Allogeneic (allo) hematopoietic cell transplantation (HCT) is the only curative treatment option for patients suffering from chemotherapy-refractory or relapsed hematological malignancies. The occurrence of morbidity and mortality after allo-HCT is still high. This is partly correlated with the immunological recovery of the T cell subsets, of which the dynamics and relations to complications are still poorly understood. Detailed information on T cell subset recovery is crucial to provide tools for better prediction and modulation of adverse events. Here, we review the current knowledge regarding CD4+ and CD8+ T cells, γδ T cells, iNKT cells, Treg cells, MAIT cells and naive and memory T cell reconstitution, as well as their relations to outcome, considering different cell sources and immunosuppressive therapies. We conclude that the T cell subsets reconstitute in different ways and are associated with distinct adverse and beneficial events; however, adequate reconstitution of all the subsets is associated with better overall survival. Although the exact mechanisms involved in the reconstitution of each T cell subset and their associations with allo-HCT outcome need to be further elucidated, the data and suggestions presented here point towards the development of individualized approaches to improve their reconstitution. This includes the modulation of immunotherapeutic interventions based on more detailed immune monitoring, aiming to improve overall survival changes.
The addition of fludarabine to cyclophosphamide as lymphodepleting regimen prior to CD19 chimeric antigen receptor (CAR) T cell therapy significantly improved outcome in patients with relapsed/refractory (r/r) B cell acute lymphoblastic leukemia (B-ALL). Fludarabine exposure, previously shown to be highly variable when dosing is based on body surface area, is a predictor for survival in allogeneic hematopoietic cell transplantation. Hence, we hypothesized that an optimal exposure of fludarabine might be of clinical importance in CD19 CAR T cell treatment. We examined the effect of cumulative fludarabine exposure during lymphodepletion defined as concentration-time curve (AUC) on clinical outcome and lymphocyte kinetics. A retrospective analysis was conducted with data from 26 patients receiving tisagenlecleucel for r/r B-ALL. Exposure of fludarabine was shown to be a predictor for leukemia-free survival, B cell aplasia, and CD19-positive relapse following CAR T cell infusion. Minimal event probability was observed at a cumulative fludarabine AUCT0−∞ ≥14 mg*h/L and underexposure was defined as an AUCT0−∞ <14 mg*h/L. In the underexposed group, the median leukemia-free survival was 1.8 months and the occurrence of CD19-positive relapse within 1 year was 100%, which was higher compared to the group with an AUCT0−∞ ≥14 mg*h/L (12.9 months; p<.001 and 27.4%; p=.0001, respectively). Furthermore, the duration of B cell aplasia within 6 months was shorter in the underexposed group (77.3% versus 37.3%; p=.009). These results suggest that optimizing fludarabine exposure may have a relevant impact on leukemia-free survival following CAR T cell therapy, which needs to be validated in a prospective clinical trial.
Genomic studies of pediatric acute lymphoblastic leukemia (ALL) have shown remarkable heterogeneity in initial diagnosis, with multiple (sub)clones harboring lesions in relapse-associated genes. However, the clinical relevance of these subclonal alterations remains unclear. We assessed the clinical relevance and prognostic value of subclonal alterations in the relapse-associated genes IKZF1, CREBBP, KRAS, NRAS, PTPN11, TP53, NT5C2, and WHSC1 in 503 ALL cases. Using Molecular Inversion Probe sequencing and breakpoint-spanning PCR we reliably detected alterations below 1% allele frequency. We identified 660 genomic alterations in 285 diagnosis samples of which 495 (75%) were subclonal. RAS pathway mutations were common, particularly in minor subclones, and comparisons between RAS hotspot mutations revealed differences in their capacity to drive clonal expansion in ALL. We did not find an association of subclonal alterations with unfavorable outcome. Particularly for IKZF1, an established prognostic marker in ALL, all clonal but none of the subclonal alterations were preserved at relapse. We conclude that, for the genes tested, there is no basis to consider subclonal alterations detected at diagnosis for risk group stratification of ALL treatment.
The outcome of allogeneic hematopoietic cell transplantation (allo-HCT) largely depends on the development and management of graft-versus-host disease (GvHD), infections, and the occurrence of relapse of malignancies. Recent studies showed a lower incidence of chronic GvHD and severe acute GvHD in patients receiving naive T cell depleted grafts compared to patients receiving complete T cell depleted grafts. On the other hand, the incidence of acute GvHD in patients receiving cord blood grafts containing only naive T cells is rather low, while potent graft-versus-leukemia (GvL) responses have been observed. These data suggest the significance of naive T cells as both drivers and regulators of allogeneic reactions. The naive T cell pool was previously thought to be a quiescent, homogenous pool of antigen-inexperienced cells. However, recent studies showed important differences in phenotype, differentiation status, location, and function within the naive T cell population. Therefore, the adequate recovery of these seemingly innocent T cells might be relevant in the imminent allogeneic reactions after allo-HCT. Here, an extensive review on naive T cells and their contribution to the development of GvHD and GvL responses after allo-HCT is provided. In addition, strategies specifically directed to stimulate adequate reconstitution of naive T cells while reducing the risk of GvHD are discussed. A better understanding of the relation between naive T cells and alloreactivity after allo-HCT could provide opportunities to improve GvHD prevention, while maintaining GvL effects to lower relapse risk.
Allogeneic hematopoietic cell transplantation (HCT) is a potentially curative therapy for patients with a variety of malignant and non-malignant diseases. Despite its life-saving potential, HCT is associated with significant morbidity and mortality. Reciprocal interactions between hematopoietic stem cells (HSCs) and their surrounding bone marrow (BM) niche regulate HSC function during homeostatic hematopoiesis as well as regeneration. However, current pre-HCT conditioning regimens, which consist of high-dose chemotherapy and/or irradiation, cause substantial short- and long-term toxicity to the BM niche. This damage may negatively affect HSC function, impair hematopoietic regeneration after HCT and predispose to HCT-related morbidity and mortality. In this review, we summarize current knowledge on the cellular composition of the human BM niche after HCT. We describe how pre-HCT conditioning affects the cell types in the niche, including endothelial cells, mesenchymal stromal cells, osteoblasts, adipocytes, and neurons. Finally, we discuss therapeutic strategies to prevent or repair conditioning-induced niche damage, which may promote hematopoietic recovery and improve HCT outcome.
The addition of fludarabine to cyclophosphamide as lymphodepleting regimen prior to adoptive transfer of CD19 chimeric antigen receptor (CAR) T cells significantly improves CAR T cell expansion and correlates with longer B cell aplasia and a decreased probability of developing a CD19+ relapse (Gardner, 2017). Dosing of fludarabine is currently based on body surface area. We previously showed that this leads to a highly variable plasma exposure that correlates with clinical outcome after allogeneic hematopoietic cell transplantation (Langenhorst, 2019). We therefore hypothesized that optimal exposure of fludarabine might be of clinical importance in the CD19 CAR T setting. An observational cohort analysis was conducted with data from 26 consecutive patients receiving tisagenlecleucel as treatment for refractory/relapsed B cell acute lymphoblastic leukemia (B-ALL; table 1). Prior to CAR T cell infusion, patients received fludarabine on 4 consecutive days at a daily dosage of 30 mg/m 2 and cyclophosphamide on 2 consecutive days at a daily dosage of 500 mg/m 2. Fludarabine concentrations were measured longitudinally after fludarabine infusion using a liquid chromatography mass spectrometry method. The total exposure (Area Under the Curve (AUC 0−∞)) was subsequently determined using a fludarabine population pharmacokinetic model (Langenhorst, 2019). The study was performed in accordance with the Declaration of Helsinki. The primary outcome parameter was leukemia free survival, defined as the time between CAR19 T cell infusion and the moment of measurable leukemic blasts (>5% or >0.01% by two subsequent measurements). The effect of fludarabine on leukemia free survival and the secondary outcome measures CD19+ relapse and B cell aplasia were explored using martingale residuals and further identified by fitting univariable Cox Proportional Hazards models. In addition, Kaplan Meier and cumulative incidence curves were plotted and compared with log-rank tests. To compare CAR T cell numbers over time in peripheral blood, the AUCs were computed and compared between exposure groups with the Mann-Whitney test. Analyses were performed using R4.03 with packages pknca, survival and survminer. The fludarabine AUC 0−∞ was highly variable, resulting in a large range of 8.7-21.8 mg*h/L. Exposure of fludarabine was shown to be a predictor for leukemia free survival, B cell aplasia, and CD19+ relapse following CAR T cell infusion. Minimal event probability was observed at a cumulative fludarabine exposure ≥14 mg*h/L and underexposure was therefore defined as an AUC 0−∞ <14 mg*h/L. In the underexposed group, leukemia free survival was lower (p<0.001; Figure 1A) and the occurrence of CD19+ relapse was higher (p<0.0001; figure 1B) compared to the group with an AUC 0−∞ ≥14 mg*h/L. Furthermore, the duration of B cell aplasia was shorter (p=0.009) and the AUCs of CAR T cell numbers lower (p=0.03) in the underexposed group. No significant differences in baseline characteristics were present between the two exposure groups. To our knowledge, this is the first study describing the effect of fludarabine exposure on outcome in a cohort of paediatric and young adults receiving CD19 CAR T cell therapy as treatment for B-ALL. These preliminary results suggest that optimizing fludarabine exposure may have a relevant impact on leukemia free survival following CAR T cell therapy. However, it should be noted that multivariate regression models are needed to show consistency of the relationship between fludarabine exposure and outcome. The limited number of patients did not allow for inclusion of potential covariates that may influence clinical outcome into the analysis. Therefore, our results need to be confirmed in a larger cohort. In conclusion, clinical outcome in patients receiving CAR19 T cell therapy might be improved by the optimization of fludarabine exposure in the lymphodepleting regimen. LD and FC contributed equally to this study. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.