Design and methods of the Ixekizumab Diabetes Intervention Trial (I-DIT): protocol for a phase 2, randomised, multicentre, placebo-controlled, double-blind trial of anti-interleukin 17 as a treatment option for adults with new-onset type 1 diabetes.

introductionType 1 diabetes is characterised by progressive loss of pancreatic beta cells. Studies have shown that interleukin (IL)-17 is likely a mediator for this destruction. Whether inhibition of IL-17 could preserve beta cell function in people with new-onset type 1 diabetes is unknown. METHODS AND ANALYSIS: In this phase 2, randomised, multicentre, placebo-controlled, double-blind trial conducted at 17 study sites in Sweden, 127 adults aged 18-45 years old with newly diagnosed type 1 diabetes will be enrolled. Participants will be randomised to receive either subcutaneous IL-17 inhibitor or placebo for 52 weeks, in addition to their conventional therapy. The primary endpoint will be change in residual insulin secretion measured by the area under the curve for C-peptide in response to 2-hour mixed meal tolerance test between baseline and week 52. Additionally, masked continuous glucose monitoring will be performed during 14 days at the run-in period, week 13, week 26 and week 52. Secondary endpoints will be change in time in glucose range (3.9-10 mmol/L), time in hypoglycaemia (<3.9 mmol/L), HbA1c and mean insulin dosage per kilogram body weight. Patient-reported outcomes will be evaluated with questionnaires at baseline, week 26 and 52. Additionally, 1 and 3 years after the end of the treatment period, the participants will be examined during a visit regarding endogenous insulin production, glycaemic control, glucose metrics and insulin doses. ETHICS AND DISSEMINATION: Approvals were obtained from the Swedish Ethical Review Authority (Dnr 2020-05098) and the Swedish Medical Products Agency (Dnr 5.1-2021-105808) before participant enrolment. Participants provide informed consent before inclusion. Results of this study will be submitted for publication in international peer-reviewed journals and key findings will be presented at international scientific conferences. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov, NCT04589325.