Transarterial chemoembolisation (TACE) is standard of care for patients with unresectable hepatocellular carcinoma that is amenable to embolisation; however, median progression-free survival is still approximately 7 months. We aimed to assess whether adding durvalumab, with or without bevacizumab, might improve progression-free survival.In this multiregional, randomised, double-blind, placebo-controlled, phase 3 study (EMERALD-1), adults aged 18 years or older with unresectable hepatocellular carcinoma amenable to embolisation, an Eastern Cooperative Oncology Group performance status of 0 or 1 at enrolment, and at least one measurable intrahepatic lesion per modified Response Evaluation Criteria in Solid Tumours (RECIST) were enrolled at 157 medical sites including research centres and general and specialist hospitals in 18 countries. Eligible patients were randomly assigned (1:1:1), stratified by TACE method, region, and portal vein invasion, using an interactive voice response or web response system, to TACE plus either durvalumab plus bevacizumab (1500 mg intravenous durvalumab once every 4 weeks, then 1120 mg durvalumab plus 15 mg/kg intravenous bevacizumab once every 3 weeks), durvalumab plus placebo (same regimen using placebo instead of bevacizumab), or placebo alone (same regimen using placebo instead of durvalumab and instead of bevacizumab). Participants, investigators, and those assessing outcomes were masked to treatment assignment until data analysis. The primary endpoint was progression-free survival, by blinded independent central review (BICR), and per RECIST version 1.1, with durvalumab plus bevacizumab versus placebo alone in the intention-to-treat population (ITT; ie, all participants assigned to treatment). Key secondary endpoints were progression-free survival by BICR per RECIST version 1.1 with durvalumab plus placebo versus placebo alone, overall survival, and time to deterioration in select patient-reported outcomes. Participants continue to be followed up for overall survival, and overall survival and patient-reported outcomes will be reported in a later publication. Safety was assessed in the safety analysis set, which included all participants assigned to treatment who received any study treatment (ie, any durvalumab, bevacizumab, or placebo) by treatment received. This study is registered with ClinicalTrials.gov, NCT03778957, and is closed to accrual.Between Nov 30, 2018, and July 19, 2021, 887 patients were screened, of whom 616 were randomly assigned to durvalumab plus bevacizumab (n=204), durvalumab plus placebo (n=207), or placebo alone (n=205; ITT population). Median age was 65·0 years (IQR 59·0-72·0), 135 (22%) of 616 participants were female, 481 (78%) were male, 375 (61%) were Asian, 176 (29%) were White, 22 (4%) were American Indian or Alaska Native, nine (1%) were Black or African American, one (<1%) was native Hawaiian or other Pacific Islander, and 33 (5%) were other races. As of data cutoff (Sept 11, 2023) median follow-up for progression-free survival was 27·9 months (95% CI 27·4-30·4), median progression-free survival was 15·0 months (95% CI 11·1-18·9) with durvalumab plus bevacizumab, 10·0 months (9·0-12·7) with durvalumab, and 8·2 months (6·9-11·1) with placebo. Progression-free survival hazard ratio was 0·77 (95% CI 0·61-0·98; two-sided p=0·032) for durvalumab plus bevacizumab versus placebo, and 0·94 (0·75-1·19; two-sided p=0·64) for durvalumab plus placebo versus placebo. The most common maximum grade 3-4 adverse events were hypertension in participants who received durvalumab and bevacizumab (nine [6%] of 154 participants), anaemia in participants who received durvalumab and placebo (ten [4%] of 232 participants), and post-embolisation syndrome in participants who received placebo alone (eight [4%] of 200 participants). Study treatment-related adverse events that led to death occurred in none of 154 participants who received durvalumab and bevacizumab, three (1%) of 232 who received durvalumab and placebo (n=1 for arterial haemorrhage, liver injury, and multiple organ dysfunction syndrome), and three (2%) of 200 who received placebo alone (n=1 for oesophageal varices haemorrhage, upper gastrointestinal haemorrhage, and dermatomyositis).Durvalumab plus bevacizumab plus TACE has the potential to set a new standard of care. With additional follow-up of the EMERALD-1 study, future analyses, including the final overall survival data and patient-reported outcomes, will help to further characterise the potential clinical benefits of durvalumab plus bevacizumab plus TACE in hepatocellular carcinoma amenable to embolisation.AstraZeneca.Copyright © 2025 Elsevier Ltd. All rights reserved, including those for text and data mining, AI training, and similar technologies.