Chimeric antigen receptor T-cell infusion for large B-cell lymphoma in complete remission: a center for international blood and marrow transplant research analysis.

CD19 CAR T-cell (CAR-T) therapy is commonly administered to patients with relapsed or refractory large B-cell lymphomas (LBCL), but salvage or bridging therapy can sometimes lead to a complete response (CR) prior to infusion. Limited studies have assessed the outcomes of patients infused in CR. A total of 134 patients with LBCL in CR prior to CAR-T infusion were identified from the CIBMTR registry, with median prior lines of therapy of 3 (range 2-9). At two years post-infusion, the probability of progression-free survival was 43.5% (95% CI 34.4-52.8) and the probability of overall survival was 63.8% (95% CI 54.4-72.6). The cumulative incidence rates of non-relapse mortality and relapse/progression at two years were 9.2% (95% CI 4.5-15.4) and 47.3% (95% CI 38.2-56.6), respectively. The rate of grade 3 or higher cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) were 2.2% and 8.2%, respectively. In summary, CAR-T in heavily pretreated patients with LBCL who are in CR following two or more lines of prior therapy demonstrate that a subset of patients may remain free of progression at two years. Additionally, the toxicity profile was impressive with very low rates of grade 3 CRS and ICANS.

ASTCT Committee on Practice Guidelines Survey on Evaluation and Management of Relapsed/Refractory Multiple Myeloma after Failure of Chimeric Antigen Receptor T Cell Therapy.

Chimeric antigen receptor T cell therapy (CAR-T) has revolutionized the management of relapsed and/or refractory multiple myeloma (RRMM). However, CAR-T treatment failure is not uncommon and remains a major therapeutic challenge. There is substantial variability across transplantation and cellular therapy programs in assessing and managing post-CAR-T failures in patients with RRMM. The American Society for Transplantation and Cellular Therapy (ASTCT) Committee on Practice Guidelines conducted an online cross-sectional survey between September 2023 and December 2023 to determine myeloma, transplantation, and cellular therapy physicians' practice patterns for the surveillance, diagnosis, and management of CAR-T failure. The intent of this survey was to understand clinical practice patterns and identify areas for further investigation. Email surveys were sent to 1311 ASTCT physician members, of whom 80 (6.1%) completed the survey. The respondents were 58% white and 66% male, and 51% had >10 years of clinical experience. Most (89%) respondents were affiliated with a university/teaching center, and 56% had a myeloma-focused transplantation and/or cellular therapy practice. Post-CAR-T surveillance laboratory studies were commonly done every 4 weeks, and surveillance bone marrow biopsies and/or imaging surveillance were most commonly done at 3 months. Sixty-four percent of the respondents would often or always consider biopsy or imaging to confirm relapse. The most popular post-CAR-T failure rescue regimen was GPRC5D-directed immunotherapy (30%) for relapses occurring ≤3 months and BCMA-directed bispecific therapies (32.5%) for relapse at >3 months. Forty-one percent of the respondents endorsed post-CAR-T prolonged cytopenia as being "often" or "always" a barrier to next-line therapy; 53% had offered stem cell boost as a mitigation approach. Substantial across-center variation in practice patterns raises the need for collaborative studies and expert clinical recommendations to describe best practices for post-CAR-T disease surveillance, optimal workup for treatment failure, and choice of rescue therapies.

Gilteritinib as Post-Transplant Maintenance for AML With Internal Tandem Duplication Mutation of FLT3.

PURPOSE: Allogeneic hematopoietic cell transplantation (HCT) improves outcomes for patients with AML harboring an internal tandem duplication mutation of FLT3 (FLT3-ITD) AML. These patients are routinely treated with a FLT3 inhibitor after HCT, but there is limited evidence to support this. Accordingly, we conducted a randomized trial of post-HCT maintenance with the FLT3 inhibitor gilteritinib (ClinicalTrials.gov identifier: NCT02997202) to determine if all such patients benefit or if detection of measurable residual disease (MRD) could identify those who might benefit. METHODS: Adults with FLT3-ITD AML in first remission underwent HCT and were randomly assigned to placebo or 120 mg once daily gilteritinib for 24 months after HCT. The primary end point was relapse-free survival (RFS). Secondary end points included overall survival (OS) and the effect of MRD pre- and post-HCT on RFS and OS. RESULTS: Three hundred fifty-six participants were randomly assigned post-HCT to receive gilteritinib or placebo. Although RFS was higher in the gilteritinib arm, the difference was not statistically significant (hazard ratio [HR], 0.679 [95% CI, 0.459 to 1.005]; two-sided P = .0518). However, 50.5% of participants had MRD detectable pre- or post-HCT, and, in a prespecified subgroup analysis, gilteritinib was beneficial in this population (HR, 0.515 [95% CI, 0.316 to 0.838]; P = .0065). Those without detectable MRD showed no benefit (HR, 1.213 [95% CI, 0.616 to 2.387]; P = .575). CONCLUSION: Although the overall improvement in RFS was not statistically significant, RFS was higher for participants with detectable FLT3-ITD MRD pre- or post-HCT who received gilteritinib treatment. To our knowledge, these data are among the first to support the effectiveness of MRD-based post-HCT therapy.

Autologous stem cell boost improves persistent immune effector cell associated hematotoxicity following BCMA directed chimeric antigen receptor T (CAR T) cell therapy in multiple myeloma.

Persistent Immune Effector Cell Associated Hematotoxicity (ICAHT) is a significant side effect of BCMA CAR T-Cell therapy in patients with relapsed multiple myeloma (MM). The use of stem cell boosts in ICAHT has been described, however studies have been limited by small patient numbers and short follow up. Herein, we report on our multi-institutional experience of ICAHT, defined by an absolute neutrophil count (ANC) of ≤ 1000, thrombocytopenia with a platelet count ≤ 50,000 or/and anemia as hemoglobin (hgb) ≤9 g/dL, in patients who received BCMA CAR T therapy, and the effects of subsequent stem cell boost on hematopoietic reconstitution and clinical outcome. In this study, ICAHT was observed in 60% (n = 61/101) of patients at D + 21, and risk factors for its development included history of a prior ASCT, higher number of prior lines of therapy, a decreased platelet count prior to lymphodepletion and history of ICANS. 28% of patients with ICAHT received a stem cell boost at a median of 116 days due to profound and prolonged cytopenias often requiring ongoing transfusion support. Stem cell boost significantly improved cytopenias at 3 and 6 months follow up without any adverse effects on PFS and OS, underscoring the safety of this procedure.

In relapsed or refractory diffuse large B-cell lymphoma, CD19 expression by immunohistochemistry alone is not a predictor of response to loncastuximab tesirine.

CD19-targeting treatments have shown promise in relapsed/refractory (R/R) diffuse large B-cell lymphoma (DLBCL). Loncastuximab tesirine (loncastuximab tesirine-lpyl [Lonca]) is a CD19-targeting antibody-drug conjugate indicated for R/R DLBCL after at least two systemic treatments. CD19 expression was evaluated in patients receiving Lonca in the LOTIS-2 clinical trial with available tissue samples obtained after last systemic therapy/before Lonca treatment. Lonca cytotoxicity was evaluated in a panel of six lymphoma cell lines with various CD19 expression levels. Quantitative systems pharmacology (QSP) modelling was used to predict Lonca responses. Lonca responses were seen in patients across all CD19 expression levels, including patients with low/no detectable CD19 expression and H-scores at baseline. Similarly, Lonca induced cytotoxicity in cell lines with different levels of CD19 expression, including one with very low expression. QSP modelling predicted that CD19 expression by immunohistochemistry alone does not predict Lonca response, whereas inclusion of CD19 surface density improved response prediction. Virtual patients responded to Lonca with estimated CD19 as low as 1000 molecules/cell of CD19, normally below the immunohistochemistry detection level. We found Lonca is an effective treatment for R/R DLBCL regardless of CD19 expression by immunohistochemistry. These results provide the basis for future studies addressing CD19-targeted agent sequencing.

SARS-CoV-2 vaccination in the first year after hematopoietic cell transplant or chimeric antigen receptor T cell therapy: A prospective, multicenter, observational study (BMT CTN 2101).

Background: The optimal timing of vaccination with SARS-CoV-2 vaccines after cellular therapy is incompletely understood. Objective: To describe humoral and cellular responses after SARS-CoV-2 vaccination initiated <4 months versus 4-12 months after cellular therapy. Design: Multicenter prospective observational study. Setting: 34 centers in the United States. Participants: 466 allogeneic hematopoietic cell transplant (HCT; n=231), autologous HCT (n=170), or chimeric antigen receptor T cell (CAR-T cell) therapy (n=65) recipients enrolled between April 2021 and June 2022. Interventions: SARS-CoV-2 vaccination as part of routine care. Measurements: We obtained blood prior to and after vaccinations at up to five time points and tested for SARS-CoV-2 spike (anti-S) IgG in all participants and neutralizing antibodies for Wuhan D614G, Delta B.1.617.2, and Omicron B.1.1.529 strains, as well as SARS-CoV-2-specific T cell receptors (TCRs), in a subgroup. Results: Anti-S IgG and neutralizing antibody responses increased with vaccination in HCT recipients irrespective of vaccine initiation timing but were unchanged in CAR-T cell recipients initiating vaccines within 4 months. Anti-S IgG ≥2,500 U/mL was correlated with high neutralizing antibody titers and attained by the last time point in 70%, 69%, and 34% of allogeneic HCT, autologous HCT, and CAR-T cell recipients, respectively. SARS-CoV-2-specific T cell responses were attained in 57%, 83%, and 58%, respectively. Humoral and cellular responses did not significantly differ among participants initiating vaccinations <4 months vs 4-12 months after cellular therapy. Pre-cellular therapy SARS-CoV-2 infection or vaccination were key predictors of post-cellular therapy anti-S IgG levels. Limitations: The majority of participants were adults and received mRNA vaccines. Conclusions: These data support starting mRNA SARS-CoV-2 vaccination three to four months after allogeneic HCT, autologous HCT, and CAR-T cell therapy. Funding: National Marrow Donor Program, Leukemia and Lymphoma Society, Multiple Myeloma Research Foundation, Novartis, LabCorp, American Society for Transplantation and Cellular Therapy, Adaptive Biotechnologies, and the National Institutes of Health.

Immunoglobulin High Throughput Sequencing (Ig-HTS) Minimal Residual Disease (MRD) Analysis is an Effective Surveillance Tool in Patients With Mantle Cell Lymphoma.

INTRODUCTION: Mantle cell lymphoma (MCL) accounts for 4% to 6% of B-cell non-Hodgkin lymphoma with historically poor outcomes. With the advent of intensive first-line, targeted, and cellular therapies, outcomes have improved, and initial remission can be 8 to 10 years or longer. As patients experience longer remissions, this raises the question of the optimal surveillance modality. Peripheral blood minimal residual disease (MRD) analysis offers a potential alternative to surveillance imaging that is sensitive, less costly, and eliminates the risk of radiation exposure. MATERIALS AND METHODS: The clonoSEQ assay (Adaptive Biotechnologies) is an FDA-cleared commercially available Ig-HTS MRD assay with a sensitivity of 1 cell in 1,000,000. We performed a retrospective analysis of 34 patients from 2015 to 2021, who underwent MRD testing after achieving remission with first-line therapy. RESULTS: With a median follow-up of 6.5 years, 10-year progression free survival (PFS) was 60% and 10-year overall survival was 92% of the entire cohort. Among 12 patients who sustained a radiographic relapse, peripheral blood became MRD+ either at or prior to the time of relapse in 11 patients (92%). The first MRD+ test had a lead time of 0 to 24 months (median 34 days) prior to radiographic relapse. Only 1 patient had a MRD- result while being found to have progressive disease on imaging. Among 22 patients who sustained continuous clinical remission, 21 have remained MRD-. Several patients were able to enjoy 2 to 4-year intervals without surveillance imaging. CONCLUSIONS: Our data suggest that the clonoSEQ MRD assay is an effective surveillance tool for MCL patients following first-line therapy and is predictive of relapse prior to imaging.

Severity and organ distribution of chronic graft-versus-host disease with posttransplant cyclophosphamide-based versus methotrexate/calcineurin inhibitor-based allogeneic hematopoietic cell transplantation.

The reduced risk of chronic graft-versus-host-disease (GVHD) with posttransplant cyclophosphamide (ptCy) in the setting of haploidentical related donor and more recently, with HLA-matched related and matched and mismatched unrelated donor allogeneic transplantation has been established. There is, however, paucity of data to show if ptCy impacts chronic GVHD pathogenesis, its phenotype and evolution after HCT regardless of the donor status. We examined the differences in chronic GVHD incidence and presentation in 314 consecutive patients after receiving their first allogeneic transplantation (HCT) using ptCy-based GVHD prophylaxis (ptCy-HCT; n = 120; including 95 with haploidentical related donor) versus conventional calcineurin inhibitor-based prophylaxis (CNI-MUD; n = 194) between 2012 and 2019. The 1-year cumulative incidence of all-grade chronic GVHD and moderate/severe chronic GVHD was 24% and 12%, respectively, after ptCy-HCT and 40% and 23% in the CNI-MUD recipients (p = 0.0003 and 0.007). Multivariable analysis confirmed that use of CNI-based GVHD prophylaxis and peripheral blood stem cell graft as the risk factors for chronic GVHD. The cumulative incidence of visceral (involving ≥1 of the following organs: liver, lungs, gastrointestinal tract, serous membranes) chronic GVHD was significantly higher with CNI-MUD vs. ptCy-HCT (27% vs. 15% at 1 year, p = 0.009). The incidence of moderate/severe visceral chronic GVHD was 20% in CNI-MUD group vs. 7.7% in the ptCy-HCT group at 1 year (p = 0.002). In addition, significantly fewer ptCy-HCT recipients developed severe chronic GVHD in ≥3 organs (0.8%) vs. 8.8% in the CNI-MUD group at 1-year posttransplant (p = 0.004). There was no significant different in relapse, non-relapse mortality, and relapse-free and overall survival between the two groups. Further investigation is needed to confirm that reduced risk and severity of chronic GVHD, less visceral organ distribution with ptCy-HCT leads to improved quality of life.

A phase 1-2 trial of DA-EPOCH-R plus ixazomib for MYC-aberrant lymphoid malignancies: the DACIPHOR regimen.

ABSTRACT: MYC-aberrant non-Hodgkin lymphoma (NHL) is associated with poor outcomes with conventional chemotherapy. Ixazomib is an orally bioavailable proteasome inhibitor that targets drivers of MYC expression and has demonstrated preclinical activity in aggressive MYC-aberrant NHL. We conducted a phase 1/2 study evaluating the safety and efficacy of DA-EPOCH-R with adjunctive ixazomib in aggressive MYC-aberrant NHL. For induction, patients received 6 cycles of DA-EPOCH-R with ixazomib administered twice per 21-day cycle; responders continued weekly ixazomib maintenance for up to 1 year. Primary objectives were to determine the maximum tolerated dose in phase 1 and efficacy of DA-EPOCH-R with ixazomib as measured by 12-month progression-free survival (PFS) rate in phase 2. Thirty-six patients were evaluable for response. Median age was 63 years (range, 31-77) and 44% had double-hit lymphoma (DHL)/triple-hit lymphoma (THL). In phase 1, 3 mg of ixazomib was established as recommended phase 2 dose. Twenty-nine (76.3%) patients completed 6 cycles of DA-EPOCH-R and 25 (65.8%) underwent dose escalations. The ORR after induction was 97% (95% confidence interval, 81-100) with a CR rate of 69%. At median follow-up of 18.8 months, the 12-month PFS and overall survival (OS) rates were 78% and 86%, respectively. For DHL/THL vs dual expressor lymphomas (DEL), 12-month PFS rates were 53% vs 95% and 12-month OS rates were 65% vs 100%, respectively. Grade ≥3 toxicities were predominantly hematologic. Twenty-seven (75%) of patients experienced neuropathy, nearly all low-grade. DA-EPOCH-R induction with adjunctive ixazomib is feasible and appears effective in patients with DEL. This trial was registered at www.clinicaltrials.gov as #NCT02481310.

Chimeric Antigen Receptor T-Cell Therapy in the Outpatient Setting: An Expert Panel Opinion from the American Society for Transplantation and Cellular Therapy.

The first series of chimeric antigen receptor T (CAR-T) cell therapy products were approved in 2017 to 2019 and have shown remarkable efficacy in both clinical trials and the real-world setting, but at the cost of prolonged patient hospitalization. As the toxicity management protocols were refined, the concept of cellular therapy administered in the outpatient setting gained steam, and single institutions began to perform certain aspects of CAR-T monitoring in the outpatient setting for select patients. However, there are many considerations for a successful outpatient program. In anticipation of increasing use of CAR-T-cell therapy in the outpatient setting as a mechanism to overcome frequent hospital bed shortages and high cost of inpatient care, the American Society for Transplantation and Cellular Therapy convened a group of experts in hematology, oncology, and cellular therapy to provide a comprehensive review of the existing publications on outpatient CAR-T cell therapy, discuss selected ongoing clinical trials of outpatient CAR-T, and describe strategies to optimize safety without compromising efficacy for patients treated and monitored in the outpatient setting.

Loncastuximab tesirine in relapsed/refractory diffuse large B-cell lymphoma: long-term efficacy and safety from the phase II LOTIS-2 study.

Therapies that demonstrate durable, long-term responses with manageable safety and tolerability are needed for patients with relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL). Loncastuximab tesirine (loncastuximab tesirine-lpyl [Lonca]), an anti-CD19 antibody conjugated to a potent pyrrolobenzodiazepine dimer, demonstrated single-agent antitumor activity in the pivotal phase II LOTIS-2 study in heavily pretreated patients with R/R DLBCL. Here we present updated efficacy and safety analyses from LOTIS-2, performed for all patients and in subsets of patients with a complete response (CR), including patients with CR who were event-free (no progressive disease or death) for ≥1 year and ≥2 years from cycle 1, day 1 of treatment. Lonca was administered every 3 weeks (0.15 mg/kg for 2 cycles; 0.075 mg/kg for subsequent cycles). As of the final data cutoff (September 15, 2022; median follow-up: 7.8 months [range, 0.3-42.6]), 70 of 145 (48.3%) patients achieved an overall response. Thirty-six (24.8%) patients achieved CR, of which 16 (44%) and 11 (31%) were event-free for ≥1 year and ≥2 years, respectively. In the all-treated population, the median overall survival was 9.5 months; the median progression-free survival was 4.9 months. Among patients with CR, median overall survival and progression-free survival were not reached, with 24-month overall and progression-free survival rates of 68.2% (95% CI: 50.0-81.0) and 72.5% (95% CI: 48.2-86.8), respectively. No new safety concerns were detected. With additional follow-up, Lonca continued to demonstrate durable, long-term responses with manageable safety and tolerability in patients with CR (clinicaltrials gov. Identifier: NCT03589469).

Lisocabtagene maraleucel for second-line relapsed or refractory large B-cell lymphoma: patient-reported outcomes from the PILOT study.

In the single-arm, open-label, multicenter, phase II PILOT study, second-line treatment with the chimeric antigen receptor (CAR) T-cell therapy lisocabtagene maraleucel (liso-cel) in patients with relapsed or refractory (R/R) large B-cell lymphoma (LBCL) for whom hematopoietic stem cell transplantation (HSCT) was not intended resulted in high response rates, durable responses, and a safety profile consistent with previous reports. Here, we analyzed changes in health-related quality of life (HRQOL) in patients who received liso-cel in PILOT. Patients received liso-cel, an autologous, CD19-directed, 4-1BB CAR T-cell product administered at equal target doses of CD8+ and CD4+ CAR+ T cells, for a total target dose of 100×106 CAR+ T cells. HRQOL, a secondary endpoint of PILOT, was assessed as prespecified using three patient-reported outcome instruments (EORTC QLQ-C30; FACT-LymS; EQ-5D-5L). Evaluable datasets for the EORTC QLQ-C30, FACT-LymS, and EQ-5D-5L health utility index, and visual analog scale (EQ-VAS) included 56 (92%), 49 (80%), 55 (90%), and 54 (89%) patients, respectively. Clinically meaningful improvement was achieved across most post-treatment visits for EORTC QLQ-C30 fatigue and FACT-LymS. Overall mean changes from baseline through day 545 showed significant improvements in EORTC QLQ-C30 fatigue, pain, and appetite loss, FACT-LymS, and EQ VAS. In within-patient analyses, clinically meaningful improvements or maintenance in scores were observed in most patients at days 90, 180, 270, and 365. HRQOL was maintained or improved in patients who received liso-cel as second-line therapy in PILOT. These findings support liso-cel as a preferred second-line treatment in patients with R/R LBCL not intended for HSCT (clinicaltrials gov. Identifier: NCT03483103).

PET/CT Biomarkers Enable Risk Stratification of Patients with Relapsed/Refractory Diffuse Large B-cell Lymphoma Enrolled in the LOTIS-2 Clinical Trial.

PURPOSE: Significant progress has occurred in developing quantitative PET/CT biomarkers in diffuse large B-cell lymphoma (DLBCL). Total metabolic tumor volume (MTV) is the most extensively studied, enabling assessment of FDG-avid tumor burden associated with outcomes. However, prior studies evaluated the outcome of cytotoxic chemotherapy or chimeric antigen receptor T-cell therapy without data on recently approved FDA agents. Therefore, we aimed to assess the prognosis of PET/CT biomarkers in patients treated with loncastuximab tesirine. EXPERIMENTAL DESIGN: We centrally reviewed screening PET/CT scans of patients with relapsed/refractory DLBCL enrolled in the LOTIS-2 (NCT03589469) study. MTV was obtained by computing individual volumes using the SUV ≥4.0 threshold. Other PET/CT metrics, clinical factors, and the International Metabolic Prognostic Index (IMPI) were evaluated. Logistic regression was used to assess the association between biomarkers and treatment response. Cox regression was used to determine the effect of biomarkers on time-to-event outcomes. We estimated biomarker prediction as continuous and binary variables defined by cutoff points. RESULTS: Across 138 patients included in this study, MTV with a cutoff point of 96 mL was the biomarker associated with the highest predictive performance in univariable and multivariable models to predict failure to achieve complete metabolic response (OR, 5.42; P = 0.002), progression-free survival (HR, 2.68; P = 0.002), and overall survival (HR, 3.09; P < 0.0001). IMPI demonstrated an appropriate performance, however, not better than MTV alone. CONCLUSIONS: Pretreatment MTV demonstrated robust risk stratification, with those patients demonstrating high MTV achieving lower responses and survival to loncastuximab tesirine in relapsed/refractory DLBCL.

Chimeric antigen receptor and bispecific T-cell engager therapies in multiple myeloma patients with prior allogeneic transplantation.

Chimeric antigen receptor T-cell (CAR-T) therapy and bispecific T-cell engagers (BsAb) have emerged as promising immunotherapeutic modalities in patients with relapsed and/or refractory multiple myeloma (RRMM). However, there is limited data on the safety and efficacy of CAR-T and BsAb therapies in MM patients with a prior history of allogeneic transplantation (allo-HCT). Thirty-three MM patients with prior allo-HCT received CAR-T (n = 24) or BsAb (n = 9) therapy. CAR-T therapy demonstrated an ORR of 92% (67% ≥ CR), and 73% were MRD negative. BsAb therapy resulted in an ORR of 44% (44% ≥ CR) and 44% MRD negative. Safety analysis showed grade ≥3 AEs in 92% of CAR-T and 56% of BsAb patients. Cytokine release syndrome (CRS) occurred in 83% of CAR-T and 78% of BsAb recipients, while immune effector cell-associated neurotoxicity syndrome (ICANS) was observed in three CAR-T patients. Infections of grade ≥3 were reported in 50% of CAR-T and 44% of BsAb recipients. No exacerbation of graft-versus-host disease occurred except in one BsAb recipient. CAR-T and BsAb therapies appear to be feasible, safe and provide deep and durable responses in MM patients with prior allo-HCT.

Results from a Phase 1 Study of ACTR707 in Combination with Rituximab in Patients with Relapsed or Refractory CD20+ B Cell Lymphoma.

The antibody-coupled T cell receptor (ACTR) platform is an autologous engineered T cell therapy combining the cell-killing ability of T cells and the tumor-targeting ability of coadministered antibodies. Activation of the T cell product ACTR707 is dependent on the engagement of antibody bound to target cells via the CD16 domain of the chimeric receptor (CD16V-CD28-CD3ζ). ACTR707 in combination with the anti-CD20 monoclonal antibody rituximab was evaluated in the ATTCK-20-03 study, a multisite, single-arm, open-label phase I trial in B cell non-Hodgkin lymphoma (NHL). The primary objectives of this study were to evaluate the safety of the combination of ACTR707 and rituximab and to determine a recommended phase 2 dose (RP2D). Secondary objectives included evaluation of antitumor activity and ACTR T cell persistence. The study design included an ACTR707 cell dose escalation phase and an expansion phase at the RP2D. Escalating dose levels of ACTR707 in combination with rituximab were explored in 5 dose cohorts, with 25 subjects receiving study treatment. Subjects received lymphodepleting chemotherapy (cyclophosphamide 400 mg/m2/day and fludarabine 30 mg/m2/day) for 3 days, followed by rituximab 375 mg/m2 and, 24 to 48 hours later, a single dose of ACTR707. Additional doses of rituximab were administered every 3 weeks until disease progression, unacceptable toxicity, or investigator decision. Blood samples were collected at various time points to assess levels of rituximab, cytokines, inflammatory markers, and ACTR707 T cells. The overall response rate of ACTR707 plus rituximab was 56% (14 of 25) across all dose levels. Ten subjects (40.0%) achieved a complete response, with the longest duration of 586 days (range, 85 to 586 days), and 4 subjects (16.0%) experienced a partial response, with the longest duration of 130 days (range, 44 to 130 days). Only 1 case of cytokine release syndrome (grade 2) and no events of neurotoxicity were reported. There were no dose-limiting toxicities or events leading to death. ACTR707 plus rituximab resulted in only 1 adverse event (neutropenia), leading to study discontinuation of rituximab. The ATTCK-20-03 trial serves as proof of principle regarding the ACTR approach that potentially could be used with other antibodies targeting other markers in other malignancies. Although the ACTR707 program has been discontinued, these results may support other programs in the use of similar novel approaches of antibody-coupled T cell activation.

Efficacy of Multiple SARS-CoV-2 Vaccine Doses in Patients with B Cell Hematologic Malignancies Receiving Chimeric Antigen Receptor T Cell Therapy: A Contemporary Cohort Analysis.

The mortality due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) approaches 40% in recipients of chimeric antigen receptor (CAR) T cell therapy (CAR-T). The efficacy of repeated vaccine doses, including bivalent boosters, remains unknown. We examined the efficacy of repeated vaccine doses among CAR-T recipients who received at least 2 or more vaccine doses after T cell infusion. This single-center retrospective study included adults age >18 years receiving CAR-T for relapsed/refractory (R/R) B cell hematologic malignancies targeting CD19, BCMA, or CD19 and CD20 between September 2018 through March 2022 and were alive beyond 2021 to receive incremental SARS-CoV-2 vaccine doses with available seroconversion data. Multivariable analyses were performed using the design-adjusted Cox regression and logistic regression approaches with stratification. In multivariable analysis, seroconversion rates were significantly greater with a total of 4 or more vaccine doses (odds ratio [OR], 8.22; P = .008). CAR-T recipients with other B cell hematologic malignancies had significantly lower seroconversion rates and diminished Ab titers compared to those with R/R multiple myeloma (OR, .07; P = .003). One patient died due to COVID-19 in this vaccinated study cohort, accounting for a COVID-19-attributable mortality rate of 1.7%. The results provide baseline vaccine response data in a contemporary cohort including patients with diverse group of SARS-COV2 variants and support the latest Centers for Disease Control and Prevention guidelines for repeated vaccinations directed against the prevalent variant of concern.