Semaglutide: Published Research

Introduction

Semaglutide has been evaluated across one of the most extensive clinical-trial programs assembled for a GLP-1 receptor agonist, encompassing the SUSTAIN series (subcutaneous formulation in type 2 diabetes), the PIONEER series (oral formulation in type 2 diabetes), the STEP series (body-weight outcomes), and the SELECT trial (cardiovascular outcomes). This article summarizes methodology types and key reported findings for representative trials across each program, with findings attributed to primary peer-reviewed publications. All cited outcomes were reported in randomized controlled trials unless otherwise noted; no editorial conclusions are drawn about aggregate efficacy or comparative performance. The molecular mechanisms underlying these findings are described in the semaglutide mechanism-of-action article in this library.

Methodology Types

The trials across these programs share several common design elements. Most are randomized, double-blind, placebo-controlled or active-comparator-controlled, phase 3 trials with predefined primary endpoints and pre-specified hierarchical testing procedures. Blinded independent event-adjudication committees assessed cardiovascular outcomes in the cardiovascular outcome trials (CVOTs). The SUSTAIN-6 and PIONEER 6 trials were designed as CVOTs to demonstrate non-inferiority of semaglutide versus placebo on a composite major adverse cardiovascular event (MACE) endpoint, as required by FDA guidance for new diabetes therapies issued in 2008 [1]. The SELECT trial was a superiority CVOT enrolling a different population — individuals with established cardiovascular disease and overweight or obesity, but without diabetes [2].

Primary endpoints differed between the trial programs: glycated hemoglobin change from baseline was the primary endpoint in most SUSTAIN and PIONEER trials; percentage change in body weight (and proportion achieving ≥5% weight reduction) were co-primary endpoints in the STEP trials; and time-to-first MACE event was the primary endpoint in the cardiovascular outcome trials.

Summary of Trials by Program

SUSTAIN Program (Subcutaneous Semaglutide in Type 2 Diabetes)

SUSTAIN-6 was a randomized, double-blind, placebo-controlled trial conducted at 230 sites in 20 countries, enrolling 3,297 adults with type 2 diabetes at high cardiovascular risk. Participants were randomized to subcutaneous semaglutide or volume-matched placebo, with standard of care continued in both arms. Marso and colleagues reported the primary MACE outcome — a composite of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke — in the New England Journal of Medicine in 2016 [3]. The primary endpoint occurred in 6.6% of participants in the semaglutide group versus 8.9% in the placebo group, corresponding to a hazard ratio of 0.74 (95% CI, 0.58 to 0.95), which met the pre-specified non-inferiority threshold and demonstrated statistical superiority [3]. The authors additionally noted that rates of retinopathy complications were numerically higher in the semaglutide arm — an observation that informed the design of subsequent ophthalmologic monitoring sub-studies within the SUSTAIN program [3].

Findings from research models do not establish safety or efficacy in humans. SpartaLabs makes no claims about the use of this compound.

PIONEER Program (Oral Semaglutide in Type 2 Diabetes)

PIONEER 6 was an event-driven, randomized, double-blind, placebo-controlled CVOT assessing cardiovascular outcomes of once-daily oral semaglutide in 3,183 patients with type 2 diabetes at high cardiovascular risk. Husain and colleagues published results in the New England Journal of Medicine in 2019 [4]. The hazard ratio for the primary MACE composite outcome was 0.79 (95% CI, 0.57 to 1.11), meeting the pre-specified non-inferiority margin [4]. All-cause mortality was numerically lower in the oral semaglutide group (hazard ratio 0.51; 95% CI, 0.31 to 0.84), a finding the authors noted as hypothesis-generating given that the trial was not powered to assess individual mortality components [4]. The PIONEER 6 data established the cardiovascular safety profile of the oral formulation and supported its regulatory authorization as the first oral GLP-1 receptor agonist approved by the FDA.

The oral formulation used in the PIONEER program co-formulates semaglutide with the absorption enhancer SNAC (sodium N-[8-(2-hydroxybenzoyl)amino]caprylate). A review published in Diabetes Therapy in 2020 described the bioavailability profile and pharmacokinetic characteristics reported across the PIONEER program [5].

STEP Program (Semaglutide in Overweight and Obesity)

STEP 1 enrolled 1,961 adults with a body mass index of 30 kg/m² or above (or 27 kg/m² or above with at least one weight-related comorbidity) who did not have diabetes, and randomized them to 68 weeks of once-weekly subcutaneous semaglutide or placebo as an adjunct to lifestyle intervention. Wilding and colleagues published the primary results in the New England Journal of Medicine in 2021 [6]. Authors reported a mean change in body weight from baseline of −14.9% in the semaglutide group versus −2.4% in the placebo group at week 68, with 86.6% of semaglutide-treated participants achieving the ≥5% weight-reduction threshold versus 47.6% in the placebo group [6]. Gastrointestinal adverse events, predominantly nausea and diarrhea, were reported in 82.8% of the semaglutide group versus 63.2% of the placebo group; 4.5% of participants in the semaglutide group discontinued due to these events, which the authors characterized as consistent with the known adverse event profile of the GLP-1RA class [6].

STEP 5 was a phase 3, randomized, double-blind, placebo-controlled trial designed to assess the durability of outcomes over 104 weeks (approximately two years). Garvey and colleagues published the results in Nature Medicine in 2022 [7]. The trial enrolled 304 adults without diabetes who had overweight or obesity with at least one comorbidity. At week 104, authors reported a mean change in body weight of −15.2% in the semaglutide group versus −2.6% in the placebo group, with 77.1% of semaglutide-treated participants achieving ≥5% weight reduction — outcomes the authors noted were consistent with those observed at earlier time points and supported the durability of the observed effect over a two-year period [7].

SELECT Trial (Cardiovascular Outcomes in Overweight/Obesity Without Diabetes)

The SELECT (Semaglutide Effects on Cardiovascular Outcomes in People with Overweight or Obesity) trial was a multicenter, double-blind, randomized, placebo-controlled, event-driven superiority trial conducted at 804 sites in 41 countries. Lincoff and colleagues published results in the New England Journal of Medicine in November 2023 [2]. The trial enrolled 17,604 participants with established cardiovascular disease and overweight or obesity but without a prior or current diabetes diagnosis — a population not evaluated in the SUSTAIN-6 or PIONEER 6 CVOTs. The primary endpoint was the first occurrence of cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke. At a mean follow-up of 39.8 months, the primary endpoint occurred in 6.5% of participants in the semaglutide group versus 8.0% in the placebo group (hazard ratio 0.80; 95% CI, 0.72 to 0.90; P<0.001 for superiority) [2]. The SELECT trial represented a significant expansion of the semaglutide evidence base to a non-diabetic cardiovascular risk population; the authors noted that the mechanistic basis for the observed risk reduction in this population remains an active area of investigation [2].

ESSENCE Trial (Metabolic Dysfunction-Associated Steatohepatitis)

The ESSENCE (Semaglutide 2.4 mg in Participants With Metabolic Dysfunction-Associated Steatohepatitis) trial is a two-part, phase 3, randomized, multicenter study evaluating semaglutide in an emerging indication. Part 1 enrolled 800 participants with biopsy-proven MASH and fibrosis stage 2 or 3, randomized 2:1 to subcutaneous semaglutide or placebo for 72 weeks, with liver biopsy endpoints. Part 1 results were presented at the American Association for the Study of Liver Diseases 2024 annual meeting. Part 2 is an ongoing long-term extension with a cirrhosis-free survival primary endpoint at week 240 [8]. Published baseline characteristics and the trial design were described by Harrison and colleagues in a 2024 publication in Hepatology [9].

Active Research Frontier

Several research questions remain under active investigation in the semaglutide literature and represent productive areas of ongoing scientific inquiry.

The mechanism underlying the cardiovascular risk reduction observed in the SELECT trial population — individuals with established cardiovascular disease and overweight or obesity but without diabetes — has been the subject of active mechanistic hypothesis generation. Proposed mechanisms (direct cardiac GLP-1R agonism, systemic anti-inflammatory effects, or indirect metabolic changes) are under investigation across multiple research groups, and the question is productively confounded by the simultaneous occurrence of changes in body weight and cardiometabolic risk factors in the semaglutide arm, offering multiple testable mechanistic pathways [2].

The long-term histological outcomes of semaglutide in MASH — including the rate of fibrosis regression or prevention of progression to cirrhosis — represent a substantial and clinically relevant research frontier currently being evaluated in Part 2 of the ESSENCE trial [8].

The neural mechanisms underlying appetite and food-intake changes reported in the STEP program — including the relative contributions of peripheral versus central GLP-1R populations — have been characterized in animal models [10] and continue to be translated through human neuroimaging and mechanistic sub-studies, an active and rapidly evolving area of GLP-1 pharmacology. Published research on related GLP-1/GIP dual agonists in this pharmacological class is summarized in the tirzepatide published research article.

Research on long-term GLP-1R agonist exposure across multiple tissue compartments is ongoing, providing the field with increasingly refined characterization of the compound's systemic pharmacological profile. Semaglutide from SpartaLabs is available as research-grade, third-party-verified material for investigators engaged in GLP-1 receptor pharmacology studies.

References

1. U.S. Food and Drug Administration. Guidance for Industry: Diabetes Mellitus — Evaluating Cardiovascular Risk in New Antidiabetic Therapies to Treat Type 2 Diabetes. December 2008. Available at: https://www.fda.gov/media/71297/download

2. Lincoff AM, Brown-Frandsen K, Colhoun HM, et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes. N Engl J Med. 2023;389(24):2221–2232. doi:10.1056/NEJMoa2307563. PubMed PMID: 37952131.

3. Marso SP, Bain SC, Consoli A, et al. Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes. N Engl J Med. 2016;375(19):1834–1844. doi:10.1056/NEJMoa1607141. PubMed PMID: 27633186.

4. Husain M, Birkenfeld AL, Donsmark M, et al. Oral Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes. N Engl J Med. 2019;381(9):841–851. doi:10.1056/NEJMoa1901118. PubMed PMID: 31185157.

5. Filippatos TD, Panagiotopoulou TV, Elisaf MS. Adverse Effects of GLP-1 Receptor Agonists. Rev Diabet Stud. 2014;11(3-4):202–230. doi:10.1900/RDS.2014.11.202. PubMed PMID: 26177485. PMC4543097.

6. Wilding JPH, Batterham RL, Calanna S, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021;384(11):989–1002. doi:10.1056/NEJMoa2032183. PubMed PMID: 33567185.

7. Garvey WT, Batterham RL, Bhatta M, et al. Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial. Nat Med. 2022;28(10):2083–2091. doi:10.1038/s41591-022-02026-4. PubMed PMID: 36216945. PMC9556320.

8. Loomba R, Hartman ML, Lawitz EJ, et al. Semaglutide 2.4 mg in Participants With Metabolic Dysfunction-Associated Steatohepatitis: Baseline Characteristics and Design of the Phase 3 ESSENCE Trial. Hepatology. 2024;81(4):1274–1286. doi:10.1097/HEP.0000000000001050. PubMed PMID: 39412509. PMC11599791.

9. Harrison SA, Bedossa P, Guy CD, et al. A Phase 3, Randomized, Controlled Trial of Resmetirom in NASH with Liver Fibrosis. N Engl J Med. 2024;390(6):497–509. doi:10.1056/NEJMoa2309000. [MASH/NASH methodology reference.]

10. Koehl M, Larrieu J, Becker AE, et al. Semaglutide drives weight loss through cAMP-dependent mechanisms in GLP1R-expressing hindbrain neurons. Nat Metab. 2026. doi:10.1038/s42255-026-01534-8.