Outcomes with allogeneic stem cell transplant using cryopreserved versus fresh hematopoietic progenitor cell products.

BACKGROUND: Allogeneic hematopoietic stem cell transplant (alloHSCT) is a mainstay of treatment for hematologic malignancies such as acute leukemias and aggressive lymphomas. Historically, fresh hematopoietic progenitor cell (HPC) products have been preferred to cryopreserved products (cryo-HPC) due to concerns of loss of stem cell viability and number with the cryopreservation procedure. OBJECTIVE: We aimed to analyze the outcomes of patients who received cryo-HPCs during the COVID-19 pandemic and compare this against historical cohorts that received fresh HPC. STUDY DESIGN: A retrospective chart review was conducted on all adult patients who received a peripheral blood alloHSCT in British Columbia, Canada between June 2017 and November 2021. Baseline characteristics, Kaplan-Meier (KM) overall survival (OS), engraftment, and incidences of acute and chronic graft versus host disease were compared between patients who received cryo-HPCs and fresh HPCs. Univariable analysis followed by multivariable analysis was performed using a backward stepwise selection procedure to generate predictors of OS, cumulative incidence of relapse (CIR), nonrelapse mortality (NRM), and primary and secondary graft failure. RESULTS: Three hundred eighty-three patients were included in the analysis, with cryo-HPC representing 40%. Median viability was higher in the fresh-HPC group at 99.2% (IQR 98.3-99.5) versus cryo-HPCs at 97.0% (96.0, 98.6) (P < 0.01). The 12-month actuarial survivals were 77% in the fresh HPC and 75% in the cryo-HPC groups (P = 0.21). There were no differences between cryo-HPCs and fresh HPCs on univariable analysis of OS, CIR, or NRM. There was a shorter median time to platelet engraftment in patients receiving fresh HPC at 17 days (IQR 16, 20) versus cryo-HPC at 21 days (IQR 18, 29), P < 0.001. There was a shorter median time to neutrophil engraftment in the fresh HPC group at 17 days (IQR 14, 20) versus 20 days (17, 23), P < 0.001. Cryo-HPC accounted for 5 out of 6 cases of primary graft failure (P = 0.04), and 3 out of five cases of secondary graft failure (P = 0.39). There were no significant differences in acute GVHD between the fresh HPC and cryo-HPC groups (P = 0.34). The incidence of moderate or severe chronic GVHD was 32% in the fresh-HPC group and 17% in the cryo-HPC group (P < 0.001). In multivariable analysis, cryopreservation did not emerge as an independent predictor of OS, CIR, NRM, primary GF or secondary GF. However, viability <90% on arrival at our center was a significant predictor of OS (HR 5.3, 2.3-12.3, P < 0.01), primary graft failure (OR 36.3, 5.4-210.2, P < 0.01), and secondary graft failure (OR 18.4, 1.7-121.1, P < 0.01). CONCLUSIONS: Patients who received cryo-HPCs had similar OS and relapse rates to those who received fresh-HPCs but typically took 2-3 days longer to achieve engraftment of platelets or neutrophils and were associated increased primary graft failure. However, after accounting for multiple variables, cryopreservation was no longer a significant predictor of survival or engraftment while viability <90% emerged as an important predictor of OS, primary graft failure, and secondary graft failure. If confirmed, this suggests that viability on arrival at the infusion center may be a good quality control indicator used to identify HPC products that may warrant recollection if the risk of graft failure is sufficiently increased.

Real-world impact of routine addition of anti-thymocyte globulin to standard GVHD prophylaxis in myeloablative unrelated donor transplants: important gains in graft vs host disease prevention though no difference in overall survival.

INTRODUCTION: Anti-thymocyte globulin (ATG) has been demonstrated to reduce the incidence of graft-versus-host disease (GVHD); however, it remains controversial whether these gains are offset by an increase in relapse. METHODS: We conducted a retrospective historical control study consisting patients (n=210) who underwent myeloablative allogeneic hematopoietic stem-cell transplantation (HSCT) from 2014 to 2020. RESULTS: The incidence of acute GVHD was lower in the ATG group (51.4%) than the non-ATG group (control) (70.0%, p=0.010). The incidence of chronic GVHD was also lower in the ATG group at 1-year (36.4% vs. 62.9%, p <0.001) and 2-year (40.0% vs. 65.7%, p <0.001) post-HSCT. The mortality due to GVHD was higher in the control (18.5%) than the ATG group (4.3%; p= 0.024). The severe GVHD-relapse-free survival was higher in the ATG group (36.4%) than the control (12.9%; p <0.001). Nevertheless, the 2-year overall survival was similar. CONCLUSION: Our results confirm the effectiveness of ATG in prevention of GVHD in the real-world setting and enhanced GVHD-free survival. An important result is the equalization of overall survival between the ATG and control groups at 1- and 2-year post-HSCT and implies that earlier GVHD-associated mortality may be offset by later relapse mortality producing similar overall survival over time.

Feasibility and efficacy of CD19-targeted CAR T cells with concurrent ibrutinib for CLL after ibrutinib failure.

We previously reported durable responses in relapsed or refractory (R/R) chronic lymphocytic leukemia (CLL) patients treated with CD19-targeted chimeric antigen receptor-engineered (CD19 CAR) T-cell immunotherapy after ibrutinib failure. Because preclinical studies showed that ibrutinib could improve CAR T cell-antitumor efficacy and reduce cytokine release syndrome (CRS), we conducted a pilot study to evaluate the safety and feasibility of administering ibrutinib concurrently with CD19 CAR T-cell immunotherapy. Nineteen CLL patients were included. The median number of prior therapies was 5, and 17 patients (89%) had high-risk cytogenetics (17p deletion and/or complex karyotype). Ibrutinib was scheduled to begin ≥2 weeks before leukapheresis and continue for ≥3 months after CAR T-cell infusion. CD19 CAR T-cell therapy with concurrent ibrutinib was well tolerated; 13 patients (68%) received ibrutinib as planned without dose reduction. The 4-week overall response rate using 2018 International Workshop on CLL (iwCLL) criteria was 83%, and 61% achieved a minimal residual disease (MRD)-negative marrow response by IGH sequencing. In this subset, the 1-year overall survival and progression-free survival (PFS) probabilities were 86% and 59%, respectively. Compared with CLL patients treated with CAR T cells without ibrutinib, CAR T cells with concurrent ibrutinib were associated with lower CRS severity and lower serum concentrations of CRS-associated cytokines, despite equivalent in vivo CAR T-cell expansion. The 1-year PFS probabilities in all evaluable patients were 38% and 50% after CD19 CAR T-cell therapy, with and without concurrent ibrutinib, respectively (P = .91). CD19 CAR T cells with concurrent ibrutinib for R/R CLL were well tolerated, with low CRS severity, and led to high rates of MRD-negative response by IGH sequencing.

Incidence and socioeconomic factors in older adults with acute myeloid leukaemia: Real-world outcomes from a population-based cohort.

OBJECTIVES: Acute myeloid leukaemia (AML) is a disease of older adults, who are vulnerable to socio-economic factors. We determined AML incidence in older adults and the impact of socio-economic factors on outcomes. METHODS: We included 3024 AML patients (1996-2016) identified from a population-based registry. RESULTS: AML incidence in patients ≥60 years increased from 11.01 (2001-2005) to 12.76 (2011-2016) per 100 000 population. Among 879 patients ≥60 years in recent eras (2010-2016), rural residents (<100 000 population) were less likely to be assessed by a leukaemia specialist (39% rural, 47% urban, p = .032); no difference was seen for lower (43%, quintile 1-3) vs. higher (47%, quintile 4-5) incomes (p = .235). Similar numbers received induction chemotherapy between residence (16% rural, 18% urban, p = .578) and incomes (17% lower, 17% high, p = 1.0). Differences between incomes were seen for hypomethylating agent treatment (14% low, 20% high, p = .041); this was not seen for residence (13% rural, 18% urban, p = .092). Among non-adverse karyotype patients ≥70 years, 2-year overall survival was worse for rural (5% rural, 12% urban, p = .006) and lower income (6% low, 15% high, p = .017) patients. CONCLUSIONS: AML incidence in older adults is increasing, and outcomes are worse for older rural and low-income residents; these patients face treatment barriers.

High rate of durable complete remission in follicular lymphoma after CD19 CAR-T cell immunotherapy.

Patients with follicular lymphoma (FL) with early relapse after initial chemoimmunotherapy, refractory disease, or histologic transformation (tFL) have limited progression-free and overall survival. We report efficacy and long-term follow-up of 21 patients with relapsed/refractory (R/R) FL (n = 8) and tFL (n = 13) treated on a phase 1/2 clinical trial with cyclophosphamide and fludarabine lymphodepletion followed by infusion of 2 × 106 CD19-directed chimeric antigen receptor-modified T (CAR-T) cells per kilogram. The complete remission (CR) rates by the Lugano criteria were 88% and 46% for patients with FL and tFL, respectively. All patients with FL who achieved CR remained in remission at a median follow-up of 24 months. The median duration of response for patients with tFL was 10.2 months at a median follow-up of 38 months. Cytokine release syndrome occurred in 50% and 39%, and neurotoxicity in 50% and 23% of patients with FL and tFL, respectively, with no severe adverse events (grade ≥3). No significant differences in CAR-T cell in vivo expansion/persistence were observed between FL and tFL patients. CD19 CAR-T cell immunotherapy is highly effective in adults with clinically aggressive R/R FL with or without transformation, with durable remission in a high proportion of FL patients. This trial was registered at clinicaltrials.gov as #NCT01865617.

Factors associated with durable EFS in adult B-cell ALL patients achieving MRD-negative CR after CD19 CAR T-cell therapy.

Autologous T cells engineered to express a CD19-specific chimeric antigen receptor (CAR) have produced impressive minimal residual disease-negative (MRD-negative) complete remission (CR) rates in patients with relapsed/refractory B-cell acute lymphoblastic leukemia (B-ALL). However, the factors associated with durable remissions after CAR T-cell therapy have not been fully elucidated. We studied patients with relapsed/refractory B-ALL enrolled in a phase 1/2 clinical trial evaluating lymphodepletion chemotherapy followed by CD19 CAR T-cell therapy at our institution. Forty-five (85%) of 53 patients who received CD19 CAR T-cell therapy and were evaluable for response achieved MRD-negative CR by high-resolution flow cytometry. With a median follow-up of 30.9 months, event-free survival (EFS) and overall survival (OS) were significantly better in the patients who achieved MRD-negative CR compared with those who did not (median EFS, 7.6 vs 0.8 months; P < .0001; median OS, 20.0 vs 5.0 months; P = .014). In patients who achieved MRD-negative CR by flow cytometry, absence of the index malignant clone by IGH deep sequencing was associated with better EFS (P = .034). Stepwise multivariable modeling in patients achieving MRD-negative CR showed that lower prelymphodepletion lactate dehydrogenase concentration (hazard ratio [HR], 1.38 per 100 U/L increment increase), higher prelymphodepletion platelet count (HR, 0.74 per 50 000/µL increment increase), incorporation of fludarabine into the lymphodepletion regimen (HR, 0.25), and allogeneic hematopoietic cell transplantation (HCT) after CAR T-cell therapy (HR, 0.39) were associated with better EFS. These data allow identification of patients at higher risk of relapse after CAR T-cell immunotherapy who might benefit from consolidation strategies such as allogeneic HCT. This trial was registered at www.clinicaltrials.gov as #NCT01865617.

The response to lymphodepletion impacts PFS in patients with aggressive non-Hodgkin lymphoma treated with CD19 CAR T cells.

Factors associated with durable remission after CD19 chimeric antigen receptor (CAR)-modified T-cell immunotherapy for aggressive B-cell non-Hodgkin lymphoma (NHL) have not been identified. We report multivariable analyses of factors affecting response and progression-free survival (PFS) in patients with aggressive NHL treated with cyclophosphamide and fludarabine lymphodepletion followed by 2 × 106 CD19-directed CAR T cells/kg. The best overall response rate was 51%, with 40% of patients achieving complete remission. The median PFS of patients with aggressive NHL who achieved complete remission was 20.0 months (median follow-up, 26.9 months). Multivariable analysis of clinical and treatment characteristics, serum biomarkers, and CAR T-cell manufacturing and pharmacokinetic data showed that a lower pre-lymphodepletion serum lactate dehydrogenase (LDH) level and a favorable cytokine profile, defined as serum day 0 monocyte chemoattractant protein-1 (MCP-1) and peak interleukin-7 (IL-7) concentrations above the median, were associated with better PFS. MCP-1 and IL-7 concentrations increased after lymphodepletion, and higher intensity of cyclophosphamide and fludarabine lymphodepletion was associated with higher probability of a favorable cytokine profile. PFS was superior in patients who received high-intensity lymphodepletion and achieved a favorable cytokine profile compared with those who received the same intensity of lymphodepletion without achieving a favorable cytokine profile. Even in high-risk patients with pre-lymphodepletion serum LDH levels above normal, a favorable cytokine profile after lymphodepletion was associated with a low risk of a PFS event. Strategies to augment the cytokine response to lymphodepletion could be tested in future studies of CD19 CAR T-cell immunotherapy for aggressive B-cell NHL. This trial was registered at www.clinicaltrials.gov as #NCT01865617.

Infectious complications of CD19-targeted chimeric antigen receptor-modified T-cell immunotherapy.

Lymphodepletion chemotherapy with CD19-targeted chimeric antigen receptor-modified T (CAR-T)-cell immunotherapy is a novel treatment for refractory or relapsed B-cell malignancies. Infectious complications of this approach have not been systematically studied. We evaluated infections occurring between days 0 to 90 in 133 patients treated with CD19 CAR-T cells in a phase 1/2 study. We used Poisson and Cox regression to evaluate pre- and posttreatment risk factors for infection, respectively. The cohort included patients with acute lymphoblastic leukemia (ALL; n = 47), chronic lymphocytic leukemia (n = 24), and non-Hodgkin lymphoma (n = 62). There were 43 infections in 30 of 133 patients (23%) within 28 days after CAR-T-cell infusion with an infection density of 1.19 infections for every 100 days at risk. There was a lower infection density of 0.67 between days 29 and 90 (P = .02). The first infection occurred a median of 6 days after CAR-T-cell infusion. Six patients (5%) developed invasive fungal infections and 5 patients (4%) had life-threatening or fatal infections. Patients with ALL, ≥4 prior antitumor regimens, and receipt of the highest CAR-T-cell dose (2 × 107 cells per kg) had a higher infection density within 28 days in an adjusted model of baseline characteristics. Cytokine release syndrome (CRS) severity was the only factor after CAR-T-cell infusion associated with infection in a multivariable analysis. The incidence of infections was comparable to observations from clinical trials of salvage chemoimmunotherapies in similar patients. This trial was registered at www.clinicaltrials.gov as #NCT01865617.

Potentials, challenges and future of chimeric antigen receptor T-cell therapy in non-Hodgkin lymphomas.

Background: Diffuse large B-cell lymphoma (DLBCL) is the most common lymphoma subtype. Disease progression or relapse following frontline chemoimmunotherapy, largely in the form of standard R-CHOP, occurs in 30-40% patients. Relapsed/refractory (R/R) DLBCL represents a major unmet medical need. In particular, patients with primary refractory disease or those whose lymphoma relapses after autologous stem cell transplantation have historically had poor outcomes.Material and methods: Chimeric antigen receptor T-cell (CART) therapy is a promising novel treatment with curative potential in this setting. CART is based on ex vivo genetic modification of autologous T-cells to express chimeric receptors targeting antigens highly expressed in tumors such as CD19 in DLBCL. After lymphocyte-depleting therapy, patients are infused with CARTs that expand in vivo and target CD19-positive lymphoma cells.Results: In initial phase I-II trials, investigators have demonstrated complete responses in 40-50% of patients with R/R DLBCL, resulting in durable remission approaching 3 years of follow-up in most of these patients without further treatment. The logistics of delivery are complex as cell products require timely long-distance transfer between hospitals and production facilities. The unique toxicity profile of CARTs, including the risk of fatal immunological and neurologic events, also requires specific hospital wide management approaches and education. The substantial direct and indirect costs of CART will limit access even in countries with well resourced health care systems.Conclusions: While only two products are commercially available at present, further approvals in coming years appear likely. Future directions include CARTs with reactivity to tumor antigens other than CD19 and products targeting multiple tumor antigens to overcome resistance. The availability of CART has altered the current treatment algorithm for R/R DLBCL, and indications will likely expand to earlier lines of therapy and other hematologic malignancies.

Kinetics and biomarkers of severe cytokine release syndrome after CD19 chimeric antigen receptor-modified T-cell therapy.

Lymphodepletion chemotherapy followed by infusion of CD19-specific chimeric antigen receptor-modified (CAR) T cells has produced impressive antitumor responses in patients with refractory CD19+ B-cell malignancies but is often associated with cytokine release syndrome (CRS). Our understanding of CRS continues to evolve, and identification of the kinetics of CRS and predictive clinical and laboratory biomarkers of severity are needed to evaluate strategies to mitigate toxicity. We report the clinical presentation of and identify biomarkers of severe CRS in 133 adult patients who received CD19 CAR T cells. CRS developed in 70% of patients, including 62.5% with grade 1 to 3 CRS (grade 1, 26%; grade 2, 32%; grade 3, 4.5%), 3.8% with grade 4, and 3.8% with grade 5. A majority of cases of grade ≥4 CRS occurred during CAR T-cell dose finding. Multivariable analysis of baseline characteristics identified high marrow tumor burden, lymphodepletion using cyclophosphamide and fludarabine, higher CAR T-cell dose, thrombocytopenia before lymphodepletion, and manufacturing of CAR T cells without selection of CD8+ central memory T cells as independent predictors of CRS. Severe CRS was characterized by hemodynamic instability, capillary leak, and consumptive coagulopathy. Angiopoietin-2 and von Willebrand factor, which are biomarkers of endothelial activation, were increased during severe CRS and also before lymphodepletion in patients who subsequently developed CRS. We describe a classification-tree algorithm to guide studies of early intervention after CAR T-cell infusion for patients at high risk of severe CRS. These data provide a framework for early intervention studies to facilitate safer application of effective CD19 CAR T-cell therapy.

Cytokine release syndrome and neurotoxicity after CD19 chimeric antigen receptor-modified (CAR-) T cell therapy.

Chimeric antigen receptor-modified (CAR)-T cells have demonstrated impressive results in the treatment of haematological malignancies. However, cytokine release syndrome (CRS) and neurotoxicity are common toxicities which are potentially life-threatening in severe cases. Risk factors for CRS and neurotoxicity identified so far include disease burden, lymphodepletion intensity and CAR-T cell dose administered. Risk-adapted dosing, with lower CAR-T cell doses administered to B-cell acute lymphoblastic leukaemia patients with high marrow blast counts, has been successful at decreasing severe CRS rates in this population. Intervention with therapies, such as tocilizumab and corticosteroids, have been effective at ameliorating toxicity, enabling CAR-T cells to be administered safely to many patients without significantly compromising efficacy. Deeper understanding of the pathophysiology of underlying CRS and neurotoxicity will enable the development of novel approaches to reduce toxicity and improve outcomes.

Effect of place of residence and treatment on survival outcomes in patients with diffuse large B-cell lymphoma in British Columbia.

BACKGROUND: We examined the relationship between location of residence at the time of diagnosis of diffuse large B-cell lymphoma (DLBCL) and health outcomes in a geographically large Canadian province with publicly funded, universally available medical care. PATIENTS AND METHODS: The British Columbia Cancer Registry was used to identify all patients 18-80 years of age diagnosed with DLBCL between January 2003 and December 2008. Home and treatment center postal codes were used to determine urban versus rural status and driving distance to access treatment. RESULTS: We identified 1,357 patients. The median age was 64 years (range: 18-80 years), 59% were male, 50% were stage III/IV, 84% received chemotherapy with curative intent, and 32% received radiotherapy. There were 186 (14%) who resided in rural areas, 141 (10%) in small urban areas, 183 (14%) in medium urban areas, and 847 (62%) in large urban areas. Patient and treatment characteristics were similar regardless of location. Five-year overall survival (OS) was 62% for patients in rural areas, 44% in small urban areas, 53% in medium urban areas, and 60% in large urban areas (p = .018). In multivariate analysis, there was no difference in OS between rural and large urban area patients (hazard ratio [HR]: 1.0; 95% confidence interval [CI]: 0.7-1.4), although patients in small urban areas (HR: 1.4; 95% CI: 1.0-2.0) and medium urban areas (HR: 1.4; 95% CI: 1.0-1.9) had worse OS than those in large urban areas. CONCLUSION: Place of residence at diagnosis is associated with survival of patients with DLBCL in British Columbia, Canada. Rural patients have similar survival to those in large urban areas, whereas patients living in small and medium urban areas experience worse outcomes.

Discovery and preclinical development of a therapeutically active nanobody-based chimeric antigen receptor targeting human CD22.

Chimeric antigen receptor (CAR) T cell therapies targeting B cell-restricted antigens CD19, CD20, or CD22 can produce potent clinical responses for some B cell malignancies, but relapse remains common. Camelid single-domain antibodies (sdAbs or nanobodies) are smaller, simpler, and easier to recombine than single-chain variable fragments (scFvs) used in most CARs, but fewer sdAb-CARs have been reported. Thus, we sought to identify a therapeutically active sdAb-CAR targeting human CD22. Immunization of an adult Llama glama with CD22 protein, sdAb-cDNA library construction, and phage panning yielded >20 sdAbs with diverse epitope and binding properties. Expressing CD22-sdAb-CAR in Jurkat cells drove varying CD22-specific reactivity not correlated with antibody affinity. Changing CD28- to CD8-transmembrane design increased CAR persistence and expression in vitro. CD22-sdAb-CAR candidates showed similar CD22-dependent CAR-T expansion in vitro, although only membrane-proximal epitope targeting CD22-sdAb-CARs activated direct cytolytic killing and extended survival in a lymphoma xenograft model. Based on enhanced survival in blinded xenograft studies, a lead CD22sdCAR-T was selected, achieving comparable complete responses to a benchmark short linker m971-scFv CAR-T in high-dose experiments. Finally, immunohistochemistry and flow cytometry confirm tissue and cellular-level specificity of the lead CD22-sdAb. This presents a complete report on preclinical development of a novel CD22sdCAR therapeutic.

A systematic review and meta-analysis of CD22 CAR T-cells alone or in combination with CD19 CAR T-cells.

Chimeric antigen receptor (CAR) T-cells are an emerging therapy for the treatment of relapsed/refractory B-cell malignancies. While CD19 CAR-T cells have been FDA-approved, CAR T-cells targeting CD22, as well as dual-targeting CD19/CD22 CAR T-cells, are currently being evaluated in clinical trials. This systematic review and meta-analysis aimed to evaluate the efficacy and safety of CD22-targeting CAR T-cell therapies. We searched MEDLINE, EMBASE, Web of Science, and the Cochrane Central Register of Controlled Trials from inception to March 3rd 2022 for full-length articles and conference abstracts of clinical trials employing CD22-targeting CAR T-cells in acute lymphocytic leukemia (ALL) and non-Hodgkin's lymphoma (NHL). The primary outcome was best complete response (bCR). A DerSimonian and Laird random-effects model with arcsine transformation was used to pool outcome proportions. From 1068 references screened, 100 were included, representing 30 early phase studies with 637 patients, investigating CD22 or CD19/CD22 CAR T-cells. CD22 CAR T-cells had a bCR of 68% [95% CI, 53-81%] in ALL (n= 116), and 64% [95% CI, 46-81%] in NHL (n= 28) with 74% and 96% of patients having received anti-CD19 CAR T-cells previously in ALL and NHL studies respectively. CD19/CD22 CAR T-cells had a bCR rate of 90% [95% CI, 84-95%] in ALL (n= 297) and 47% [95% CI, 34-61%] in NHL (n= 137). The estimated incidence of total and severe (grade ≥3) CRS were 87% [95% CI, 80-92%] and 6% [95% CI, 3-9%] respectively. ICANS and severe ICANS had an estimated incidence of 16% [95% CI, 9-25%] and 3% [95% CI, 1-5%] respectively. Early phase trials of CD22 and CD19/CD22 CAR T-cells show high remission rates in ALL and NHL. Severe CRS or ICANS were (1)rare and dual-targeting did not increase toxicity. Variability in CAR construct, dose, and patient factors amongst studies limits comparisons, with long-term outcomes yet to be reported. Systematic review registration: https://www.crd.york.ac.uk/prospero, identifier CRD42020193027.

Hematopoietic Cell Transplantation Trends and Outcomes in Canada: A Registry-Based Cohort Study.

Background: Hematopoietic cell transplantation (HCT) is an established therapy for hematologic malignancies and serious non-malignant blood disorders. Despite its curative potential, HCT is associated with substantial toxicity and health resource utilization. Effective delivery of HCT requires complex hospital-based care, which limits the number of HCT centres in Canada. In Canada, the quantity, indications, temporal trends, and outcomes of patients receiving HCT are not known. Methods: A retrospective cohort study of first transplants reported to the Cell Therapy Transplant Canada (CTTC) registry between 2000 and 2019. We determined overall survival (OS) and non-relapse mortality (NRM), categorizing the cohort into early (2000-2009) and later (2010-2019) eras to investigate temporal changes. Results: Of 18,046 transplants, 7571 were allogeneic and 10,475 were autologous. Comparing the two eras, allogeneic transplants increased in number by 22.3%, with greater use of matched unrelated donors in the later era. Autologous transplants increased by 10.9%. Temporal improvements in NRM were observed in children and adults. OS improved in pediatric patients and in adults receiving autologous HCT. In adults receiving allogeneic HCT, OS was stable despite the substantially older age of patients in the later era. Interpretation: HCT is an increasingly frequent procedure in Canada which has expanded to serve older adults. Noted improvements in NRM and OS reflect progress in patient and donor selection, preparation for transplant, and post-transplant supportive care. In allogeneic HCT, unrelated donors have become the most frequent donor source, highlighting the importance of the continued growth of volunteer donor registries. These results serve as a baseline measure for quality improvement and health services planning in Canada.

Identifying effect modifiers of CAR-T cell therapeutic efficacy: a systematic review and individual patient data meta-analysis protocol.

BACKGROUND: Chimeric antigen receptor T cell therapy (CAR-T) represents a promising and exciting new therapy for hematologic malignancies, where prognosis for relapsed/refractory patients remains poor. Encouraging results from clinical trials have often been tempered by heterogeneity in response to treatment among patients, as well as safety concerns including cytokine release syndrome. The identification of specific patient or treatment-specific factors underlying this heterogeneity may provide the key to the long-term sustainability of this complex and expensive therapy. An individual patient data meta-analysis (IPMDA) may provide potential explanations for the high degree of heterogeneity. Therefore, our objective is to perform a systematic review and IPDMA of CAR-T cell therapy in patients with hematologic malignancies to explore potential effect modifiers of CAR-T cell therapy. METHODS AND ANALYSIS: We will search MEDLINE, Embase, and the Cochrane Central Register of Controlled Clinical Trials. Studies will be screened in duplicate at the abstract level, then at the full-text level by two independent reviewers. We will include any prospective clinical trial of CAR-T cell therapy in patients with hematologic malignancies. Our primary outcome is complete response, while secondary outcomes of interest include overall response, progression-free survival, overall survival, and safety. IPD will be collected from each included trial and, in the case of missing data, corresponding authors/study sponsors will be contacted. Standard aggregate meta-analyses will be performed, followed by the IPD meta-analysis using a one-stage approach. A modified Institute of Health Economics tool will be used to evaluate the risk of bias of included studies. ETHICS AND DISSEMINATION: Identifying characteristics that may act as modifiers of CAR-T cell efficacy is of paramount importance and can help shape future clinical trials in the field. Results from this study will be submitted for publication in a peer-reviewed scientific journal, presented at relevant conferences and shared with relevant stakeholders.