Efficacy and Safety of Once-Weekly Subcutaneous Semaglutide 2.4 MG in Adults With Overweight or Obesity (STEP 1)

Background: Despite the increasing global adverse health impact of obesity, there are few pharmacological options for effective weight management. STEP 1 investigated the efficacy and safety of the glucagon-like peptide-1 analogue, subcutaneous (s.c.) semaglutide, for weight management in adults with overweight or obesity.

Methods: This randomized, double-blind, placebo-controlled, phase 3 trial was conducted at 129 sites across 16 countries (NCT03548935). Adults aged ≥18 years with either body mass index (BMI) ≥30 kg/m2 or BMI ≥27 kg/m2 with ≥1 weight-related comorbidity, without type 2 diabetes, were randomized 2:1 to 68 weeks’ treatment with once-weekly s.c. semaglutide 2.4 mg or placebo, both as adjunct to lifestyle intervention. The co-primary endpoints were percentage change in body weight and achievement of weight loss ≥5%. Cardiometabolic risk factors, patient-reported outcomes, and safety/tolerability were also assessed. Two estimands were defined: treatment policy (effect regardless of treatment adherence and use of rescue intervention) and trial product (effect assuming treatment adherence and without rescue intervention); results are presented for the treatment policy estimand, unless stated otherwise. P values for parameters marked with # were not controlled for multiplicity.

Results: 1961 randomized participants (mean age 46 years, body weight 105.3 kg, BMI 37.9 kg/m2; 74.1% female) were included. Mean body weight change from baseline to week 68 was −14.9% in the semaglutide group vs −2.4% with placebo (estimated treatment difference [ETD]: −12.4%; 95% confidence interval (CI): −13.4, −11.5; p<0.0001). Similar results were obtained with the trial product estimand: mean body weight change# was -16.9% for semaglutide vs -2.4% for placebo (ETD: -14.4%; 95% CI: -15.3, -13.6; p<0.0001). Participants were more likely to achieve weight loss ≥5%, ≥10%, ≥15%, and ≥20%# with semaglutide vs placebo (86.4% vs 31.5%, 69.1% vs 12.0%, 50.5% vs 4.9%, and 32.0% vs 1.7%, respectively; p<0.0001 for all). Greater improvements were seen with semaglutide vs placebo in waist circumference, BMI#, systolic and diastolic# blood pressure, glycated hemoglobin#, fasting plasma glucose#, C-reactive protein#, fasting lipid profile#, and self-reported physical functioning (p<0.05 for all). No new safety signals with semaglutide were observed. The most frequent adverse events with semaglutide were gastrointestinal disorders (typically transient and mild-to-moderate).

Conclusion: In adults with overweight or obesity, once-weekly s.c. semaglutide 2.4 mg plus lifestyle intervention induced a mean weight loss of approximately 15% by week 68. Clinically beneficial weight loss of ≥10% was achieved by over two-thirds of participants and ≥20% by one-third of participants, along with associated improvements in cardiometabolic risk factors and physical functioning.