Challenges in developing endpoints for type 1 diabetes intervention studies

Development of efficient and safe intervention strategies for preserving and/or restoring endogenous insulin production in type 1 diabetes has encountered a wide range of challenges, including lack of standardized trial protocols and of consensus on appropriate efficacy endpoints. For the greatest part, difficulties resided in choosing the most suitable assay(s) and parameter(s) to assess the beta-cell function. It is now an accepted approach to evaluate endogenous insulin secretion by measuring C-peptide levels (with highly sensitive and normalized measurement methods) in response to a physiologic stimulus (liquid mixed-meal) under standardized conditions. Preventive interventions mandate the identification of well-defined, reliable and validated mechanistic or immunological markers of efficacy that would correlate with (and predict) the clinical outcome. This has not been consistently achieved to date. However, it has been generally agreed that for preventive studies performed very early in the disease course (in subjects without signs of autoimmunity against beta-cells) development of two or more islet related autoantibodies could be employed as biomarkers of disease and thereafter, diagnostic criteria of diabetes serve as suitable endpoints.This report summarizes the conclusions of the D-Cure workshop of international experts held in Barcelona in April 2007 and the current recommendations and updates in the field.