Intralymphatic Glutamic Acid Decarboxylase With Vitamin D Supplementation in Recent-Onset Type 1 Diabetes: A Double-Blind, Randomized, Placebo-Controlled Phase IIb Trial

Diabetes Care. 2021 Jul;44(7):1604-1612. doi: 10.2337/dc21-0318. Epub 2021 May 21.


Objective: To evaluate the efficacy of aluminum-formulated intralymphatic glutamic acid decarboxylase (GAD-alum) therapy combined with vitamin D supplementation in preserving endogenous insulin secretion in all patients with type 1 diabetes (T1D) or in a genetically prespecified subgroup.

Research design and methods: In a multicenter, randomized, placebo-controlled, double-blind trial, 109 patients aged 12-24 years (mean ± SD 16.4 ± 4.1) with a diabetes duration of 7-193 days (88.8 ± 51.4), elevated serum GAD65 autoantibodies, and a fasting serum C-peptide >0.12 nmol/L were recruited. Participants were randomized to receive either three intralymphatic injections (1 month apart) with 4 μg GAD-alum and oral vitamin D (2,000 IE daily for 120 days) or placebo. The primary outcome was the change in stimulated serum C-peptide (mean area under the curve [AUC] after a mixed-meal tolerance test) between baseline and 15 months.

Results: Primary end point was not met in the full analysis set (treatment effect ratio 1.091 [CI 0.845-1.408]; P = 0.5009). However, GAD-alum-treated patients carrying HLA DR3-DQ2 (n = 29; defined as DRB1*03, DQB1*02:01) showed greater preservation of C-peptide AUC (treatment effect ratio 1.557 [CI 1.126-2.153]; P = 0.0078) after 15 months compared with individuals receiving placebo with the same genotype (n = 17). Several secondary end points showed supporting trends, and a positive effect was seen in partial remission (insulin dose-adjusted HbA1c ≤9; P = 0.0310). Minor transient injection site reactions were reported.

Conclusion: Intralymphatic administration of GAD-alum is a simple, well-tolerated treatment that together with vitamin D supplementation seems to preserve C-peptide in patients with recent-onset T1D carrying HLA DR3-DQ2. This constitutes a disease-modifying treatment for T1D with a precision medicine approach.

Trial registration: NCT03345004.

Publication types

  • Clinical Trial, Phase II
  • Multicenter Study
  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • C-Peptide
  • Diabetes Mellitus, Type 1* / drug therapy
  • Dietary Supplements
  • Double-Blind Method
  • Glutamate Decarboxylase*
  • Humans
  • Vitamin D


  • C-Peptide
  • Vitamin D
  • Glutamate Decarboxylase

Associated data

  • figshare/10.2337/figshare.14427956