Background: There is a great unmet need for advanced therapies that provide rapid, robust, and sustained disease control for patients with ulcerative colitis. We assessed the efficacy and safety of upadacitinib, an oral selective Janus kinase 1 inhibitor, as induction and maintenance therapy in patients with moderately to severely active ulcerative colitis., Methods: This phase 3, multicentre, randomised, double-blind, placebo-controlled clinical programme consisted of two replicate induction studies (U-ACHIEVE induction [UC1] and U-ACCOMPLISH [UC2]) and a single maintenance study (U-ACHIEVE maintenance [UC3]). The studies were conducted across Europe, North and South America, Australasia, Africa, and the Asia-Pacific region at 199 clinical centres in 39 countries (UC1), 204 clinical centres in 40 countries (UC2), and 195 clinical centres in 35 countries (UC3). Patients aged 16-75 years with moderately to severely active ulcerative colitis (Adapted Mayo score 5-9; endoscopic subscore 2 or 3) for at least 90 days were randomly assigned (2:1) to oral upadacitinib 45 mg once daily or placebo for 8 weeks (induction studies). Patients who achieved clinical response following 8-week upadacitinib induction were re-randomly assigned (1:1:1) to upadacitinib 15 mg, upadacitinib 30 mg, or placebo for 52 weeks (maintenance study). All patients were randomly assigned using web-based interactive response technology. The primary endpoints were clinical remission per Adapted Mayo score at week 8 (induction) and week 52 (maintenance). The efficacy analyses in the two induction studies were based on the intent-to-treat population, which included all randomised patients who received at least one dose of treatment. In the maintenance study, the primary efficacy analyses reported in this manuscript were based on the first 450 (planned) clinical responders to 8-week induction therapy with upadacitinib 45 mg once daily. The safety analysis population in the induction studies consisted of all randomised patients who received at least one dose of treatment; in the maintenance study, this population included all patients who received at least one dose of treatment as part of the primary analysis population. These studies are registered at ClinicalTrials.gov, NCT02819635 (U-ACHIEVE) and NCT03653026 (U-ACCOMPLISH)., Findings: Between Oct 23, 2018, and Sept 7, 2020, 474 patients were randomly assigned to upadacitinib 45 mg once daily (n=319) or placebo (n=155) in UC1. Between Dec 6, 2018, and Jan 14, 2021, 522 patients were randomly assigned to upadacitinib 45 mg once daily (n=345) or placebo (n=177) in UC2. In UC3, a total of 451 patients (21 from the phase 2b study, 278 from UC1, and 152 from UC2) who achieved a clinical response after 8 weeks of upadacitinib induction treatment were randomly assigned again to upadacitinib 15 mg (n=148), upadacitinib 30 mg (n=154), and placebo (n=149) in the primary analysis population. Statistically significantly more patients achieved clinical remission with upadacitinib 45 mg (83 [26%] of 319 patients in UC1 and 114 [34%] of 341 patients in UC2) than in the placebo group (seven [5%] of 154 patients in UC1 and seven [4%] of 174 patients; p<0·0001; adjusted treatment difference 21·6% [95% CI 15·8-27·4] for UC1 and 29·0% [23·2-34·7] for UC2). In the maintenance study, clinical remission was achieved by statistically significantly more patients receiving upadacitinib (15 mg 63 [42%] of 148; 30 mg 80 [52%] of 154) than those receiving placebo (18 [12%] of 149; p<0·0001; adjusted treatment difference 30·7% [21·7-39·8] for upadacitinib 15 mg vs placebo and 39·0% [29·7-48·2] for upadacitinib 30 mg vs placebo). The most commonly reported adverse events in UC1 were nasopharyngitis (15 [5%] of 319 in the upadacitinib 45 mg group vs six [4%] of 155 in the placebo group), creatine phosphokinase elevation (15 [4%] vs three [2%]), and acne (15 [5%] vs one [1%]). In UC2, the most frequently reported adverse event was acne (24 [7%] of 344 in the upadacitinib 45 mg group vs three [2%] of 177 in the placebo group). In both induction studies, serious adverse events and adverse events leading to discontinuation of treatment were less frequent in the upadacitinib 45 mg group than in the placebo group (serious adverse events eight [3%] vs nine (6%) in UC1 and 11 [3%] vs eight [5%] in UC2; adverse events leading to discontinuation six [2%] vs 14 [9%] in UC1 and six [2%] vs nine [5%] in UC2). In UC3, the most frequently reported adverse events (≥5%) were worsening of ulcerative colitis (19 [13%] of 148 in the upadacitinib 15 mg group vs 11 [7%] of 154 in the upadacitinib 30 mg group vs 45 [30%] of 149 in the placebo group), nasopharyngitis (18 [12%] vs 22 [14%] vs 15 [10%]), creatine phosphokinase elevation (nine [6%] vs 13 [8%] vs three [2%]), arthralgia (nine [6%] vs five [3%] vs 15 [10%]), and upper respiratory tract infection (seven [5%] vs nine [6%] vs six [4%]). The proportion of serious adverse events (ten [7%] vs nine [6%] vs 19 [13%]) and adverse events leading to discontinuation (six [4%] vs ten [6%] vs 17 [11%]) was lower in both upadacitinib groups than in the placebo group. Events of cancer, adjudicated major adverse cardiac events, or venous thromboembolism were reported infrequently. There were no treatment-related deaths., Interpretation: Upadacitinib demonstrated a positive efficacy and safety profile and could be an effective treatment option for patients with moderately to severely active ulcerative colitis., Funding: AbbVie., Competing Interests: Declaration of interests SD reports consultancy fees from AbbVie, Allergan, Amgen, AstraZeneca, Biogen, Boehringer Ingelheim, Celgene, Celltrion, Eli Lilly, Enthera, Ferring Pharmaceuticals, Gilead, Hospira, Janssen, Johnson & Johnson, Merck Sharp and Dohme (MSD), Mundipharma, Mylan, Pfizer, Roche, Sandoz, Sublimity Therapeutics, Takeda, TiGenix, UCB, and Vifor. SV reports grants from AbbVie, Johnson & Johnson, Pfizer, Galapagos, and Takeda; and consulting or speaking fees from AbbVie, Abivax, Alimentiv (formerly Robarts Clinical Trials), Arena Pharmaceuticals, Avaxia, Boehringer Ingelheim, Celgene, Dr Falk Pharma, Ferring, Galapagos, Genentech-Roche, Gilead, Hospira, Janssen, Mundipharma, MSD, Pfizer, Prodigest, Progenity, Prometheus, Second Genome, Shire, Takeda, Theravance, and Tillots Pharma. WZ, YSG, BH, WX, and JL are full-time employees of AbbVie, and might hold AbbVie stock or stock options. MAW and ALP are former employees of AbbVie, and might hold AbbVie stock or stock options. JS has received support, consulting fees, and speaker fees from AbbVie, Janssen, Amgen, Bristol Myers Squibb, Merck, Allergan, Takeda, Ferring, Shire, and Pfizer Pharmaceuticals. XH reports support from AbbVie, Abivax, Alphasigma, Arena, Cellgen, Gilead, Eli Lilly, Enterome, Janssen, InDex Pharmaceuticals, Pfizer, Promotheus, Roche, Salix, Sangamo, Takeda, and Theravance for clinical research; consulting fees from AbbVie, Abivax, Arena, Galapagos, Gilead, Janssen, Pfizer, Roche, Sangamo, Takeda, and Viatris; and lecture fees from AbbVie, Abivax, Amgen, Arena, Galapagos, Gilead, Fresenius-Kabi, Janssen, Pfizer, Roche, Sangamo, Takeda, and Mylan. GD has served as an advisor for AbbVie, Ablynx, Active Biotech, Agomab Therapeutics, Alimentiv, Allergan, Alphabiomics, Amakem, Amgen, AM Pharma, Applied Molecular Therapeutics, Arena, AstraZeneca, Avaxia, Biogen, Bristol Myers Squibb/Celgene, Boehringer Ingelheim, Celltrion, Cosmo, DSM Pharma, Echo Pharmaceuticals, Eli Lilly, Engene, Exeliom Biosciences, Ferring, Dr Falk Pharma, Galapagos, Genentech/Roche, Gilead, GlaxoSmithKline, Gossamerbio, Immunic, Johnson & Johnson, Kintai Therapeutics, Lument, Lycera, Medimetrics, Medtronic, Mitsubishi Pharma, MSD, Mundipharma, Nextbiotics, Novonordisk, Otsuka, Photopill, ProciseDx, Prodigest, Prometheus Laboratories/Nestle, Progenity, Protagonist, RedHill, Salix, Samsung Bioepis, Sandoz, Seres/Nestec/Nestle, Setpoint, Shire, Teva, Takeda, Tigenix, Tillotts, Topivert, Versant, and Vifor; and has received speaker fees from AbbVie, Biogen, Ferring, Galapagos/Gilead, Johnson & Johnson, MSD, Mundipharma, Norgine, Pfizer, Samsung Bioepis, Shire, Millennium/Takeda, Tillotts, and Vifor. HN has received support from AbbVie, Celgene Corporation, Daiichi Sankyo Company, EA Pharma, Janssen, JIMRO, Kissei Pharmaceutical, Kyorin Pharmaceutical, Mitsubishi Tanabe Pharma Corporation, Mochida Pharmaceutical, Nippon Kayaku, Pfizer, Takeda, and Zeria Pharmaceutical; and grants for commissioned or joint research from Boehringer Ingelheim, Bristol Myers Squibb, and Hoya Group Pentax Medical. JP has received grants from AbbVie and Pfizer; consultancy fees or honorarium from AbbVie, Arena, Athos, Boehringer Ingelheim, Celgene, Galapagos, Genentech/Roche, GSK, Janssen, Mirum, Morphic, Nestlé, Origo, Pandion, Pfizer, Progenity, Takeda, Theravance, and Wasserman; support for travel to meetings from AbbVie and Takeda during the conduct of the study; payment for lectures, including service on speaker bureaux, from Abbott, Janssen, Pfizer, and Takeda; and payment for development of educational presentations from Abbott, Janssen, Pfizer, and Roche. PDRH has received grants from AbbVie, Connectome Coordination Facility, National Institute of Health, and Takeda; and has served as a consultant for Eli Lilly, Takeda, Pfizer, Vindico Medical Education, Imedex, and GI Health Foundation. PJ has received consulting or speaker fees from AbbVie, Arena, Bristol Myers Squibb, Ferring Pharmaceuticals, Gilead, Janssen Pharma, Lilly, MSD, Pfizer, Pierre Fabre, Roche, Sandoz, Takeda, UCB Pharma, and Vifor; and investigator-led research grants from Vifor. JOL has received consulting or speaker fees from AbbVie, Allergan (Warner Chilcott), Atlantic Healthcare, Bristol Myers Squibb, Celgene, Celltrion, Ferring Pharmaceuticals, Galapagos, Gilead, GSK, Janssen, Lilly, MSD, Napp, Pfizer, Shire, Takeda, and Vifor; and investigator-led research grants from AbbVie, Gilead, Pfizer, Shire, and Takeda. EVL has received consulting fees from AbbVie, Amgen, Arena, Boehringer Ingelheim, Bristol Myers Squibb, Calibr, Celgene, Eli Lilly, Genentech, Gilead, Gossamer Bio, Iterative Scopes, Janssen, Ono Pharma, Pfizer, Scipher Medicine, Sun Pharma, Takeda, and UCB; and research support from AbbVie, Bristol Myers Squibb, Celgene, Genentech, Gilead, Gossamer Bio, Janssen, Pfizer, Receptos, Alimentiv, Takeda, Theravance, and UCB. WJS has received research grants from AbbVie, Abivax, Arena Pharmaceuticals, Boehringer Ingelheim, Celgene, Genentech, Gilead Sciences, Glaxo Smith Kline, Janssen, Lilly, Pfizer, Prometheus Biosciences, Seres Therapeutics, Shire, Takeda, and Theravance Biopharma; consulting fees from AbbVie, Abivax, Admirx, Alfasigma, Alimentiv, Alivio Therapeutics, Allakos, Allergan, Amgen, Applied Molecular Transport, Arena Pharmaceuticals, Avexegen Therapeutics, Bausch Health (Salix), Beigene, Bellatrix Pharmaceuticals, Boehringer Ingelheim, Boston Pharmaceuticals, Bristol Myers Squibb, Celgene, Celltrion, Cellularity, Conatus, Cosmo Pharmaceuticals, Escalier Biosciences, Ferring, Forbion, Equillium, Genentech/Roche, Gilead Sciences, Glenmark Pharmaceuticals, Gossamer Bio, Immunic (Vital Therapies), Incyte, Index Pharmaceuticals, Intact Therapeutics, Janssen, Kyowa Kirin Pharmaceutical Research, Kyverna Therapeutics, Landos Biopharma, Lilly, Miraca Life Sciences, Nivalis Therapeutics, Novartis, Nutrition Science Partners, Oppilan Pharma (acquired by Ventyx Biosciences), Otsuka, Pandion Therapeutics, Paul Hastings, Pfizer, Progenity, Prometheus Biosciences, Prometheus Laboratories, Protagonists Therapeutics, Provention Bio, Reistone Biopharma, Ritter Pharmaceuticals, Seres Therapeutics, Shanghai Pharma Biotherapeutics, Shire, Shoreline Biosciences, Sienna Biopharmaceuticals, Sigmoid Biotechnologies, Sterna Biologicals, Sublimity Therapeutics, Surrozen, Takeda, Theravance Biopharma, Thetis Pharmaceuticals, Tigenix, Tillotts Pharma, UCB Pharma, Vendata Biosciences, Ventyx Biosciences, Vimalan Biosciences, Vivelix Pharmaceuticals, Vivreon Biosciences, Zealand Pharma; stock or stock options from Allakos, BeiGene, Gossamer Bio, Oppilan Pharma (acquired by Ventyx Biosciences), Prometheus Biosciences, Prometheus Laboratories, Progenity, Shoreline Biosciences, Ventyx Biosciences, Vimalan Biosciences, and Vivreon Biosciences; and is an employee at Shoreline Biosciences. His spouse is a consultant (with stock options) for Iveric Bio, Oppilan Pharma (acquired by Ventyx Biosciences), Prometheus Laboratories; has stock or stock options from Progenity, Ventyx Biosciences, Vimalan Biosciences; and is employed (with stock options) at Prometheus Biosciences. WR has served as a speaker for Abbott, AbbVie, Aesca, Aptalis, Astellas, Centocor, Celltrion, Danone Austria, Elan, Falk Pharma, Ferring, Immundiagnostik, Medice, Mitsubishi Tanabe, MSD, Otsuka, PDL, Pharmacosmos, PLS Education, Schering-Plough, Shire, Takeda, Therakos, Vifor, and Yakult; served as a consultant for Abbott, AbbVie, Aesca, Algernon, Amgen, AM Pharma, AMT, AOP Orphan, Arena Pharmaceuticals, Astellas, AstraZeneca, Avaxia, Roland Berger, Bioclinica, Biogen IDEC, Boehringer Ingelheim, Bristol Myers Squibb, Calyx, Cellerix, Chemocentryx, Celgene, Centocor, Celltrion, Covance, Danone Austria, DSM, Elan, Eli Lilly, Ernest & Young, Falk Pharma, Ferring, Galapagos, Gatehouse Bio, Genentech, Gilead, Grünenthal, ICON, Index Pharma, Inova, Intrinsic Imaging, Janssen, Johnson & Johnson, Kyowa Hakko Kirin Pharma, Landos Biopharma, Lipid Therapeutics, LivaNova, Mallinckrodt, Medahead, MedImmune, Millennium, Mitsubishi Tanabe Pharma Corporation, MSD, Nash Pharmaceuticals, Nestle, Nippon Kayaku, Novartis, Ocera, OMass, Otsuka, Parexel, PDL, Periconsulting, Pharmacosmos, Philip Morris Institute, Pfizer, Procter & Gamble, Prometheus, Protagonist, Provention, Quell Therapeutics, Alimentiv, Sandoz, Schering-Plough, Second Genome, Seres Therapeutics, Setpointmedical, Sigmoid, Sublimity, Takeda, Teva Pharma, Therakos, Theravance, Tigenix, UCB, Vifor, Zealand, Zyngenia, and 4SC; served as an advisory board member for Abbott Laboratories, AbbVie, Aesca, Amgen, AM Pharma, Astellas, AstraZeneca, Avaxia, Biogen IDEC, Boehringer Ingelheim, Bristol Myers Squibb, Cellerix, Chemocentryx, Celgene, Centocor, Celltrion, Danone Austria, DSM, Elan, Ferring, Galapagos, Genentech, Grünenthal, Inova, Janssen, Johnson & Johnson, Kyowa Hakko Kirin Pharma, Lipid Therapeutics, MedImmune, Millennium, Mitsubishi Tanabe Pharma Corporation, MSD, Nestle, Novartis, Ocera, Otsuka, PDL, Pharmacosmos, Pfizer, Procter & Gamble, Prometheus, Sandoz, Schering-Plough, Second Genome, Setpointmedical, Takeda, Therakos, Tigenix, UCB, Zealand, Zyngenia, and 4SC; and has received research funding from Abbott, AbbVie, Aesca, Centocor, Falk Pharma, Immundiagnostik, Janssen, MSD, Sandoz, and Takeda. M-HC has received support for clinical research from Janssen and Takeda; served as an advisory board member for Boehringer Ingelheim and Janssen; and provided educational activities for AbbVie, China Medical System, IPSEN, Janssen, and Takeda. RP has received consulting fees, speaker fees, and research support from AbbVie, Abbott, Alimentiv, Amgen, Arena Pharmaceuticals, AstraZeneca, Bristol Myers Squibb, Boehringer Ingelheim, Celgene, Celltrion, Cosmos Pharmaceuticals, Eisai, Elan, Eli Lilly, Ferring, Galapagos, Genentech, Gilead Sciences, Glaxo-Smith Kline, Janssen, Merck, Mylan, Oppilan Pharma, Pandion Pharma, Pfizer, Progenity, Protagonist Therapeutics, Roche, Satisfai Health, Sandoz, Schering-Plough, Shire, Sublimity Therapeutics, Theravance Biopharma, UCB, and Takeda Pharmaceuticals. SG declares no competing interests., (Copyright © 2022 Elsevier Ltd. All rights reserved.)