Abstract 2335: DHODH inhibition modulates T cell metabolism reducing GVHD and prevents relapse following allogeneic HCT
Authors: Braunreiter Kara M. , Neidemire-Colley Lotus , Sell Natalie , Gao Yandi , Vibhute Sandip , Bennett Chad , Elgamal Ola A. , Goodwin Thomas , Hertlein Erin K. , Byrd John C. , Ranganathan Parvathi 
Published: June 2022

Introduction: The use of allogeneic hematopoietic cell transplantation to treat acute myeloid leukemia (AML) has risen in recent years. However, relapse remains the major cause of mortality post-transplant; while graft-versus-host disease (GVHD) - a T cell mediated immunological disorder is the major cause of non-relapse mortality. Dihydroorotate dehydrogenase (DHODH) supports T cell proliferation by playing a critical role in de novo pyrimidine synthesis and oxidative phosphorylation. We hypothesized that alloreactive T cells may rely on increased levels of pyrimidine pools and ATP to support rapid cell proliferation, making DHODH an interesting target to prevent GVHD. Additionally, DHODH inhibition is currently being pursued as a therapeutic option for AML. Therefore, we hypothesize that DHODH inhibition post-transplant will serve a dual purpose - i) target T cell metabolism to reduce GVHD and ii) prevent relapse due to direct anti-leukemic effects, thereby resulting in superior post-transplant outcomes.

Methods: We tested the efficacy of a novel DHODH inhibitor (Cmpd 41), a lead clinical candidate, in preventing GVHD and retaining graft-versus-leukemia (GVL) effect. Human T cells isolated from PBMCs were activated with CD3/CD28 Dynabeads ± Cmpd 41. Cell proliferation (flow cytometry) and ATP production (Agilent Seahorse) was assessed. GVHD and GVL was assessedevaluated in a xenogeneic model where irradiated NSG mice received human PBMCS (~17x106 cells) and treated with vehicle or Cmpd 41 (10mg/kg, 2x/week) with addition of MOLM-13 cells (~1x104) for GVL. Splenocytes were harvested for analysis of cytokine production (intracellular flow cytometry).

Results: DHODH inhibition with Cmpd 41 significantly reduced T cell proliferation and ATP production from both glycolysis and OXPHOS (fold change: Cmpd 41 vs. control- 0.56 and 0.68 respectively, p&lt;0.01) compared to vehicle. DHODH inhibition significantly improved survival (mean survival: Cmpd 41 vs. vehicle: 56 days vs. 40 days, p&lt;0.01) and reduced clinical scores (Cmpd 41 vs. vehicle: 1.8 vs. 4.2, p&lt;0.05) compared to vehicle in the xenogeneic GVHD model. There was a significant reduction in IFN-γ and TNF-α cytokine producing T cells in the Cmpd 41 treated cohort compared to vehicle (Cmpd 41 vs. vehicle, IFN-γ: 8.33% vs. 31.28%, p&lt;0.01; TNF-α: 1.37% vs. 27.25%, p&lt;0.01). In a GVL model, mice that received both human PBMCs and Cmpd 41 showed decreased tumor growth and improved overall survival over mice given either treatment alone (p&lt;0.01), showing that DHODH inhibition maintains GVL.

Conclusion: DHODH inhibition is a novel approach to prevent and mitigate GVHD while retaining GVL effects. Combined with direct anti-leukemic effects, we propose that Cmpd 41 treatment in post-transplant relapse in the setting of past or active graft versus host disease will provide dual treatment of AML and GVHD thereby leading to improved patient outcomes.

Citation Format: Kara M. Braunreiter, Lotus Neidemire-Colley, Natalie Sell, Yandi Gao, Sandip Vibhute, Chad Bennett, Ola A. Elgamal, Thomas Goodwin, Erin K. Hertlein, John C. Byrd, Parvathi Ranganathan. DHODH inhibition modulates T cell metabolism reducing GVHD and prevents relapse following allogeneic HCT [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2335.