How was SUSTAIN-7 different from other SUSTAIN trials?

SUSTAIN-7 was the only trial in the SUSTAIN program that used an active GLP-1 RA comparator (dulaglutide). Other SUSTAIN trials compared semaglutide to placebo, sitagliptin, insulin glargine, or canagliflozin. This made SUSTAIN-7 uniquely valuable for within-class prescribing decisions.

Was SUSTAIN-7 blinded?

No. It was an open-label trial, meaning both patients and investigators knew which drug was assigned. The primary endpoint (A1C) is an objective lab measure, which reduces but does not eliminate the risk of bias from open-label design.

How long did SUSTAIN-7 last?

The treatment period was 40 weeks. This is sufficient for assessing glycemic and weight endpoints but too short for cardiovascular or long-term safety conclusions.

Did semaglutide cause more side effects than dulaglutide?

GI side effects (nausea, vomiting, diarrhea) were numerically more common with semaglutide at both dose levels. Discontinuation rates due to adverse events were approximately 3 percentage points higher with semaglutide compared to the corresponding dulaglutide dose.

What doses were compared in SUSTAIN-7?

The trial compared semaglutide 0.5 mg versus dulaglutide 0.75 mg (low-dose arms) and semaglutide 1.0 mg versus dulaglutide 1.5 mg (high-dose arms). These represent the approved maintenance doses of each drug for type 2 diabetes.

Did SUSTAIN-7 measure cardiovascular outcomes?

No. SUSTAIN-7 was not designed or powered for cardiovascular endpoints. Cardiovascular outcome data for semaglutide comes from SUSTAIN-6, which showed a 26% reduction in major adverse cardiovascular events versus placebo over 104 weeks.

Can SUSTAIN-7 results be applied to patients on insulin?

Not directly. All participants were on metformin monotherapy at baseline. Patients using basal insulin or other oral agents were excluded, so the efficacy and safety profile in those populations requires separate evidence.

How did SUSTAIN-7 influence insurance coverage for GLP-1 RAs?

The head-to-head design gave formulary committees direct comparative data to differentiate between agents in the same class. Several large payers restructured preferred drug lists or step therapy requirements after SUSTAIN-7 publication, though cost and supply factors also played major roles.

Is the 0.4% A1C difference between semaglutide and dulaglutide clinically meaningful?

Yes. Based on UKPDS data, each 1% A1C reduction is associated with significant reductions in microvascular complications and diabetes-related mortality. A 0.4% advantage from one active agent over another in the same class is considered clinically relevant by most endocrinologists.

Does SUSTAIN-7 apply to the oral form of semaglutide?

No. SUSTAIN-7 tested subcutaneous semaglutide only. Oral semaglutide (Rybelsus) was evaluated in the separate PIONEER trial program, which showed somewhat smaller effect sizes likely related to variable oral bioavailability.

What SUSTAIN-7 Actually Changes in Clinical Practice

By HealthRX Medical Team

Published May 25, 2026Updated May 25, 2026Last reviewed May 25, 2026

At a glance

| Trial Detail | Value | |---|---| | Trial name | SUSTAIN-7 | | N | 1,201 | | Intervention | Semaglutide 0.5 mg or 1.0 mg once weekly | | Comparator | Dulaglutide 0.75 mg or 1.5 mg once weekly | | Duration | 40 weeks | | Primary endpoint | Change in HbA1c from baseline | | Key secondary endpoint | Change in body weight from baseline | | Key result | Semaglutide superior to dulaglutide on A1C and weight at both dose levels | | Publication | Lancet Diabetes Endocrinol, 2018 |

Why a Head-to-Head Trial Mattered

Before SUSTAIN-7, GLP-1 receptor agonist (GLP-1 RA) trials mostly compared agents against placebo or older drug classes. Clinicians choosing between semaglutide and dulaglutide relied on cross-trial comparisons, which are unreliable due to differences in patient populations, baseline A1C, and background therapy. SUSTAIN-7 was the first large randomized trial to directly compare these two weekly injectables in a four-arm design that matched clinical doses against each other.

This matters because dulaglutide (Trulicity) was already the most prescribed GLP-1 RA in the United States at the time. If semaglutide could prove superiority, it would force a re-evaluation of prescribing defaults across endocrinology and primary care.

Methodology: What the Abstract Doesn't Tell You

SUSTAIN-7 randomized 1,201 adults with type 2 diabetes (T2D) inadequately controlled on metformin monotherapy. Participants were split into four groups:

Semaglutide 0.5 mg vs dulaglutide 0.75 mg (low-dose comparison)
Semaglutide 1.0 mg vs dulaglutide 1.5 mg (high-dose comparison)

The trial was open-label, not blinded. This is a real limitation, but the primary endpoint (A1C) is an objective lab value, reducing the risk that open-label design biased the core finding. Weight, however, is more susceptible to behavioral modification when patients know their assignment. The authors acknowledged this.

Baseline characteristics were well matched across arms. Mean age was approximately 56 years. Mean baseline A1C was 8.2%. Mean BMI was around 33.5 kg/m². About 53% of participants were male. The population was predominantly white (about 66%), with representation from Asia, Latin America, and other regions.

Dose-escalation schedules differed between the drugs. Semaglutide used a four-week titration (starting at 0.25 mg), while dulaglutide started directly at the randomized dose. This is clinically relevant: semaglutide's slower ramp-up may reduce early GI side effects but also delays full pharmacologic exposure.

The trial used a treatment policy estimand (intention-to-treat), meaning results include data regardless of whether participants stayed on treatment. A separate trial product estimand (on-treatment) analysis was also reported.

Results: The Numbers That Changed Prescribing

HealthRX Dose-Matched Efficacy Framework

The table below organizes the primary and key secondary results by dose tier. This framework highlights something most summaries miss: the magnitude of semaglutide's advantage was consistent across both dose levels, suggesting a class-wide pharmacologic edge rather than a dose-specific artifact.

A1C Reduction (Primary Endpoint)

| Comparison | Semaglutide | Dulaglutide | Estimated Treatment Difference | P-value | |---|---|---|---|---| | 0.5 mg vs 0.75 mg | −1.5% | −1.1% | −0.40% (95% CI: −0.55 to −0.25) | <0.0001 | | 1.0 mg vs 1.5 mg | −1.8% | −1.4% | −0.41% (95% CI: −0.57 to −0.25) | <0.0001 |

A 0.4 percentage-point difference in A1C is clinically meaningful. The UKPDS established that each 1% reduction in A1C correlates with roughly 21% reduction in diabetes-related death and 37% reduction in microvascular complications. A 0.4% gap between two active agents within the same drug class is uncommon.

Weight Change (Key Secondary Endpoint)

| Comparison | Semaglutide | Dulaglutide | Estimated Treatment Difference | |---|---|---|---| | 0.5 mg vs 0.75 mg | −4.6 kg | −2.3 kg | −2.26 kg (95% CI: −3.02 to −1.51) | | 1.0 mg vs 1.5 mg | −6.5 kg | −3.0 kg | −3.55 kg (95% CI: −4.32 to −2.78) |

The weight advantage was even more pronounced. At the higher dose, semaglutide produced more than double the weight loss of dulaglutide. For a patient with a baseline weight of 95 kg, this translates to roughly 6.8% body weight loss with semaglutide 1.0 mg versus 3.2% with dulaglutide 1.5 mg.

A1C Target Achievement

| Target | Semaglutide 0.5 mg | Dulaglutide 0.75 mg | Semaglutide 1.0 mg | Dulaglutide 1.5 mg | |---|---|---|---|---| | A1C <7.0% | 68% | 52% | 79% | 67% | | A1C ≤6.5% | 53% | 34% | 67% | 44% |

These proportions matter because guidelines set specific A1C targets. A prescriber aiming for <7.0% can expect roughly 12 to 16 more patients per 100 to reach target with semaglutide than with dulaglutide.

Safety: Comparable GI Profiles With a Caveat

Gastrointestinal adverse events were the most common side effects in all arms, as expected for GLP-1 RAs.

| Event | Semaglutide 0.5 mg | Dulaglutide 0.75 mg | Semaglutide 1.0 mg | Dulaglutide 1.5 mg | |---|---|---|---|---| | Nausea | 21.2% | 18.9% | 22.7% | 21.2% | | Diarrhea | 13.5% | 11.6% | 14.2% | 12.6% | | Vomiting | 7.3% | 5.7% | 9.1% | 6.3% | | Discontinuation due to AEs | 6.0% | 3.0% | 8.4% | 5.4% |

Semaglutide had numerically higher rates of nausea and vomiting at both dose levels, with roughly 3% more discontinuations. This is the tradeoff: greater efficacy comes with modestly more GI intolerance, particularly at the 1.0 mg dose. For patients who struggled with nausea on liraglutide or exenatide, this finding is directly relevant to shared decision-making.

Severe hypoglycemia was rare across all arms (<1%), consistent with the semaglutide prescribing information and the known safety profile of GLP-1 RAs on metformin background.

What Actually Changed in Clinical Practice

Guideline Updates

The 2019 ADA/EASD consensus report incorporated SUSTAIN-7 among the evidence supporting GLP-1 RAs as preferred second-line therapy after metformin when weight management is a priority. While the consensus did not name a preferred GLP-1 RA, the head-to-head data gave formulary committees and individual prescribers a basis for distinguishing between agents in a class that was previously treated as interchangeable.

By 2022, the ADA Standards of Care moved further, recommending GLP-1 RAs with proven cardiovascular benefit (semaglutide qualified via SUSTAIN-6) as first-line alongside or even before metformin in patients with established atherosclerotic cardiovascular disease.

Prescribing Volume Shifts

SUSTAIN-7 contributed to a documented shift in GLP-1 RA market share. Semaglutide (branded as Ozempic) overtook dulaglutide (Trulicity) as the most prescribed GLP-1 RA in the U.S. by late 2022, according to IQVIA prescription data. Price, insurance coverage, and supply constraints also played roles, but the clinical evidence base, anchored by head-to-head trials like SUSTAIN-7, gave the medical justification for payer and prescriber decisions.

Formulary and Prior Authorization

Many insurance plans used SUSTAIN-7 data to justify step therapy policies requiring a trial of semaglutide before approving newer or more expensive agents. Others used it to remove dulaglutide from preferred status. The trial's clean dose-matched design made it unusually useful for pharmacy and therapeutics committees evaluating within-class positioning.

Limitations the Authors Acknowledged

Open-label design. Patients and investigators knew group assignment. While A1C is objective, weight and patient-reported outcomes could be influenced by expectations.
40-week duration. Long enough to assess glycemic efficacy, but too short to capture cardiovascular outcomes or durability of weight loss beyond one year. The SUSTAIN-6 cardiovascular outcomes trial ran 104 weeks but used placebo, not an active comparator.
Metformin-only background. Most real-world T2D patients are on multiple agents. Applicability to patients on sulfonylureas, SGLT2 inhibitors, or insulin was not tested.
Predominantly white population. About 66% white, which limits generalizability to populations with different metabolic risk profiles. GLP-1 RA responses may differ by ethnicity, though this has not been definitively established.
No patient-reported outcome measures. Quality of life, treatment satisfaction, and injection burden were not systematically captured.

What the Trial Implies for Patients Who Differ From the Study Population

SUSTAIN-7 enrolled patients with a mean BMI of ~33.5 and baseline A1C of ~8.2%. Patients with higher BMIs may see even greater absolute weight loss with semaglutide, based on dose-response data from STEP trials at the higher 2.4 mg dose. Patients with lower baseline A1C (say 7.2%) will see smaller absolute A1C reductions in both arms, but the relative advantage of semaglutide should persist.

Older adults (over 65) were underrepresented. GI tolerability may be a bigger concern in this group, where nausea and reduced appetite carry higher risk of sarcopenia and malnutrition. The 3% higher discontinuation rate with semaglutide becomes more clinically significant when the patient is already frail.

Patients with chronic kidney disease were largely excluded. Subsequent data from FLOW showed kidney-specific benefits for semaglutide, but SUSTAIN-7 itself cannot support that extrapolation.

The Bottom Line for Prescribers

SUSTAIN-7 did not just show that semaglutide is statistically superior to dulaglutide. It showed that the difference is large enough to matter at the individual patient level: roughly 0.4% more A1C reduction and 2 to 3.5 kg more weight loss, depending on dose. That gap is clinically actionable. It should inform first-line GLP-1 RA selection for most patients with T2D, tempered by cost, insurance access, and individual GI tolerability.

Frequently asked questions

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References

Pratley RE, Aroda VR, Lingvay I, et al. Semaglutide versus dulaglutide once weekly in patients with type 2 diabetes (SUSTAIN 7): a randomised, open-label, phase 3b trial. Lancet Diabetes Endocrinol. 2018;6(4):275-286. PubMed
U.S. Food and Drug Administration. Ozempic (semaglutide) prescribing information. FDA Label
Davies MJ, D'Alessio DA, Fradkin J, et al. Management of hyperglycemia in type 2 diabetes, 2018. A consensus report by the ADA and EASD. Diabetes Care. 2018;41(12):2669-2701. PubMed
UK Prospective Diabetes Study (UKPDS) Group. Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes (UKPDS 33). Lancet. 1998;352(9131):837-853. PubMed
Wilding JPH, Batterham RL, Calanna S, et al. Once-weekly semaglutide in adults with overweight or obesity (STEP 1). N Engl J Med. 2021;384(11):989-1002. PubMed
Perkovic V, Tuttle KR, Rossing P, et al. Effects of semaglutide on chronic kidney disease in patients with type 2 diabetes (FLOW). N Engl J Med. 2024. PubMed