Series: Landmark Trials in Endocrinology & Metabolism | Study #14
Category: GLP-1 Receptor Agonists · Obesity & Weight Management | Design: Multicentre, double-blind, placebo-controlled RCT | n: 3,731 | Follow-up: 56 weeks
📋 Summary
Authors: Pi-Sunyer X et al., for the SCALE Obesity and Prediabetes NN8022-1839 Study Group
Journal: N Engl J Med 2015;373:11–22 | DOI: 10.1056/NEJMoa1411892
SCALE was the pivotal registration trial for liraglutide 3.0 mg as a treatment for chronic weight management. The trial enrolled 3,731 adults with a BMI of 30 or more, or 27 or more in the presence of treated or untreated dyslipidaemia or hypertension, who did not have type 2 diabetes. Notably, 61.2% of participants had prediabetes at baseline. Participants were randomly assigned in a 2:1 ratio to once-daily subcutaneous liraglutide 3.0 mg or placebo, both in conjunction with dietary counselling and physical activity guidance, for 56 weeks. The three co-primary endpoints were the percentage change in body weight, the proportion achieving 5% or more weight loss, and the proportion achieving more than 10% weight loss. At week 56, participants in the liraglutide group had lost a mean of 8.4 kg compared with 2.8 kg in the placebo group (difference −5.6 kg; 95% CI −6.0 to −5.1; p<0.001). A weight reduction of 5% or more was achieved by 63.2% of the liraglutide group versus 27.1% of the placebo group, and a reduction of more than 10% by 33.1% versus 10.6% (both p<0.001). Among participants with prediabetes at baseline, the proportion who reverted to normoglycaemia at week 56 was significantly higher in the liraglutide group, and the rate of progression to type 2 diabetes over 160 weeks in a pre-specified extension analysis was 2% in the liraglutide group versus 6% in the placebo group (hazard ratio 0.21; 95% CI 0.10 to 0.45; p<0.0001). The most common adverse events were nausea (40.0% liraglutide vs 11.5% placebo) and diarrhoea (20.9% vs 9.9%).
📊 Key Findings
| Outcome | Liraglutide 3.0 mg | Placebo | Effect Size |
|---|---|---|---|
| Mean weight change | −8.4 kg | −2.8 kg | Difference −5.6 kg (−6.0 to −5.1) · p<0.001 |
| Mean % body weight change | −8.0% | −2.6% | Difference −5.4% |
| ≥5% weight loss | 63.2% | 27.1% | p<0.001 |
| >10% weight loss | 33.1% | 10.6% | p<0.001 |
| Prediabetes → T2DM (160-week extension) | 2% | 6% | HR 0.21 (0.10–0.45) · 79% risk reduction |
| Nausea | 40.0% | 11.5% | Most common AE — typically transient |
💬 Expert Commentary
SCALE established liraglutide 3.0 mg as the first GLP-1 receptor agonist approved specifically for chronic weight management, preceding the higher-dose semaglutide and tirzepatide programmes by several years. At the time of publication, the mean weight loss of 8.0% represented a substantial improvement over the 5–7% typically achieved with orlistat and was associated with meaningful cardiometabolic improvements. The prediabetes-to-diabetes prevention finding from the 160-week extension analysis was a particularly important secondary observation: an 79% reduction in the rate of T2DM progression in a population that was already at high risk by definition of prediabetes at enrolment. This finding positioned liraglutide 3.0 mg as not only an obesity treatment but a diabetes prevention intervention, a claim that had previously been made only for intensive lifestyle programmes (the Diabetes Prevention Program) and metformin.
In the context of the subsequent STEP and SURMOUNT programmes, the weight loss achieved in SCALE (8.0%) is now recognised as modest compared with semaglutide 2.4 mg (−14.9%) and tirzepatide 15 mg (−20.9%). However, SCALE retains important clinical relevance for several reasons. Liraglutide 3.0 mg is administered daily rather than weekly, which may suit some patient preferences. Its long-term safety database is substantially larger than for the newer agents. The prediabetes reversal and diabetes prevention data are specific to liraglutide 3.0 mg and have not been replicated in dedicated trials for higher-dose semaglutide or tirzepatide in the obesity setting. The tolerability profile, with 40% nausea rates, is a meaningful clinical consideration and tends to improve over the first weeks of treatment with dose titration. SCALE remains the foundational registration study for GLP-1 receptor agonist obesity pharmacotherapy and established the regulatory pathway that semaglutide and tirzepatide subsequently followed.
Limitations: Weight loss of 8.0% is modest relative to subsequent agents in the class. The 56-week duration does not address long-term maintenance. The high nausea rate (40%) may limit tolerability in clinical practice. Hard cardiovascular endpoint data were not generated for liraglutide 3.0 mg in the obesity indication, and this distinguishes it from semaglutide 2.4 mg, which has SELECT data. The study was industry-sponsored by Novo Nordisk.
🔑 BOTTOM LINE
SCALE established liraglutide 3.0 mg as the first approved GLP-1 receptor agonist for chronic weight management, demonstrating a mean weight loss of 8.0% and a 79% reduction in progression from prediabetes to type 2 diabetes, setting the regulatory and clinical precedent for the higher-efficacy obesity pharmacotherapy agents that followed.
⭐ Clinical Impact Rating: ●●●●○ Practice-changing (foundational approval trial)
Next in the series: Study #15 Look AHEAD: Intensive Lifestyle Intervention for Weight Loss in Type 2 Diabetes — The Unexpected Null
