Aims: The STEP 4 clinical trial programme investigated weight loss maintenance with continued subcutaneous semaglutide (a GLP-1 analogue) vs switching to placebo in overweight or obese participants reaching semaglutide 2.4 mg during a 20-week study run-in.
Methods: This was a randomised, quadruple-blind, placebo-controlled, phase 3 trial of 803 adults with a body mass index (BMI) ≥30 kg/m2 or ≥27 kg/m2 with ≥1 weight-related comorbidity, without diabetes, who reached 2.4 mg of once-weekly subcutaneous semaglutide following dose escalation over 20 weeks (NCT03548987). Participants were randomised 2:1 to continue semaglutide 2.4 mg or switch to placebo for 48 weeks, both with lifestyle intervention. The primary endpoint was body weight change between weeks 20─68. Treatment policy estimand results are presented.
Results: Mean (±SD) body weight was 107.2 (±22.7) kg at week 0 and 96.1 (±22.6) kg at randomisation (mean change −10.6%). In randomised participants (mean age 46 years, BMI 34.4 kg/m2; 84% white, 79% female), mean body weight change between weeks 20─68 was −7.9% (semaglutide 2.4 mg) vs +6.9% (placebo) (estimated treatment difference [ETD]: −14.8%; 95% CI: −16.0, −13.5; p<0.0001). Similar results were obtained with the trial product estimand. For participants continuing semaglutide 2.4 mg, body weight change from week 0─68 was −17.4%. Continued semaglutide 2.4 mg led to improvements in cardiometabolic risk factors vs placebo. During run-in, 5.3% of participants discontinued treatment due to adverse events (AEs); after randomisation, 2.4% (semaglutide 2.4 mg) and 2.2% (placebo) of patients discontinued because of AEs. Most frequent AEs with semaglutide 2.4 mg were nausea, diarrhoea and constipation (mostly transient and mild-to-moderate).
Conclusions: In adults with overweight or obesity, continued semaglutide 2.4 mg after dose escalation led to clinically relevant weight loss, while switching to placebo led to weight regain. These findings underscore the chronicity and relapsing nature of obesity and the need for continued treatment.