROUND: Patient outcomes are poor for aggressive B-cell non-Hodgkin's lymphomas not responding to or progressing within 12 months after first-line therapy. Tisagenlecleucel is an anti-CD19 chimeric antigen receptor T-cell therapy approved for diffuse large B-cell lymphoma after at least two treatment lines. METHODS: We conducted an international phase 3 trial involving patients with aggressive lymphoma that was refractory to or progressing within 12 months after first-line therapy. Patients were randomly assigned to receive tisagenlecleucel with optional bridging therapy (tisagenlecleucel group) or salvage chemotherapy and autologous hematopoietic stem-cell transplantation (HSCT) (standard-care group). The primary end point was event-free survival, defined as the time from randomization to stable or progressive disease at or after the week 12 assessment or death. Crossover to receive tisagenlecleucel was allowed if a defined event occurred at or after the week 12 assessment. Other end points included response and safety. RESULTS: A total of 322 patients underwent randomization. At baseline, the percentage of patients with high-grade lymphomas was higher in the tisagenlecleucel group than in the standard-care group (24.1% vs. 16.9%), as was the percentage with an International Prognostic Index score (range, 0 to 5, with higher scores indicating a worse prognosis) of 2 or higher (65.4% vs. 57.5%). A total of 95.7% of the patients in the tisagenlecleucel group received tisagenlecleucel; 32.5% of the patients in the standard-care group received autologous HSCT. The median time from leukapheresis to tisagenlecleucel infusion was 52 days. A total of 25.9% of the patients in the tisagenlecleucel group had lymphoma progression at week 6, as compared with 13.8% of those in the standard-care group. The median event-free survival in both groups was 3.0 months (hazard ratio for event or death in the tisagenlecleucel group, 1.07; 95% confidence interval, 0.82 to 1.40; P = 0.61). A response occurred in 46.3% of the patients in the tisagenlecleucel group and in 42.5% in the standard-care group. Ten patients in the tisagenlecleucel group and 13 in the standard-care group died from adverse events. CONCLUSIONS: Tisagenlecleucel was not superior to standard salvage therapy in this trial. Additional studies are needed to assess which patients may obtain the most benefit from each approach. (Funded by Novartis; BELINDA ClinicalTrials.gov number, NCT03570892.).

Complement inhibition for the treatment of COVID-19 triggered thrombotic microangiopathy with cardiac failure: a case report.

BACKGROUND: Severe coronavirus disease 2019 (COVID-19) has been increasingly recognized as a multisystem disease. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can infect literally any cell type that expresses its target receptor angiotensin-converting enzyme 2. However, COVID-19-associated organ dysfunction is not only mediated by direct viral effects but also by the interaction between the host's immune response, endotheliopathy, and microvascular coagulopathy. It has been proposed that the activation of the complement system plays a central role in the pathophysiology of severe COVID-19 and the associated endotheliopathy. CASE SUMMARY: A 76-year-old male patient with indeterminate cardiogenic shock in the setting of confirmed SARS-CoV-2 infection was admitted to our intensive care unit. Coronary angiography did not reveal a plausible explanation for his symptoms. The patient developed renal failure, neurological symptoms, severe thrombocytopenia, and a Coombs-negative haemolytic anaemia with schistocytes. All together the clinical picture was highly suggestive of a thrombotic microangiopathy (TMA) with microvascular cardiac involvement. Conventional therapeutic strategies including high-dose steroids and seven sessions of therapeutic plasma exchange were all unsuccessful. Interestingly, complement inhibition with Eculizumab as rescue approach led to a rapid clinical and laboratory improvement and the patients were discharged with normalized organ functions at Day 36. CONCLUSION: The aetiology of cardiogenic shock observed in this patient cannot simply be explained by his focal and chronic coronary findings. Although viral myocarditis was not formally excluded, both the clinical features of TMA and the rapid resolution of all clinical signs and symptoms after pharmacological complement inhibition suggest a SARS-CoV-2-driven microangiopathic origin of heart failure.

Neurological complications of cancer immunotherapy.

Immunotherapy has emerged as a powerful therapeutic approach in many areas of clinical oncology and hematology. The approval of ipilimumab, a monoclonal antibody targeting the immune cell receptor CTLA-4, has marked the beginning of the era of immune checkpoint inhibitors. In the meantime, numerous antibodies targeting the PD-1 pathway have expanded the class of clinically approved immune checkpoint inhibitors. Furthermore, novel antibodies directed against other immune checkpoints are currently in clinical evaluation. More recently, bispecific antibodies, which link T cells directly to tumor cells as well as adoptive T cell transfer with immune cells engineered to express a chimeric antigen receptor, have been approved in certain indications. Neurological complications associated with the use of these novel immunotherapeutic concepts have been recognized more and more frequently. Immune checkpoint inhibitors may cause various neurological deficits mainly by alterations of the peripheral nervous system's integrity. These include radiculopathies, neuropathies, myopathies as well as myasthenic syndromes. Side effects involving the central nervous system are less frequent but may result in severe clinical symptoms and syndromes. The administration of chimeric antigen receptor (CAR) T cell is subject to rigorous patient selection and their use is frequently associated with neurological complications including encephalopathy and seizures, which require immediate action and appropriate therapeutic measures. Close clinical monitoring for neurological symptoms is key for early recognition of immunotherapy-related side effects. Comprehensive diagnostic work-up and adequate therapeutic measures are essential to avoid further clinical deterioration and residual neurological deficits.

NK Cells and Innate-Like T Cells After Autologous Hematopoietic Stem Cell Transplantation in Multiple Sclerosis.

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system, in which autoreactive T and B cells play important roles. Other lymphocytes such as NK cells and innate-like T cells appear to be involved as well. To name a few examples, CD56bright NK cells were described as an immunoregulatory NK cell subset in MS while innate-like T cells in MS were described in brain lesions and with proinflammatory signatures. Autologous hematopoietic stem cell transplantation (aHSCT) is a procedure used to treat MS. This procedure includes hematopoietic stem/progenitor cell (HSPC) mobilization, then high-dose chemotherapy combined with anti-thymocyte globulin (ATG) and subsequent infusion of the patients own HSPCs to reconstitute a functional immune system. aHSCT inhibits MS disease activity very effectively and for long time, presumably due to elimination of autoreactive T cells. Here, we performed multidimensional flow cytometry experiments in peripheral blood lymphocytes of 27 MS patients before and after aHSCT to address its potential influence on NK and innate-like T cells. After aHSCT, the relative frequency and absolute numbers of CD56bright NK cells rise above pre-aHSCT levels while all studied innate-like T cell populations decrease. Hence, our data support an enhanced immune regulation by CD56bright NK cells and the efficient reduction of proinflammatory innate-like T cells by aHSCT in MS. These observations contribute to our current understanding of the immunological effects of aHSCT in MS.

Anti-human CD117 CAR T-cells efficiently eliminate healthy and malignant CD117-expressing hematopoietic cells.

Acute myeloid leukemia (AML) initiating and sustaining cells maintain high cell-surface similarity with their cells-of-origin, i.e., hematopoietic stem and progenitor cells (HSPCs), and identification of truly distinguishing leukemia-private antigens has remained elusive to date. To nonetheless utilize surface antigen-directed immunotherapy in AML, we here propose targeting both, healthy and malignant human HSPC, by chimeric antigen receptor (CAR) T-cells with specificity against CD117, the cognate receptor for stem cell factor. This approach should spare most mature hematopoietic cells and would require CAR T termination followed by subsequent transplantation of healthy HSPCs to rescue hematopoiesis. We successfully generated anti-CD117 CAR T-cells from healthy donors and AML patients. Anti-CD117 CAR T-cells efficiently targeted healthy and leukemic CD117-positive cells in vitro. In mice xenografted with healthy human hematopoiesis, they eliminated CD117-expressing, but not CD117-negative human cells. Importantly, in mice xenografted with primary human CD117-positive AML, they eradicated disease in a therapeutic setting. Administration of ATG in combination with rituximab, which binds to the co-expressed CAR T-cell transduction/selection marker RQR8, led to CAR T-cell depletion. Thus, we here provide the first proof of concept for the generation and preclinical efficacy of CAR T-cells directed against CD117-expressing human hematopoietic cells.