Exploring Low-Dose Antithymocyte Globulin Therapy in Type 1 Diabetes: Real-World Insights Using Modified Quantitative Response of C-Peptide

Highlight

• Low-dose antithymocyte globulin (ATG) therapy in type 1 diabetes is feasible and safe in a real-world clinical setting.
• A modified quantitative response (mQR) metric using 90-minute post-meal C-peptide measurements effectively estimates beta-cell function over one year.
• Majority of patients showed a positive mQR indicating preserved or improved endogenous insulin secretion after low-dose ATG treatment.
• HbA1c levels improved significantly over 12 months, suggesting clinical benefit beyond biomarker changes.

Study Background

Type 1 diabetes mellitus (T1DM) is characterized by autoimmune destruction of pancreatic beta cells leading to insulin deficiency. Despite advancements in insulin therapies, preserving residual beta-cell function remains a crucial unmet need to improve metabolic control and reduce complications. Immunomodulatory therapies, including antithymocyte globulin (ATG), have been evaluated to delay beta-cell loss. While high-dose ATG has shown efficacy, it is often associated with significant adverse effects. Low-dose ATG regimens offer a potential therapeutic window balancing efficacy and safety but lack extensive real-world data, especially outside tightly controlled clinical trials. Assessing treatment impact using practical and accessible biomarkers like C-peptide can guide therapeutic decision-making. However, traditional methods requiring multiple blood draws over mixed-meal tolerance tests (MMTT) are resource-intensive.

Study Design

This exploratory observational study included 39 individuals with stage 2 or stage 3 type 1 diabetes treated clinically with low-dose ATG (2.5 mg/kg). The cohort comprised six stage 2 (pre-symptomatic) and 33 stage 3 (clinical) diabetes patients. Following ATG administration, participants obtained C-peptide levels 90 minutes after consuming a standardized Boost nutritional drink (6 mL/kg) measured in commercial laboratories, thereby simplifying data collection.

Of the total cohort, 30 patients (77%) completed one year of follow-up, and 22 (73% of completers) provided paired pre-ATG and one-year post-ATG 90-minute C-peptide measurements. The study introduced a modified quantitative response (mQR) estimate based on area under the curve C-peptide approximated from these single time-point values to evaluate endogenous beta-cell function and response to therapy over time.

Key Findings

Among the 22 evaluable patients with paired data, the average mQR value at one year was 0.072, indicating a quantifiable preservation or improvement in C-peptide secretion. Importantly, 15 individuals were classified as responders (positive mQR), whereas 7 were nonresponders (negative mQR).

Clinically, mean glycated hemoglobin (HbA1c) improved substantially from 7.1% (54 mmol/mol) before treatment to 6.0% (42 mmol/mol) at one year, suggesting improved glycemic control concomitant with preserved beta-cell function. No unexpected adverse effects associated with low-dose ATG treatment were reported, supporting the safety profile of this regimen in routine practice.

The mQR methodology demonstrated feasibility and practicality for real-world monitoring, enabling simpler yet meaningful evaluation of beta-cell function compared with traditional multipoint MMTT testing, which often limits longitudinal follow-up.

Expert Commentary

Low-dose ATG is emerging as a viable immunomodulatory strategy to preserve endogenous insulin secretion in T1DM patients. This real-world observation reinforces earlier controlled trial findings and adds pragmatic evidence supporting wider clinical adoption. The use of a modified quantitative response from a single 90-minute postprandial C-peptide measurement represents an innovative approach to balance pragmatic clinical workflows with rigorous efficacy assessment.

Nevertheless, several limitations warrant consideration. The study’s single-arm design without a placebo or comparator group limits definitive efficacy inferences. The small sample size, potential selection bias, and incomplete follow-up data reduce generalizability. Additionally, relying on a single post-meal C-peptide time point to estimate AUC may introduce measurement variability compared with standard multi-sampling protocols.

Future randomized controlled trials employing this mQR approach could validate its utility as a clinical and research tool. Moreover, mechanistic studies exploring how low-dose ATG modulates immune-mediated beta-cell destruction and the durability of response will enhance biological plausibility and guide patient selection.

Conclusion

Low-dose antithymocyte globulin therapy in type 1 diabetes is feasible, safe, and associated with preservation of endogenous beta-cell function as measured by an innovative modified quantitative response (mQR) using a practical single-time-point C-peptide assay. This real-world experience provides encouraging clinical signals that warrant further validation in larger prospective studies and randomized trials.

The mQR method holds promise as a practical monitoring tool in clinical practice to assess beta-cell function longitudinally, supporting personalized immunotherapy management in T1DM.

Funding and ClinicalTrials.gov

The published exploratory study did not specify external funding sources or clinical trial registration details. Further large-scale investigations may require formal trial registration and sponsorship disclosure.

References

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2. Herold KC, et al. Type 1 diabetes: pathogenesis and clinical interventions. Lancet. 2019;394(10205):2445-2458.
3. Lachin JM, et al. Residual beta-cell function and risk of hypoglycemia in type 1 diabetes. J Clin Endocrinol Metab. 2014;99(4):1453-1460.
4. The ability of single-sample C-peptide measurements to approximate MMTT AUC. Diabetes Technol Ther. 2021;23(2):95-102.