Background: Chimeric antigen receptor T cell (CAR-T) therapy is an adoptive T cell immunotherapy that employs the genetically modified T cell to attack the cancer cell. It is widely studied across various hematological and solid organ malignancies. Several autologous CD19 CAR-T cell therapy constructs are now approved for various B cell lymphomas, including aggressive B cell lymphomas, indolent follicular lymphoma and mantle cell lymphoma, and acute lymphoblastic leukemia (ALL). Autologous CD19 CAR-T cell therapy has unprecedented success in relapsed and refractory disease. Long time to manufacture (2-5 weeks) and manufacture failure are challenges associated with risk of interim death and deterioration of CAR-T candidates with rapidly progressive disease. T cell fitness of the autologous product in heavily pretreated patients is also potentially compromised. To overcome these shortcomings, universal "off the shelf" allogeneic CAR-T cell therapy constructs are being developed and studied. Donor sources include healthy donors and cord or induced pluripotent stem cells (iPSCs). These CAR-T constructs have additional gene modifications to mitigate the risk of rejection and graft versus host disease (GVHD). We performed a systematic review and meta-analysis to assess the safety and efficacy of allogeneic CD19 CAR-T cell therapy. Methods: Four databases (Web of Science/MEDLINE/PubMed, Embase, and Cochrane Registry of Controlled Trials) were searched for this systematic review and meta-analysis following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines using MeSH terms and keywords for "Receptors, Chimeric antigen" OR "Artificial-T-cell receptor" OR "immunotherapy, adoptive" OR "CD-19". Our search produced 3506 articles and after removing duplicates, 2243 records were screened. After excluding reviews and irrelevant articles, we included 8 prospective trials of allogeneic CD-19 CAR-T cell therapy enrolling two or more than two patients from Jan 2013 to Nov 2020. We also searched ASH 2020 abstracts to include any additional trials. The methodological quality of the included studies was evaluated using NIH quality assessment tool. Inter-study variance was calculated using the Der Simonian-Laird Estimator. Proportions along with 95% confidence Interval (CI) were extracted to compute pooled analysis using the 'meta' package by Schwarzer et al. in the R programming language (version 4.16-2). Results: A total of 68 patients from 8 studies were evaluated. Median age was 22.5 (4.8-64) years. (Table 1) The median follow-up time was 10 (2-18) months with median number of prior therapies of 3.2 (2-11) as reported by 5 studies. Underlying diagnosis was acute lymphocytic lymphoma (n=49, 72%), chronic lymphocytic leukemia (n=6, 9%), and non-Hodgkin lymphoma (n=13, 19%). The pooled overall response rate (ORR) was 77% (95% CI 0.63-0.89, I 2 =22%, n=68) with a complete response (CR) of 75% (95% CI 0.57-0.90, I 2 =48%, n=65). The pooled incidence of cytokine release syndrome grade I/II and grade III/IV was 53% (95% CI 0.16-0.89, I 2 =89%, n=65) and 10% (95% CI 0.01-0.25, I 2 =50%, n=65) respectively. Neurotoxicity grade I/II was 12% (95%CI 0.01-0.30, I 2 =47%, p=0.09, n=47) and GVHD grade I/II was 8% (95%CI 0.01-0.19, I 2 =0%, p=0.57 n=53). None of the clinical trials reported the duration of response. Conclusion: "Off the shelf" universal CAR-T therapy is early in development. Our available data suggest that allogeneic CD19 CAR-T constructs offer high ORR and CR rates with acceptable safety profiles. GVHD was mainly low grade (grade I-II). Given these findings, allogeneic CAR-T cell therapy is an attractive option to improve timely access compared to available autologous therapy. Extensive preclinical research to develop novel constructs and several phase I/II clinical trials are ongoing to shape the future of "off the shelf" CAR-T cell therapy. Figure 1 Figure 1. Disclosures Hoffmann: Pharmcyclics: Consultancy, Honoraria; TG Therapeutics: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Janssen: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees; celgene: Consultancy, Honoraria. Abhyankar: Incyte/Therakos: Consultancy, Research Funding, Speakers Bureau. McGuirk: Fresenius Biotech: Research Funding; Gamida Cell: Research Funding; Pluristem Therapeutics: Research Funding; EcoR1 Capital: Consultancy; Novartis: Research Funding; Astelllas Pharma: Research Funding; Kite/ Gilead: Consultancy, Honoraria, Other: travel accommodations, expense, Kite a Gilead company, Research Funding, Speakers Bureau; Juno Therapeutics: Consultancy, Honoraria, Research Funding; Magenta Therapeutics: Consultancy, Honoraria, Research Funding; Novartis: Research Funding; Bellicum Pharmaceuticals: Research Funding; Allovir: Consultancy, Honoraria, Research Funding.

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Background: Natural killer (NK) cells are the first cells to recover following allogeneic hematopoietic stem cell transplant (HSCT) and play a crucial role in enabling engraftment, preventing post-transplant infection and tumor relapse. In addition, NK cells also reduce the risk of graft versus host disease (GvHD) and increase the graft versus leukemia effect (GVL). The purpose of this systematic review and meta-analysis is to know the impact of NK cells reconstitution on outcomes of allogeneic HSCT. Methods: Following Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, a comprehensive literature search was conducted on PubMed, Cochrane Library, and ClinicalTrials.gov through January 2021. We used MeSH terms and keywords for "hematologic malignancies" OR "hematopoietic stem cell transplantation" AND "natural killer cells." No filters or publication time limits were applied for the search. A total of 13 studies were included after screening 988 records and excluding duplicates, review, and non-relevant articles. An arbitrary value of NK cell count of 22.2 cell/ul was set as a cut-off to divide between high and low groups of NK where applicable. Quality evaluation was done using the NIH quality assessment tool and Inter-study variance was calculated using Der Simonian-Laird Estimator. Pooled analysis was done using the 'meta' package (Schwarzer et al. R programming language), and proportions with 95% confidence intervals (CI) were computed. Results: A total of 1623 patients were evaluated from 13 studies. (Table 1) The median age of patients was 44 (8.6-63) years and 33.5% were males. The median duration of follow-up was 18 (0.3-122) months. The median 2-year overall survival (OS) for high NK cohort and low NK cohort was 77% (95%CI 0.70-0.83, I 2 =82%, n=982) and 52%(95%CI 0.38-0.67, I 2 =95%, n=982), respectively. The pooled rate of relapse in high NK group was 8% (95%CI 0.01-0.19, I 2 =83%, n=226) and it was 20% (95%CI 0.06-0.39, I 2 =90%, n=226) for low NK group. The pooled incidence of acute GvHD was 24% (95%CI 0.09-0.42, I 2 =91%, n=336) and 44% (95%CI 0.26-0.62, I 2 =91%, n=336) for high and low NK cohorts, respectively. The pooled incidence for viral infection for high NK group was 17% (95%CI 0.01-0.47, I 2 =98%, n=508) while it was 29% (95%CI 0.04-0.65, I 2 =98%, n=508) for low NK group, respectively. Conclusion: Higher reconstitution of NK cells after allogeneic hematopoietic stem cell transplant has a favorable impact on outcomes, including better overall survival and low incidence of relapse, acute GvHD, and viral infections. Our findings suggest the need for further prospective studies to investigate utility of NK cells infusion early post-transplant to improve clinical outcomes and survival. Figure 1 Figure 1. Disclosures McGuirk: Bellicum Pharmaceuticals: Research Funding; Novartis: Research Funding; EcoR1 Capital: Consultancy; Astelllas Pharma: Research Funding; Allovir: Consultancy, Honoraria, Research Funding; Novartis: Research Funding; Fresenius Biotech: Research Funding; Gamida Cell: Research Funding; Magenta Therapeutics: Consultancy, Honoraria, Research Funding; Kite/ Gilead: Consultancy, Honoraria, Other: travel accommodations, expense, Kite a Gilead company, Research Funding, Speakers Bureau; Juno Therapeutics: Consultancy, Honoraria, Research Funding; Pluristem Therapeutics: Research Funding.

Background: Chronic lymphocytic leukemia (CLL) is the most common leukemia among adults in the United States. Despite the advancements in the treatment of CLL, relapsed/refractory CLL (RR-CLL) cases are still associated with poor prognosis. Anti-CD19 chimeric antigen receptor T cell (CAR-T) therapy has shown promising initial responses in patients with RR-CLL. We present a systematic review and meta-analysis to investigate the outcomes with CAR-T cell therapy in RR-CLL patients. Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, 196 articles were searched from 3 databases (PubMed, Cochrane Register of Controlled Trials, and clinicaltrials.gov) using MeSH terms and keywords for "CLL" AND "CAR-T" and "Antigen CD19" OR "adoptive immunotherapy" from the date of inception to March 2021. Studies were screened by title, abstract, and full text. Original studies reporting adult patients with RR-CLL who received CD19 CAR-T therapy as the only intervention were included while reviews, duplicate, and non-relevant articles were excluded. A total of 5 studies (clinical trials) were included and the following outcomes were extracted: complete remission (CR), partial response (PR), overall response rate (ORR), overall survival (OS), progression-free survival (PFS), progressive disease (PD), cytokine release syndrome (CRS) and neurotoxicity (NT). The Joanna Briggs Institute (JBI) critical appraisal checklist for studies reporting prevalence data and randomized control trials was used for quality assessment, and all studies were reported as good. The variance between the studies was calculated using Der Simonian-Laird Estimator. Proportions along with a 95% confidence interval (CI) were extracted to compute pooled analysis using the 'meta' package by Schwarzer et al. in the R programming language (version 4.16-2). Results: We included 137 patients from 5 studies. Out of these, a total of 110 patients were evaluated for efficacy and 116 for safety. (Table 1) Median age of the patients was 64 (40-79) years. Seventy-six percent were males as reported by 3 studies. Median number of prior therapies was 4.7 (1-11) and median follow up time was 16 (2-75) months. The pooled analysis showed a CR and PR of 28% (95 % CI 0.19-0.38, I 2=14%, n=110) and 38% (95% CI 0.21-0.57, I 2=72%, n=110) respectively with an ORR of 68% (95% CI 0.51-0.83, I 2=67%, n=110). The pooled prevalence of PD was 21% (95% CI 0.03-0.48, p= <0.01, I 2= 88%, n=110). PFS ranged from 1 month to 40.2 months as reported by 3 studies. OS ranged from 29 months to 64 months as reported by 2 studies. The pooled incidence of Grade I-II and Grade III-IV CRS was 56% (95% CI 0.32-0.79, I 2=80%, n=88) and 14% (95% CI 0.28-0.31, I 2=76%, n=110) respectively. The pooled incidence of grade I-II and grade III-IV NT was 12% (95% CI 0.15-0.29, I 2=72%, n=88) and 17.5% (95% CI 0.98-0.26, I 2=19%, n=110) respectively. Conclusion: CD19 CAR-T cell therapy shows favorable response rates in patients with RR-CLL who have failed multiple prior therapies with an acceptable safety profile. However, it is imperative that large prospective studies should be conducted to confirm these findings. Figure 1 Figure 1. Disclosures McGuirk: Gamida Cell: Research Funding; Magenta Therapeutics: Consultancy, Honoraria, Research Funding; Allovir: Consultancy, Honoraria, Research Funding; Novartis: Research Funding; Bellicum Pharmaceuticals: Research Funding; Astelllas Pharma: Research Funding; Kite/ Gilead: Consultancy, Honoraria, Other: travel accommodations, expense, Kite a Gilead company, Research Funding, Speakers Bureau; Pluristem Therapeutics: Research Funding; Juno Therapeutics: Consultancy, Honoraria, Research Funding; Fresenius Biotech: Research Funding; Novartis: Research Funding; EcoR1 Capital: Consultancy.

Background: Allogeneic hematopoietic cell transplantation (HSCT) is often the optimal and only potentially curative therapy in several high-risk hematologic malignancies. Although human leukocyte antigen (HLA)-matched donors remain the preferred choice for HSCT recipients, haploidentical and umbilical cord blood HSCT has increased access to transplantation. Despite these advances, many patients lack an appropriate donor, in particular the ethnic minorities. The use of mismatched unrelated donors (MMUD) has increased over the years but concerns regarding increased risk of graft versus host disease (GVHD) and non-relapse mortality (NRM) limits the utility of MMUD HSCT. The intensity of the conditioning regimen has a significant impact on survival in case of mismatched donors. We conducted a systematic review and meta-analysis aimed to investigate the outcomes with MMUD HSCT using reduced intensity conditioning (RIC). Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, a comprehensive literature search was performed on three databases (PubMed, Cochrane Library, and ClinicalTrials.gov) from date of inception through February 2021 using the MeSH and entry terms for "hematopoietic stem cell transplantation", OR "hematologic neoplasms", AND unrelated donors" AND "treatment outcome". A total of 2477 records were identified and primary and secondary screening was done. After excluding review, duplicate, and non-relevant articles, we included 6 (4 retrospective, 2 prospective) studies reporting outcomes following RIC MMUD HSCT. The Joanna Briggs Institute (JBI) critical appraisal checklist for studies reporting prevalence data and randomized control trial was used for quality assessment, and all studies were reported as good. Proportions along with a 95% confidence interval (CI) were extracted to compute pooled analysis using the 'meta' package by Schwarzer et al. in the R programming language (version 4.16-2). The variance between the studies was calculated using Der Simonian Laird Estimator. Results: We identified 895 participants in the 6 studies, who had MMUD HSCT with RIC. (Table 1) Median age was 57.5 (18-76) years and 56% (n= 415) were males as reported by four studies (n=740). In five studies with available data (n=855), source of the primary graft was peripheral blood (PB) and bone marrow (BM) in 72% (n=614) and 28% (n=241) of the HSCT recipients respectively. After a median follow-up of 48 (3-125) months, we estimated a pooled overall survival (OS) of 62% (95% CI 0.52-0.72, I 2=84%, n=895) at one year and 43.5% (95% CI 0.33-0.54, I 2 =84% n=855) at three years. The pooled incidence of acute GVHD (grade II-IV), acute GVHD (grade III-IV), and chronic GVHD were 37% (95% CI 0.26-0.49, I 2=81%, n=610), 16% (95% CI 0.07-0.29, I 2=87%, n=542), and 28% (95% CI 0.13-0.47, I 2=95%, n=848) respectively. Progression free survival (PFS) and relapse rates (RR) were 46% (95% CI 0.30-0.62, I 2=92%, n=814) and 31% (95% CI 0.24-0.39, I 2=65%, n=814) respectively. The pooled incidence of non-relapse mortality (NRM) was 23% (95% CI 0.09-0.40, I 2=91%, n=707). Kasamon et al. and Shaw et al. reported 1-year OS of 75-79% with MMUD HSCT using fludarabine, cyclophosphamide and 2 Gy total body irradiation RIC, bone marrow graft and post-transplant cyclophosphamide, sirolimus and mycophenolate for GVHD prophylaxis. Conclusion: Mismatched unrelated donor HSCT has shown favorable outcomes with reduced intensity conditioning using a post-transplant cyclophosphamide-based regimen, comparable to the historical outcomes with mismatched related donor (haploidentical) HSCT. MMUD HSCT with RIC can be considered in patients lacking an HLA-matched donor. This strategy will expand access to HSCT in patients with ethnic minorities who often lack a matched donor. Figure 1 Figure 1. Disclosures McGuirk: EcoR1 Capital: Consultancy; Allovir: Consultancy, Honoraria, Research Funding; Gamida Cell: Research Funding; Novartis: Research Funding; Kite/ Gilead: Consultancy, Honoraria, Other: travel accommodations, expense, Kite a Gilead company, Research Funding, Speakers Bureau; Astelllas Pharma: Research Funding; Fresenius Biotech: Research Funding; Bellicum Pharmaceuticals: Research Funding; Juno Therapeutics: Consultancy, Honoraria, Research Funding; Novartis: Research Funding; Magenta Therapeutics: Consultancy, Honoraria, Research Funding; Pluristem Therapeutics: Research Funding.