Search

Delayed immune reconstitution is a major challenge after matched unrelated donor (MUD) stem cell transplant (SCT). In this randomized phase 2 multi-center trial, Adoptive Immunotherapy with CD25/71 allodepleted donor T cells to improve immunity after unrelated donor stem cell transplant (NCT01827579), the authors tested whether allodepleted donor T cells (ADTs) can safely be used to improve immune reconstitution after alemtuzumab-based MUD SCT for hematological malignancies.Patients received standard of care or up to three escalating doses of ADTs generated through CD25+/CD71+ immunomagnetic depletion. The primary endpoint of the study was circulating CD3+ T-cell count at 4 months post-SCT. Twenty-one patients were treated, 13 in the ADT arm and eight in the control arm.The authors observed a trend toward improved CD3+ T-cell count at 4 months in the ADT arm versus the control arm (230/µL versus 145/µL, P = 0.18), and three ADT patients achieved normal CD3+ T-cell count at 4 months (700/µL). The rates of significant graft-versus-host disease (GVHD) were comparable in both cohorts, with grade ≥2 acute GVHD in seven of 13 and four of eight patients and chronic GVHD in three of 13 and three of eight patients in the ADT and control arms, respectively.These data suggest that adoptive transfer of ADTs is safe, but that in the MUD setting the benefit in terms of T-cell reconstitution is limited. This approach may be of more use in the context of more rigorous T-cell depletion.

PD-1-TALEN activity screen in murine thymoma EL4 cells.PD-1 gene inactivation in pmel-1 CD8+T cells and functional analysis. PD-1-TALEN activity in TRL from MCA205. Effector/memory phenotype of TRL from MCA205.

Legends for supplemental figures

Despite the promising efficacy of adoptive cell therapies (ACT) in melanoma, complete response rates remain relatively low and outcomes in other cancers are less impressive. The immunosuppressive nature of the tumor microenvironment and the expression of immune-inhibitory ligands, such as PD-L1/CD274 by the tumor and stroma are considered key factors limiting efficacy. The addition of checkpoint inhibitors (CPI) to ACT protocols bypasses some mechanisms of immunosuppression, but associated toxicities remain a significant concern. To overcome PD-L1–mediated immunosuppression and reduce CPI-associated toxicities, we used TALEN technology to render tumor-reactive T cells resistant to PD-1 signaling. Here, we demonstrate that inactivation of the PD-1 gene in melanoma-reactive CD8+ T cells and in fibrosarcoma-reactive polyclonal T cells enhanced the persistence of PD-1 gene-modified T cells at the tumor site and increased tumor control. These results illustrate the feasibility and potency of approaches incorporating advanced gene-editing technologies into ACT protocols to silence immune checkpoints as a strategy to overcome locally active immune escape pathways. Cancer Res; 76(8); 2087–93. ©2016 AACR.

Relapse following CD19-directed chimeric antigen receptor T-cells (CAR-T) for relapsed/refractory large B-cell lymphoma (r/r LBCL) is commonly ascribed to antigen loss or CAR-T exhaustion. Multi-antigen targeting and PD-1 blockade are rational approaches to prevent relapse. Here, we test CD19/22 dual-targeting CAR-T (AUTO3) plus pembrolizumab in r/r LBCL as inpatient or outpatient therapy (NCT03289455, https://clinicaltrials.gov/ct2/show/NCT03289455). Endpoints include toxicity (primary) and response rates (secondary). AUTO3 was manufactured for 62 patients using autologous leukapheresis, modified with a bicistronic transgene. 52 patients received AUTO3 (7/52,50x106; 45/52,150-450x106) and 48/52 received pembrolizumab. Median age was 59 years (range,27-83) and 46/52 had stage III/IV disease. Median follow-up was 21.6 months (range,15.1-51.3) at last data cut (Feb 28, 2022). AUTO3 was safe: grade 1-2 and grade 3 CRS affected 18/52 (34.6%) and 1/52 (1.9%) patients, neurotoxicity arose in 4 patients (2/4, grade 3-4), HLH affected 2 patients, and no Pembrolizumab-associated autoimmune sequalae were observed. On this basis, outpatient administration was tested in 20 patients, saving a median of 14 hospital days/patient. AUTO3 was effective: overall response rates were 66% (48.9%, CR; 17%, PR). For patients with CR, median DOR was not reached, with 54.4% (CI: 32.8, 71.7) projected to remain progression-free beyond 12 months after onset of remission. DOR for all responding patients was 8.3 months (95% CI: 3.0, NE) with 42.6% projected to remain progression-free beyond 12 months after onset of remission. Overall, AUTO3 +/- pembrolizumab for r/r LBCL was safe, lending itself to outpatient administration, and delivered durable remissions in 54.4% of complete responders, associated with robust CAR-T expansion. Neither dual-targeting CAR-T nor pembrolizumab prevented relapse in a significant proportion of patients, and future developments include next-generation-AUTO3, engineered for superior expansion/persistence in vivo, and selection of CAR binders active at low antigen densities.

Decreased cytomegalovirus (CMV)-specific immunity after hematopoietic cell transplantation (HCT) is associated with late CMV reactivation and increased mortality. Whether letermovir prophylaxis-associated reduction in viral exposure influences CMV-specific immune reconstitution is unknown. In a prospective cohort of allogeneic HCT recipients who received letermovir, we compared polyfunctional CMV-specific T-cell responses to those of controls who received PCR-guided preemptive therapy before the introduction of letermovir. Thirteen-color flow cytometry was used to assess T-cell responses at 3 months after HCT following stimulation with CMV immediate early-1 (IE-1) antigen and phosphoprotein 65 (pp65) antigens. Polyfunctionality was characterized by combinatorial polyfunctionality analysis of antigen-specific T-cell subsets. Use of letermovir and reduction of viral exposure were assessed for their association with CMV-specific T-cell immunity. Polyfunctional T-cell responses to IE-1 and pp65 were decreased in letermovir recipients and remained diminished after adjustment for donor CMV serostatus, absolute lymphocyte count, and steroid use. Among letermovir recipients, greater peak CMV DNAemia and increased viral shedding were associated with stronger CD8+ responses to pp65, whereas the CMV shedding rate was associated with greater CD4+ responses to IE-1. In summary, our study provided initial evidence that letermovir may delay CMV-specific cellular reconstitution, possibly related to decreased CMV antigen exposure. Evaluating T-cell polyfunctionality may identify patients at risk for late CMV infection after HCT.

PURPOSE Prognosis for adult B-cell acute lymphoblastic leukemia (B-ALL) is poor, and there are currently no licensed CD19 chimeric antigen receptor (CAR) therapeutics. We developed a novel second-generation CD19-CAR (CAT19-41BB-Z) with a fast off rate, designed for more physiologic T-cell activation to reduce toxicity and improve engraftment. We describe the multicenter phase I ALLCAR19 ( NCT02935257 ) study of autologous CAT19-41BB-Z CAR T cells (AUTO1) in relapsed or refractory (r/r) adult B-ALL. METHODS Patients age ≥ 16 years with r/r B-ALL were eligible. Primary outcomes were toxicity and manufacturing feasibility. Secondary outcomes were depth of response at 1 and 3 months, persistence of CAR-T, incidence and duration of hypogammaglobulinemia and B-cell aplasia, and event-free survival and overall survival at 1 and 2 years. RESULTS Twenty-five patients were leukapheresed, 24 products were manufactured, and 20 patients were infused with AUTO1. The median age was 41.5 years; 25% had prior blinatumomab, 50% prior inotuzumab ozogamicin, and 65% prior allogeneic stem-cell transplantation. At the time of preconditioning, 45% had ≥ 50% bone marrow blasts. No patients experienced ≥ grade 3 cytokine release syndrome; 3 of 20 (15%) experienced grade 3 neurotoxicity that resolved to ≤ grade 1 within 72 hours with steroids. Seventeen of 20 (85%) achieved minimal residual disease–negative complete response at month 1, and 3 of 17 underwent allogeneic stem-cell transplantation while in remission. The event-free survival at 6 and 12 months was 68.3% (42.4%-84.4%) and 48.3% (23.1%-69.7%), respectively. High-level expansion (Cmax 127,152 copies/µg genomic DNA) and durable CAR-T persistence were observed with B-cell aplasia ongoing in 15 of 20 patients at last follow-up. CONCLUSION AUTO1 demonstrates a tolerable safety profile, high remission rates, and excellent persistence in r/r adult B-ALL. Preliminary data support further development of AUTO1 as a stand-alone treatment for r/r adult B-ALL.

Cytomegalovirus (CMV) infection is widely prevalent but mostly harmless in immunocompetent individuals. In the post hematopoietic stem cell transplant (HSCT) setting unrestricted viral replication can cause end-organ damage (CMV disease) and, in a small proportion, mortality. Current management strategies are based on sensitive surveillance programmes, with the more recent introduction of an effective prophylactic antiviral drug, letermovir, but all aim to bridge patients until reconstitution of endogenous immunity is sufficient to constrain viral replication.Over the past 25 years, the adoptive transfer of CMV-specific T-cells has developed from the first proof of concept transfer of CD 8 + T-cell clones, to the development of 'off the shelf' third party derived Viral-Specific T-cells (VSTs). In this review, we cover the current management of CMV, and discuss the developments in CMV adoptive cellular therapy.Due to the adoption of letermovir as a prophylaxis in standard therapy, the incidence of CMV reactivation is likely to decrease, and any widely adopted cellular therapy needs to be economically competitive. Current clinical trials will help to identify the patients most likely to gain the maximum benefit from any form of cell therapy.

Intratumoral regulatory T (Treg) cell abundance associates with diminished antitumor immunity and poor prognosis in human cancers. Recent work demonstrates that CD25, the high-affinity receptor subunit for interleukin (IL)-2, is a selective target for Treg depletion in mouse and human malignancies; however, anti-human CD25 antibodies have failed to deliver clinical responses against solid tumors due to bystander IL-2 receptor signaling blockade on effector T cells, which limits their antitumor activity. Here we demonstrate potent single-agent activity of anti-CD25 antibodies optimized to deplete Treg cells, while preserving IL-2-STAT5 signaling on effector T cells and show synergy with immune checkpoint blockade in vivo. Pre-clinical evaluation of an anti-human CD25 (RG6292) antibody with equivalent features demonstrates, in both nonhuman primates and humanized mouse models, efficient Treg cell depletion with no overt immune-related toxicities. Our data support the clinical development of RG6292 and evaluation of new combination therapies incorporating non-IL-2-blocking anti-CD25 antibodies in clinical studies. Quezada and colleagues develop improved anti-CD25 antibodies that preserve IL-2 signaling and enhance single-agent antitumor immunity and immunotherapy through specific and efficient Treg cell depletion.

The most widely accepted starting materials for chimeric antigen receptor T-cell manufacture are autologous CD3+ T cells obtained via the process of leukapheresis, also known as T-cell harvest. As this treatment modality gains momentum and apheresis units struggle to meet demand for harvest slots, strategies to streamline this critical step are warranted.This retrospective review of 262 T-cell harvests, with a control cohort of healthy donors, analyzed the parameters impacting CD3+ T-cell yield in adults with B-cell malignancies. The overall aim was to design a novel predictive algorithm to guide the required processed blood volume (PBV) (L) on the apheresis machine to achieve a specific CD3+ target yield.Factors associated with CD3+ T-cell yield on multivariate analysis included peripheral blood CD3+ count (natural log, ×10The authors propose a transferrable model that incorporates clinical and laboratory variables accessible pre-harvest for use across the field of T-cell therapy. Pending further validation, such a model may be used to generate an individual leukapheresis plan and streamline the process of cell harvest, a well-recognized bottleneck in the industry.

Allogeneic hematopoietic cell transplantation (HCT) is used to treat many blood-based disorders and malignancies. While this is an effective treatment, it can result in serious adverse events, such as the development of acute graft-versus-host disease (aGVHD). This study aimed to develop a donor-specific epigenetic classifier that could be used in donor selection in HCT to reduce the incidence of aGVHD.The discovery cohort of the study consisted of 288 donors from a population receiving HLA-A, -B, -C and -DRB1 matched unrelated donor HCT with T cell replete peripheral blood stem cell grafts for treatment of acute leukaemia or myelodysplastic syndromes after myeloablative conditioning. Donors were selected based on recipient aGVHD outcome; this cohort consisted of 144 cases with aGVHD grades III-IV and 144 controls with no aGVHD that survived at least 100 days post-HCT matched for sex, age, disease and GVHD prophylaxis.Genome-wide DNA methylation was assessed using the Infinium Methylation EPIC BeadChip (Illumina), measuring CpG methylation at >850,000 sites across the genome. Following quality control, pre-processing and exploratory analyses, we applied a machine learning algorithm (Random Forest) to identify CpG sites predictive of aGVHD. Receiver operating characteristic (ROC) curve analysis of these sites resulted in a classifier with an encouraging area under the ROC curve (AUC) of 0.91.To test this classifier, we used an independent validation cohort (n=288) selected using the same criteria as the discovery cohort. Different attempts to validate the classifier using the independent validation cohort failed with the AUC falling to 0.51. These results indicate that donor DNA methylation may not be a suitable predictor of aGVHD in an HCT setting involving unrelated donors, despite the initial promising results in the discovery cohort.Our work highlights the importance of independent validation of machine learning classifiers, particularly when developing classifiers intended for clinical use.

The Electron-Ion Collider (EIC) presently under construction at Brookhaven National Laboratory will collide polarized high energy electron beams with hadron beams with design luminosities up to 1 × 1034cm−2s−1 in center mass energy range of 20-140 GeV. We studied the planned electron-proton collisions using a Particle-In-Cell (PIC) based Poisson solver in strong-strong beam-beam simulation. We observed a much larger proton emittance growth rate than in weak-strong simulation. To understand the numerical noise and its impact on strong-strong simulation results, we carried out extensive studies to identify all possible causes for artificial emittance growth and quantify their contributions. In this article, we summarize our study activities and findings. This work will help us better understand the simulated emittance growth and the limits of the PIC based strong-strong beam-beam simulation.

Despite the clinical success of checkpoint inhibitors, a substantial gap still exists in our understanding of their mechanism of action. While antibodies to cytotoxic T lymphocyte-associated protein-4 (CTLA-4) were developed to block inhibitory signals in T cells, several recent studies have demonstrated that Fcγ receptor (FcγR)-dependent depletion of regulatory T cells (T

Chimeric antigen receptor (CAR) T cell therapy is rapidly emerging as one of the most promising therapies for hematologic malignancies. Two CAR T products were recently approved in the United States and Europe for the treatment ofpatients up to age 25years with relapsed or refractory B cell acute lymphoblastic leukemia and/or adults with large B cell lymphoma. Many more CAR T products, as well as other immunotherapies, including various immune cell- and bi-specific antibody-based approaches that function by activation of immune effector cells, are in clinical development for both hematologic and solid tumor malignancies. These therapies are associated with unique toxicities of cytokine release syndrome (CRS) and neurologic toxicity. The assessment and grading of these toxicities vary considerably across clinical trials and across institutions, making it difficult to compare the safety of different products and hindering the ability to develop optimal strategies for management of these toxicities. Moreover, some aspects of these grading systems can be challenging to implement across centers. Therefore, in an effort to harmonize the definitions and grading systems for CRS and neurotoxicity, experts from all aspects of the field met on June 20 and 21, 2018, at a meeting supported by the American Society for Transplantation and Cellular Therapy (ASTCT; formerly American Society for Blood and Marrow Transplantation, ASBMT) in Arlington, VA. Here we report the consensus recommendations of that group and propose new definitions and grading for CRS and neurotoxicity that are objective, easy to apply, and ultimately more accurately categorize the severity of these toxicities. The goal is to provide a uniform consensus grading system for CRS and neurotoxicity associated with immune effector cell therapies, for use across clinical trials and in the postapproval clinical setting.

Intratumoral regulatory T cell (Treg) abundance associates with diminished anti-tumor immunity and poor prognosis in human cancers. Recent work demonstrates that CD25, the high affinity receptor subunit for IL-2, is a selective target for Treg depletion in mouse and human malignancies; however, anti-human CD25 antibodies have failed to deliver clinical responses against solid tumors due to bystander IL-2 receptor signaling blockade on effector T cells, which limits their anti-tumor activity. Here we demonstrate potent single-agent activity of anti-CD25 antibodies optimized to deplete Tregs whilst preserving IL-2-STAT5 signaling on effector T cells, and demonstrate synergy with immune checkpoint blockade in vivo. Pre-clinical evaluation of an anti-human CD25 (RG6292) antibody with equivalent features demonstrates, in both non-human primates and humanized mouse models, efficient Treg depletion with no overt immune-related toxicities. Our data supports the clinical development of RG6292 and evaluation of novel combination therapies incorporating non-IL-2 blocking anti-CD25 antibodies in clinical studies.

Epstein-Barr virus (EBV) load monitoring after allogeneic hematopoietic stem cell transplantation (HSCT) enables earlier detection of EBV replication and often serves as a trigger for preemptive therapies aimed at reducing EBV-related diseases. Our institutional strategy is to treat patients with clinical signs of EBV-related disease accompanied by a rising viral load, rather than to intervene based solely on viral load. This affords an opportunity to study the natural history of EBV replication and to assess whether our strategy reduces overtreatment without compromising outcomes. The objectives of the present study were to assess the natural history of untreated EBV replication in patients who underwent an alemtuzumab-based allogeneic HSCT and to examine whether our clinical strategy reduced overtreatment without compromising patient outcomes. In this retrospective single-center observational study of 515 consecutive patients (age ≥18 years) undergoing T cell-depleted allogeneic HSCT incorporating alemtuzumab, patients underwent surveillance monitoring for EBV by quantitative PCR in the peripheral blood at least weekly up to 100 days post-transplantation and longer if they remained on immunosuppressive therapy. The cumulative incidence of EBV detection and EBV-related disease were assessed. Among the 515 patients, 192 had EBV DNA detectable on ≥1 occasion, with a cumulative incidence of 35.8% (31.8% to 40.4%), although this remained below the limit of quantification in 93 patients. The median time to first detection was 89.5 days (range, 0 to 2254 days). The incidence was higher in recipients of sibling donor transplants (45.4% versus 30%; P = .00021) compared with recipients of unrelated donor transplants. Twenty patients developed EBV-related disease (cumulative incidence, 3.9%). Two patients had immunosuppression reduction alone, 18 received rituximab, and 5 required additional therapies. Five patients died from post-transplantation lymphoproliferative disorder, all of whom had received rituximab. The positive predictive value of EBV load for disease was higher in the unrelated donor cohort but remained75% regardless of EBV threshold (57.1% to 72.7%). The cumulative incidence of EBV-related disease in our study (3.9%) is comparable to that reported in other studies incorporating alemtuzumab, and our clinical strategy reduced overtreatment in this patient population. PCR-based surveillance strategies have limitations, as reflected in the relatively low sensitivity of the assay coupled with the low positive predictive value, which may influence the potential choice of a threshold for preemptive intervention. We conclude that it remains unclear whether treatment based on a rising EBV viral load alone provides superior overall results to treatment based on the development of clinical signs of EBV-related disease in the context of a rising viral load.

Poor graft function is a serious complication following allogeneic hematopoietic stem cell transplantation. Infusion of CD34+-selected stem cells without pre-conditioning has been used to correct poor graft function, but predictors of recovery are unclear. We report the outcome of 62 consecutive patients who had primary or secondary poor graft function who underwent a CD34+-selected stem cell infusion from the same donor without further conditioning. Forty-seven of 62 patients showed hematologic improvement and became permanently transfusion- and growth factorindependent. In multivariate analysis, parameters significantly associated with recovery were shared cytomegalovisur seronegative status of both the recipient and donor, the absence of active infection and matched recipientdonor sex. Recovery was similar in patients with mixed and full donor chimerism. Five-year overall survival rates were 74.4% (95% confidence interval [95% CI: 59-89]) in patients demonstrating complete recovery, 16.7% (95% CI: 3-46) in patients with partial recovery and 22.2% (CI 95% 5-47) in those who had no response. In patients with blood count recovery, those with poor graft function in one or two lineages had a better 5-year overall survival (93.8%, 95% CI: 82-99) than those with trilineage failure (53%, 95% CI: 34-88). New strategies including cytokine or agonist support, or a second transplant need to be investigated in patients whose blood counts do not recover.

Background aims: Around 50 000 autologous stem cell transplantations are done each year worldwide using cryopreserved peripheral blood stem cells (PBSCs). Cryopreservation is time-consuming and expensive. Since 2007, several retrospective studies have shown that PBSCs can be stored at 4 degrees C for 2-3 days, allowing autologous stem cell transplantation in patients with multiple myeloma receiving high-dose melphalan. Data with non-cryopreserved PBSCs in patients autografted for lymphoma following longer pre-conditioning regimens are limited. In addition, no controlled comparison has been able to detect unforeseen differences.Methods: The authors compared outcomes of 94 consecutive adult patients with lymphoma (66 with Hodgkin lymphoma) autografted in our department in Oran (Algeria) using PBSCs stored at 4 degrees C, from 2009 to 2018, with patients receiving cryopreserved stem cells reported to the European Society for Blood and Marrow Transplantation registry. Patients autografted in Oran were matched with patients receiving cryopreserved PBSCs in the registry (four controls per patient in Oran).Results: Neutrophil engraftment was significantly faster with cryopreserved PBSCs (P = 0.003). By day 10, only 17% of patients receiving non-cryopreserved PBSCs engrafted versus 48% for cryopreserved PBSCs. Likewise, platelet recovery to 20 000/mm(3) was significantly faster in patients receiving cryopreserved PBSCs (P = 0.01). However, all patients in both groups had recovered by day 20. There were no significant differences in non relapse mortality (9% versus 7%, P = 0.4), relapse incidence (22% versus 32%, P = 0.13), progression-free survival (70% versus 61%, P = 0.4) or overall survival (85% versus 75%, P = 0.3).Conclusions: This analysis suggests that, in patients with lymphoma receiving pre-transplant regimens such as carmustine, etoposide, cytarabine and melphalan, PBSCs stored at 4 degrees C for up to 6 days can be used safely in centers with no cryopreservation facility. However, the kinetics of hematopoietic recovery showed a significant, albeit small, delay in engraftment for both neutrophils and platelets, which favors the use of cryopreservation if available. (c) 2021 International Society for Cell & Gene Therapy. Published by Elsevier Inc. All rights reserved.

Background Regulatory T cell (Treg) depletion with antibodies against CD25 is effective in tumor models but response rates are low in poorly infiltrated B16 melanomas. Combination with a tumor vaccine enhances efficacy, but relapse usually occurs following partial control, similar to what is seen clinically. How resistance develops is unknown. Materials and Methods C57BL/6 mice were injected subcutaneously with B16 cells. Treatments included a depleting mouse IgG2a αCD25 antibody and/or a genetically modified, granulocyte-macrophage colony-stimulating factor (GM-CSF) secreting whole B16 tumor vaccine (Gvax). Changes in the immune landscape were assessed with high dimensional flow cytometry. Results Compared to monotherapies, combined Gvax/αCD25 significantly delayed tumour growth and prolonged survival, in association with enhanced infiltration of T cells with an activated phenotype. Approximately 50% of mice achieved partial response with relapse at day 35–45 post tumor injection. To characterize immune evolution prior to relapse, we analysed stable, partially responding tumors and paired draining lymph nodes (DLNs). Over time, activated PD-1+ICOS+TCF7- T cells with an effector memory (CD44+CD62L-) phenotype fell from 30% to 10% whilst resting, TCF7+ early differentiated cells rose in abundance towards levels seen in untreated tumors. Abundance of Ki67-, resting Tregs also recovered. Similar results were obtained in analysis of DLNs. Conclusions Combined Treg depletion/whole tumor vaccination therapy is effective in a poorly infiltrated B16 melanoma model. Combined treatment promotes T cell infiltration and activation. In mice achieving a partial response, treatment effects on the immune landscape were observed to decay over time suggesting a return to immune equilibrium. Further studies to explore the mechanistic basis of this observation are underway. Disclosure Information C. Qing: None. E. Ghorani: None. I. Solomon: None. F. Galvez-Cancino: None. F. Vargas: None. K. Peggs: None. S. Quezada: B. Research Grant (principal investigator, collaborator or consultant and pending grants as well as grants already received); Significant; F. HOFFMANN-LA ROCHE LTD.

Background Effective anti-tumour immunity requires cancer antigen expression, but persistent antigen exposure in chronic viral infections and autoimmunity has a detrimental effect on immune function. This is associated with a decline of early differentiated T cell populations in favour of later differentiated, dysfunctional subsets, resulting in an unfavourable skewing of the immune landscape. It is unknown whether this occurs locally within the antigen rich tumour microenvironment, driving immune failure. Materials and Methods We combined tumour infiltrating lymphocyte (TIL) high dimensional flow cytometry, bulk exome and RNA sequencing data from multiregional samples obtained from surgically resected tumours of treatment naive patients with non-small cell lung cancer (NSCLC) amongst the first 100 recruited to the prospective, UK-wide lung TRACERx study. Clonal relationship between T cell populations was determined by T cell receptor (TCR) sequencing. We additionally analysed publically available single T cell RNA sequencing data and bulk RNA sequencing data within TCGA. Results T cell differentiation skewing (TDS) occurred amongst TILs in association with tumour mutational burden (TMB). Surprisingly, this was most evident within the CD4 compartment that had a greater abundance of central memory cells expressing the key transcription factor TCF7. Amongst CD4 cells, loss of a PD1-CCR7+ T central memory population was accompanied by gain in abundance of PD1+ populations with exhausted (CD57-ICOShiCTLA4hi) and terminally differentiated effector (CD57+Eomes+) features. TCR sequencing revealed early and dysfunctional differentiated populations to be clonally related and CDR3 clustering analysis showed greater similarity of sequences shared vs. non-shared between subsets, consistent with an antigen driven differentiation process. Similar patterns were observed within the CD8 compartment. Identification of these subsets within single T cell RNA sequencing data revealed shared and distinct functional regulators, suggesting the enhanced effector capability of early compared to dysfunctionally differentiated populations. A validated transcriptional signature of TDS generated using TRACERx samples with paired flow cytometry and RNA sequencing data reflected loss of gene expression downstream of TCF7, and predicted worse survival within TRACERx and multiple TCGA cohorts including lung adenocarcinoma (LUAD). Conclusions Our finding support a model of neoantigen driven T cell differentiation within the tumour microenvironment that drives the depletion of progenitor-like cells and gain in abundance of dysfunctional subsets, resulting in a loss of immune fitness. Our analysis of transcriptomic data elucidates potential regulatory mechanisms and therapeutic targets within the subsets identified. Disclosure Information E. Ghorani: None. J. Reading: None. J. Henry: None. M. Robert de Massy: None. R. Rosenthal: E. Ownership Interest (stock, stock options, patent or other intellectual property); Modest; Achilles Therapeutics. F. Consultant/Advisory Board; Modest; Achilles Therapeutics. V. Turati: None. A. Furness: None. A. Ben Aissa: None. S. Kumar Saini: None. S. Ramskov: None. A. Georgiou: None. M. Vila De Mucha: None. I. Uddin: None. T. Ronel: None. R. Salgado: None. T. Lund: None. J. Herrero: None. T. Enver: None. S. Hadrup: None. A. Hackshaw: None. K. Peggs: E. Ownership Interest (stock, stock options, patent or other intellectual property); Modest; Achilles Therapeutics. N. McGranahan,: E. Ownership Interest (stock, stock options, patent or other intellectual property); Modest; Achilles Therapeutics. F. Consultant/Advisory Board; Modest; Achilles Therapeutics. B. Chain: None. C. Swanton: B. Research Grant (principal investigator, collaborator or consultant and pending grants as well as grants already received); Modest; Pfizer, AstraZeneca, BMS, Roche–Ventana and Boehringer Ingelheim. E. Ownership Interest (stock, stock options, patent or other intellectual property); Modest; ApoGen Biotechnologies, Epic Bioscience and GRAIL, and has stock options in and is co-founder of Achilles Therapeutics. F. Consultant/Advisory Board; Modest; Pfizer, Novartis, GlaxoSmithKline, MSD, BMS, Celgene, AstraZeneca, Illumina, Genentech, Roche–Ventana, GRAIL, Medicxi and the Sarah Cannon Research Institute. S. Quezada: E. Ownership Interest (stock, stock options, patent or other intellectual property); Modest; Achilles Therapeutics.

BACKGROUND: Adoptive transfer of donor-derived EBV-specific cytotoxic T-lymphocytes (EBV-CTLs) can eradicate EBV-associated lymphomas (EBV-PTLD) after transplantation of hematopoietic cell (HCT) or solid organ (SOT) but is unavailable for most patients. METHODS: We developed a third-party, allogeneic, off-the-shelf bank of 330 GMP-grade EBV-CTL lines from specifically consented healthy HCT donors. We treated 46 recipients of HCT (n = 33) or SOT (n = 13) with established EBV-PTLD, who had failed rituximab therapy, with third-party EBV-CTLs. Treatment cycles consisted of 3 weekly infusions of EBV-CTLs and 3 weeks of observation. RESULTS: EBV-CTLs did not induce significant toxicities. One patient developed grade I skin graft-versus-host disease. Complete remission (CR) or sustained partial remission (PR) was achieved in 68% of HCT recipients and 54% of SOT recipients. For patients who achieved CR/PR or stable disease after cycle 1, one year overall survival was 88.9% and 81.8%, respectively. In addition, 3 of 5 recipients with POD after a first cycle who received EBV-CTLs from a different donor achieved CR or durable PR (60%) and survived longer than 1 year. Maximal responses were achieved after a median of 2 cycles. CONCLUSION: Third-party EBV-CTLs of defined HLA restriction provide safe, immediately accessible treatment for EBV-PTLD. Secondary treatment with EBV-CTLs restricted by a different HLA allele (switch therapy) can also induce remissions if initial EBV-CTLs are ineffective. These results suggest a promising potential therapy for patients with rituximab-refractory EBV-associated lymphoma after transplantation. TRIAL REGISTRATION: Phase II protocols (NCT01498484 and NCT00002663) were approved by the Institutional Review Board at Memorial Sloan Kettering Cancer Center, the FDA, and the National Marrow Donor Program. FUNDING: This work was supported by NIH grants CA23766 and R21CA162002, the Aubrey Fund, the Claire Tow Foundation, the Major Family Foundation, the Max Cure Foundation, the Richard “Rick” J. Eisemann Pediatric Research Fund, the Banbury Foundation, the Edith Robertson Foundation, and the Larry Smead Foundation. Atara Biotherapeutics licensed the bank of third-party EBV-CTLs from Memorial Sloan Kettering Cancer Center in June 2015.

Cytomegalovirus (CMV) infection is common following allogeneic hematopoietic stem cell transplant (HSCT) and is a major cause of morbidity and increased mortality. Whilst pharmacotherapy can be effective in the prevention and treatment of CMV, these agents are often expensive, toxic and in some cases ineffective due to viral resistance mechanisms. Immunotherapeutic approaches are compelling and early clinical trials of adoptively transferred donor-derived virus-specific T (VST) cells against CMV have demonstrated efficacy. However, significant logistical challenges limit their broad application. Strategies to optimize VST manufacture and cell banking alongside scientific developments to enhance efficacy whilst minimizing toxicity are ongoing. This review will discuss the development of CMV-specific T-cell therapies, the challenges of widespread delivery of VSTs for CMV and explore how VST therapy can change outcomes in CMV infection following HSCT.

BACKGROUND: The treatment of patients with Hodgkin lymphoma (HL) who develop disease progression after undergoing allogeneic stem cell transplantation (allo‐SCT) remains challenging. METHODS: The authors assessed outcomes in 184 adult patients with HL who developed disease recurrence or progression after a matched related or unrelated allo‐SCT at European Society for Blood and Marrow Transplantation–participating centers between 2010 and 2014. RESULTS: Eighty patients who received brentuximab vedotin (BV) salvage therapy were compared with 104 patients who did not. Patients in the BV group were younger (median age of 30 years vs 34 years) and were more likely to receive pretransplant BV (65% vs 46%) or posttransplant donor lymphocyte infusion (66% vs 33%). The 2 groups otherwise were comparable. Patients in the BV group received a median of 6 doses of posttransplant BV, resulting in a complete remission rate of 29%, a partial response rate of 45%, and a stable disease rate of 26%. Response to BV after allo‐SCT did not appear to be affected by receipt of pretransplant BV. Despite a longer median follow‐up for surviving patients in the BV group (33 months vs 23 months; P

The generation and maintenance of CD8+ T cell memory is crucial to long-term host survival, yet the basic tenets of CD8+ T cell immunity are still being established. Recent work has led to the discovery of tissue-resident memory cells and refined our understanding of the transcriptional and epigenetic basis of CD8+ T cell differentiation and dysregulation. In parallel, the unprecedented clinical success of immunotherapy has galvanized an intense, global research effort to decipher and de-repress the anti-tumor response. However, the progress of immunotherapy is at a critical juncture, since the efficacy of immuno-oncology agents remains confined to a fraction of patients and often fails to provide durable benefit. Unlocking the potential of immunotherapy requires the design of strategies that both induce a potent effector response and reliably forge stable, functional memory T cell pools capable of protecting from recurrence or relapse. It is therefore essential that basic and emerging concepts of memory T cell biology are rapidly and faithfully transposed to advance therapeutic development in cancer immunotherapy. This review highlights seminal and recent reports in CD8+ T cell memory and tumor immunology, and evaluates recent data from solid cancer specimens in the context of the key paradigms from preclinical models. We elucidate the potential significance of circulating effector cells poised downstream of neoantigen recognition and upstream of T cell dysfunction and propose that cells in this immunological 'sweet spot' may be key anti-tumor effectors.

Reduced-intensity allogeneic stem cell transplantation (RIST) is usually reserved for patients with mantle cell lymphoma who relapse after an autoSCT. However, the long-term efficacy of RIST and its curative potential have not been clearly demonstrated. We studied the long-term outcome of patients receiving a RIST for MCL as reported to the EBMT. A total of 324 patients, median age 57 years (range 31-70), underwent a RIST between 2000 and 2008; 43% of the patients had received >3 lines of prior therapy, including an autoSCT in 46%. Non-relapse mortality (NRM) was 10% at 100 days and 24% at 1 year and was lower for patients receiving anti-thymocyte globulin (ATG)/ALG (RR 0.59, p = 0.046). After a median follow-up of 72 months (range 3-159), 118 patients relapsed at a median of 8 months post RIST (range 1-117). The cumulative incidence of relapse was 25% and 40% at 1 and 5 years, respectively, and was associated with chemorefractory disease (HR 0.49, p = 0.01) and the use of CAMPATH (HR 2.59, p = 0.0002). The 4-year progression-free survival rate and overall survival rate was 31 and 40%, respectively. RIST results in long-term disease-free survival in about 30% of the patients, including those patients relapsing after a prior autoSCT.

Background Cancer mutations generate novel (neo-)peptides recognised by T cells, but the determinants of recognition are not well characterised. The difference in predicted class I major histocompatibility complex (MHC-I) binding affinity between wild-type and corresponding mutant peptides (differential agretopicity index; DAI) may reflect clinically relevant cancer peptide immunogenicity. Our aim was to explore the relationship between DAI, measures of immune infiltration and patient outcomes in advanced cancer. Patients and methods Cohorts of patients with advanced non-small-cell lung cancer (NSCLC; LUAD, n = 66) and melanoma (SKCM, n = 72) were obtained from The Cancer Genome Atlas. Three additional cohorts of immunotherapy treated patients with advanced melanoma (total n = 131) and NSCLC (n = 31) were analysed. Neopeptides and their clonal status were defined using genomic data. MHC-I binding affinity was predicted for each neopeptide and DAI values summarised as the sample mean DAI. Correlations between mean DAI and markers of immune activity were evaluated using measures of lymphocyte infiltration and immune gene expression. Results In univariate and multivariate analyses, mean DAI significantly correlated with overall survival in 3/5 cohorts, with evidence of superiority over nonsynonymous mutational and neoantigen burden. In these cohorts, the effect was seen for mean DAI of clonal but not subclonal peptides. In SKCM, the association between mean DAI and survival bordered significance (P = 0.068), reaching significance in an immunotherapy-treated melanoma cohort (P = 0.003). Mean DAI but not mutational nor neoantigen burden was positively correlated with independently derived markers of immune infiltration in both SKCM (P = 0.027) and LUAD (P = 0.024). Conclusions The association between mean DAI, survival and measures of immune activity support the hypothesis that DAI is a determinant of cancer peptide immunogenicity. Investigation of DAI as a marker of immunologically relevant peptides in further datasets and future clinical studies of neoantigen based immunotherapies is warranted.

INTRODUCTION We have previously described AUTO1, a CD19 CAR with a fast off-rate CD19 binding domain, designed to reduce CAR-T immune toxicity and improve engraftment. Its clinical activity has been tested in r/r paediatric and adult B-ALL. Cumulatively, this data confirms the intended function of the receptor, with low levels of CRS/ICANS and long-term engraftment of CAR T-cells observed in both patient groups. Recently, CAR-T therapy has been explored in indolent lymphomas such as follicular (FL) and mantle cell lymphoma (MCL), but a high incidence of toxicity including Grade 3-4 ICANS has been reported. We have initiated testing of AUTO1 in the setting of indolent and high-grade B-NHL and CLL (NCT02935257). METHODS Manufacturing: CAR T-cell products were generated using a semi-automated closed process from non-mobilised leukapheresate. Study design: Subjects ≥ 16y underwent lymphodepletion with fludarabine (30mg/m 2 x3) and cyclophosphamide (60mg/kg x1) prior to AUTO1 infusion, with the exception of the DLBCL cohort who additionally received a single dose of pembrolizumab (200mg) on day -1 to potentiate CAR-T expansion. AUTO1 dose varies based on the indication. Split dosing of 230 x10^6 CD19 CAR T-cells at day 0 and day 9 is employed in the CLL cohort. A single dose of 200 x10^6 CD19 CAR T-cells is delivered to patients with B-NHL. Study endpoints include feasibility of manufacture, grade 3-5 toxicity and remission rates at 1 and 3 months. RESULTS As of 17th May 2021, we recruited 13 patients: 7 with FL, 4 with MCL, 1 DLBCL and 1 CLL. Apheresis and product manufacture was successful in all 13 patients and 9 patients were infused: 7 with FL and 2 with MCL. Three patients (1 DLBCL, 1 CLL and 1 MCL) were pending infusion at time of data cut-off and 1 patient (MCL) died due to Covid-19 prior to infusion. Patients treated with AUTO1 had a median age of 56 years (range 39-68y), had received a median of 3 prior lines of treatment (range 2-5) and all patients had stage IV disease at screening. Grade 1 CRS was reported in 4/9 and Grade 2 CRS in 1/9. 1/9 developed MAS which resolved with anakinra/dexamethasone. No ICANS was observed on study. Excellent CAR engraftment was observed and 9/9 patients were in CMR by 18FDG PET-CT post-treatment. At a median of 6.1 months (range 4.0-8.1m), 8/9 patients were disease free at last follow-up. One patient died in CMR at month 5.6 of COVID-19. CONCLUSION AUTO1 has a tolerable safety profile in adult patients with r/r B-NHL despite high disease burden. Early data shows 100% complete remission rates and excellent CAR engraftment/expansion. Additional MCL, CLL and DLBCL patients, updated data and longer follow up will be presented. Disclosures Roddie: Celgene: Consultancy, Speakers Bureau; Novartis: Consultancy; Gilead: Consultancy, Speakers Bureau. Hartley: Astra Zeneca: Ended employment in the past 24 months; ADC Therapeutics: Consultancy, Current equity holder in publicly-traded company, Current holder of stock options in a privately-held company. Farzaneh: Autolus: Consultancy, Current equity holder in publicly-traded company. Lowdell: Autolus: Consultancy, Current equity holder in publicly-traded company. Linch: Autolus: Consultancy, Current equity holder in publicly-traded company. Pule: Autolus: Current Employment, Current equity holder in publicly-traded company. Peggs: Autolus: Consultancy, Current equity holder in publicly-traded company.

Introduction The clinical manifestations of COVID-19 infection in recipients of allogeneic hematopoietic stem cell transplantation (HSCT) have been reported in multiple retrospective cohorts of patients, but there have been no prospective studies to date. Previous studies report that HSCT recipients are at higher risk, with cumulative incidence of death between 17-35%. Although an excessive pro-inflammatory viral response has been documented in the general population, its role in the immune incompetent HSCT setting has not been documented. We present a combined prospective and retrospective national study run through the UK IMPACT trial network to characterize the clinical and immunological features of COVID-19 infection in 96 adult and pediatric recipients of HSCT in the United Kingdom. Methods HSCT recipients of any age and transplanted for any indication, with an RT-PCR-proven COVID-19 infection, were eligible for this study. Patients within 72 hours of COVID-19 diagnosis, who had not received cytokine-targeted treatment, were recruited to a prospective cohort. All other patients were eligible for a retrospective cohort. Prospective patients provided blood samples within 72 hours of COVID-19 diagnosis, and again within 72 hours of clinical deterioration (defined as requirement for oxygen administration) if applicable. Follow-up data were collected on patients 30 and 100 days after COVID-19 diagnosis. Results 100 patients were recruited from 16 sites across the UK between May 2020-June 2021, comprising 12 in a prospective cohort and 88 recruited retrospectively. 96 patients were evaluable, as 4 proved ineligible post-registration. Patients were diagnosed with COVID-19 at a median of 11 months after HSCT. Patient/HSCT characteristics are shown Table 1. The most common symptoms associated with the onset of COVID-19 were fever in 8 prospective (73%) and 35 (41%) retrospective patients, followed by cough in 5 (45%) prospective and 35 (41%) retrospective patients and dyspnea in 4 (36%) prospective and 16 (19%) retrospective patients. 8 (73%) prospective and 40 (47%) retrospective patients were actively immunosuppressed at the time of COVID-19 infection. 16% of the patients had moderate/severe disease at baseline. At day 30 (±2 days) after COVID-19 diagnosis, 2 prospective and 8 retrospective patients continued to demonstrate SARS-CoV-2 positivity on respiratory PCR testing. The median time to viral clearance was 40 (IQR 17-78) days for the prospective and 34 (IQR 15-70) days for the retrospective cohort. Prolonged (more than 14 days) neutropenia was reported in 4 (5%) patients in the retrospective cohort, prolonged thrombocytopenia in 2 (18%) prospective and 11 (13%) retrospective patients. 1 retrospective patient developed secondary hemophagocytic lymphohistiocytosis, and graft rejection was reported in 1 (1%) retrospective patient, within 30 days of COVID-19 diagnosis. In the prospective cohort, 3 (27%) patients died, all by day 30, and all due to COVID-19. In the retrospective cohort, 13 (17%) patients died by day 30, rising to 18 (21%) by day 100, 61% of deaths were attributed to COVID-19. Lower baseline platelets (p=0.013, Mann-Whitney U test), lymphocytes (p=0.012), albumin (p=0.028), and higher baseline CRP (p=0.007), were seen in patients who died following COVID-19 diagnosis. Additionally, exploratory univariate logistic regression of the retrospective cohort found mortality at day 100 to be associated with increased age at diagnosis (OR 1.04, 95% CI 1.01-1.08, p=0.04), and no requirement compared with requirement for invasive ventilation (OR 0.02, 95% CI 0.00-0.16, p=0.001). The 11 prospective patients showed normal levels of interleukin (IL)-2, -4, -10, interferon gamma and tumor necrosis factor alpha at COVID-19 presentation. IL-6 was minimally raised (up to 127 pg/ml, nv Conclusion Our study confirms a significant mortality rate in patients affected by COVID-19 post HSCT and confirms age as well as requirement for invasive ventilation to be independent risk factors associated with death at day 100. Baseline laboratory data at disease presentation can identify patients at higher risk of COVID-19 related death. In the prospective cohort of our study, pathophysiology of the viral disease did not seem related to cytokine storm-mediated inflammation. Figure 1 Figure 1. Disclosures Protheroe: Jazz Pharmaceuticals: Honoraria; Astellas: Honoraria; Kite Gilead: Honoraria. Peggs: Autolus: Consultancy, Current equity holder in publicly-traded company. Craddock: Novartis Pharmaceuticals: Other: Advisory Board ; Celgene/BMS: Membership on an entity's Board of Directors or advisory committees, Research Funding. Nicholson: BMS/Celgene: Consultancy; Kite, a Gilead Company: Other: Conference fees, Speakers Bureau; Novartis: Consultancy, Other: Conference fees; Pfizer: Consultancy. Amrolia: ADC Therapeutics: Other: Named inventor on a patent which is being transferred to ADCT.; Autolus: Patents & Royalties.