Novo Nordisk and Eli Lilly are battling for dominance in one of medicine’s largest and fastest-growing markets: drugs for obesity and weight loss.
On Monday, Novo announced encouraging results for its experimental drug CagriSema. In a Phase 3 study of patients with type 2 diabetes, CagriSema produced 12.4% average weight loss after 60 weeks, compared with 9.1% for Lilly’s tirzepatide, sold as Mounjaro for diabetes and Zepbound for obesity.
Novo’s headline was less qualified: “CagriSema delivers superior weight loss versus tirzepatide.”
That statement comes with an important qualifier.
The trial compared CagriSema 1.0 mg/1.0 mg with tirzepatide 5 mg weekly.
There is nothing improper about that comparison. REIMAGINE 5 was designed to answer precisely that dose-specific question, and Novo prominently disclosed the doses in its announcement.
But the distinction matters clinically.
Before retiring, I prescribed tirzepatide. Patients started at 2.5 mg weekly and moved to 5 mg after four weeks. In my practice, most patients who tolerated the medication and needed a greater effect were titrated further, often to 10 or 15 mg.
That is consistent with Lilly’s prescribing information: after the 2.5 mg starting dose, patients move to 5 mg and may subsequently increase in 2.5 mg increments to a maximum of 15 mg weekly.
And tirzepatide has a substantial dose-response.
In the pivotal SURMOUNT-1 obesity trial, patients lost 15.0% of their body weight with 5 mg tirzepatide, 19.5% with 10 mg, and 20.9% with 15 mg.
So REIMAGINE 5 establishes something useful and quite specific: CagriSema 1.0/1.0 mg produced more weight loss than tirzepatide 5 mg in this population. It does not establish that CagriSema is generally superior to tirzepatide across the drugs’ dose ranges. Novo knows that distinction particularly well.
In July, the company sued Lilly over advertisements portraying Zepbound and Mounjaro as superior to Novo’s drugs. Novo complained that Lilly was drawing broad conclusions from trials involving particular doses while newer, higher-dose Novo products had not been included.
The principle behind Novo’s complaint was reasonable: dose context matters. A technically accurate comparison can still create a misleading impression if the qualifications disappear when the result reaches consumers.
Now consider Novo’s own headline.
“CagriSema delivers superior weight loss versus tirzepatide” sounds considerably broader than “CagriSema 1.0/1.0 mg produced greater weight loss than tirzepatide 5 mg.”
The latter is what REIMAGINE 5 demonstrated.
And we do not have to speculate about what happens when higher doses of these drugs are compared in patients with diabetes. Novo has already done that study.
In REIMAGINE 4, CagriSema 2.4/2.4 mg was compared directly with tirzepatide 15 mg. Patients receiving CagriSema lost 15.2% of their body weight, compared with 15.8% for tirzepatide. CagriSema demonstrated non-inferiority for weight loss — not superiority — and failed to demonstrate non-inferiority for HbA1c reduction.
That does not negate REIMAGINE 5. The two trials asked different questions at different doses. That is precisely the point.
Clinical trials answer specific questions about specific doses in specific patients over specific periods of time. Those qualifications are not fine print. They determine what the evidence actually means.
Novo itself offers a reasonable explanation for studying the lower doses: treatment is individualized, and not every patient receives or remains on the highest dose. Fine.
Then the clearest description of the result is the simplest one: CagriSema 1.0/1.0 mg beats tirzepatide 5 mg for weight loss in REIMAGINE 5.
That is good news for Novo and potentially useful information for physicians. It is not the same as establishing that CagriSema is superior to tirzepatide.
The distinction matters beyond these two companies. Head-to-head randomized trials are among medicine’s most valuable forms of evidence because they allow physicians to compare treatments under the same conditions.
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But the science can be sound while the public message outruns it. Which dose? Which patients? Which endpoint? Which duration? Those questions determine what a trial can legitimately tell us.
Novo has spent months insisting that Lilly respect that distinction. Novo should take its own advice.
Arie Blitz is a retired physician and independent writer in Weslaco, Texas, who writes on foreign policy, medical ethics, and public policy.