Relapsed/refractory T-cell acute lymphoblastic leukemia (ALL; T-ALL)/lymphoma (LBL) represent a significant unmet medical need. WU-CART-007 is a CD7-targeting, allogeneic, fratricide-resistant chimeric antigen receptor T-cell product generated from healthy donor T cells. WU-CART-007 was evaluated in a phase 1/2 study with a 3+3 dose-escalation design followed by cohort expansion in relapsed/refractory T-ALL/LBL. Patients received 1 infusion of WU-CART-007 after standard or enhanced lymphodepleting chemotherapy. The primary objectives, to characterize safety and assess the composite complete remission rate, were met. Of 28 patients enrolled, 13 received the recommended phase 2 dose (RP2D) of 900 × 106 cells of WU-CART-007 with enhanced lymphodepletion. The most common treatment-related adverse event was cytokine release syndrome (88.5%; 19.2% grade 3-4). Two grade 1 immune effector cell–associated neurotoxicity syndrome events (7.7%) and 1 grade 2 acute graft-versus-host disease event occurred (3.8%). One grade 2 immune effector cell–associated hemophagocytic lymphohistiocytosis–like syndrome was observed. Among the 11 patients evaluable for response at the RP2D who received enhanced lymphodepleting chemotherapy, the overall response rate was 90.9%, and the composite complete remission rate was 72.7%. WU-CART-007 at the RP2D demonstrated a high response rate in patients with relapsed/refractory T-ALL/LBL and has the potential to provide a new treatment option. This trial was registered at www.ClinicalTrials.gov as #NCT04984356.

Antithymocyte globulin (ATG) is used in pediatric allogeneic hematopoietic cell transplantation (HCT) to prevent graft-versus-host disease (GVHD) and graft failure (GF). Poor T-cell recovery, associated with increased mortality, is the main toxicity of ATG. Model-based precision dosing of ATG (MBD-ATG) minimizes toxicity while maintaining efficacy. We report updated results of the single-arm phase 2 PARACHUTE trial investigating MBD-ATG, combined with real-world experience using identical MBD-ATG. Consecutive patients receiving a first T-cell–replete HCT for any indication were evaluated. Results were compared with historical patients receiving conventional fixed ATG dosing (FIX-ATG). Primary outcome was overall survival (OS). The MBD-ATG group consisted of 214 patients (58 trial patients; 156 real-world patients); 100 patients received FIX-ATG. MBD-ATG led to superior OS compared with FIX-ATG (hazard ratio [HR] for death, 0.56; 95% confidence interval [CI], 0.34-0.93; P = .026), and lower treatment-related mortality (TRM; HR, 0.51; 95% CI, 0.29-0.92; P = .025). Successful T-cell reconstitution (>0.05 × 109/L CD4+ T cells twice within 100 after HCT) was improved in MBD-ATG vs FIX-ATG (87% ± 2% vs 47% ± 5%; P < .0001). The improved T-cell reconstitution led to lower TRM (HR, 0.19; 95% CI, 0.09-0.36; P < .0001). Incidence of grade 2-4 acute GVHD was comparable, whereas chronic GVHD (HR, 0.35; 95% CI, 0.17-0.72; P = .004) and GF (HR, 0.36; 95% CI, 0.13-0.97; P = .044) were both less frequent in MBD-ATG compared with FIX-ATG. MBD-ATG results in improved OS and reduced TRM, while reducing chronic GVHD and GF. This easy-to-implement approach improves outcomes after pediatric HCT, confirmatory studies are needed. The PARACHUTE trial is registered with the Dutch Trial Register as #NL4836.

Immunotherapeutic agents may be an attractive option to further improve outcomes and to reduce treatment-related toxicity for pediatric AML. While improvements in outcome have been observed with immunotherapy in many cancer types, immunotherapy development and implementation into patient care for both adult and pediatric AML has been hampered by an incomplete understanding of the bone marrow environment and a paucity of tumor-specific antigens. Since only a minority of patients respond in most immunotherapy trials across different cancer types, it will be crucial to understand which children with AML are likely to respond to or may benefit from immunotherapies. Immune cell profiling efforts hold promise to answer this question, as illustrated by the development of predictive scores in solid cancers. Such information on the number and phenotype of immune cells during current treatment regimens will be pivotal to generate hypotheses on how and when to intervene with immunotherapy in pediatric AML. In this review, we discuss the current understanding of the number and phenotype of immune cells in the bone marrow in pediatric AML, ongoing immunotherapy trials and how comprehensive immune profiling efforts may pave the way for successful clinical trials (and, ultimately, implementation into patient care).