CagriSema beat tirzepatide on weight loss even as Novo's stock fell

On September 21, Novo Nordisk announced that its experimental drug CagriSema beat Eli Lilly's tirzepatide head-to-head on weight loss in a randomized trial of adults with type 2 diabetes — the first time Novo's newest metabolic drug has topped its biggest rival in a direct comparison. The same day, on the same stage, Novo's stock fell as much as 8 to 9%.

Both things are true, and the gap between them is the story: a genuine clinical win, in a market that has stopped grading Novo Nordisk on clinical wins alone.

What the trial found

The trial, called REIMAGINE 5, put a once-weekly 1.0 mg/1.0 mg dose of CagriSema against a 5 mg weekly dose of tirzepatide in adults with type 2 diabetes whose blood sugar was inadequately controlled on metformin, an SGLT2 inhibitor, or both (Novo Nordisk, September 21, 2026). At 60 weeks, the company reported, patients on CagriSema had lost an average of 12.4% of their body weight, compared with 9.1% on tirzepatide — enough of a gap to count as statistical superiority, not just a tie. On blood sugar, CagriSema was non-inferior: a 1.71-percentage-point drop in HbA1c versus 1.67 points for tirzepatide. Novo's own summary called the safety profile "consistent with previous studies," without publishing a side-by-side adverse-event table.

How the two drugs work

Tirzepatide, already approved by the FDA for type 2 diabetes and for chronic weight management, activates two gut-hormone receptors at once: GLP-1, which slows stomach emptying and blunts appetite, and GIP, a second hormone thought to add extra metabolic benefit on top of that. CagriSema takes a different second ingredient. It pairs semaglutide, a GLP-1 drug on its own, with cagrilintide, a long-acting version of amylin — a hormone the pancreas releases alongside insulin that also signals fullness to the brain, through a different pathway than GLP-1 does. The pitch behind CagriSema has always been that stacking two different fullness signals, rather than two variations on one, might add up to more than either alone. REIMAGINE 5 is the first big trial where that argument produced a clear head-to-head win over tirzepatide specifically.

CagriSema is not approved for anything yet. Novo filed for FDA approval of the drug for weight management in December 2025, based on separate trials (REDEFINE 1 and 2), with a decision expected in the last quarter of 2026; it has not been filed for a diabetes indication.

What the trial doesn't settle

Treat this as one data point, not a verdict. The result came out as a company announcement at Novo's investor day, not as a peer-reviewed paper — there's no published manuscript yet to check the statistics or the full adverse-event breakdown against. Novo itself flagged the limit: as a Zacks Equity Research summary of the release put it, the comparison "should be viewed within the specific study design and doses studied rather than as a direct comparison with every approved tirzepatide regimen." Tirzepatide is approved up to a 15 mg dose; this trial used 5 mg.

It also isn't CagriSema's first head-to-head with tirzepatide, and the earlier one cuts the other way. In a different trial in the same REIMAGINE program, reported in early August (Fierce Biotech, August 5, 2026), a higher 2.4 mg/2.4 mg dose of CagriSema was non-inferior to tirzepatide on weight loss (15.2% versus 15.8%) but missed its own target on blood sugar (a 1.9-point HbA1c drop versus 2.2 points for tirzepatide). Line the two trials up and the honest summary is: which drug looks better depends on which doses you compare, and Novo has now published one trial that favors CagriSema and one that doesn't.

Why the stock fell anyway

The trial data came out during Novo's Capital Markets Day in London, where the company also laid out its plan through 2030: more than five major drug launches, over $23 billion in additional pipeline sales targeted by 2035, and roughly 13,000 fewer jobs than the year before. Novo's Copenhagen-listed shares fell as much as 8%, and its U.S. shares a similar amount, closing out a stretch that has left the stock down roughly a third over the past year (Alex Philippidis, Genetic Engineering & Biotechnology News, September 21, 2026). One analyst, Per Hansen of Nordnet, said bluntly that investors had been hoping for a dramatic, near-term turnaround story, and that the numbers Novo presented simply didn't deliver one. Another, BMO's Evan Seigerman, said Novo's guidance of 2026–2030 revenue growth roughly in line with the rest of the industry was "likely underwhelming for investors" who are used to Novo growing faster than its peers.

The mismatch isn't really about the science. It's that Novo's semaglutide patents start expiring in 2032, and the company is betting its next growth phase on a deep pipeline of new drugs rather than one blockbuster. CagriSema winning a single trial, however real, doesn't answer the bigger question Wall Street was actually asking that day: can Novo Nordisk build a second act. Somewhere, a biostatistician is having a very good week and a very confusing one at the same time.

What this means for researchers

The REIMAGINE 5 result adds a real, if preliminary, data point to a genuinely open question in metabolic-peptide research: whether pairing GLP-1 with a second, different satiety signal — amylin, in CagriSema's case, versus GIP in tirzepatide's — produces a durable edge, or whether outcomes mostly track which doses happen to get compared. The fact that Novo's own two head-to-head trials point in different directions, depending on dose, is itself the more interesting finding for anyone trying to understand the biology rather than the stock price.

What would resolve it is what's still missing here: a peer-reviewed publication with full statistics and safety data, longer follow-up beyond 60 weeks, and a trial comparing CagriSema against tirzepatide's own top approved dose rather than a middle one. Until then, REIMAGINE 5 is best read as one comparison, in one dose combination, in one patient population — useful, honestly reported by Novo as far as it goes, and not yet the full picture. Related background on how GLP-1 and amylin-based peptides are studied is in Torrey Labs' compound guide; the Journal has also covered GLP-1 drugs' unexpected association with lower rates of Alzheimer's diagnosis in a separate analysis.