Peptides

Semaglutide (Ozempic/Wegovy) Research Overview

Research overview of semaglutide, the GLP-1 receptor agonist behind Ozempic and Wegovy. Clinical trial data, mechanism of action, and Australian research context.

Semaglutide (Ozempic/Wegovy) Research Overview

Semaglutide is a synthetic glucagon-like peptide-1 receptor agonist (GLP-1 RA) developed for type 2 diabetes and chronic weight management. It is marketed as Ozempic (injectable, for type 2 diabetes), Wegovy (injectable, for weight management), and Rybelsus (oral, for type 2 diabetes). The compound is among the most tested incretin-based agents in Phase 3 clinical trials, with data published across the SUSTAIN, PIONEER, STEP, and SELECT programmes.

Mechanism of Action

As a synthetic analogue of native human GLP-1, semaglutide binds to the GLP-1 receptor and stimulates insulin secretion in a glucose-dependent manner while suppressing glucagon release. This dual mechanism regulates blood glucose with a lower risk of hypoglycaemia compared to earlier insulin secretagogues.

Structurally, semaglutide differs from native GLP-1 in two key ways. First, a fatty diacid chain attached to position 26 via a linker enables strong, non-covalent binding to serum albumin, extending the circulating half-life to approximately 168 hours (one week). Second, an alpha-aminoisobutyric acid (Aib) substitution at position 8 confers resistance to dipeptidyl peptidase-4 (DPP-4) enzymatic degradation. These modifications support once-weekly subcutaneous dosing - a significant advance over exenatide (twice daily) and liraglutide (daily).

Clinical Trial Programme

SUSTAIN Programme (Type 2 Diabetes)

The SUSTAIN (Semaglutide Unabated Sustainability in Treatment of Type 2 Diabetes) programme comprised a series of Phase 3 trials evaluating semaglutide in adults with type 2 diabetes:

  • SUSTAIN 1 (monotherapy): HbA1c reductions of 1.5% (0.5 mg) to 1.8% (1.0 mg) versus 0.1% with placebo at 30 weeks.
  • SUSTAIN 2: At 56 weeks, semaglutide 1.0 mg achieved superior HbA1c reduction compared to sitagliptin 100 mg (1.6% vs 0.5%).
  • SUSTAIN 6: Published in November 2016, this cardiovascular outcomes trial (n=3,297) demonstrated a 26% relative risk reduction in major adverse cardiovascular events (MACE) with semaglutide versus placebo (HR 0.74, 95% CI 0.58-0.95) (Marso et al. (2016)). This was the first CV outcomes signal for the GLP-1 RA class in a dedicated trial. The trial is registered at ClinicalTrials.gov.
  • SUSTAIN 7: In a head-to-head comparison with dulaglutide, semaglutide produced statistically superior HbA1c reductions and weight loss at both matched dose pairs.

PIONEER Programme (Oral Semaglutide)

Oral semaglutide uses sodium N-(8-[2-hydroxybenzoyl]amino) caprylate (SNAC) as an absorption enhancer to achieve systemic delivery via the gastrointestinal tract:

  • PIONEER 1: Published in November 2019, oral semaglutide 14 mg reduced HbA1c by 1.0% versus 0.3% with placebo at 26 weeks (Aroda et al. (2019)).
  • PIONEER 4: At 52 weeks, oral semaglutide 14 mg demonstrated non-inferior HbA1c reduction and superior weight loss compared to liraglutide 1.8 mg.
  • PIONEER 6: The cardiovascular safety trial (n=3,183) showed no increased cardiovascular risk, with a numerical trend toward MACE reduction (HR 0.79, 95% CI 0.57-1.11).

STEP Programme (Weight Management)

The STEP (Semaglutide Treatment Effect in People with Obesity) trials evaluated semaglutide 2.4 mg weekly for chronic weight management:

  • STEP 1: Published in March 2021, participants receiving semaglutide 2.4 mg lost a mean of 14.9% of baseline body weight versus 2.4% with placebo at 68 weeks. Over 86% of the semaglutide group achieved at least 5% weight loss (Wilding et al. (2021)). This trial is registered at ClinicalTrials.gov.
  • STEP 2: Published in March 2021, adults with type 2 diabetes receiving semaglutide 2.4 mg lost 9.6% of body weight versus 3.4% with placebo (Davies et al. (2021)).
  • STEP 3: Published in April 2021, semaglutide combined with intensive behavioural therapy produced 16.0% weight reduction at 68 weeks (Wadden et al. (2021)).
  • STEP 5: Published in October 2022, this trial demonstrated sustained weight loss over 104 weeks (two years), with participants maintaining approximately 15.2% weight reduction (Garvey et al. (2022)).

Oral vs Injectable Formulations

Two routes of administration are available, with distinct pharmacokinetic and practical differences:

  • Injectable (subcutaneous): Ozempic (up to 2.0 mg weekly for diabetes) and Wegovy (2.4 mg weekly for weight management). The injectable route delivers higher and more consistent bioavailability.
  • Oral: Rybelsus (up to 14 mg daily for diabetes). Fasting administration with a small amount of water is required, followed by a 30-minute wait before eating. Bioavailability is lower and more variable than the injectable route.

Higher-dose oral semaglutide formulations (25 mg and 50 mg) are under investigation in the OASIS programme, which may narrow the efficacy gap between oral and injectable routes.

SELECT Trial (Cardiovascular Outcomes in Obesity)

Published in November 2023, the SELECT trial randomised 17,604 adults with overweight or obesity and established cardiovascular disease (but without diabetes) to semaglutide 2.4 mg or placebo. Semaglutide reduced the composite MACE endpoint by 20% (HR 0.80, 95% CI 0.72-0.90) over a median follow-up of 39.8 months (Lincoff et al. (2023)). This was the first trial to show cardiovascular benefit of a GLP-1 RA in a population without diabetes. The trial is registered at ClinicalTrials.gov.

Ongoing Research

Semaglutide is being evaluated across several additional therapeutic areas:

  • EVOKE and EVOKE+: Trials investigating semaglutide in early Alzheimer’s disease, based on preclinical data showing GLP-1 receptor-mediated neuroprotective effects.
  • STEP-HFpEF: Evaluating semaglutide in heart failure with preserved ejection fraction in people with obesity.
  • OASIS: Testing oral semaglutide 50 mg for weight management.

The compound remains central to the field of incretin-based research, which has expanded to include dual and triple agonist approaches.

Regulatory Status in Australia

In Australia, semaglutide-containing products are classified as Schedule 4 (Prescription Only) by the Therapeutic Goods Administration (TGA):

  • Ozempic (semaglutide injection) is TGA-approved for glycaemic control in adults with type 2 diabetes and is listed on the Pharmaceutical Benefits Scheme (PBS) for eligible patients.
  • Wegovy (semaglutide 2.4 mg injection) was approved by the TGA for chronic weight management and has been listed on the PBS under specific criteria for adults with obesity.
  • Rybelsus (oral semaglutide) is TGA-approved for type 2 diabetes.

Supply constraints have periodically affected availability of semaglutide products in Australia, reflecting global demand patterns.

Disclaimer: This page is for research and educational purposes only. No therapeutic claims are made. Semaglutide is a Schedule 4 (Prescription Only) compound in Australia. This information does not constitute medical advice. Consult a qualified healthcare professional for any health-related decisions. All data referenced is drawn from published peer-reviewed clinical trials.