Multicenter, open-label, two-arm pilot trial for safety reduction of basal insulin dose combined with SGLT2 inhibitor in type 1 diabetes mellitus: A study protocol for RISING-STAR

Background SGLT2 inhibitor combined with insulin is a novel therapy for patients with type 1 diabetes mellitus. Without the reduction of basal insulin, hypoglycemia could occur frequently in this therapy. However, ketoacidosis is an undesirable adverse effect in cases with basal insulin reduction. Methods This was a multicenter, open-label, two-arm study. Sixty subjects with type 1 diabetes mellitus were recruited from 7 hospitals. Subjects whose basal insulin daily dose to total daily insulin dose (TDD) ratio was < 0.4 were instructed not to reduce the basal insulin dose but to reduce the bolus insulin dose by 10% (Group A), and subjects with a basal-to-TDD ratio > 0.4 were instructed to reduce the basal insulin dose by 10% (Group B). We hypothesized that the frequency of hypoglycemia would be reduced in Group B. The primary outcome was the frequency of hypoglycemia per day during the intervention period (administration of SGLT2 inhibitor) as determined by self-monitoring of blood glucose (SMBG). The baseline number of hypoglycemic attacks was set at 7 ± 6 times/month. The minimum sample size required to achieve a significance of 0.05 for a one-sided t-test with a statistical power of 80% was determined. When the sample size was 26 patients in one group, the percent increase in hypoglycemia was more than 60%; thus, the sample size was estimated to be sufficient. The secondary outcome was the frequency of ketosis before and after the intervention. We aimed to confirm that the frequency of ketosis does not increase in Group B compared with Group A. The frequency of adverse events, including the frequency of hypoglycemia detected using flash glucose monitoring (FGM), was set as the safety endpoint. Discussion The RISING-STAR study will contribute results from a two-arm randomized trial in which a reduction in basal insulin dose is indicated or no reduction in basal insulin dose is instructed for concomitant use of SGLT2 inhibitors in patients with type 1 diabetes to prevent the development of hypoglycemia.Trial registration Registered with the Japan Registry of Clinical Trials (jRCTs051190114) on March 2, 2020.