Mounjaro Real-World Response Rate: What Patients Actually Experience

What counts as a response in these trials

The weight trials used two co-primary endpoints: percentage change in weight and the proportion of participants who lost at least 5% of body weight [1]. The type 2 diabetes trial that compared tirzepatide with semaglutide used change in HbA1c from baseline as its primary endpoint [2]. When you read "responder" here, it means someone who cleared one of those bars.

How often does tirzepatide produce 5% weight loss?

SURMOUNT-1 enrolled 2,539 adults with a BMI of 30 or higher, or 27 or higher with at least one weight-related complication, and without diabetes. Treatment ran 72 weeks and included a 20-week dose-escalation period [1].

By week 72, 85% of the 5 mg group, 89% of the 10 mg group and 91% of the 15 mg group had lost at least 5% of body weight, against 35% on placebo [1]. That leaves 15%, 11% and 9% who did not reach 5%, depending on dose.

Mean weight change was -15.0% on 5 mg, -19.5% on 10 mg and -20.9% on 15 mg, against -3.1% on placebo (P<0.001 for all three comparisons) [1]. A loss of 20% or more occurred in 30.0% of the 5 mg group, 50.1% of the 10 mg group and 56.7% of the 15 mg group, against 3.1% on placebo [1].

These weight figures come from trials in people without diabetes, the studies behind Zepbound's weight-management approval. Mounjaro itself is not labeled for weight loss [3].

How often does it work for type 2 diabetes?

SURPASS-2 randomized 1,879 adults with type 2 diabetes on metformin, mean HbA1c 8.28% and mean weight 93.7 kg, to tirzepatide 5, 10 or 15 mg or semaglutide 1 mg for 40 weeks [2].

HbA1c fell 2.01, 2.24 and 2.30 percentage points on tirzepatide 5, 10 and 15 mg, against 1.86 points on semaglutide 1 mg; all three tirzepatide doses were noninferior and superior to semaglutide [2]. The share reaching HbA1c under 7% was 82%, 86% and 86% on tirzepatide, against 79% on semaglutide, and weight fell 7.6 kg, 9.3 kg and 11.2 kg, against 5.7 kg [2].

In a separate cardiovascular-outcomes trial, SURPASS-CVOT, 13,299 adults with type 2 diabetes and atherosclerotic cardiovascular disease were randomized; after 134 were excluded, the modified intention-to-treat population included 13,165 patients. The trial compared tirzepatide up to 15 mg against dulaglutide 1.5 mg. The composite of cardiovascular death, heart attack or stroke occurred in 12.2% on tirzepatide and 13.1% on dulaglutide (hazard ratio 0.92, 95.3% CI 0.83 to 1.01), meeting noninferiority (P=0.003) but not superiority (P=0.09) [6].

Weight response in people with type 2 diabetes

SURMOUNT-2 enrolled 938 adults with a BMI of 27 or higher and HbA1c of 7% to 10%, treated for 72 weeks. Mean weight change was -12.8% on 10 mg and -14.7% on 15 mg, against -3.2% on placebo, and at least 5% weight loss occurred in 79.2% and 82.8%, against 32.5% on placebo [7]. SURMOUNT-1 reported 89% and 91% at 10 and 15 mg in adults without diabetes [1]. These results come from separate trial populations and are not a direct comparison.

What clinical trials report: nausea, vomiting and stopping

The Mounjaro label pools two placebo-controlled trials in adults with type 2 diabetes (SURPASS-1 and SURPASS-5; 718 patients, mean exposure 36.6 weeks). Nausea occurred in 12%, 15% and 18% of the 5, 10 and 15 mg groups against 4% on placebo; diarrhea in 12%, 13% and 17% against 9%; vomiting in 5%, 5% and 9% against 2%; decreased appetite in 5%, 10% and 11% against 1%; constipation in 6%, 6% and 7% against 1% [3].

Gastrointestinal adverse reactions of any kind were reported by 37.1%, 39.6% and 43.6% of patients on 5, 10 and 15 mg, against 20.4% on placebo. Treatment was discontinued for a gastrointestinal reaction in 3.0%, 5.4% and 6.6%, against 0.4% on placebo [3]. Severe gastrointestinal reactions occurred in 1.3%, 0.4% and 1.2% against 0.9%, and the label says Mounjaro is not recommended in patients with severe gastroparesis [3].

The label adds that most reports of nausea, vomiting or diarrhea occurred during dose escalation and decreased over time [3]. It also says adverse reaction rates from clinical trials cannot be directly compared between trials and may not reflect the rates seen in practice [3].

What happens when the treatment stops

SURMOUNT-4 enrolled 783 adults for 36 weeks of open-label tirzepatide at the maximum tolerated dose of 10 or 15 mg; the 670 who were then randomized had lost a mean 20.9% of body weight. They continued tirzepatide or switched to placebo for 52 more weeks. From week 36 to week 88, weight changed -5.5% with continued treatment and +14.0% after the switch, a difference of 19.4 percentage points [4].

If the response is smaller than expected

The Mounjaro label says the recommended starting dosage is 2.5 mg injected subcutaneously once weekly. If more glycemic control is needed, the label increases the dose in 2.5 mg steps after at least 4 weeks on the current dose, to a maximum of 15 mg weekly in adults and 10 mg weekly in pediatric patients 10 years and older [3].

Dose shows up in the trial numbers. In SURMOUNT-1 (adults without diabetes) the gap between 5 mg and 15 mg was 15.0% versus 20.9% mean weight loss, and the share losing at least 5% rose from 85% to 91% [1].