A growing body of evidence has implicated various forms of beta cell dysfunction in the pathogenesis of Type 1 Diabetes (T1D). Recently we discovered that during the natural history of T1D, a subpopulation of β cells become senescent. Senescence is a cell type-specific form of permanent growth arrest, which occurs during aging, tissue damage or stress and involves progressively acquired phenotypes including activation of a DNA damage response, upregulation of cyclin-dependent kinase inhibitors, an apoptosis resistance phenotype and a senescence-associated secretory phenotype (SASP). Using nPOD pancreas specimens from a small cohort of donors, we previously found that β cells expressing senescence markers indicating the DNA damage response, cyclin-dependent kinase activation and SASP accumulated in islets of autoantibody-positive (1 or 2 autoantibodies) and recent onset T1D donors (diagnosed ≥11-12 years of age, 0-6 years post-diagnosis) relative to control donors without T1D. Studies in the nonobese diabetic (NOD) model demonstrated that senescent β cells are pathologic and accelerate T1D development, as small molecule targeting of the apoptosis resistance phenotype of these cells prevents T1D. Therefore,ourprevious studies suggest that the apoptosis resistance phenotype of senescent β cells is a target for therapeutic intervention to delay or prevent T1D. However, the proteins that confer the apoptosis resistance phenotype in senescent human β cells are not known, therefore it remains to be determined whether senescent human β cells can be selectively targeted by small molecule therapy. The goals of this project are to define the apoptosis resistance phenotype in senescent human β cells that accumulate in autoantibody-positive and recent onset T1D donors and to evaluate the efficacy of small molecule inhibitors of apoptosis resistance in targeting senescent β cell in islets ex vivo. These studies will take us closer towards the clinical translation of anti-senescence therapies for T1D.