Tirzepatide vs Semaglutide

Tirzepatide is a dual GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) receptor agonist developed by Eli Lilly. It is the first approved drug to activate both increin receptors. The dual agonism distinguishes it from semaglutide, which acts only on the GLP-1 receptor.

Tirzepatide received FDA approval as Mounjaro for Type 2 diabetes in May 2022 and as Zepbound for chronic weight management in November 2023. Both are once-weekly subcutaneous injections. No oral formulation has been approved.

The SURPASS trial program established efficacy for Type 2 diabetes. SURPASS-2 (Heisler et al., 2021, NEJM) directly compared tirzepatide to semaglutide and demonstrated superior A1C reduction. The SURMOUNT trial program established efficacy for weight loss. SURMOUNT-1 (Jastreboff et al., 2022, NEJM) reported mean weight loss of 22.5% at 72 weeks at the highest dose.

SURMOUNT-5 (Garvey et al., 2024, NEJM) was the pivotal head-to-head trial comparing tirzepatide to semaglutide for weight loss. It reported greater mean weight loss with tirzepatide (approximately 20.9%) than with semaglutide (approximately 17.3%) at 72 weeks. Results are specific to the trial population and dosing protocol and should not be generalized to all patients.

Cardiovascular outcomes trials for tirzepatide are ongoing. The SURMOUNT-5 trial provides comparative weight loss data, but semaglutide currently has a more mature cardiovascular outcomes evidence base (SELECT, SUSTAIN-6).

Tirzepatide is widely available through prescription channels, including telehealth platforms that prescribe it for its FDA-approved indications. Compounded versions are not FDA-approved and are subject to FDA enforcement.

Semaglutide is a GLP-1 receptor agonist developed by Novo Nordisk. It activates only the GLP-1 receptor, not GIP. It is available as a once-weekly subcutaneous injection (Ozempic for diabetes, Wegovy for weight management) and as a once-daily oral tablet (Rybelsus for diabetes).

Semaglutide received FDA approval as Ozempic for Type 2 diabetes in 2017, Rybelsus as an oral formulation for Type 2 diabetes in 2019, and Wegovy for chronic weight management in 2021. The oral formulation is a key differentiator from tirzepatide, which has no approved oral form.

The STEP trial program established efficacy for weight loss. STEP 1 (Wilding et al., 2021, NEJM) reported mean weight loss of 14.9% at 68 weeks with the 2.4 mg weekly dose. The SUSTAIN program established diabetes efficacy, and SUSTAIN-6 established cardiovascular safety in Type 2 diabetes.

The SELECT cardiovascular outcomes trial (Ryan et al., 2023, NEJM) demonstrated that semaglutide reduced major adverse cardiovascular events in non-diabetic patients with obesity — a landmark finding. Tirzepatide's cardiovascular outcomes data is less mature, though trials are ongoing.

Semaglutide has been the subject of extensive public discussion about compounded alternatives and telehealth prescribing patterns. The FDA has taken enforcement actions against compounded semaglutide products that do not meet regulatory standards. Compounded versions are not FDA-approved.

Semaglutide is widely available through prescription channels, including telehealth platforms. The oral formulation (Rybelsus) provides an alternative to injection, though it is only approved for Type 2 diabetes, not for weight management.