Targeting Pathogenic Effector T Cells with a Novel Small-Peptide Approach in Type 1 Diabetes: A First-in-Human, Randomized, Double-Blind, Phase 1b Clinical Trial

Background: Type 1 diabetes (T1D) is a complex autoimmune disease demonstrating substantial heterogeneity in age of onset, residual C-peptide levels, clinical outcomes, and therapeutic response. Although the autoimmune classification of T1D has traditionally relied on detection of autoantibodies indicating B-cell involvement, studies targeting total CD3+ T cells have underscored the importance of T-cell regulation. Th40 cells, a pathogenic subset of CD3+ T cells, first identified in NOD mice, become significantly increased during diabetogenesis. Human subjects with T1D exhibit variable but significantly elevated Th40 levels in peripheral blood. Methods: To target pathogenic effector Th40 cells, we developed OPT101, a 15-mer peptide, and found that it interacts with CD40 in association with an activated integrin, identifying a novel inflammatory receptor complex. We conducted a phase 1b, double-blind, first-in-human clinical trial to evaluate OPT101 and met the primary objectives of safety and tolerability. Results: OPT101 generated only Grade 1 and 2 adverse events. Across eight doses, administered over six weeks, no product-related immune suppression was observed. Secondary objectives included immunologic outcomes and potential efficacy. Subjects with higher Th40 levels had low or undetectable C-peptide, higher (>7.0%) HbA1c, and elevated inflammatory cytokines. Th40 levels were significantly higher in subjects diagnosed before age eighteen. OPT101 treatment significantly reduced Th40 percentages without cell ablation, increased Treg levels, and decreased inflammatory cytokines. Serum blood glucose levels and HbA1c were significantly reduced by visit 8 in treated subjects. In two subjects, 11 and 13 years post-diagnosis, with undetectable C-peptide at screening, C-peptide became detectable post-treatment. Conclusions: OPT101 proved safe and effective in human T1D subjects with only mild and a few moderate adverse events. In this short-term study, OPT101 improved beta cell functions thus warranting further exploration.