Switching from dulaglutide to tirzepatide helped in every patient group tested, analysis finds
The trial's subgroup breakdown suggests the switch benefit held across ages, weights, diabetes durations and doses, though the size of each subgroup difference was not reported.
A new subgroup analysis of the phase IV SURPASS-SWITCH trial found that adults with type 2 diabetes who switched from weekly dulaglutide to weekly tirzepatide (sold as Mounjaro and Zepbound) lowered their A1c and lost more weight at week 40 than those who stayed on dulaglutide, and the advantage showed up in every patient group the researchers tested [1].
The analysis, published in 2026 by BMJ Group, comes from a randomized, open-label, active-controlled, parallel-group, multicenter, multinational trial [1]. Participants were adults with A1c between 7.0% and 9.5%, on a stable dose of dulaglutide for at least six months, on zero to three oral diabetes medications for at least three months, with stable body weight and a body mass index of at least 25 kg/m2 at screening [1]. They were assigned 1:1 either to continue dulaglutide and escalate to 4.5 mg or the maximum tolerated dose, or to switch to tirzepatide and escalate to 15 mg or the maximum tolerated dose [1].
This new paper breaks the 40-week results out by prespecified baseline characteristics: age (under 65 and 65 or older), starting A1c (8.5% or below, and above 8.5%), duration of type 2 diabetes (5 years or less, more than 5 to 10 years, more than 10 years), baseline dulaglutide dose (0.75 mg or 1.5 mg), how long participants had been on that dulaglutide dose (under 1 year, 1 year or more), body mass index (under 27 and 27 or above; and under 30, 30 to under 35, 35 or above), ethnicity (Hispanic or Latino, non-Hispanic or non-Latino) and sex [1].
Across all of those subgroups, reductions in A1c and body weight at week 40 were significant and consistently greater with tirzepatide than with dulaglutide [1]. A1c reduction was larger in the subgroups with higher starting A1c and lower starting BMI, and weight reduction was greater for participants in the non-Hispanic or non-Latino subgroup [1]. The published abstract does not report the size of the differences within each subgroup, so how many points of A1c or pounds of weight the switch produced in each group is not yet known [1].
The safety profile was similar across subgroups, with nausea and diarrhea usually the most frequently reported treatment-emergent adverse events in each subgroup [1]. The authors concluded that switching was generally well tolerated and may offer a clinical option across a range of baseline characteristics when treatment goals are not being met with dulaglutide [1]. Four of the six authors are employees and shareholders of Eli Lilly and Company, which makes tirzepatide; the other two reported no conflicts of interest [1].
Why it matters for patients
Many people with type 2 diabetes on dulaglutide are told their A1c is not where it needs to be. This analysis suggests that, on average, switching to tirzepatide improved both A1c and weight over 40 weeks, and that the pattern was not limited to one narrow slice of patients — it held for older and younger adults, for people who had diabetes for a few years or many, for different starting doses and body sizes, and for both sexes [1].
Two limits are worth knowing. The results are based on averages within groups, so they do not predict what will happen to any one person [1]. And the comparison was against dulaglutide escalated to 4.5 mg or the maximum tolerated dose, not against a standard dulaglutide dose [1]. This analysis is also about tirzepatide only; it does not compare tirzepatide with semaglutide products such as Ozempic, Wegovy or Rybelsus [1].
Side effects followed the same pattern the drugs are known for in this class, with nausea and diarrhea most commonly reported, and no subgroup stood out as clearly higher-risk in this analysis [1].
What happens next
The trial is registered as NCT05564039, and the abstract reports results through week 40 only [1]. Whether the differences between the two drugs widen, shrink or hold steady after 40 weeks has not been reported, and no timeline for longer follow-up or for any regulatory action based on this analysis has been disclosed [1]. The main SURPASS-SWITCH results were reported earlier; this paper adds the breakdown by patient characteristics [1].
Sources
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