THU277 Deletion Or inhibition Of Ornithine Decarboxylase Protects Islet β-cell Health And Is Associated With Preserved Residual C-peptide In Persons With Recent Onset Type 1 Diabetes

Abstract

Abstract Disclosure: B. Hammoud: None. L.A. DiMeglio: None. A. Kulkarni: None. A. Hull: None. S. Woerner: None. S. Cabrera: None. L.D. Mastrandrea: None. F. Ouyang: None. S.N. Perkins: None. C. Evans-Molina: None. T.L. Mastracci: None. S.A. Tersey: None. S. Sarkar: None. E. Nakayasu: None. B. Webb-Robertson: None. E. Gerner: None. R.G. Mirmira: None. E.K. Sims: None. Inhibition of polyamine biosynthesis using α-difluoromethylornithine (DFMO), an inhibitor of ornithine decarboxylase, reduces β cell stress and type 1 diabetes (T1D) incidence in preclinical animal models. However, the cellular and molecular mechanisms by which polyamines promote β-cell stress and the tolerability and effectiveness of their depletion by DFMO in humans with T1D remain unknown. We hypothesized that β-cell protection from stress occurs via cell-autonomous effects of polyamine depletion. To test this hypothesis, we generated β-cell specific knockout of ornithine decarboxylase in mice, performed comprehensive proteomics and transcriptomics on human islets treated with DFMO under inflammatory conditions in vitro, and performed a clinical study of DFMO tolerability, safety, and efficacy in persons with new-onset T1D. β-cell-specific deletion of the gene encoding ornithine decarboxylase in mice demonstrated protection of these animals against toxin (streptozotocin)-induced β-cell loss and hyperglycemia, implicating a cell-autonomous role for ornithine decarboxylase in β-cell stress. RNA sequencing and proteomics analyses of human islets exposed to a cytokine mix (1000 U/mL IFNγ + 50 U/mL IL-1β) +/- 5 mM DFMO identified 130 differentially regulated transcripts and 701 differentially regulated proteins. Pathway analysis implicated endosomal transport, vesicle organization and regulation of exocytosis, mRNA processing, and antigen cross presentation as mechanisms underlying DFMO effects on the islet response. To test DFMO in humans, we performed a 3-site randomized, placebo-controlled, double masked dose-ranging study of 3 months daily oral DFMO in persons with recent-onset T1D (<100 days). Dosing at 125, 250, 500, 750 or 1000 mg/m2/day was tested in 41 persons (12-34 y/o, 59% male, mean HbA1c 7.3%), with 6-10 participants/dosing group. Only mild and moderate adverse effects (AEs) were noted. Possible drug-related AEs included mild-moderate gastrointestinal symptoms, headache, upper respiratory infections, a pump site infection, and anemia. Urinary levels of the ODC product putrescine were decreased (p=0.05) in the 1000 mg/m2 dosing group. Compared to placebo, individuals receiving 750 and 1000 mg/m2 doses had significantly higher mixed-meal C-peptide area under the curve values at the 6-month post-randomization visit (p<0.05 vs. placebo). In conclusion, β-cell ODC inhibition protects β-cell health and function in the context of the proinflammatory T1D milieu. A 3-month course of oral DFMO was well tolerated with a favorable AE profile in persons with recent-onset T1D. Higher doses were associated with greater β-function compared to placebo. DFMO may have utility as a β-cell preservation therapy in recent-onset T1D. Presentation: Thursday, June 15, 2023