The Importance of C-Peptide for Developing T1D Disease-Modifying Therapies

In type 1 diabetes (T1D), preservation of β-cell function is correlated with improved long-term clinical outcomes, such as better glycemic control, fewer microvascular complications, and lower hypoglycemia risk. However, current interventions thus far are unable to stop the destruction of β-cells after clinical onset of T1D. Disease-modifying therapies must follow a long, complex regulatory path requiring clinical end points for full regulatory approval. To facilitate the development of new therapies, regulatory bodies should reinstate C-peptide, the most reliable and feasible measure of endogenous insulin secretion, as an end point for full, unconditional approval. T1D organizations and networks have accepted C-peptide as a primary efficacy end point for years, as did the U.S. Food and Drug Administration (FDA) from 2008 to 2023, followed by its failure to appear on the Surrogate Endpoint Table by the FDA, for unclear reasons. A C-peptide–based policy would substantially decrease the time for disease-modifying therapies to become available and increase investment in them, improving clinical outcomes and easing burden in those living with T1D.