INTRODUCTION: Tirzepatide, an anti-obesity medication, demonstrated significant weight loss efficacy in the SURMOUNT-1 randomized controlled trial. This analysis evaluates the cost-efficiency of tirzepatide in the UK by linking clinical outcomes to drug acquisition costs. METHODS: Data from SURMOUNT-1 (2539 participants across global sites) were used to assess tirzepatide's (5, 10, and 15 mg) impact on weight reduction over 72 weeks (72W), with a focus on drug acquisition costs and cost/weight loss outcome. Cost needed to treat and cost-to-target analyses were performed to determine the economic value of achieving specific weight loss goals and improvements in body mass index (BMI). RESULTS: Tirzepatide demonstrated significant weight loss, with greater reductions at higher doses. Cost/kilogram of weight loss at 72W was £102.86, £85.41, and £89.24 for 5, 10, and 15 mg, respectively. Average per-patient costs at 72W for 5% weight loss were £1852, £1971, and £2186 (5, 10, and 15 mg, respectively
average 28-day costs: £102.90, £109.52, and £121.47). Average per-patient costs for 10% weight loss were £2258, £2209, and £2338 (28-day costs: £125.43, £122.69, and £129.88). The 15 mg dose was the most cost-efficient for achieving higher weight loss targets (15% and 20%). CONCLUSIONS: In the SURMOUNT-1 study, tirzepatide was cost-efficient in the UK for weight management, demonstrating favourable economic outcomes relative to its efficacy in reducing body weight and improving BMI. It provided additional health benefits, including reduced risks for type 2 diabetes and cardiovascular events and improved mental health. Tirzepatide contributed to cost savings and improved efficiency within the healthcare system by decreasing the burden of obesity-related conditions, thus enhancing overall healthcare resource allocation. These findings support its inclusion in clinical practice guidelines and healthcare formularies. Further research is needed to explore real-world adherence, patient-centred outcomes, and the long-term sustainability of weight loss with tirzepatide.