Type 1 diabetes and peptides — the indispensable hormone, the one approved adjunct, and the slow arrival of disease-modifying therapy

Why this dossier exists

Type 1 diabetes is the indication in which peptide pharmacology has always mattered the most and the indication in which the gap between the indispensable peptide therapy and every candidate adjunct on top of it is the widest. The indispensable therapy is insulin — without exogenous administration, the disease is rapidly fatal. The candidate adjuncts cluster across three categories: a single FDA-approved insulin-coadministered amylin analogue (pramlintide), an FDA-approved disease-delay monoclonal antibody (teplizumab/Tzield), and a growing off-label and investigational layer that includes glucagon-like peptide-1 receptor agonists (liraglutide, semaglutide), engineered glucagon for hypoglycemia rescue, C-peptide replacement, and a long-running peptide-vaccine programme around GAD65. The peptide-class signal across that landscape is real but constrained, and the constraints are what this dossier exists to walk.

Type 1 diabetes is fundamentally different from type 2 diabetes — the diabetic neuropathy and peptides and chronic kidney disease and peptides dossiers touch type-2 contexts where peptide-class therapy can compete with metabolic standard of care; this dossier is type-1 specific. The pathophysiology is autoimmune β-cell destruction with absolute insulin deficiency, not insulin resistance with progressive β-cell dysfunction. The disease presents at any age — historically with a pediatric and adolescent peak, but adult-onset T1D and latent autoimmune diabetes in adults (LADA) account for a substantial and increasingly recognised share of new diagnoses (Naik, Brooks-Worrell, and Palmer, J Clin Endocrinol Metab 2009, 94:4635–4644). Approximately 2 million Americans live with type 1 diabetes by the CDC's mid-2020s surveillance estimate, with annual incidence on the order of 15–30 per 100,000 person-years in pediatric populations and a smaller but non-trivial adult-onset incidence. The 1.6 million figure that circulated in patient-advocacy literature through the late 2010s has been progressively revised upward as adult-onset cases have been better catalogued; the current operational figure for US prevalence is in the 1.8 to 2.07 million range across recent estimates.

This dossier walks the peptide and peptide-adjacent evidence base for type 1 diabetes, separates the trial-supported signals from mechanism extrapolation, and frames the entire conversation against the closed-loop automated insulin delivery infrastructure that has reshaped routine T1D management more profoundly than any peptide adjunct on this list. The honest read across the corpus: insulin remains everything; pramlintide is the only FDA-approved non-insulin peptide adjunct and is a small drug commercially; teplizumab is the first disease-modifying immunotherapy approved for any autoimmune diabetes indication and operates upstream of clinical onset rather than at it; GLP-1 receptor agonist use in T1D is off-label, mechanistically motivated, hemodynamically real, and tempered by hypoglycemia and DKA signals that the registrational trials surfaced clearly; C-peptide replacement is the editorial parable of how a real signal in T1D-specific biology nevertheless failed at pivotal scale; and the closed-loop automated insulin delivery ecosystem is doing more for type 1 outcomes in 2026 than any candidate adjunct.