Literatura académica sobre el tema "Txell"

22 Background: End-of-life anti-neoplastic treatment does not improve quality of life nor prolong survival of advanced cancer patients. It is also not cost-effective. To-date, there has been little data examining real-world patterns of chemotherapy and immunotherapy treatment at end of life. We investigated use of chemotherapy and/or immunotherapy in the last 14 days of life across a community oncology network of 5 practices, 100 sites of care, and 160 oncology providers. Methods: Using a real-time, network-wide database, we identified patients with solid tumor malignancies who died during an episode of active treatment, defined as having received intravenous (IV) chemotherapy and/or immunotherapy within 90 days of death. We then identified patients in this cohort who received IV chemotherapy and/or IV immunotherapy within 14 days of death (TxEoL). We studied TxEoL patterns by cancer type, treatment type, line of therapy, patient age, patient race, and oncology provider years in practice. Statistical significance was assessed using Pearson’s Chi-squared test. Results: 2,858 qualifying solid tumor cancer patients with dates of death between 1/1/2019 and 5/31/2020 were identified. Observed rates of TxEoL were 16.7% for immunotherapy alone vs. 19.6% for chemotherapy +/- immunotherapy (p = 0.09). We found high variation in TxEoL across 132 oncologists that had 5 or more deceased patients (range: 0% to 50%, mean: 19.2%, median: 19.6%). We found no association of TxEOL with physician years in practice, patient age or race. Rates of TxEoL in the first-line setting were significantly higher than in second-line setting or later (23.3% versus 16.4%, p < 0.01). Patients with head and neck, pancreatic, and hepatobiliary malignancies were the most likely to receive TxEoL, while patients with prostate, brain, and ovarian malignancies were the least likely to receive TxEoL. Conclusions: Our data and method identified wide variation in TxEoL patterns across a large community oncology network, suggesting room for provider-level interventions to improve treatment decisions in patients at high risk of death. Studies within our group, such as examining the impact of palliative care referrals on IV anti-cancer treatment in patients potentially facing end of life, are ongoing.

6513 Background: Clinical trials are critical for improving outcomes for patients with cancer. However, there is some concern from health insurers that clinical trial participation can increase total cost of care for cancer patients. We investigated the impact of clinical trial participation on total costs paid by Medicare during the OCM program in a large community-based practice. Methods: Tennessee Oncology (TO) is a community oncology practice comprising over 90 oncologists across 30 sites of care. We linked TO trial data and electronic medical record data with OCM data for episodes of care from 2016-2018. To assess the impact of trial participation on total cost relative to routine care, we created matched comparator groups for each OCM episode based on cancer type, metastatic status, number of comorbidities, performance status, and age. Patients with breast cancer receiving hormone therapy only were excluded. Absolute and percent cost differences between groups were calculated for episodes that had a comparator group size of five or greater. Differences in total cost for trial episodes were compared to non-trial episodes, and significance was assessed using the Mann–Whitney U test. We also studied the impact of trial participation on receipt of active treatment in the last 14 days of life (TxEOL), hospice use, and hospitalizations. Results: During the study period, 8,026 completed OCM episodes met study criteria. Patients were enrolled in a clinical trial for 459 of these episodes. On average, episodes during which patients were on trial cost $5,973 less than matched non-trial episodes (Table), independent of early versus late-phase trial. Most savings resulted from decreased drug costs. There were no differences in rates of TxEOL (15% vs. 14% p=1.0), rates of hospitalizations (31% vs. 30% p=0.54), or hospice use (52% vs. 62% p=0.08) between trial and non-trial episodes. Median difference from comparator group average cost was significantly lower for clinical trial episodes (-18% vs. -6%, p<0.01). Conclusions: In the community setting, total costs paid by Medicare for patients participating in clinical trials during OCM episodes were lower than costs for similar patients receiving routine care. Clinical trial participation did not adversely impact end-of-life care or likelihood of hospitalization. These findings suggest that patient participation in clinical trials does not increase total cost of care nor enhance financial risk to payers.[Table: see text]

Adoptive T cell therapy exploits the ability of T lymphocytes to recognize and destroy specific targets, on microbes or tumors, through their T cell receptors (TCR), leading to efficient killing and long-term protection against diseases. Unfortunately, tumor antigens are often overexpressed, unmodified self-antigens, subject to tolerance mechanisms; so tumor-specific T lymphocytes are rare cells. Conversely, neoantigens derive from oncogenic mutations can elicit productive T cell responses, but for tumors with a low mutational load, such as the majority of hematological malignancies, such tumor-specific T cells are rarely identified. These limitations can be overcome by genetic engineering of T lymphocyte specificity. Recently, unprecedented clinical results were obtained with chimeric antigen receptor (CAR) engineered T cells in patients affected by B-cell malignancies, raising high expectations among the scientific community, patient associations, biotech companies and general public. While clearly proving the ability of redirected T cells to recognize and efficiently kill cancer cells, CAR therapy has also shown some limitations: the nature of CAR-mediated recognition imposes to restrict the array of targeted antigens to those expressed on the surface of cancer cells. As a consequence, antigens involved in the oncogenic process, that are often expressed as intracellular molecules, cannot be targeted by current CARs. Furthermore, when the natural counterpart of cancer cells cannot be spared, the identification of a proper CAR target on cancer cell surface might become a real challenge. TCR genetic engineering represents a suitable alternative to CAR T cell therapy for several tumors. The core of this approach is the transfer in patients' T cells of genes encoding for rare tumor-specific TCR. TCRs recognize antigen-derived peptides processed and presented on HLA molecules, thus allowing to largely increasing the array of potential targets. However, the simple transfer of tumor specific TCR genes into T cells is affected by other limitations: genetically modified T cells shall express four different TCR chains, that might mispair, leading to unpredictable toxicity and to an overall dilution of the tumor specific TCR on lymphocyte surface, thus limiting the efficacy of therapeutic cellular product. To overcome these issues, we developed a TCR gene editing procedure, based on the knockout of the endogenous TCR genes by transient exposure to alfa and beta chain specific Zinc Finger Nucleases (ZFNs), followed by the introduction of tumor-specific TCR genes by lentiviral vectors (Provasi et al, Nature Medicine 2012). The TCR gene editing technology, proved safer and more effective than conventional TCR gene transfer in vitro and in animal studies. Early differentiated T cells, such as memory stem T cells and central memory T cells, cells endowed with long term persistence capacity, can be genetically engineered by TCR gene transfer and TCR gene editing, thus allowing to produce long-lasting living drugs, with the aim of eliminating cancer cells and patrol the organism for tumor recurrence To enter the phase of clinical practice adoptive T cell therapy needs today to face several challenges: compliance to the dynamic and heterogeneous regulatory framework, susceptibility to automated processes, reproducibility, and sustainability shall be relevant variables in determining the fate of these innovative cellular products. Disclosures Bonini: TxCell: Membership on an entity's Board of Directors or advisory committees; Molmed SpA: Consultancy.

Abstract Introduction Voriconazoleis a second-generationtriazolebroad-spectrum antifungal agent indicated in adults and children aged 2 years and above as treatment of invasive aspergillosis, treatment ofcandidaemiain non-neutropenic patients (pts), treatment of fluconazole-resistant serious invasive Candida infections, treatment of serious fungal infections caused byScedosporiumspp. and Fusarium spp. Voriconazoleis associated with a broad spectrum of dermatologically adverse reactions: it seems to be responsible for a multistep process beginning with acute and chronicphototoxicity, followed by actinic keratosis (AK), and finally skin squamous cell carcinoma (SCC), especially if therapy is maintained. Strictphotoprotectionis mandatory; drug replacement by anothertriazolemust be discussed in case of acutephototoxicity.Voriconazolemust be stopped in pts with chronicphototoxicity, and a long-term dermatologic follow-up of skin lesions is required even after withdrawal. It is now established thatvoriconazoleis an independent risk factor for the development of cutaneous malignancy in lung transplant recipients. Recently, a retrospective study from the Mayo Clinic (WojenskiDJ et al, Transplant Infectious Disease 2015, 17, 250-58) confirmed the association betweenvoriconazoleand SCC also after allo-HSCT (allogeneic hematopoietic stem cell transplantation) and identified cumulative days ofvoriconazoleas a risk factor for SCC. Methods The current study seeks to analyze the correlation betweenvoriconazoleexposure and non-melanoma skin cancer (NMSC) in our Center, where it is available an intensive dedicated follow-up after allo-HSCT to prevent and early detect second solid tumors. Results We analyze data prospectively collected at our Long-Term Follow-Up clinic between 2011 and 2016 including 302 adult pts with a minimum follow-up of 24 months. A written consent was given by pts allowing the use of medical records for research in accordance with the Declaration of Helsinki. Baseline characteristics of the 302 pts are outlined in table 1. In total, 25 pts developed NMSC - median time from allo-HSCT 42 months (range, 9 months - 20 years) - median follow-up after NMSC diagnosis 2 years (range, 2 months - 12 years). The estimated cumulative incidence of NMSC at 3 years was 3.2% and at 5 years 6.2%. At the dermatological annual evaluation 3 pts were presenting AK, only one progress to basal cell carcinoma (BCC), the 2 pts with AK are under dermatological follow-up. All pts were treated withvoriconazolefor more than 180 days. In total 19 pts were diagnosed with BCC and 6 pts with SCC. Five pts with SCC and 17 with BCC were treated withvoriconazole, overall 16/22 (4 SCC) for more than 180 days. All pts were treated according to standard practice for NMSC, unfortunately 1 pts deceased due to SCC progression. Only 2 pts were diagnosed and treated for NMSC before transplantation. Six pts had antecedent acute GvHD and 8 pts had antecedent moderate to severe chronic GvHD. History ofvoriconazoleexposure, cumulative days ofvoriconazoleuse, gender, age at transplant, TBI based conditioning regimen, acute/chronic GvHD and skin cancer pre-transplant were considered for analysis. Age at transplant above 48 years (p <0.0001),voriconazoleexposure (p 0.0088) and cumulative days ofvoriconazoleexposure greater than 180 days (p 0.0038) were associated with higher risk of NMSC. Conclusions Our experience confirms the correlation betweenvoriconazoleand occurrence of NMSC after allo-HSCT. Incidence of NMSC is higher than previously reported in registry reports, and the occurrence of NMSC in pts exposed tovoriconazoleseems to be precocious. This observation confirms the relevance of counseling and prevention of NMSC in patients benefiting fromvoriconazoleas a crucialmold-active antifungal prophylaxis and treatment. Disclosures Bonini: Molmed SpA: Consultancy; TxCell: Membership on an entity's Board of Directors or advisory committees. Ciceri:MolMed SpA: Consultancy.

Abstract Background: Allogeneic stem cell transplantation is a potentially curative procedure to a long list of hematological malignancies, but involves substantial risk of morbidity and mortality. Means for accurately predicting outcome and assessing risk are thus greatly needed. The Disease Risk Index (DRI) is a prognostic tool developed and validated by Armand et al. across a wide range of hematological malignancies (Blood 2012, Blood 2014) on cohorts of American patients. The Index stratifies patients into 4 distinct risk groups (low, intermediate, high, very high) and has yet to be validated in an international cohort. We sought to evaluate the validity of the DRI in a large cohort of European patients. Methods: This was a retrospective validation study on an independent cohort of patients undergoing allogeneic HSCT and reported the European Society for Blood and Marrow Transplantation (EBMT). Patients included had a hematological malignancy and underwent allogeneic transplantation between the years of 2000 and 2015. Risk groups were coded in accordance with the refined DRI (Blood, 2014). Outcomes were evaluated 4 years after the allogeneic HSCT. Overall survival (OS) was calculated with the Kaplan-Meier method. The log-rank test was used for comparisons of Kaplan-Meier curves. Cumulative incidence curves for nonrelapse mortality (NRM) and relapse with or without death were constructed reflecting time to relapse and time to NRM, respectively, as competing risks. The difference between cumulative incidence curves in the presence of a competing risk was tested with the Gray method. The prognostic effect of the DRI strata was estimated using a Cox proportional hazard model for OS and a Fine and Gray model for NRM and relapse. Results: A total of 89,061 patients from 423 transplantation centers were included in the analysis. Median age was 48.3 (IQR 36.2-57.5). The most frequent indication for transplantation was AML (39,530 patients) followed by ALL (16,206) and MDS (9,750); other indications spanned the spectrum of hematological malignancies. The majority of patients were in 1st or 2nd complete remission (54%). The median follow-up period was 3.6 years. Approximately 63% of patients were classified as intermediate risk by DRI, suggesting that this group could be further partitioned. The 4 year overall survival (95% CI) of the low, intermediate, high, and very high risk groups was 60.8% (59.9-61.8), 51.3% (50.8‐51.8), 27.0% (26.1‐27.8), 18.4% (17.1-19.8) (Figure 1). The same groups corresponded with increasing cumulative incidence of relapse; 8.9% (8.3-9.4), 19.3% (18.9-19.7), 39.0% (37.8-39.6), 45.1% (43.4-46.7), respectively. The DRI groups also showed increasing hazard between strata in the overall survival setting; intermediate risk was associated with a hazard ratio of 1.32, high risk 2.67 and very high risk 3.71 relative to low risk. Relapse showed a similar pattern. NRM was less strongly stratified by DRI (Table 1). The DRI groups maintained a similar risk, regardless of whether the transplantation was performed prior or after 2008. DRI was the strongest determinant of overall survival and relapse when introduced to a multivariable model with additional covariates. AUC for the index at 4 years was 62.5 for OS, 58.5 for NRM and 68.2 for relapse. Conclusions: We have validated the Disease Risk Index in a massive European data set. The groupings suggested by the DRI corresponded with distinct risk groups for overall mortality and relapse. Overall, our results indicate the international applicability of this robust prognostic tool. Figure 1. Kaplan-Meyer survival curves for overall survival, stratified by DRI Figure 1. Kaplan-Meyer survival curves for overall survival, stratified by DRI Table 1 Table 1. Disclosures Bader: Medac: Consultancy, Research Funding; Riemser: Research Funding; Neovii Biotech: Research Funding; Servier: Consultancy, Honoraria; Novartis: Consultancy, Honoraria. Bonini:Molmed SpA: Consultancy; TxCell: Membership on an entity's Board of Directors or advisory committees. Dreger:Gilead: Consultancy; Janssen: Consultancy; Novartis: Speakers Bureau; Gilead: Speakers Bureau; Novartis: Consultancy; Roche: Consultancy. Kuball:Gadeta B.V,: Membership on an entity's Board of Directors or advisory committees. Montoto:Roche: Honoraria; Gilead: Research Funding.

Abstract Background: Patient-derived xenografts (PDXs) are key models for interrogating the biology of tumor cells that poorly survive in vitro. In particular, over the last decade, immunodeficient mouse models have been extensively used to assess the in vivo growth potential of human leukemia, to provide insights into its biology, and to perform preclinical validation of therapies. Still, only a fraction of the cases of acute myeloid leukemia (AML) are able to engraft into mice, and the biological and clinical correlates of the ability to generate PDXs are unknown. Methods: Primary AML harvested from 52 patients at diagnosis (n=37, 71%), at relapse after treatments (n=15, 29%), or both (n=6) were purified and infused into non-irradiated NOD-SCID γ-chain null (NSG) mice. Upon leukemia engraftment, assessed by multiparametric flow cytometry, mice were sacrificed and leukemic cells were isolated, characterized, and reinfused in serial recipients, in up to four serial passages. Gene expression profile was analyzed using Illumina microarray, and deregulated genes and processes identified by pairwise LIMMA analysis and classified using Gene Ontology (GO) and Gene Set Enrichment Analysis (GSEA) curated databases. The mutational asset of infused AML was assessed through targeted resequencing, using a custom panel comprising 192 targets and based on the Agilent Haloplex HS technology. Results: Twenty-six out of 52 primary AML samples (50%) generated xenografts. Engraftment and growth kinetics of the human leukemic cells were highly consistent among littermates, and specific for each tested leukemia. Circulating leukemic cells were firstly detected in the peripheral blood of animals at a median time of 22.5 days (range 14 - 150). In vivo growth allowed expansion of infused AMLs in bone marrows and spleens of the animal, with a median fold increase of 3.5 (range 0.1 - 351.4). The gene expression profile of xenografts was reproducible amongst littermates and recapitulated the features of parental AML: genes deregulated in xenografts accounted for 9.1% of the transcript assessed, with substantial overlap in the genes and processes deregulated in each of the studied cases. GO and GSEA demonstrated the selective deregulation of genes involved in cell proliferation (CDC20, AURKA), syster chromatyde organization (CENPF CEP170) and myeloid differentiation (AZU1, MPO, MYADM, CTSG). Of note, the ability to generate xenografts was conserved when AML cells were challenged at different time-points during the clinical history of the patients, with leukemia harvested at relapse after transplantation displaying a more aggressive behavior. Similarly, upon serial transfer AML exhibited an accelerated growth kinetic. Engraftment in mice significantly correlated with poor patient prognosis: AML engrafters had dramatically lower leukemia free-survival rates compared to non-engrafters (median 5.9 vs. 21.8 months after induction chemotherapy, p=0.0022, Fig. 1A), confirmed also by multivariate analysis (p=0.002). Also the mutational profile differed greatly between engrafters and non-engrafters, as summarized in Fig. 1B. In particular, while the presence of an aberrant karyotype was not associated with PDX generation, FLT3 internal tandem duplication, DNMT3A and NPM1 mutation were all significantly associated to engraftment (p=0.0244, p=0.009 and p=0.0437 respectively). In particular the co-occurrence of mutations in these three genes, recently reported to confer very poor prognosis to AML patients (Papaemmanuil et al, NEJM 2016), markedly enhanced the ability to generate PDXs (Fig.1C). Conclusion: These data show that engraftment into immunodeficient mice mirrors the biology of primary human leukemia, providing a proxy to select cases with a higher chance to generate PDXs. Further comparisons between AML capable or not to generate PDXs might provide novel markers of leukemia aggressiveness and rationales for targeted therapies. Figure 1 Figure 1. Disclosures Bonini: TxCell: Membership on an entity's Board of Directors or advisory committees; Molmed SpA: Consultancy. Ciceri:MolMed SpA: Consultancy.

Abstract Introduction Tyrosine kinase inhibitor (TKi) has become the standard of care in patients (pts) with chronic myeloid leukemia (CML) and an unavoidable tool in the combined therapy for pts with Philadelphia chromosome positive (Ph+) acute lymphoblastic leukemia (ALL). Nevertheless, because of resistance to TKI and side-effects, allogeneic stem cell transplantation (HSCT) remains the standard therapy of ALL Ph+ and of CML pts failing 1st line therapy with TKi, with failure or insufficient response or intolerance or mutations resistant to 2nd generation TKI, or in the advanced phase at diagnosis (accelerated phase and blast crisis). Unfortunately, despite greater remission with the use of TKi pre-transplant, HSCT transplant outcome have not improved largely due to high incidence of relapse after transplant. In the past decade several multi-institutional studies confirmed the feasibility and safety of post-HSCT imatinib administration as prophylactic or therapeutic strategy. Second and 3rd generation TKi administration after HSCT - targeting mutational status and according to pre-HSCT activity - is today under investigation. Methods Here we are reporting our experience in post-HSCT treatment with the 3rd generation TKi ponatinib in 5 pts (4 CML, 1 ALL Ph+) treated between 2011 and 2016 at our Institution. Pts data and information were collected from Institutional database and chapters revision. A written consent was given by pts allowing the use of medical records for research in accordance with the Declaration of Helsinki. Results Pts and diseases features are reported in table 1. Stem cell source was peripheral blood in all cases, 3 pts were transplanted from a family mismatched donor (haplo), 1 from a family matched donor, 1 from a matched unrelated donor (MUD). The 3 haplo-transplanted pts previously underwent a MUD HSCT. All pts received a treosulfan based conditioning regimen and GvHD prophylaxis consisted on co-administration of MMF and rapamycin. Pre-transplant treatment for the ALL Ph+ consisted of chemotherapy combined with dasatinib, followed by a first MUD HSCT and dasatinib in maintenance. The patient relapsed 1 year after HSCT with documentation of mutation V299L. Ponatinib was introduced as salvage treatment to bridge second haplo HSCT. Pre-transplant treatment for the CML patients consisted of TKi therapy with combination of chemotherapy in case of uncontrolled progression of disease. Two pts received a first MUD HSCT but relapsed respectively 5 months and 4 years later. Four pts received ponatinib 45 mg daily before the last HSCT: one patient achieved sustained major molecular response, 3 pts obtained transient response. All pts were presenting 2nd generation TKi resistant mutation (ref table 1). Ponatinib was started at a median time of 157 days after HSCT (range, 117-583): in 3 cases as salvage treatment in overt relapse, while in one case as prophylaxis and one case as preemptive therapy. Acute GvHD was diagnosed in 4 pts before ponatinib administration, 2 of them also experienced chronic GvHD. No new cases of GvHD were observed after initiation of ponatinib. Immunosuppressive treatment and azoles treatment were discontinued before ponatinib in all but one patient who was under combined treatment for chronic GvHD: therapeutic drug monitoring was closely performed without evidence drug-drug interaction. Pts were regularly evaluated for toxicities. No serious adverse events were reported in our experience: we administered ponatinib at a median maximum dosage of 30 mg daily (range, 15-45 mg), for a median of 24 weeks (range, 4 - 116 weeks). Two pts required anti hypertension drugs. One patient was closely monitored for multifactorial liver cholestasis never requiring ponatinib discontinuation. At last evaluation one patient maintained the status of molecularly undetectable leukemia (follow-up post HSCT 30 months) and two pts obtained molecular response (follow-up post HSCT 25 months and 5 months). Two patients who received therapeutic ponatinib in overt relapse didn't respond and died for progressive disease. Conclusions Ponatinib is safe and well tolerated as bridge to HSCT and to maintain the disease control after transplant. Prophylaxis targeted therapy and pre-emptive therapy with ponatinib may lead the reduction of disease relapse for high-risk Ph+ leukemia. Disclosures Bonini: Molmed SpA: Consultancy; TxCell: Membership on an entity's Board of Directors or advisory committees. Ciceri:MolMed SpA: Consultancy.

Abstract Background: Chimeric antigen-receptor (CAR)-engineered T cells promise to cure chronic and acute leukemias refractory to standard treatments. Before this promise is fulfilled, however, two crucial issues need to be solved: i) how to circumvent the emergence of secondary resistance (e.g. due totarget-antigen loss; leukemic lineage switch); ii) how to manage associated toxicities (e.g. the cytokine release syndrome, CRS; lineage aplasias). Unfortunately, all these issues cannot be addressed pre-clinically in currently available NSG mouse models, because they lack human hematopoiesis and, furthermore, ultimately develop xenograft-versus-host disease (X-GVHD), preventing the evaluation of long-term effects. Methods: We have developed an innovative xenotolerant model by transplanting human hematopoietic stem cells (HSCs) intraliver in newborn NSG mice triple transgenic for human SCF, GM-SCF and IL-3 (SGM3). Differently from "classical" NSG, SGM3 mice reconstituted high levels of human T cells (>1000 cells per microL at week 8), which, once transferred in secondary recipients, persisted up to 200d without causing X-GVHD, even after irradiation. Robust and specific xenotolerance was confirmed by in vitrohyporesponsiveness to NSG, bot not to C57/Bl6 antigens (irradiated splenocytes) or human HLAs (PBMCs). Secondary transfer experiments in leukemic and/or HSC-humanized SGM-3 mice have been then designed for studying the determinants of CAR-T cell efficacy and associated toxicities in the absence of confounding xenoreactivity. Results: SGM3-derived T cells were transduced ex vivo with either a CD19 or a CD44v6 CAR (both having a CD28 2G design) after activation with CD3/CD28-beads and IL-7/IL-15, resulting in a preferential and functional CD45RA+/CD62L+/CD95+ stem memory T cell (TSCM) phenotype. Once transferred in secondary recipients previously engrafted with a CD19+/CD44v6 leukemic cell line, CD19 or CD44v6 CAR-T cells equally mediated rapid tumor clearance both in low and high tumor-burden settings, in the absence of malaise or elevated human IL-6 levels in vivo. At later time points (after 100d), however, approximately 50% of responding mice relapsed despite significant CAR-T cell persistence in vivo (>50 cells per microL). A significant fraction of leukemia relapses were characterized by post-transcriptional down-regulation of CD44v6 expression or CD19 loss, respectively. Conversely, secondary transfer of SGM3-derived CAR-T cells in leukemic SGM3 mice that had been previously humanized with HSCs resulted in the development of a clinical syndrome similar to the CRS observed in clinical trials (high fevers, elevated IL-6, TNF-alpha and serum amyloid A levels - mouse analog of C-reactive protein in humans), resulting in 30% lethality. This CRS was anticipated and shortened for CD44v6 compared with CD19 CAR-T cells and worse in the case of 4-1BB compared with the original CD28 2G CAR designs. Strikingly, mice recovering from the CRS benefited from durable leukemic remissions, yet experienced long-lasting CD19+ B-cell or CD44v6+ monocyte aplasias. Deepness of remission was confirmed in "tertiary" recipients, which did not develop leukemia after the infusion of bone-marrow cells from mice in remission 150d since CAR-T cell infusion. Interestingly, in this model, tocilizumab administration at the time of either CD19 or CD44v6 CAR-T cell infusion efficiently prevented the CRS, but did not interfere with their comparable and long-term anti-leukemic effects. Conversely, depleting monocytes/macrophages before therapeutic CAR-T cell infusion by either lyposomal clodronate or by the prophylactic CD44v6 CAR-T cells inhibited CRS development, but also resulted in significantly worse leukemia-free survival (at 250d, 0% vs 80%, P<0.0001). Conclusions: A number of lessons can be learned from this innovative xenotolerant mouse model of CAR-T cell immunotherapy: monocytes are required for both i) optimal anti-leukemic efficacy, and ii) the occurrence of CRS; iii) tocilizumab prevents the CRS without interfering with efficacy; iv) monocyte aplasia induced by CD44v6 CAR-T cells does not impact on their efficacy, at least in the theraeputic setting, and may ameliorate CRS toxicity. As for CD44v6 CAR-T cells, this model could be used for effectively predicting the efficacy and associated toxicities of new CAR-T cell therapies, speeding up their clinical development. Disclosures Traversari: MolMed SpA: Employment. Bordignon:MolMed SpA: Employment. Ciceri:MolMed SpA: Consultancy. Bonini:TxCell: Membership on an entity's Board of Directors or advisory committees; Molmed SpA: Consultancy. Bondanza:Formula Pharmaceuticals: Honoraria; TxCell: Research Funding; MolMed SpA: Research Funding.