Efficacy of GAD-alum immunotherapy associated with HLA-DR3-DQ2 in recently diagnosed type 1 diabetes

Aims/hypothesis The aim of this study was to determine if retention of C-peptide following immunotherapy using recombinant GAD65 conjugated to aluminium hydroxide (GAD-alum) is influenced by HLA risk haplotypes DR3-DQ2 and DR4-DQ8. Methods HLA-dependent treatment effect of GAD-alum therapy on C-peptide retention in individuals with recent-onset type 1 diabetes was evaluated using individual-level patient data from three placebo-controlled, randomised clinical trials using a mixed repeated measures model. Results A significant and dose-dependent effect was observed in individuals positive for the genotypes that include HLA-DR3-DQ2 but not HLA-DR4-DQ8 and in the broader subgroup of individuals positive for all genotypes that include HLA-DR3-DQ2 (i.e. including those also positive for HLA-DR4-DQ8). Higher doses (three or four injections) showed a treatment effect ratio of 1.596 (95% CI 1.132, 2.249; adjusted p = 0.0035) and 1.441 (95% CI 1.188, 1.749; adjusted p = 0.0007) vs placebo for the two respective HLA subgroups. Conclusions/interpretation GAD65-specific immunotherapy has a significant effect on C-peptide retention in individuals with recent-onset type 1 diabetes who have the DR3-DQ2 haplotype.