OASIS 1: oral semaglutide 50 mg for weight loss over 68 weeks

Why this study matters

The weight-management dose of semaglutide (Wegovy, Ozempic) is given as a weekly injection. OASIS 1 was the first large trial to test a daily tablet at a high dose, 50 mg, for weight management in adults without diabetes. Many people would prefer a pill to an injection, so this trial matters to Canadian readers who want to know whether a tablet form was tested and what it showed. The tablet regimen in this trial is a research description, not a statement about what is available in Canada.

Who was in the study

Between 13 September and 22 November 2021, 709 adults were screened and 667 were randomized: 334 to oral semaglutide 50 mg and 333 to placebo. Everyone had a BMI of at least 30, or at least 27 with weight-related health problems. BMI (body mass index) compares weight with height. No one had type 2 diabetes.

The trial ran at 50 outpatient clinics in nine countries across Asia, Europe and North America. The summary we reviewed does not name the countries. It lasted 68 weeks.

What the researchers did

This was a randomized, double-blind, placebo-controlled, phase 3 trial. Randomized means chance decided the treatment. Double-blind means participants, investigators and the people measuring results did not know who was on the medicine. Placebo means an inactive tablet that looked the same. Phase 3 means a large trial designed to confirm benefit and safety.

People were assigned 1:1 to oral semaglutide, built up gradually to 50 mg once a day, or to matching placebo, for 68 weeks. Everyone also received a lifestyle intervention with support for food and activity.

The two main outcomes were percentage change in body weight and the share of people reaching at least 5% weight loss at week 68. The analysis counted everyone who was randomized, regardless of whether they stopped treatment or used other weight-lowering therapies. This is called an intention-to-treat analysis.

What they found

The estimated mean weight change from the start to week 68 was -15.1% with oral semaglutide 50 mg and -2.4% with placebo (R32-C19). The estimated difference was -12.7 percentage points, with a 95% confidence interval of -14.2 to -11.3. A confidence interval is the range where the true difference most likely sits. The result was very unlikely to be chance (P less than 0.0001).

The odds ratios for reaching these marks with semaglutide versus placebo were 12.6 (95% CI 8.5 to 18.7) for 5%, 14.7 (9.6 to 22.6) for 10%, 17.9 (10.4 to 30.7) for 15%, and 18.5 (8.8 to 38.9) for 20%. An odds ratio above 1 means the outcome was more likely with the medicine.

Side effects and people who stopped

Adverse events of any kind were reported by 307 of 334 people (92%) on oral semaglutide and 285 of 333 (86%) on placebo. Stomach and gut side effects were reported by 268 people (80%) on oral semaglutide and 154 (46%) on placebo, and most were mild to moderate (R32-C20). The summary we reviewed does not report how many people stopped treatment, or how many stopped because of side effects.

What this study does not tell you

• The trial compared the 50 mg tablet with placebo. It did not compare the tablet directly with the weekly injection, so the two cannot be ranked from this trial.
• No one had type 2 diabetes.
• Both groups had lifestyle support, so the result shows what the tablet added on top of it.
• The trial ran for 68 weeks and measured weight, not heart attacks, strokes or other long-term outcomes.
• It does not say what happens after the tablet is stopped.
• The trial was funded by the maker of semaglutide.
• Our data extraction relied on the abstract only.

What it means in Canada

OASIS 1 shows what a daily 50 mg semaglutide tablet did in a research setting. This page does not state whether an oral form is approved or available for weight management in Canada, or at what dose. For current information, see semaglutide in Canada and public drug coverage by province.

Related reading

Other studies in this library that bear on the same question.

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