What is the history and development background of Mounjaro?

Mounjaro was developed by the pharmaceutical company Eli Lilly and first approved for medical use in 2022. It’s based on years of research into dual hormone therapies that target both GIP and GLP-1 pathways. Its effectiveness has since been demonstrated in large international trials, helping establish it as a new generation of treatment for type 2 diabetes and weight management.

How Mounjaro began

The story of Mounjaro started in the early 2010s, when researchers explored ways to improve on existing GLP-1-based drugs such as liraglutide and semaglutide. Scientists at Eli Lilly studied how combining GLP-1 and GIP hormone activity could produce a stronger, more balanced effect on blood-sugar regulation and appetite. The molecule that resulted — tirzepatide — was designed to mimic both hormones at once, making it the first dual-receptor agonist of its kind. Early laboratory studies showed that activating GIP alongside GLP-1 improved insulin release and reduced side effects such as nausea. This dual-pathway concept became the foundation for what NICE (TA1026, 2025) now calls a “first-in-class” therapy.

Clinical research and early trials

Between 2018 and 2021, Eli Lilly conducted a global series of trials known as SURPASS, focusing on people with type 2 diabetes. Published in The New England Journal of Medicine and The Lancet Diabetes & Endocrinology, these studies found tirzepatide significantly lowered HbA1c and body weight compared with established medicines such as insulin degludec and semaglutide. Participants achieved average reductions of about 2 percentage points in HbA1c and up to 12 kg in weight. Some people have found it helpful to think of these trials as a “proof of concept” — demonstrating that the medicine could go beyond glucose control to address the root metabolic issues linked with excess weight.

Expansion into weight management

Following the success of SURPASS, new studies called SURMOUNT explored tirzepatide’s effects in people without diabetes. These trials, completed between 2021 and 2023, included thousands of participants and were among the largest obesity-treatment studies ever conducted. Nature Medicine and JAMA Network Open reported that average weight loss reached 15 – 22 % after 72 weeks, depending on dose. NICE later reviewed these results and concluded that tirzepatide “delivers clinically meaningful and sustained weight reduction” when used alongside diet and physical activity. This evidence led to Mounjaro’s formal authorisation for weight management in 2025 under TA1026.

Regulatory approval and global rollout

The U.S. Food and Drug Administration (FDA) first approved tirzepatide for type 2 diabetes in May 2022. The European Medicines Agency (EMA) followed in 2023, and the UK MHRA granted approval soon after through its international reliance procedure. Each regulator assessed large-scale safety and efficacy data, confirming that Mounjaro’s benefits outweighed potential risks. NICE then undertook its health-technology appraisal, considering cost-effectiveness for NHS use. The final guidance — published in 2025 — recommended Mounjaro for adults with obesity who meet specific body-mass-index and comorbidity criteria. NHS England incorporated it into its obesity-care framework later the same year.

The science behind dual-hormone design

Before Mounjaro, all GLP-1-based medicines targeted a single receptor. Adding GIP activity represented a major scientific step forward. GIP works primarily on fat tissue and the pancreas, enhancing insulin’s effect and moderating the digestive system’s response to food. GLP-1, meanwhile, slows gastric emptying and influences brain centres that regulate appetite. By merging both actions, tirzepatide offers more comprehensive metabolic control. Nature Metabolism (2024) described it as “a paradigm shift from single-pathway modulation to integrated metabolic signalling.” NHS clinicians often summarise this as “helping the body run on balanced energy rather than fighting hunger and sugar swings.”

Evolution of use within the NHS

In 2024, NHS England began pilot implementation through diabetes-care networks, initially for people with type 2 diabetes who had not reached target HbA1c with metformin and lifestyle support. After NICE’s obesity guidance in 2025, access widened through Tier 3 and Tier 4 weight-management services. Each patient’s eligibility is confirmed by a specialist team that provides medical, dietetic, and behavioural support. Those adjusting to the medicine often discover it helps to approach treatment as part of a broader plan, not a stand-alone fix. NHS clinicians encourage using the first months to establish healthy routines around food, sleep, and physical activity — building habits that will sustain results long after the dose stabilises.

Ongoing research and innovation

Research continues into how tirzepatide affects cardiovascular, kidney, and liver outcomes. Studies published in The Lancet and Nature Cardiovascular Research show promising signs of improved vascular function and reduced fatty-liver markers. The SURPASS-CVOT trial, currently underway, will assess whether these benefits translate into fewer heart attacks and strokes. Several users have said they feel more confident after learning that the medicine’s long-term safety is monitored continuously by agencies such as the MHRA and EMA. In real-world NHS data, side effects have remained consistent with clinical-trial findings — mostly mild gastrointestinal symptoms that ease as dosing progresses.

Economic and social context

Mounjaro’s arrival coincided with rising demand for effective weight-management therapies across the UK. Parliament briefings on obesity policy (2025) note that dual-hormone drugs like tirzepatide could ease NHS pressures linked to diabetes and cardiovascular disease. NICE’s cost analysis estimated that sustained weight loss of 15 % could prevent thousands of obesity-related admissions each year. In clinic feedback, people frequently report that Mounjaro not only helps with weight but improves confidence, mobility, and participation in social activities. A helpful approach shared by others is to see treatment as a stepping stone — using the period of reduced appetite to rebuild healthier habits and long-term wellbeing.

What the research tells us

The development of Mounjaro marks one of the most significant advances in metabolic medicine in recent decades. From early GIP-GLP-1 research to its multi-phase global trials, every stage has been guided by rigorous evaluation and independent review by NICE, MHRA, and other regulators.

 Understanding this background helps users appreciate that Mounjaro is not a trend or shortcut but the result of years of collaboration between scientists, clinicians, and public-health authorities. The essential point is that Mounjaro’s innovation lies in balance — harnessing two natural hormones to restore the body’s own ability to regulate hunger, energy, and glucose for the long term.