IL17A and type 1 diabetes mellitus: Ustekinumab was deemed safe to progress to efficacy studies at doses used to treat psoriasis in adults with T1D. A 90 mg maintenance dosing schedule reduced proinsulin-specific IFN-γ and IL-17A-producing T cells. Further studies are warranted to determine whether Ustekinumab can prevent C-peptide AUC decline and induce a clinical response.