Background: Orforglipron, an oral, non-peptide glucagon-like peptide-1 (GLP-1) receptor agonist, is in development for type 2 diabetes and obesity. We assessed the efficacy and safety of orforglipron versus placebo or dulaglutide in participants with type 2 diabetes., Methods: In this 26-week, phase 2, double-blind, randomised, multicentre study, participants were recruited from 45 centres (private clinics, hospitals, and research centers) in the USA, Hungary, Poland, and Slovakia. Adult participants aged 18 years or older with type 2 diabetes treated with diet and exercise, with or without metformin, and with a glycated haemoglobin (HbA 1c ) of 7·0-10·5%, and stable BMI of 23 kg/m 2 or more, were randomly assigned (5:5:5:5:5:3:3:3:3) via an interactive web-response system to placebo, dulaglutide 1·5 mg once per week, or orforglipron 3 mg, 12 mg, 24 mg, 36 mg (group 1), 36 mg (group 2), 45 mg (group 1), or 45 mg (group 2) once per day with no food or water restrictions. Two different dose escalation regimens were evaluated for each of the 36 mg and 45 mg cohorts. Participants were masked to the study drug, dulaglutide, and placebo. The primary efficacy outcome The primary efficacy outcome was mean change in HbA 1c from baseline with orforglipron versus placebo at week 26. Efficacy was analysed in all randomly assigned participants who received at least one dose of study drug and excluded data after the permanent discontinuation of study drug or initiation of rescue medication. Safety was analysed in all participants who received at least one dose of study treatment. This trial is registered at ClinicalTrials.gov (NCT05048719) and is completed., Findings: Between Sept 15, 2021, and Sept 30, 2022, 569 participants were screened and 383 were enrolled and randomly assigned to a group. 352 (92%) completed the study and 303 (79%) completed 26 weeks of treatment. At baseline, the mean age was 58·9 years, HbA 1c was 8·1%, BMI was 35·2 kg/m 2 , 226 (59%) were men, and 157 (41%) were women. At week 26, mean change in HbA 1c with orforglipron was up to -2·10% (-1·67% placebo adjusted), versus -0·43% with placebo and -1·10% with dulaglutide. HbA 1c reduction was statistically superior with orforglipron versus placebo (estimated treatment difference -0·8% to -1·7%). Change in mean bodyweight at week 26 was up to -10·1 kg (95% CI -11·5 to -8·7; 7·9 kg placebo adjusted [-9·9 to -5·9]) with orforglipron versus -2·2 kg (-3·6 to -0·7) for placebo and -3·9 kg (-5·3 to -2·4) for dulaglutide. The incidence of treatment-emergent adverse events ranged from 61·8% to 88·9% in orforglipron-treated participants, compared with 61·8% with placebo and 56·0% with dulaglutide. The majority were gastrointestinal events (44·1% to 70·4% with orforglipron, 18·2% with placebo, and 34·0% with dulaglutide) of mild to moderate severity. Three participants receiving orforglipron and one participant receiving dulaglutide had clinically significant (<54 mg/dL [<3 mmol/L]) hypoglycaemia and no participants had severe hypoglycaemia. One death occurred in the placebo group and was not related to study treatment., Interpretation: In this phase 2 trial the novel, oral, non-peptide GLP-1 receptor agonist orforglipron at doses of 12 mg or greater showed significant reductions in HbA 1c and bodyweight compared with placebo or dulaglutide. The adverse event profile was similar to other GLP-1 receptor agonists in similar stage of development. Orforglipron might provide an alternative to injectable GLP-1 receptor agonists and oral semaglutide, with the prospect of less burdensome administration to achieve treatment goals in people with type 2 diabetes., Funding: Eli Lilly and Company., Competing Interests: Declaration of interests JPF reports research funding from Akero, AstraZeneca, Boehringer Ingelheim, 89bio, Eli Lilly, Intercept, Ionis, Janssen, Madrigal, Metacrine, Merck, NorthSea Therapeutics, Novartis, Novo Nordisk, Oramed, Pfizer, Poxel, and Sanofi; consulting fees from Akero, Altimmune, Boehringer Ingelheim, Carmot Therapeutics, Echosens, 89bio, Eli Lilly, Merck, Novo Nordisk, Pfizer, and Sanofi; speaker bureau from Eli Lilly; support for attending meetings or travel from Eli Lilly, Novo Nordisk, Pfizer, and Sanofi; participant advisory boards and consulting for Altimmune, Becton Dickinson, Boehringer Ingelheim, Carmot Therapeutics, Eli Lilly, Gilead, Intercept, Merck, Novo Nordisk, Pfizer, and Sanofi; and is on the board of directors for T1D Exchange. SH reports research funding from Eli Lilly. SE reports funding from Eli Lilly for statistical services provided by employer Tigermed and travel support from Eli Lilly. RL, XM, MK, CK, KJM, AH, and EP are employees and shareholders of Eli Lilly. DR is a shareholder and retired employee of Eli Lilly., (Copyright © 2023 Elsevier Ltd. All rights reserved.)