Lymphodepletion – an essential but undervalued part of the chimeric antigen receptor T-cell therapy cycle

Abstract

Lymphodepletion (LD) or conditioning is an essential step in the application of currently used autologous and allogeneic chimeric antigen receptor T-cell (CAR-T) therapies as it maximizes engraftment, efficacy and long-term survival of CAR-T. Its main modes of action are the depletion and modulation of endogenous lymphocytes, conditioning of the microenvironment for improved CAR-T expansion and persistence, and reduction of tumor load. However, most LD regimens provide a broad and fairly unspecific suppression of T-cells as well as other hematopoietic cells, which can also lead to severe side effects, particularly infections. We reviewed 1271 published studies (2011-2023) with regard to current LD strategies for approved anti-CD19 CAR-T products for large B cell lymphoma (LBCL). Fludarabine (Flu) and cyclophosphamide (Cy) (alone or in combination) were the most commonly used agents. A large number of different schemes and combinations have been reported. In the respective schemes, doses of Flu and Cy (range 75-120mg/m2 and 750-1.500mg/m2) and wash out times (range 2-5 days) differed substantially. Furthermore, combinations with other agents such as bendamustine (benda), busulfan or alemtuzumab (for allogeneic CAR-T) were described. This diversity creates a challenge but also an opportunity to investigate the impact of LD on cellular kinetics and clinical outcomes of CAR-T. Only 21 studies explicitly investigated in more detail the influence of LD on safety and efficacy. As Flu and Cy can potentially impact both the in vivo activity and toxicity of CAR-T, a more detailed analysis of LD outcomes will be needed before we are able to fully assess its impact on different T-cell subsets within the CAR-T product. The T2EVOLVE consortium propagates a strategic investigation of LD protocols for the development of optimized conditioning regimens.

Distinct host preconditioning regimens differentially impact the antitumor potency of adoptively transferred Th17 cells

“…Patients with melanoma are often given a dual CTX and fludarabine lymphodepletion regimen prior to receiving ACT. 46 Thus, we tested how CTX+FLU would impact Th17 therapy. To evaluate this question, we preconditioned mice with either TBI, single-agent chemotherapy (FLU or CTX), or dual chemotherapy (FLU+CTX).…”

Current advances in experimental and computational approaches to enhance CAR T cell manufacturing protocols and improve clinical efficacy

“…Additionally, models can give insight into the impact of dosing and lymphodepletion regimens on resulting therapy kinetics ( Hardiansyah and Ng, 2019 ; Stein et al, 2019 ; Kimmel et al, 2021 ; Owens and Bozic, 2021 ). Parameters derived from these models can help elucidate kinetic rate constants for target cytolysis and CAR T cell proliferation ( Kimmel et al, 2020 ; Liu et al, 2021 ; Amini et al, 2022 ; Lickefett et al, 2023 ). These parameters can potentially be used in conjunction with functional assays and other variables to help evaluate future products.…”

Comparing 2-day vs 3-day flu-CY lymphodepleting regimens for CD19 CAR T-cell therapy in patients with non-hodgkin’s lymphoma

“…Chimeric antigen receptor (CAR) T-cell therapy that targets CD19 has shown efficacy in patients with relapsed and refractory large B-cell lymphoma (LBCL). Lymphodepleting chemotherapy (LDC) prior to cell infusion is critical to the adoptive cell therapy process, however there is relatively little prospective data dedicated to determining the optimal regimen ( 1 ). LDC can impact both short and long-term CAR T-cell efficacy by creating a favorable immune environment for in vivo product expansion and by promoting the formation of memory T-cells ( 2 , 3 ).…”

“…LDC can impact both short and long-term CAR T-cell efficacy by creating a favorable immune environment for in vivo product expansion and by promoting the formation of memory T-cells ( 2 , 3 ). A more favorable immune environment is created through several mechanisms including the activation and recruitment of innate immune cells, increased availability of the cytokine pool, and reduction in the number of immunoregulatory T-cells ( 1 ). Despite the importance of these factors, there is significant heterogeneity among the LDC regimens reported in the literature.…”

“…Despite the importance of these factors, there is significant heterogeneity among the LDC regimens reported in the literature. A recent review of 1271 publications on CAR T-cell therapy for LBCL found that fludarabine and cyclophosphamide were the most common drugs used, however, the cumulative dose varied from a total dose of 75–120 mg/m 2 for fludarabine and 750–1500 mg/m 2 for cyclophosphamide ( 1 ). The pivotal ZUMA-1 trial that led to the FDA approval of axicabtagene ciloleucel (axi-cel, Kite Pharma, Inc. Santa Monica, CA) in LBCL used fludarabine 30 mg/m 2 and cyclophosphamide 500 mg/m 2 for 3 days ( 4 ).…”