Murine precursors to type 1 conventional dendritic cells induce tumor cytotoxicity and exhibit activated PD-1/PD-L1 pathway

Impact of post-transplant cyclophosphamide with bendamustine on immune reconstitution in young patients undergoing T-cell replete haploidentical bone marrow transplantation: results from a phase Ia/Ib clinical trial

Introduction

Post-transplant cyclophosphamide (PT-CY) has been pivotal in controlling graft-versus-host disease (GvHD) following T-cell-replete haploidentical bone marrow transplantation (haplo-BMT). However, the widely adopted regimen is associated with high relapse rates, particularly in patients without GvHD. Our preclinical studies indicate that pre- or post-transplant bendamustine (PT-BEN) may reduce GvHD, enhance graft-versus-leukemia (GvL) effects, and induce significant alterations in the proportion, phenotype, and function of various immune cell subsets.

Methods

We initiated a Phase Ia/Ib, single-center trial with a standard 3 + 3 dose-escalation design, sequentially replacing post-transplant (PT)-CY with BEN (PT-CY/BEN). Multi-parameter flow cytometry and TCR β sequencing of genomic DNA was performed on isolated PBMCs on PT days +30, +60, +100, +180, and +365.

Results

Overall, the PT-CY/BEN (n=14) regimen was associated with earlier neutrophil and platelet engraftment, reduced transfusion requirements, and comparable clinical outcomes to PT-CY (n=10), including survival and relapse rates. PT-CY/BEN patients exhibited distinct immune reconstitution patterns, characterized by earlier CD4+ T-cell recovery, impaired CD8+ T-cell engraftment, and reduced NK-cell counts. Notably there were no significant changes in B-cells, Tregs, or MDSCs. Enhanced T-cell repertoire diversity in the PT-CY/BEN cohort was associated with improved CMV control.

Conclusion

Our Phase Ia findings demonstrate the well-tolerability of PT-CY/BEN and its association with early engraftment, a more diverse T-cell repertoire, and earlier CD4+ T-cell reconstitution. Future studies are warranted to confirm our findings and investigate potential additional benefits of PT-CY/BEN over PT-CY alone.

Comparable efficacy of oral bendamustine versus intravenous administration in treating hematologic malignancies

PURPOSE

The purpose of this study was to analyze potential differences in antitumor efficacy and pharmacokinetics between intravenous (IV) bendamustine and a novel orally administered (PO) bendamustine agent that is utilizing the beneficial properties of superstaturated solid dispersions formulated in nanoparticles.

METHODS

Pharmacokinetics of IV versus PO bendamustine were determined by analysis of plasma samples collected from NSG mice treated with either IV or PO bendamustine. Plasma samples were analyzed using liquid chromatography-mass spectrometry following a liquid-liquid extraction to determine peak bendamustine concentration, area under the concentration-time curve, and the half-life in-vivo. In-vitro cytotoxicity of bendamustine against human non-Hodgkin Burkitt's Lymphoma (Raji), multiple myeloma (MM.1s), and B-cell acute lymphoblastic leukemia (RS4;11) cell lines was determined over time using MTS assays. Luciferase-tagged versions of the aforementioned cell lines were used to determine in-vivo bendamustine cytotoxicity of IV versus PO bendamustine at two different doses.

RESULTS

Bendamustine at a high dose in-vitro causes cell death. There was no significant difference in antitumor activity between IV and novel PO bendamustine at a physiologically relevant concentration in all three xenograft models. In-vivo pharmacokinetics showed the oral bioavailability of bendamustine in mice to be 51.4%.

CONCLUSIONS

The novel oral bendamustine agent tested exhibits good oral bioavailability and systemic exposure for in-vivo antitumor efficacy comparable to IV bendamustine. An oral bendamustine formulation offers exciting clinical potential as an additional method of administration for bendamustine and warrants further evaluation in clinical studies.

Comparable Efficacy of Oral Bendamustine versus Intravenous Administration in Treating Hematologic Malignancies

Purpose

The purpose of this study was to analyze potential differences in antitumor efficacy and pharmacokinetics between intravenous (IV) bendamustine (BEN) and a novel orally administered bendamustine agent (PO) that is utilizing the beneficial properties of superstaturated solid dispersions formulated in nanoparticles.

Methods

Pharmacokinetics of IV versus PO BEN were determined by analysis of plasma samples collected from NSG mice treated with either IV or PO BEN. Plasma samples were analyzed using liquid chromatography-mass spectrometry (LC/MS/MS) following a liquid-liquid extraction to determine peak BEN concentration (Cmax), area under the concentration-time curve (AUC) and the half-life (t1/2) in-vivo. in-vitro cytotoxicity of BEN against human non-Hodgkin's Burkitt's Lymphoma (Raji), multiple myeloma (MM.1s), and B-cell acute lymphoblastic leukemia (RS4;11) cell lines was determined over time using MTS assays. Luciferase-tagged versions of the aforementioned cell lines were used to determine in-vivo BEN cytotoxicity of IV versus PO BEN at two different doses.

Results

Bendamustine at a high dose in-vitro causes cell death. There was no significant difference in antitumor efficacy between IV and novel PO BEN at a physiologically relevant concentration in all three xenograft models. In-vivo pharmacokinetics showed the oral bioavailability of BEN in mice to be 51.4%.

Conclusions

The novel oral BEN agent tested exhibits good oral bioavailability and systemic exposure for in-vivo antitumor efficacy comparable to IV BEN. An oral BEN formulation offers exciting clinical potential as an additional method of administration for bendamustine and warrants further evaluation in clinical studies.

Has the shortage of fludarabine altered the current paradigm of lymphodepletion in favor of bendamustine?

The most common lymphodepletion regimen used prior to infusion of chimeric antigen receptor-T cells (CAR-T) is cyclophosphamide (CY) in combination with fludarabine (Flu) (CY-FLU). While cyclophosphamide (CY) possesses lymphotoxic effects, it concurrently preserves regulatory T cell activity, potentially affecting the efficacy of CAR-T cells. Moreover, the use of fludarabine (FLU) has been linked to neurotoxicity, which could complicate the early detection of immune effector cell-associated neurotoxicity syndrome (ICANS) observed in CAR-T cell therapy. Given the ongoing shortage of FLU, alternative lymphodepleting agents have become necessary. To date, only a limited number of studies have directly compared different lymphodepleting regimens, and most of these comparisons have been retrospective in nature. Herein, we review the current literature on lymphodepletion preceding CAR-T cell therapies for lymphoid hematologic malignancies, with a specific focus on the use of bendamustine (BEN). Recent evidence suggests that administering BEN before CAR-T cell infusion yields comparable efficacy, possibly with a more favorable toxicity profile when compared to CY-FLU. This warrants further investigation through randomized prospective studies.

Multiagent Intratumoral Immunotherapy Can Be Effective in A20 Lymphoma Clearance and Generation of Systemic T Cell Immunity

The use of immunotherapies has shown promise against selective human cancers. Identifying novel combinations of innate and adaptive immune cell-activating agents that can work synergistically to suppress tumor growth and provide additional protection against resistance or recurrence is critical. The A20 murine lymphoma model was used to evaluate the effect of various combination immunotherapies administered intratumorally. We show that single-modality treatment with Poly(I:C) or GM-CSF-secreting allogeneic cells only modestly controls tumor growth, whereas when given together there is an improved benefit, with 50% of animals clearing tumors and surviving long-term. Neither heat nor irradiation of GM-CSF-secreting cells enhanced the response over use of live cells. The use of a TIM-3 inhibitory antibody and an OX40 agonist in combination with Poly(I:C) allowed for improved tumor control, with 90% of animals clearing tumors with or without a combination of GM-CSF-secreting cells. Across all treatment groups, mice rejecting their primary A20 tumors were immune to subsequent challenge with A20, and this longstanding immunity was T-cell dependent. The results herein support the use of combinations of innate and adaptive immune activating agents for immunotherapy against lymphoma and should be investigated in other cancer types.