GAD-alum antigen-specific immunotherapy (Diamyd)

Screening: who is found, and why it matters

Type 1 diabetes (T1D) has a long silent phase before symptoms. The immune system can be caught attacking the insulin-producing beta cells years early by testing for islet autoantibodies — antibodies against insulin, GAD65, IA-2, and ZnT8. The field uses a three-stage model: stage 1 is two or more autoantibodies with normal blood sugar; stage 2 adds abnormal (dysglycemic) blood sugar but still no symptoms; stage 3 is clinical diabetes needing insulin.¹ Two or more autoantibodies is a powerful signal: in pooled cohorts, about 70% of such children progressed to diabetes within 10 years and the lifetime risk approaches certainty.² Finding people early lets families act before a crisis — monitored children are far less likely to arrive in diabetic ketoacidosis (DKA), a dangerous and sometimes fatal presentation, and early detection opens a window for disease-modifying therapy.¹

For GAD-alum specifically, screening also asks a genetic question. The therapy appears to work only in people carrying the HLA DR3-DQ2 tissue type — roughly 40% of the T1D population — so candidates are screened for both GAD65 antibodies and this genotype.³⁴

Therapy: what GAD-alum does, and how well

GAD-alum (recombinant GAD65 protein bound to an aluminium adjuvant; trade name Diamyd) is an antigen-specific immunotherapy: instead of suppressing the whole immune system, it presents one of the proteins the immune system mistakenly targets, aiming to teach tolerance and spare beta cells.⁵ The current approach injects it directly into a lymph node (intralymphatic), three doses a month apart, alongside oral vitamin D.⁵

The honest picture is mixed-then-focused. An early subcutaneous trial in recent-onset patients missed its main C-peptide endpoint but hinted at preserved insulin secretion.⁶ The phase IIb DIAGNODE-2 trial (NCT03345004; 109 patients aged 12-24) again missed its primary endpoint in the full group, but in the pre-specified HLA DR3-DQ2 subgroup it preserved stimulated C-peptide markedly better than placebo (treatment effect ratio 1.56, p=0.008 at 15 months).⁵ A pooled re-analysis of three randomized trials found a significant, dose-dependent benefit confined to DR3-DQ2 carriers,⁴ and continuous-glucose-monitor data from DIAGNODE-2 showed those patients held more time-in-range.⁷ The treatment is well tolerated, with only minor transient injection-site reactions.⁵

So the effect is slower loss of the body's own insulin production in a genetically defined subgroup — not a proven delay of onset, and not in everyone. Durability beyond ~15 months and any preventive (stage 1-2) benefit remain unproven.

Access and what's coming

GAD-alum is not approved anywhere; it is investigational.³ Its future rests on the precision-medicine phase 3 DIAGNODE-3 (NCT05018585): ~330 recently diagnosed, DR3-DQ2-positive patients aged 12-28, across the US and eight European countries, with C-peptide and HbA1c at month 15 as co-primary outcomes.⁸ The US FDA has granted Fast Track (stages 1-3) and Orphan Drug designations and has accepted C-peptide as a surrogate "reasonably likely to predict benefit," opening a possible accelerated-approval route.³ A pre-specified interim efficacy readout was expected around early 2026 and, if positive, could support a US filing.⁹ If it succeeds, GAD-alum would be a first-of-kind, low-burden, genotype-targeted therapy — but it would help only the minority who carry the right genetic type, tying its value tightly to genetic screening.

References

1. Holt RIG, et al. (citing the JDRF/Endocrine Society/ADA staging framework); ADA & partners. Consensus guidance on monitoring islet-autoantibody-positive pre-stage 3 type 1 diabetes. Diabetes Care (2024). https://diabetesjournals.org/care/article/47/8/1276/156880/Consensus-Guidance-for-Monitoring-Individuals-With ↩ ↩²

2. Ziegler AG, Rewers M, Simell O, et al. Seroconversion to multiple islet autoantibodies and risk of progression to diabetes in children. JAMA (2013). https://doi.org/10.1001/jama.2013.6285 ↩

3. Diamyd Medical. Diamyd Medical to pursue accelerated approval pathway for Type 1 Diabetes precision medicine. PR Newswire (2024). https://www.prnewswire.com/news-releases/diamyd-medical-to-pursue-accelerated-approval-pathway-for-type-1-diabetes-precision-medicine-302241745.html ↩ ↩² ↩³

4. Hannelius U, Beam CA, Ludvigsson J. Efficacy of GAD-alum immunotherapy associated with HLA-DR3-DQ2 in recently diagnosed type 1 diabetes. Diabetologia (2020). https://doi.org/10.1007/s00125-020-05227-z ↩ ↩²

5. Ludvigsson J, Sumnik Z, Pelikanova T, et al. Intralymphatic glutamic acid decarboxylase with vitamin D supplementation in recent-onset type 1 diabetes: a double-blind, randomized, placebo-controlled phase IIb trial (DIAGNODE-2). Diabetes Care (2021). https://doi.org/10.2337/dc21-0318 ↩ ↩² ↩³ ↩⁴

6. Ludvigsson J, Faresjö M, Hjorth M, et al. GAD treatment and insulin secretion in recent-onset type 1 diabetes. N Engl J Med (2008). https://doi.org/10.1056/NEJMoa0804328 ↩

7. Nowak C, Lind M, Sumnik Z, et al. Intralymphatic GAD-alum (Diamyd) improves glycemic control in type 1 diabetes with HLA DR3-DQ2. J Clin Endocrinol Metab (2022). https://doi.org/10.1210/clinem/dgac343 ↩

8. A Phase III Study to Investigate if Diamyd Can Preserve Insulin Production and Improve Glycemic Control in Patients Newly Diagnosed With Type 1 Diabetes (DIAGNODE-3). ClinicalTrials.gov NCT05018585. https://clinicaltrials.gov/study/NCT05018585 ↩

9. Diamyd Medical. Pivotal Phase 3 Type 1 Diabetes trial clears last safety review ahead of early readout in March 2026. PR Newswire (2025). https://www.prnewswire.com/news-releases/diamyd-medicals-pivotal-phase-3-type-1-diabetes-trial-clears-last-safety-review-ahead-of-early-readout-in-march-2026-302615393.html ↩