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Glucagon-like peptide-1 (GLP-1) receptor agonists are effective treatments for type 2 diabetes, lowering glycated haemoglobin (HbA1c) and weight, but are currently only approved for use as subcutaneous injections. Oral semaglutide, a novel GLP-1 agonist, was compared with subcutaneous liraglutide and placebo in patients with type 2 diabetes. In this randomised, double-blind, double-dummy, phase 3a trial, we recruited patients with type 2 diabetes from 100 sites in 12 countries. Eligible patients were aged 18 years or older, with HbA1c of 7·0–9·5% (53–80·3 mmol/mol), on a stable dose of metformin (≥1500 mg or maximum tolerated) with or without a sodium-glucose co-transporter-2 inhibitor. Participants were randomly assigned (2:2:1) with an interactive web-response system and stratified by background glucose-lowering medication and country of origin, to once-daily oral semaglutide (dose escalated to 14 mg), once-daily subcutaneous liraglutide (dose escalated to 1·8 mg), or placebo for 52 weeks. Two estimands were defined: treatment policy (regardless of study drug discontinuation or rescue medication) and trial product (assumed all participants were on study drug without rescue medication) in all participants who were randomly assigned. The treatment policy estimand was the primary estimand. The primary endpoint was change from baseline to week 26 in HbA1c (oral semaglutide superiority vs placebo and non-inferiority [margin: 0·4%] and superiority vs subcutaneous liraglutide) and the confirmatory secondary endpoint was change from baseline to week 26 in bodyweight (oral semaglutide superiority vs placebo and liraglutide). Safety was assessed in all participants who received at least one dose of study drug. This trial is registered on Clinicaltrials.gov, number NCT02863419, and the European Clinical Trials registry, number EudraCT 2015-005210-30. Between Aug 10, 2016, and Feb 7, 2017, 950 patients were screened, of whom 711 were eligible and randomly assigned to oral semaglutide (n=285), subcutaneous liraglutide (n=284), or placebo (n=142). 341 (48%) of 711 participants were female and the mean age was 56 years (SD 10). All participants were given at least one dose of study drug, and 277 (97%) participants in the oral semaglutide group, 274 (96%) in the liraglutide group, and 134 (94%) in the placebo group completed the 52-week trial period. Mean change from baseline in HbA1c at week 26 was −1·2% (SE 0·1) with oral semaglutide, −1·1% (SE 0·1) with subcutaneous liraglutide, and −0·2% (SE 0·1) with placebo. Oral semaglutide was non-inferior to subcutaneous liraglutide in decreasing HbA1c (estimated treatment difference [ETD] −0·1%, 95% CI −0·3 to 0·0; p<0·0001) and superior to placebo (ETD −1·1%, −1·2 to −0·9; p<0·0001) by use of the treatment policy estimand. By use of the trial product estimand, oral semaglutide had significantly greater decreases in HbA1c than both subcutaneous liraglutide (ETD −0·2%, 95% CI −0·3 to −0·1; p=0·0056) and placebo (ETD −1·2%, −1·4 to −1·0; p<0·0001) at week 26. Oral semaglutide resulted in superior weight loss (−4·4 kg [SE 0·2]) compared with liraglutide (−3·1 kg [SE 0·2]; ETD −1·2 kg, 95% CI −1·9 to −0·6; p=0·0003) and placebo (−0·5 kg [SE 0·3]; ETD −3·8 kg, −4·7 to −3·0; p<0·0001) at week 26 (treatment policy). By use of the trial product estimand, weight loss at week 26 was significantly greater with oral semaglutide than with subcutaneous liraglutide (−1·5 kg, 95% CI −2·2 to −0·9; p<0·0001) and placebo (ETD −4·0 kg, −4·8 to −3·2; p<0·0001). Adverse events were more frequent with oral semaglutide (n=229 [80%]) and subcutaneous liraglutide (n=211 [74%]) than with placebo (n=95 [67%]). Oral semaglutide was non-inferior to subcutaneous liraglutide and superior to placebo in decreasing HbA1c, and superior in decreasing bodyweight compared with both liraglutide and placebo at week 26. Safety and tolerability of oral semaglutide were similar to subcutaneous liraglutide. Use of oral semaglutide could potentially lead to earlier initiation of GLP-1 receptor agonist therapy in the diabetes treatment continuum of care. Novo Nordisk A/S.

Early treatment intensification leading to sustained good glycaemic control is essential to delay diabetic complications. Although initial combination therapy has been suggested to offer more opportunities than a traditional stepwise approach, its validity remains to be determined. Vildagliptin Efficacy in combination with metfoRmIn For earlY treatment of type 2 diabetes (VERIFY) was a randomised, double-blind, parallel-group study of newly diagnosed patients with type 2 diabetes conducted in 254 centres across 34 countries. The study consisted of a 2-week screening visit, a 3-week metformin-alone run-in period, and a 5-year treatment period, which was further split into study periods 1, 2, and 3. Patients aged 18–70 years were included if they had type 2 diabetes diagnosed within 2 years prior to enrolment, and centrally confirmed glycated haemoglobin A1c (HbA1c) of 48–58 mmol/mol (6·5–7·5%) and a body-mass index of 22–40 kg/m2. Patients were randomly assigned in a 1:1 ratio either to the early combination treatment group or to the initial metformin monotherapy group, with the help of an interactive response technology system and simple randomisation without stratification. Patients, investigators, clinical staff performing the assessments, and data analysts were masked to treatment allocation. In study period 1, patients received either the early combination treatment with metformin (stable daily dose of 1000 mg, 1500 mg, or 2000 mg) and vildagliptin 50 mg twice daily, or standard-of-care initial metformin monotherapy (stable daily dose of 1000 mg, 1500 mg, or 2000 mg) and placebo twice daily. If the initial treatment did not maintain HbA1c below 53 mmol/mol (7·0%), confirmed at two consecutive scheduled visits which were 13 weeks apart, patients in the metformin monotherapy group received vildagliptin 50 mg twice daily in place of the placebo and entered study period 2, during which all patients received the combination therapy. The primary efficacy endpoint was the time from randomisation to initial treatment failure, defined as HbA1c measurement of at least 53 mmol/mol (7·0%) at two consecutive scheduled visits, 13 weeks apart from randomisation through period 1. The full analysis set included patients who received at least one randomised study medication and had at least one post-randomisation efficacy parameter assessed. The safety analysis set included all patients who received at least one dose of randomised study medication. This study is registered with ClinicalTrials.gov, NCT01528254. Trial enrolment began on March 30, 2012, and was completed on April 10, 2014. Of the 4524 participants screened, 2001 eligible participants were randomly assigned to either the early combination treatment group (n=998) or the initial metformin monotherapy group (n=1003). A total of 1598 (79·9%) patients completed the 5-year study: 811 (81·3%) in the early combination therapy group and 787 (78·5%) in the monotherapy group. The incidence of initial treatment failure during period 1 was 429 (43·6%) patients in the combination treatment group and 614 (62·1%) patients in the monotherapy group. The median observed time to treatment failure in the monotherapy group was 36·1 (IQR 15·3–not reached [NR]) months, while the median time to treatment failure time for those receiving early combination therapy could only be estimated to be beyond the study duration at 61·9 (29·9–NR) months. A significant reduction in the relative risk for time to initial treatment failure was observed in the early combination treatment group compared with the monotherapy group over the 5-year study duration (hazard ratio 0·51 [95% CI 0·45–0·58]; p<0·0001). Both treatment approaches were safe and well tolerated, with no unexpected or new safety findings, and no deaths related to study treatment. Early intervention with a combination therapy of vildagliptin plus metformin provides greater and durable long-term benefits compared with the current standard-of-care initial metformin monotherapy for patients with newly diagnosed type 2 diabetes. Novartis.

Metformin, the world’s most prescribed anti-diabetic drug, is also effective in preventing type 2 diabetes in people at high risk 1 , 2 . More than 60% of this effect is attributable to the ability of metformin to lower body weight in a sustained manner 3 . The molecular mechanisms by which metformin lowers body weight are unknown. Here we show—in two independent randomized controlled clinical trials—that metformin increases circulating levels of the peptide hormone growth/differentiation factor 15 (GDF15), which has been shown to reduce food intake and lower body weight through a brain-stem-restricted receptor. In wild-type mice, oral metformin increased circulating GDF15, with GDF15 expression increasing predominantly in the distal intestine and the kidney. Metformin prevented weight gain in response to a high-fat diet in wild-type mice but not in mice lacking GDF15 or its receptor GDNF family receptor α-like (GFRAL). In obese mice on a high-fat diet, the effects of metformin to reduce body weight were reversed by a GFRAL-antagonist antibody. Metformin had effects on both energy intake and energy expenditure that were dependent on GDF15, but retained its ability to lower circulating glucose levels in the absence of GDF15 activity. In summary, metformin elevates circulating levels of GDF15, which is necessary to obtain its beneficial effects on energy balance and body weight, major contributors to its action as a chemopreventive agent. In mouse studies, metformin treatment results in increased secretion of growth/differentiation factor 15 (GDF15), which prevents weight gain in response to high-fat diet, and GDF15-independent lowering of circulating blood glucose.

Aims/hypothesis The aim of this work was to evaluate the efficacy and safety of canagliflozin vs placebo and sitagliptin in patients with type 2 diabetes who were being treated with background metformin. Methods This randomised, double-blind, four-arm, parallel-group, Phase 3 study was conducted at 169 centres in 22 countries between April 2010 and August 2012. Participants ( N  = 1,284) with type 2 diabetes aged ≥18 and ≤80 years who had inadequate glycaemic control (HbA 1c ≥7.0% [53 mmol/mol] and ≤10.5% [91 mmol/mol]) on metformin therapy received canagliflozin 100 mg or 300 mg, sitagliptin 100 mg, or placebo ( n  = 368, 367, 366, 183, respectively) for a 26 week, placebo- and active-controlled period followed by a 26 week, active-controlled period (placebo group switched to sitagliptin [placebo/sitagliptin]) and were included in the modified intent-to-treat analysis set. Randomisation was performed using a computer-generated schedule; participants, study centres and the sponsor were blinded to group assignment. The primary endpoint was change from baseline in HbA 1c at week 26; secondary endpoints included changes in HbA 1c (week 52) and fasting plasma glucose (FPG), body weight, and systolic blood pressure (BP; weeks 26 and 52). Adverse events (AEs) were recorded throughout the study. Results At week 26, canagliflozin 100 mg and 300 mg reduced HbA 1c vs placebo (−0.79%, –0.94%, –0.17%, respectively; p  < 0.001). At week 52, canagliflozin 100 mg and 300 mg demonstrated non-inferiority, and canagliflozin 300 mg demonstrated statistical superiority, to sitagliptin in lowering HbA 1c (−0.73%, –0.88%,–0.73%, respectively); differences (95% CI) vs sitagliptin were 0% (−0.12, 0.12) and −0.15% (−0.27, –0.03), respectively. Canagliflozin 100 mg and 300 mg reduced body weight vs placebo (week 26: –3.7%, –4.2%, –1.2%, respectively; p  < 0.001) and sitagliptin (week 52: –3.8%, –4.2%, –1.3%, respectively; p  < 0.001). Both canagliflozin doses reduced FPG and systolic BP vs placebo (week 26) and sitagliptin (week 52) ( p  < 0.001). Overall AE and AE-related discontinuation rates were generally similar across groups, but higher with canagliflozin 100 mg. Genital mycotic infection and osmotic diuresis-related AE rates were higher with canagliflozin; few led to discontinuations. Hypoglycaemia incidence was higher with canagliflozin. Conclusions/interpretation Canagliflozin improved glycaemia and reduced body weight vs placebo (week 26) and sitagliptin (week 52) and was generally well tolerated in patients with type 2 diabetes on metformin. Clinical trial registry ClinicalTrials.gov NCT01106677 Funding This study was supported by Janssen Research & Development, LLC.

Aims/hypothesisIntra-abdominal or visceral obesity is associated with insulin resistance and an increased risk for cardiovascular disease. This study aimed to compare the effects of semaglutide 1.0 mg and canagliflozin 300 mg on body composition in a subset of participants from the SUSTAIN 8 Phase IIIB, randomised double-blind trial who underwent whole-body dual-energy x-ray absorptiometry (DXA) scanning.MethodsAdults (age ≥18 years) with type 2 diabetes, HbA1c 53–91 mmol/mol (7.0–10.5%), on a stable daily dose of metformin (≥1500 mg or maximum tolerated dose) and with an eGFR ≥60 ml min−1 [1.73 m]−2 were randomised 1:1 to semaglutide 1.0 mg once weekly and canagliflozin placebo once daily, or canagliflozin 300 mg once daily and semaglutide placebo once weekly. Body composition was assessed using whole-body DXA scans. The study participants and investigator remained blinded throughout the trial, and quality of DXA scans was evaluated in a blinded manner. Change from baseline to week 52 in total fat mass (kg) was the confirmatory efficacy endpoint.ResultsA subset of 178 participants (semaglutide, n = 88; canagliflozin, n = 90) underwent DXA scanning at screening and were randomised into the substudy. Of these, 114 (semaglutide, n = 53; canagliflozin, n = 61) participants had observed end-of-treatment data included in the confirmatory efficacy analysis. Of the 178 participants in the substudy, numerical improvements in body composition (including fat mass, lean mass and visceral fat mass) were observed after 52 weeks with both treatments. Total fat mass (baseline 33.2 kg) was reduced by 3.4 kg and 2.6 kg with semaglutide and canagliflozin, respectively (estimated treatment difference: –0.79 [95% CI −2.10, 0.51]). Although total lean mass (baseline 51.3 kg) was also reduced by 2.3 kg and 1.5 kg with semaglutide and canagliflozin, respectively (estimated treatment difference: −0.78 [−1.61, 0.04]), the proportion of lean mass (baseline 59.4%) increased by 1.2%- and 1.1%-point, respectively (estimated treatment difference 0.14 [−0.89, 1.17]). Changes in visceral fat mass and overall changes in body composition (assessed by the fat to lean mass ratio) were comparable between the two treatment groups.Conclusions/interpretationIn individuals with uncontrolled type 2 diabetes on stable-dose metformin therapy, the changes in body composition with semaglutide and canagliflozin were not significantly different. Although numerical improvements in body composition were observed following treatment in both treatment arms, the specific impact of both treatments on body composition in the absence of a placebo arm is speculative at this stage.Trial registrationClinicalTrials.gov NCT03136484.FundingThis trial was supported by Novo Nordisk A/S, Denmark.

The prevalence of, and mortality from, colorectal cancer is increasing worldwide, and new strategies for prevention are needed to reduce the burden of this disease. The oral diabetes medicine metformin might have chemopreventive effects against cancer, including colorectal cancer. However, no clinical trial data exist for the use of metformin for colorectal cancer chemoprevention. Therefore, we devised a 1-year clinical trial to assess the safety and chemopreventive effects of metformin on sporadic colorectal cancer (assessed by adenoma and polyp recurrence) in patients with a high risk of adenoma recurrence. This trial was a multicentre, double-blind, placebo-controlled, randomised phase 3 trial. Non-diabetic adult patients who had previously had single or multiple colorectal adenomas or polyps resected by endoscopy were enrolled into the study from five hospitals in Japan. Eligible patients were randomly assigned (1:1) to receive oral metformin (250 mg daily) or identical placebo tablets by a stratified computer-based randomisation method, with stratification by institute, age, sex, and body-mass index. All patients, endoscopists, doctors, and investigators were masked to drug allocation until the end of the trial. After 1 year of administration of metformin or placebo, colonoscopies were done to assess the co-primary endpoints: the number and prevalence of adenomas or polyps. Our analysis included all participants who underwent random allocation, according to the intention-to-treat principle. This trial is registered with University Hospital Medical Information Network (UMIN), number UMIN000006254. Between Sept 1, 2011, and Dec 30, 2014, 498 patients who had had single or multiple colorectal adenomas resected by endoscopy were enrolled into the study. After exclusions for ineligibility, 151 patients underwent randomisation: 79 were assigned to the metformin group and 72 to the placebo group. 71 patients in the metformin group and 62 in the placebo group underwent 1-year follow-up colonoscopy. The prevalence of total polyps (hyperplastic polyps plus adenomas) and of adenomas in the metformin group was significantly lower than that in the placebo group (total polyps: metformin group 27 [38·0%; 95% CI 26·7–49·3] of 71 patients, placebo group 35 [56·5%; 95% CI 44·1–68·8] of 62; p=0·034, risk ratio [RR] 0·67 [95% CI 0·47–0·97]; adenomas: metformin group 22 [30·6%; 95% CI 19·9–41·2] of 71 patients, placebo group 32 [51·6%; 95% CI 39·2–64·1] of 62; p=0·016, RR 0·60 [95% CI 0·39–0·92]). The median number of polyps was zero (IQR 0–1) in the metformin group and one (0–1) in the placebo group (p=0·041). The median number of adenomas was zero (0–1) in the metformin group and zero (0–1) in the placebo group (p=0·037). 15 (11%) of patients had adverse events, all of which were grade 1. We recorded no serious adverse events during the 1-year trial. The administration of low-dose metformin for 1 year to patients without diabetes was safe. Low-dose metformin reduced the prevalence and number of metachronous adenomas or polyps after polypectomy. Metformin has a potential role in the chemoprevention of colorectal cancer. However, further large, long-term trials are needed to provide definitive conclusions. Ministry of Health, Labour and Welfare, Japan.

OBJECTIVE: This 24-week trial assessed the efficacy and safety of saxagliptin as add-on therapy in patients with type 2 diabetes with inadequate glycemic control with metformin alone. RESEARCH DESIGN AND METHODS: This was a randomized, double-blind, placebo-controlled study of saxagliptin (2.5, 5, or 10 mg once daily) or placebo plus a stable dose of metformin (1,500-2,500 mg) in 743 patients (A1C greater-than-or-equal7.0 and [less-than or equal to]10.0%). Efficacy analyses were performed using an ANCOVA model using last observation carried forward methodology on primary (A1C) and secondary (fasting plasma glucose [FPG] and postprandial glucose [PPG] area under the curve [AUC]) end points. RESULTS: Saxagliptin (2.5, 5, and 10 mg) plus metformin demonstrated statistically significant adjusted mean decreases from baseline to week 24 versus placebo in A1C (-0.59, -0.69, and -0.58 vs. +0.13%; all P < 0.0001), FPG (-14.31, -22.03, and -20.50 vs. +1.24 mg/dl; all P < 0.0001), and PPG AUC (-8,891, -9,586, and -8,137 vs. -3,291 mg · min/dl; all P < 0.0001). More than twice as many patients achieved A1C <7.0% with 2.5, 5, and 10 mg saxagliptin versus placebo (37, 44, and 44 vs. 17%; all P < 0.0001). β-Cell function and postprandial C-peptide, insulin, and glucagon AUCs improved in all saxagliptin treatment groups at week 24. Incidence of hypoglycemic adverse events and weight reductions were similar to those with placebo. CONCLUSIONS: Saxagliptin once daily added to metformin therapy was generally well tolerated and led to statistically significant improvements in glycemic indexes versus placebo added to metformin in patients with type 2 diabetes inadequately controlled with metformin alone.

OBJECTIVE: To test the safety and efficacy of exenatide once weekly (EQW) compared with metformin (MET), pioglitazone (PIO), and sitagliptin (SITA) over 26 weeks, in suboptimally treated (diet and exercise) drug-naive patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: Patients were randomized to subcutaneous (SC) EQW 2.0 mg + oral placebo (n = 248), MET 2,000 mg/day + SC placebo (n = 246), PIO 45 mg/day + SC placebo (n = 163), or SITA 100 mg/day + SC placebo (n = 163) for 26 weeks. MET and PIO therapies were increased to maximum-tolerated dosages. Injections with EQW or placebo were administered weekly, while oral medication or placebo was administered daily. RESULTS: Baseline characteristics were as follows: 59% men, 67% Caucasian, mean age 54 years, HbA1c 8.5%, fasting serum glucose 9.9 mmol/L, body weight 87.0 kg, and diabetes duration 2.7 years. HbA1c reductions (%) at 26 weeks (least-squares means) with EQW versus MET, PIO, and SITA were –1.53 vs. –1.48 (P = 0.620), –1.63 (P = 0.328), and –1.15 (P < 0.001), respectively. Weight changes (kg) were –2.0 vs. –2.0 (P = 0.892), +1.5 (P < 0.001), and –0.8 (P < 0.001), respectively. Common adverse events were as follows: EQW, nausea (11.3%) and diarrhea (10.9%); MET, diarrhea (12.6%) and headache (12.2%); PIO, nasopharyngitis (8.6%) and headache (8.0%); and SIT, nasopharyngitis (9.8%) and headache (9.2%). Minor (confirmed) hypoglycemia was rarely reported. No major hypoglycemia occurred. CONCLUSIONS: EQW was noninferior to MET but not PIO and superior to SITA with regard to HbA1c reduction at 26 weeks. Of the agents studied, EQW and MET provided similar improvements in glycemic control along with the benefit of weight reduction and no increased risk of hypoglycemia.

Chronic hyperglycemia impairs insulin action, resulting in glucotoxicity, which can be ameliorated in animal models by inducing glucosuria with renal glucose transport inhibitors. Here, we examined whether reduction of plasma glucose with a sodium-glucose cotransporter 2 (SGLT2) inhibitor could improve insulin-mediated tissue glucose disposal in patients with type 2 diabetes. Eighteen diabetic men were randomized to receive either dapagliflozin (n = 12) or placebo (n = 6) for 2 weeks. We measured insulin-mediated whole body glucose uptake and endogenous glucose production (EGP) at baseline and 2 weeks after treatment using the euglycemic hyperinsulinemic clamp technique. Dapagliflozin treatment induced glucosuria and markedly lowered fasting plasma glucose. Insulin-mediated tissue glucose disposal increased by approximately 18% after 2 weeks of dapagliflozin treatment, while placebo-treated subjects had no change in insulin sensitivity. Surprisingly, following dapagliflozin treatment, EGP increased substantially and was accompanied by an increase in fasting plasma glucagon concentration. Together, our data indicate that reduction of plasma glucose with an agent that works specifically on the kidney to induce glucosuria improves muscle insulin sensitivity. However, glucosuria induction following SGLT2 inhibition is associated with a paradoxical increase in EGP. These results provide support for the glucotoxicity hypothesis, which suggests that chronic hyperglycemia impairs insulin action in individuals with type 2 diabetes.

Metformin is a widely used anti-diabetic drug. Several studies have suggested that metformin has anticancer activity in some malignancies, including prostate cancer. Metformin might also mitigate the adverse metabolic effects of androgen-deprivation therapy (ADT). We hypothesised that metformin might improve survival in patients with metastatic hormone-sensitive prostate cancer and reduce metabolic complications associated with ADT. The STAMPEDE multi-arm, multi-stage, randomised phase 3 trial recruited patients with high-risk locally advanced or metastatic adenocarcinoma of the prostate staged by conventional imaging with isotope bone and CT scanning. This publication reports findings for the most recent STAMPEDE research question, testing the addition of metformin to standard of care for non-diabetic (glycated haemoglobin [HbA1c] <48 mmol/mol [equivalent to <6·5%]) patients with metastatic disease with adequate renal function (glomerular filtration rate ≥45 ml/min/1·73 m2) and WHO performance status 0–2. This trial recruited from 112 hospitals in the UK and Switzerland to the STAMPEDE protocol. Patients were randomly allocated (1:1) to standard of care or standard of care plus metformin 850 mg twice daily. Random assignment was by telephone using minimisation with a random element of 20% (developed and maintained by the MRC Clinical Trials Unit at UCL), stratified for randomising hospital, age (<70 years vs ≥70 years), WHO performance status (0 vs 1 or 2), type of ADT, regular long-term use of aspirin or non-steroidal anti-inflammatory drugs (NSAIDs; yes vs no), pelvic nodal status (positive vs negative), planned radiotherapy (yes vs no), and planned docetaxel or androgen receptor pathway inhibitor (ARPI) use (docetaxel vs abiraterone, enzalutamide, or apalutamide vs none). Standard of care comprised ADT with or without radiotherapy and with or without docetaxel or ARPI. The primary outcome measure was overall survival, defined as the time to death from any cause, assessed in the intention-to-treat population. Safety was assessed in patients who started treatment. The trial is registered with ClinicalTrials.gov, NCT00268476 and ISRCTN, ISRCTN78818544. Between Sep 5, 2016, and Mar 31, 2023, 1874 patients with metastatic disease were randomly allocated to standard of care (n=938) or standard of care plus metformin (n=936). The median patient age was 69 years (IQR 63-73) and the median PSA was 84 ng/mL (24–352). 1758 (94%) of 1874 patients were newly diagnosed with metastatic disease and 116 (6%) were diagnosed with metachronous relapsing disease. 1543 (82%) of 1874 patients received ADT plus docetaxel and 52 (3%) received abiraterone, enzalutamide, or apalutamide. The median time to most recent case report form follow-up was 60 months (IQR 49–72). 473 deaths were reported in the standard of care group; median survival was 61·8 months (IQR 29·7 to not reached). There were 453 deaths in the metformin group; median survival was 67·4 months (32·5 to not reached; HR 0·91, 95% CI 0·80–1·03; p=0·15). Grade 3 or worse adverse events were reported in 487 (52%) of 938 patients in the standard of care group and 523 (57%) of 921 patients in the standard of care plus metformin group. 61 (7%) patients in the standard of care group and 84 (9%) patients in the standard of care plus metformin group reported at least one grade 3 or worse gastrointestinal adverse event; all other body systems showed no difference in grade 3 adverse events. There were six drug-related deaths in the standard of care group and one in the standard of care plus metformin group. We did not find significant evidence of an overall survival benefit of adding metformin to standard of care in the overall population of patients with metastatic hormone-sensitive prostate cancer. The side-effect profile of metformin was as expected and consisted mainly of diarrhoea. Adverse metabolic side-effects of ADT were significantly reduced in the metformin group compared with the standard of care group. Cancer Research UK, Prostate Cancer UK, and UK Research and Innovation Medical Research Council.