Efficacy and safety of tirzepatide monotherapy compared with dulaglutide in Japanese patients with type 2 diabetes (SURPASS J-mono): a double-blind, multicentre, randomised, phase 3 trial

Background As the disease progresses, many patients with type 2 diabetes have difficulty in reaching treatment goals. We aimed to assess the efficacy and safety of tirzepatide, a novel GIP and GLP-1 receptor agonist, compared with dulaglutide in Japanese patients with type 2 diabetes. Methods This multicentre, randomised, double-blind, parallel, active-controlled, phase 3 trial was conducted in 46 medical research centres and hospitals in Japan. Adults aged 20 years or older with type 2 diabetes who had discontinued oral antihyperglycaemic monotherapy or were treatment-naïve were included. Participants were randomly assigned (1:1:1:1) to receive tirzepatide (5, 10, or 15 mg) or dulaglutide (0·75 mg) once per week using a computer-generated random sequence with an Interactive Web Response System. Participants were stratified based on baseline HbA1c (≤8·5% or >8·5%), baseline BMI (<25 or ≥25 kg/m2), and washout of antidiabetic medication. Participants, investigators, and the sponsor were masked to treatment assignment. The starting dose of tirzepatide was 2·5 mg once per week for 4 weeks, which was then increased to 5 mg in the tirzepatide 5 mg treatment group. For the tirzepatide 10 and 15 mg treatment groups, increases by 2·5 mg occurred once every 4 weeks until the assigned dose was reached. The primary endpoint was mean change in HbA1c from baseline at week 52 measured in the modified intention-to-treat population. This trial is registered with ClinicalTrials.gov, NCT03861052. Findings Between May 7, 2019, and March 31, 2021, 821 participants were assessed for study eligibility and 636 were randomly assigned to receive at least one dose of tirzepatide 5 mg (n=159), 10 mg (n=158), or 15 mg (n=160), or dulaglutide 0·75 mg (n=159). 615 (97%) participants completed the study and 21 (3%) discontinued. Participants had a mean age of 56·6 years (SD 10·3) and were mostly male (481 [76%]). At week 52, HbA1c decreased from baseline by a least squares mean of −2·4 (SE 0·1) for tirzepatide 5 mg, −2·6 (0·1) for tirzepatide 10 mg, −2·8 (0·1) for tirzepatide 15 mg, and −1·3 (0·1) for dulaglutide. Estimated mean treatment differences versus dulaglutide were −1·1 (95% CI −1·3 to −0·9) for tirzepatide 5 mg, −1·3 (−1·5 to −1·1) for tirzepatide 10 mg, and −1·5 (−1·71 to −1·4) for tirzepatide 15 mg (all p<0·0001). Tirzepatide was associated with dose-dependent reductions in bodyweight with a least square mean difference of −5·8 kg (SE 0·4; −7·8% reduction) for 5 mg, −8·5 kg (0·4; −11·0% reduction) for 10 mg, and −10·7 kg (0·4; −13·9% reduction) for 15 mg of tirzepatide compared with −0·5 kg (0·4; –0·7% reduction) for dulaglutide. The most common treatment-emergent adverse events were nausea (19 [12%] participants in the 5 mg group vs 31 [20%] in the 10 mg group vs 32 [20%] in the 15 mg group all receiving tirzepatide vs 12 (8%) in the group receiving dulaglutide), constipation (24 [15%] vs 28 [18%] vs 22 [14%] vs 17 [11%]), and nasopharyngitis (29 [18%] vs 25 [16%] vs 22 [14%] vs 26 [16%]). The most frequent adverse events were gastrointestinal (23 [4%] of 636). Interpretation Tirzepatide was superior compared with dulaglutide for glycaemic control and reduction in bodyweight. The safety profile of tirzepatide was consistent with that of GLP-1 receptor agonists, indicating a potential therapeutic use in Japanese patients with type 2 diabetes. Funding Eli Lilly and Company. Translation For the Japanese translation of the abstract see Supplementary Materials section.