Summarize the different SURPASS phase 3 clinical trials of tirzepatide (Mounjaro).

SURPASS Phase 3 Clinical Trial Program for Tirzepatide

Overview of the SURPASS Program

The SURPASS phase 3 clinical development program established tirzepatide's efficacy across five major trials (SURPASS-1 through SURPASS-5), demonstrating superior glycemic control and weight reduction compared to placebo and active comparators including semaglutide, insulin degludec, and insulin glargine. 1

Individual SURPASS Trials

SURPASS-1: Monotherapy Trial

• Design: 40-week, double-blind, placebo-controlled trial in 478 treatment-naive patients with inadequate glycemic control on diet and exercise alone 1, 2
• Population: Mean age 54 years, baseline HbA1c 7.9%, mean BMI 32 kg/m², diabetes duration 4.7 years 1, 2
• Interventions: Tirzepatide 5 mg, 10 mg, or 15 mg once weekly versus placebo 1, 2

Key Results at 40 weeks:

• HbA1c reduction: -1.87% (5 mg), -1.89% (10 mg), -2.07% (15 mg) versus +0.04% with placebo (all p<0.0001) 1, 2
• HbA1c <7% achievement: 82-85% with tirzepatide versus 23% with placebo 1, 2
• HbA1c <5.7% achievement: 31-52% with tirzepatide versus 1% with placebo 2
• Weight loss: -6.3 kg (5 mg), -7.0 kg (10 mg), -7.8 kg (15 mg) versus -1.0 kg with placebo 1, 2
• Safety: Most common adverse events were mild-to-moderate gastrointestinal symptoms (nausea 12-18%, diarrhea 12-14%, vomiting 2-6%); no clinically significant hypoglycemia reported 2

SURPASS-2: Head-to-Head Comparison with Semaglutide

• Design: 40-week, open-label trial in 1,879 patients comparing tirzepatide directly to semaglutide 1 mg 1, 3
• Population: Mean baseline HbA1c 8.28%, mean age 56.6 years, mean weight 93.7 kg 3
• Interventions: Tirzepatide 5 mg, 10 mg, or 15 mg versus semaglutide 1 mg, all as add-on to metformin, SGLT2 inhibitors, and/or sulfonylureas 1, 3

Key Results at 40 weeks:

• HbA1c reduction: -2.01% (5 mg), -2.24% (10 mg), -2.30% (15 mg) with tirzepatide versus -1.86% with semaglutide 3
• Treatment differences versus semaglutide: -0.15% (5 mg, p=0.02), -0.39% (10 mg, p<0.001), -0.45% (15 mg, p<0.001) 3
• Weight loss superiority: Greater reductions with tirzepatide by -1.9 kg (5 mg), -3.6 kg (10 mg), -5.5 kg (15 mg) compared to semaglutide (all p<0.001) 3
• Safety: Gastrointestinal events similar between groups (nausea 17-22% vs 18%, diarrhea 13-16% vs 12%); hypoglycemia <54 mg/dL occurred in 0.2-1.7% with tirzepatide versus 0.4% with semaglutide 3

SURPASS-3: Comparison with Insulin Degludec

• Design: 52-week trial comparing tirzepatide to insulin degludec as add-on therapy to metformin with or without SGLT2 inhibitors 1, 4
• Key Results: Tirzepatide demonstrated superior HbA1c reduction (mean difference -1.08%, 95% CI -1.37 to -0.78) and weight loss (mean difference -10.61 kg, 95% CI -13.24 to -7.97) compared to insulin degludec 4
• Hypoglycemia advantage: Lower risk of hypoglycemia (blood glucose ≤70 mg/dL) with tirzepatide (RR 0.46,95% CI 0.28-0.75) 4

SURPASS-4: Long-term Cardiovascular Safety Trial

• Design: 52-week trial in patients with increased cardiovascular risk, comparing tirzepatide to insulin glargine 1, 4
• Population: Patients with established cardiovascular disease or multiple cardiovascular risk factors 1
• Key Results: Consistent superiority in glycemic control and weight reduction; tirzepatide probably reduces severe hypoglycemia compared to insulin (RR 0.21,95% CI 0.11-0.38, moderate certainty of evidence) 5

SURPASS-5: Combination with Basal Insulin

• Design: 40-week trial evaluating tirzepatide as add-on to basal insulin with or without metformin 1
• Key Results: Demonstrated efficacy in patients already on insulin therapy, with significant improvements in glycemic control and weight reduction 1

Meta-Analysis Findings Across SURPASS Trials

Glycemic Control

• Network meta-analysis: Tirzepatide achieved mean HbA1c reduction of approximately -2.0 to -2.3% across doses, though substantial heterogeneity limited precise pooled estimates due to variable use of rescue medications 5

Weight Loss

• Exceptional efficacy: Tirzepatide produced mean weight reduction of -8.47 kg (95% CI -9.49 to -7.45 kg) compared to usual care, substantially exceeding GLP-1 agonists (-2.22 kg) and SGLT2 inhibitors (-2.48 kg) 5
• 10% weight loss achievement: 3-67% of tirzepatide-treated patients achieved ≥10% weight reduction (dose-dependent) versus 0% with insulin glargine and 6.7% with usual care 5

Cardiovascular and Metabolic Effects

• Lipid improvements: Significant reductions in total cholesterol (-4.78%), triglycerides (-14.49%), LDL cholesterol (-5.98%), and VLDL cholesterol (-14.18%), with increased HDL cholesterol (+7.13%) 4
• Blood pressure: Reductions in systolic BP (-6.47 mmHg) and diastolic BP (-2.30 mmHg) 4

Safety Profile

• Hypoglycemia: Tirzepatide does not differ from usual care for severe hypoglycemia (RR 1.32,95% CI 0.78-2.22, moderate certainty of evidence), but probably reduces severe hypoglycemia compared to insulin (RR 0.21,95% CI 0.11-0.38) 5
• Serious adverse events: Tirzepatide does not differ from usual care (RR 0.79,95% CI 0.51-1.22, high certainty of evidence) 5
• Gastrointestinal events: Consistent mild-to-moderate nausea (12-22%), diarrhea (12-16%), and vomiting (2-10%) across all trials 2, 3

Patient-Reported Outcomes

Quality of life improvements were consistently demonstrated across all five SURPASS trials using validated instruments including EQ-5D-5L, Impact of Weight on Self-Perceptions, and Diabetes Treatment Satisfaction Questionnaire, with higher doses generally producing greater improvements. 6

Clinical Implications

• Dose-dependent efficacy: All three doses (5 mg, 10 mg, 15 mg) showed superiority, with 10 mg and 15 mg demonstrating the most robust effects 1, 3
• Effectiveness across populations: Benefits were consistent regardless of age, gender, race, ethnicity, baseline BMI, HbA1c, diabetes duration, or renal function 1
• Positioning: The SURPASS program established tirzepatide as the most potent glucose and weight-lowering agent available for type 2 diabetes management 7