Certolizumab pegol (CZP) is an Fc-free, PEGylated anti-tumour necrosis factor biologic.Report three-year efficacy, pooled from CIMPASI-1 (NCT02326298) and CIMPASI-2 (NCT02326272) CZP in plaque psoriasis (PSO) phase 3 trials.Adults with moderate to severe PSO for ≥6 months were randomised 2:2:1 to CZP 200 mg, CZP 400 mg, placebo, every two weeks (Q2W) for up to 48 weeks. Patients entering the open-label period (Weeks 48-144) from double-blinded CZP initially received CZP 200 mg Q2W. Patients not achieving Week 16 PASI 50 entered an open-label CZP 400 mg Q2W escape arm (Weeks 16-144). Dose adjustments based on Psoriasis Area and Severity Index (PASI) response were permitted during open-label treatment. Outcomes included PASI 75, PASI 90, and PGA 0/1 responder rates, based on a logistic regression model (missing data imputed using Markov Chain Monte Carlo methodology).186 patients were randomised to CZP 200 mg Q2W, 175 to CZP 400 mg Q2W. At Week 48, PASI 75/90 was achieved by 72.7%/51.3% CZP 200 mg-randomised and 84.4%/62.7% CZP 400 mg-randomised patients. Patients entering the open-label period at Week 48, from blinded treatment, received CZP 200 mg Q2W. At Week 144, PASI 75/90 was achieved by 70.6%/48.7% CZP 200 mg-randomised and 72.9%/42.7% CZP 400 mg-randomised patients. At Week 16, 72 placebo-randomised patients entered the CZP 400 mg Q2W escape arm; 75.7%/58.5% achieved PASI 75/90 at Week 144.Both CZP 200 mg and 400 mg Q2W demonstrated sustained, durable efficacy, with numerically higher responses for some outcomes with 400 mg Q2W.