Lilly and Novo Report GLP-1 Drugs Reduced Biological Age on Molecular Aging Clocks

Protein-based clocks come from observational research, not from drug trials. One example is a study published in Nature medicine in 2024. Researchers used blood samples from 45,441 UK Biobank participants, measuring 2,897 plasma proteins. They built a model from 204 proteins that predicts chronological age closely (Pearson r = 0.94). The study did not test any drug, and neither source we reviewed says Novo used this particular clock.

The paper shows what such a clock can and cannot say. Its "proteomic age gap" is the difference between protein-predicted age and actual age. A larger gap was associated with 18 major chronic diseases, multimorbidity and all-cause mortality. It was also linked to frailty, telomere length and reaction time. These are associations. The study does not show that changing the gap changes disease risk.

The authors also checked the clock in other populations. In China (3,977 people) and Finland (1,990 people), age prediction was similar (r = 0.92 and r = 0.94). In the UK data, people in the top 5% of the age gap were about 6.3 years "older" than their actual age. Those in the bottom 5% were about 6 years "younger". That is a mean difference of roughly 12.3 years between the two groups.

Now the commercial claim. According to MIT Technology Review, Novo Nordisk and Eli Lilly presented data at the Aging Research & Drug Discovery conference. Novo took blood from 10,052 people, half on semaglutide and half on placebo, and measured protein clocks. Lilly ran a smaller study of tirzepatide using clocks based on DNA changes. These results were described in conference presentations as reported by the magazine. We have not seen them in a peer-reviewed paper, and the coverage does not give the full study design beyond the placebo comparison. We cannot say from it whether the data came from randomised, placebo-controlled trials.

According to the magazine, Novo's Nikolaj Roed put the difference at about two to three years. The reduction reached as much as four years on a clock based on heart proteins. Lilly's Kevin Duffin said the clocks tell "a consistent story" of lower age, but added that "it's not like we're going to reverse age by 30 years." Steve Horvath of UCLA, credited with inventing aging clocks, called two years "a pretty strong effect, in my book."

The 2024 study sets the limit on how far to read this. It shows that a protein clock tracks risk in people who are not on treatment. It does not show that a drug-driven shift in the clock lowers risk. The paper also notes that the 204 proteins span many functions, including inflammation and immune response. A drug could move some of them without changing the underlying risk. The company readouts go further than the study supports if they are read as proof of slower aging. This is the weakest point in the commercial case.

Even so, the strategic stakes are clear. According to the magazine, tirzepatide earned Lilly more than $36 billion last year, with semaglutide a close second. A credible aging claim could widen the case for these drugs beyond obesity and diabetes. It would also give aging-clock makers the validation they have sought. The commentary was careful, though. Vadim Gladyshev of Harvard, who assisted Novo, said: "In an unhealthy population, I do think it's an anti-aging drug. But in a healthy population, no one knows." Horvath said he had not seen enough evidence that thin people would benefit. Several people at the meeting also noted side effects, including muscle loss. Asked whether a reasonable person should start taking semaglutide, a Novo scientist said he was not a physician and could not answer.

Regulation is the gate. According to MIT Technology Review, ARPA-H committed $38 million in January to a Texas study of whether semaglutide has anti-aging effects in healthy people over 60. It will look at cognition, mobility and the senses, and aims to help define a regulatory path for anti-aging drugs. A clock reading alone is not a clinical outcome. Full peer-reviewed data from Novo and Lilly have not yet appeared. The magazine reports that early answers from the ARPA-H study could come in a year or two.

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