Exploring a Novel Anti-Inflammatory Peptide As a Potential Treatment for Acute Graft-Versus-Host Disease (aGVHD)

Introduction: Allogeneic hematopoietic cell transplantation (allo-HCT) is indicated for the treatment of many hematological diseases, including leukemia. The goal is to eradicate residual leukemic cells and to replace the recipient’s diseased stem cells with healthy ones from a donor. However, this therapy’s success is limited by graft-versus-host disease (GVHD), caused by allogeneic T cells that recognize the recipient’s body as foreign and attack its tissues, leading to inflammation and tissue damage.

We have previously shown that neutrophils can exacerbate tissue damage caused by conditioning regimens, particularly in the small intestine (SI), and amplify the immune response by releasing inflammatory cytokines, neutrophil extracellular traps (NETs) and reactive oxygen species (ROS), thereby promoting T cell activation. In in vivo models of aGVHD, neutrophil depletion improves survival. However, neutrophils also play an important role in tissue homeostasis. Thus, inhibition of the pro-inflammatory activity of neutrophils could be an interesting therapeutic target of aGVHD. RLS-0071 (Pegtarazimod) is a synthetic peptide derived and optimized from the capsid protein of human astrovirus serotype 1 (HAstV-1). RLS-0071 has previously been shown to have multiple modes of action, including inhibition of the classical and lectin pathways of the complement system as well as reduction of NET formation and inhibition of myeloperoxidase (MPO) activity, resulting in reduced ROS, which makes it a promising therapeutic candidate for the treatment of aGVHD.

Methods: The effect of RLS-0071 was tested using different major mismatch models of aGVHD in which mice were treated with the peptide or a vehicle. Survival, clinical symptoms and tissue damage were examined. The underlying mechanism was investigated using different methods, including flow cytometry of immune cells in GVHD target organs, ELISA of pro-inflammatory proteins in the serum, and qPCR to investigate gene expression in target cell types and tissues.

Results: RLS-0071 significantly improves the survival of mice in multiple in vivo models of aGVHD, both when treatment is used to prevent the development of aGVHD and to alleviate existing aGVHD. Furthermore, it reduces clinical symptoms and decreases tissue damage in GVHD target organs. Mechanistically, RLS-0071 reduces inflammation by decreasing ROS production both in vitro and in vivo and lowering levels of the NET marker neutrophil elastase in vivo. In addition, inflammatory cytokines are reduced in splenic neutrophils and in the SI of mice with aGVHD. Additionally, RLS-0071 could also be protective for intestinal cells, as preliminary in vitro experiments with cell lines and organoids of epithelial cells of the small intestine suggest.

Conclusion: Our results suggest the use of RLS-0071 (Pegtarazimod) for both prophylactic and therapeutic treatment of aGVHD. Further mechanistic studies will provide additional knowledge on the mechanism of action. Based on these promising results, RLS-0071 will be evaluated in a phase 2, open label clinical trial for hospitalized patients with acute GVHD (NCT06343792).