Novo Nordisk told the Aging Research & Drug Discovery conference this month that a 10,052-patient proteomic study found semaglutide recipients aged roughly 2-3 years slower on molecular clocks than placebo recipients, with heart-tissue clocks registering up to 4 years of deceleration.

The Danish drugmaker drew blood from half on the drug, half on placebo, at baseline and again months later, then measured samples with proteomic clocks that predict age and mortality risk from circulating protein levels. Company global project leader Nikolaj Roed said the data showed "improved biological age in our patients across trials and across different tissues."

Eli Lilly reported parallel findings from a smaller epigenetic-clock study of tirzepatide, its dual GIP/GLP-1 agonist that generated more than $36 billion in revenue last year under the Mounjaro and Zepbound brands. Lilly's Kevin Duffin, vice president for aging research, called the readouts consistent: "All the clocks are telling a consistent story that we're seeing a reduction in age. It's not like we're going to reverse age by 30 years or something, but it's a significant reduction."

How large is the effect across tissue types?

The 2-3 year average masks wide variation. Magnitude depends on which clock is applied and which organ is sampled, with heart protein clocks producing Novo's largest signal.

UCLA's Steve Horvath, credited with inventing epigenetic clocks, called the magnitude meaningful. "Two years is a pretty strong effect, in my book," he said. He framed GLP-1s as candidates for "geroprotectors — medications that slow or possibly even reverse biologic aging."

What are the limits of the data?

Both companies tested overweight or diabetic patients. Findings do not extend to healthy populations, a caveat several researchers emphasized.

• Novo's study used proteomic clocks, which read circulating proteins
• Lilly's study used epigenetic clocks, which count DNA methylation changes
• GLP-1 drugs cause muscle loss among other side effects
• The "unhealthy population" caveat applies to most published data

Harvard biologist Vadim Gladyshev, who assisted Novo with molecular measurements, drew a hard line: "In an unhealthy population, I do think it's an anti-aging drug. But in a healthy population, no one knows." Yuge Ji, founder of Reflector Bio and a former clock researcher, called the data a milestone for the field: "The clock people have been pushing for a decade to get this kind of study done. It's huge for them."

What comes next?

In January, ARPA-H committed $38 million to a University of Texas study that will test semaglutide in healthy adults over 60, with cognition, mobility, and sensory acuity as endpoints. The project also aims to map a regulatory path for anti-aging therapeutics.

The Texas trial could begin to answer the question posed publicly at the conference by Alex Zhavoronkov, Insilico Medicine's founder and the meeting's organizer: whether semaglutide should be taken by a "reasonable person" outside an at-risk population. Novo's Alejandro Aguayo-Orozco, a senior scientific director, declined to opine: "I am not a physician. I cannot answer that question."

Zhavoronkov disclosed during the event that he personally microdoses both tirzepatide and semaglutide, though he is not overweight — a statement that will draw scrutiny from trial designers and regulators. Insilico itself reported last month that an experimental lung-fibrosis drug reversed aging-clock signals, adding a second candidate to the longevity pipeline.

Answers on the broader longevity question should start emerging within two years, contingent on enrollment in the ARPA-H-funded study and any confirmatory trials Lilly and Novo launch in healthier cohorts.