Safety and efficacy of tirzepatide as an add-on to single oral antihyperglycaemic medication in patients with type 2 diabetes in Japan (SURPASS J-combo): a multicentre, randomised, open-label, parallel-group, phase 3 trial.

Background: Due to potential ethnic differences in the pathophysiology of type 2 diabetes, new therapeutics need to be evaluated in Japanese patients. We aimed to assess the safety and glycaemic efficacy of tirzepatide as an add-on treatment in Japanese patients with type 2 diabetes who had inadequate glycaemic control with stable doses of various oral antihyperglycaemic monotherapies.

Methods: This multicentre, open-label, parallel-group, randomised, phase 3 trial was conducted at 34 medical research centres and hospitals in Japan. Eligible participants were aged 20 years or older with inadequately controlled (HbA_1c ≥7·0% to <11·0%) type 2 diabetes and were receiving oral antihyperglycaemic monotherapy (sulfonylureas, biguanides, α-glucosidase inhibitors, thiazolidinedione, glinides, or SGLT2 inhibitors) for at least 3 months (stable dose for ≥8 weeks before screening), had a BMI of 23 kg/m² or higher, and stable bodyweight (±5%) for at least 3 months before screening. After a 2-week screening and 2-week lead-in period, all participants were randomly assigned (1:1:1) to receive 5, 10, or 15 mg of tirzepatide, administered once per week subcutaneously for 52 weeks followed by a 4 week safety follow-up period, using a computer-generated random sequence and interactive web response system, stratified by oral antihyperglycaemic medication group. All participants started receiving 2·5 mg tirzepatide and doses were escalated by 2·5 mg every 4 weeks until the assigned dose was reached. The primary endpoint was safety and tolerability during 52 weeks of treatment, assessed as incidence of treatment-emergent adverse events in the modified intention-to-treat (mITT) population. This trial is registered with ClinicalTrials.gov, NCT03861039.

Findings: Between March 30, 2019, and Feb 16, 2021, with recruitment and enrolment continuing until Feb 4, 2020, 484 participants were assessed for eligibility and 443 were randomly assigned to receive at least one dose of tirzepatide (148 [33%] in the 5 mg group, 147 [33%] in the 10 mg group, and 148 [33%] in the 15 mg group). 398 (90%) participants completed the study and treatment. Most participants (343 [77%] of 443) had at least one treatment-emergent adverse event. Treatment-emergent adverse events were more frequent in the tirzepatide 15 mg group (125 [84%] of 148) than the 5 mg (109 [74%] of 148) and 10 mg groups (109 [74%] of 147). The most frequent treatment-emergent adverse events with tirzepatide were mild or moderate nasopharyngitis (75 [17%]), nausea (74 [17%]), constipation (54 [12%]), diarrhoea (51 [12%]), and decreased appetite (44 [10%]). At week 52, mean changes from baseline in bodyweight were -3·8 kg (SE 0·5; -5·1% reduction) in the 5 mg group, -7·5 kg (0·5; -10·1% reduction) in the 10 mg group, and -10·2 kg (0·5; -13·2% reduction) in the 15 mg group. Least squares mean HbA_1c at baseline reduced from 8·5% (SE 0·1) to 6·0% (0·1) in the 5 mg tirzepatide group, from 8·6% (0·1) to 5·6% (0·1) in the 10 mg group, and from 8·6% (0·1) to 5·6% (0·1) in the 15 mg group at week 52. No adjudication-confirmed deaths were reported.

Interpretation: Tirzepatide was well tolerated as an add-on to oral antihyperglycaemic monotherapy in Japanese participants with type 2 diabetes and showed improvement in glycaemic control and bodyweight, irrespective of background oral antihyperglycaemic medication. Tirzepatide is a potential new treatment option for Japanese patients with type 2 diabetes that is inadequately controlled with single oral antihyperglycaemic medication.

Funding: Eli Lilly and Company.

Translation: For the Japanese translation of the abstract see Supplementary Materials section.