PIONEER 6 is the cardiovascular safety trial for oral semaglutide (Rybelsus). It is a useful example of a result whose confidence interval crosses 1.0, and of why that is not the same as "no effect".
What the trial asked
Whether once-daily oral semaglutide is noninferior to placebo for major adverse cardiovascular events (MACE) in people with type 2 diabetes at high cardiovascular risk. The design was to rule out an 80 percent excess risk: a noninferiority margin of 1.8 for the upper bound of the 95% confidence interval of the hazard ratio.
Design
Event-driven, randomised, double-blind, placebo-controlled. Primary outcome: time to first MACE (cardiovascular death, nonfatal myocardial infarction or nonfatal stroke). Median time in the trial was 15.9 months. The abstract does not state the oral dose.
Who was enrolled
3183 patients: age 50 or over with established cardiovascular or chronic kidney disease, or age 60 or over with cardiovascular risk factors only. Mean age 66; 2695 (84.7 percent) were 50 or older with established disease.
Primary endpoint and result
MACE occurred in 61 of 1591 (3.8 percent) on oral semaglutide and 76 of 1592 (4.8 percent) on placebo. Hazard ratio 0.79 (95% CI 0.57 to 1.11; P less than 0.001 for noninferiority).
The interval runs from 0.57 to 1.11. That comfortably excludes 1.8, so noninferiority was met. It does not exclude 1.0, so superiority was not shown. Both statements are true at once.
Key secondary results
| Component | Oral semaglutide | Placebo | HR (95% CI) |
|---|---|---|---|
| Death from cardiovascular causes | 15 (0.9%) | 30 (1.9%) | 0.49 (0.27 to 0.92) |
| Nonfatal myocardial infarction | 37 (2.3%) | 31 (1.9%) | 1.18 (0.73 to 1.90) |
| Nonfatal stroke | 12 (0.8%) | 16 (1.0%) | 0.74 (0.35 to 1.57) |
| Death from any cause | 23 (1.4%) | 45 (2.8%) | 0.51 (0.31 to 0.84) |
Event counts are small. The cardiovascular-death and all-cause-death intervals exclude 1.0; the others do not.
Adverse events and discontinuation
Gastrointestinal adverse events leading to discontinuation were more common with oral semaglutide. The abstract gives no percentages.
Funding and registration
Novo Nordisk. ClinicalTrials.gov NCT02692716.
What this trial does not show
- It does not show cardiovascular superiority for oral semaglutide. A later, larger trial would be needed for that; this one was sized to rule out harm.
- 16 months of median follow-up is short for cardiovascular outcomes.
- With 15 versus 30 cardiovascular deaths, the death results rest on small numbers and should be read with their wide intervals.
- No weight data in the abstract; this was a diabetes population and a safety question.
Where the numbers come from
PubMed abstract of the primary paper (PubMed 31185157), fetched 4 September 2026. For the newer oral GLP-1, orforglipron, see ATTAIN-1, which is a weight trial rather than a cardiovascular one.
Sources
- Oral Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes (PIONEER 6). N Engl J Med 2019;381(9):841-851. PubMed 31185157 Accessed September 4, 2026.
- ClinicalTrials.gov NCT02692716 Accessed September 4, 2026.
Canonical URL: https://formblendsresearch.com/trials/pioneer-6. Written by the FormBlends editorial team. This page is educational and is not medical advice; see the medical disclaimer.