Session: 203. Lymphocytes and Acquired or Congenital Immunodeficiency Disorders: Delineating Immunity from Mice to Humans
Hematology Disease Topics & Pathways:
Research, autoimmune disorders, Biological therapies, Diseases, Immune Disorders, Therapies
Methods: We designed a series of de novo IL-2Ra independent agonists of the IL-2 receptor that demonstrate reduced binding affinity to CD122 and CD132, the beta and gamma chains of the IL-2 receptor complex, by up to 5 logs when compared to IL-2. These non-alpha IL-2 mimetic variants were fused to a humanized anti-CD25 mAb that lacks effector function for cis-targeting to Tregs. Candidate molecules were screened on primary human T cells to assess pSTAT5 signaling. Treg-specific molecules were administered to humanized NSG mice weekly (four times) and peripheral blood was collected for immune cell profiling via flow cytometry.
Results: Screening of TRA candidates in primary human T cells identified several highly selective Treg agonists, including NEO-TRA1 (Fig1). At all concentrations, CD8+ and CD4+ non-Tregs showed low or negligible levels of pSTAT5 signaling upon treatment with NEO-TRA1. Nevertheless, CD4+CD25highCD127low Tregs show increasing pSTAT5 signaling at a wide range of concentrations starting at 20pM, and demonstrate preferential signaling in Tregs by NEO-TRA1.
To establish the ability of our TRA to expand Treg in vivo, NSG mice engrafted with human hematopoietic stem cells to create a humanized immune system received weekly injections of NEO-TRA1, vehicle control, or a previously described Treg selective IL-2 mutein (IL-2v-Fc). Characterization of Day 13 CD4+CD25+Foxp3+ Treg percentages in peripheral blood mononuclear cells show that the Treg population expanded to ~30% of total CD4+ cells in mice receiving NEO-TRA1, while Treg percentages reached ~22% in mice receiving IL-2v-Fc (Fig2). Despite a slight decrease at Day 20, the Treg percentages remained higher in NEO-TRA1-treated cohorts than in control groups throughout the study.
Conclusions: NEO-TRA1 exhibits potent expansion of Treg populations within primary human samples and in humanized mouse models. The observed profile of STAT5 phosphorylation demonstrates selective activation of Tregs over other lymphocyte populations. NEO-TRA1 is the first Treg agonist based on de novo protein design. NEO-TRA1 is both specific and potent and has high therapeutic potential for the treatment of GVHD and other autoimmune or inflammation diseases.
Disclosures: Chen: Neoleukin Therapeutics, Inc.: Ended employment in the past 24 months; Mozart Therapeutics: Current Employment. Tampella: Neoleukin Therapeutics, Inc: Current Employment. Quijano-Rubio: Neoleukin Therapeutics, Inc.: Current equity holder in publicly-traded company, Ended employment in the past 24 months, Patents & Royalties; Monod Bio, Inc: Current Employment, Current holder of stock options in a privately-held company. Walker: Neoleukin Therapeutics, Inc.: Ended employment in the past 24 months. Barber: Neoleukin Therapeutics, Inc.: Current Employment. Hare: Neoleukin Therapeutics, Inc.: Ended employment in the past 24 months; Novo Nordisk: Current Employment. Huard: Neoleukin Therapeutics, Inc.: Current Employment. Van Citters: Neoleukin Therapeutics, Inc.: Current Employment. Moss: Neoleukin Therapeutics, Inc.: Current Employment. Rincon: Neoleukin Therapeutics, Inc.: Current Employment. Arthur: Neoleukin Therapeutics, Inc.: Current Employment.
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