In mice, such a peptide prevented and reversed type 1 diabetes.<h4>Methods</h4>We utilized a CD40-targeting peptide, OPT501, to treat CDM dogs via an intravenous or subcutaneous route and followed their disease status and clinical outcomes as well as their inflammatory status.<h4>Results</h4>Treatment with OPT501 significantly decreased pathogenic Th40 cells, the systemic inflammatory index, and fructosamine (an analog to human HbA1c). This evidence concerns the gene CD40 and type 1 diabetes mellitus.