An experimental drug for a scarring lung disease, designed with the help of artificial intelligence, was associated with lower biological age readings on six blood-protein aging clocks in a small group of patients, according to an analysis published September 7 in Nature Biotechnology. The findings come from 42 patients with idiopathic pulmonary fibrosis and rely on biomarkers, not on whether anyone lived longer or stayed healthier.
Headlines have described the drug, rentosertib, as potentially reversing biological aging by several years. The study itself is more limited. Its authors write that the clocks cannot separate an effect on aging from the drug's effect on the lung disease it was built to treat.
The distinction matters for readers weighing longevity claims for themselves or aging parents. Rentosertib is not approved, is available only in clinical trials, and has not been tested for aging in healthy people. Companies selling biological age tests or anti-aging products may cite studies like this one, but this result does not support any consumer use.
A Reanalysis of a 12-Week Lung Disease Trial
Rentosertib is a TNIK inhibitor developed by Insilico Medicine, which says both the drug target and the molecule were identified with generative AI. Its Phase 2a trial, registered as NCT05938920, randomly assigned 71 adults with idiopathic pulmonary fibrosis at sites across China to one of three dosing regimens or placebo for 12 weeks. The original trial results, published in 2025, reported that the highest dose improved a measure of lung capacity compared with placebo.
For the new analysis, 43 participants agreed to have their stored blood tested, and 42 had complete samples. All were Asian, with an average age of 67. Researchers measured 2,841 proteins at four time points and applied six published proteomic aging clocks, statistical models that estimate biological age from patterns of proteins in the blood.
The clocks were developed by several research groups; Insilico says their developers include teams at Harvard, Oxford, Peking University and Insilico itself. One widely cited model, ProtAge, was built from UK Biobank data and first described in a Nature Medicine study.
Aging Clock Readings Fell, Then Leveled Off
All six clocks predicted lower biological age in the treated groups than in the placebo group. Of 54 comparisons across clocks, doses, and time points, 21 reached statistical significance, 11 of them at week 4. On the four clocks trained to predict chronological age, the group taking 60 milligrams once daily read about 2.7 to 3.5 years younger at week 4 than at the start, a change that was statistically significant compared with placebo. The findings held when six participants with more serious side effects were excluded.
The twice-daily 30-milligram dose produced the most consistent signal across clocks. By week 12, the readings had leveled off rather than continuing to fall. Insilico's announcement described a peak reversal of roughly three to four years in that group, and up to six years on one clock.
Some organ-specific clocks, including one estimating artery aging, showed even larger predicted reductions, but those models are less established and harder to interpret. Pathway analyses suggested lower levels of proteins tied to cellular senescence and growth factor signaling in treated patients. In the placebo group, protein changes tracked the direction of normal aging, which the authors link to ongoing disease progression.
The Evidence Check on Aging Claims
The authors state that proteomic clocks "cannot deconvolute aging- and disease-specific effects." Put simply, a drug that eases lung scarring could make blood proteins look younger because the patient is less sick. The team offered indirect evidence against that explanation, noting that the dose with the best lung results did not produce the strongest aging signal and that changes in lung capacity explained little of the change in clock readings. They acknowledge that direct testing in people without the disease is still required.
Other limits are substantial. The sample was small and the trial short; all participants were Asian adults with a serious lung disease, and the aging analysis was exploratory. Most proteomic clocks have had little validation in clinical settings. Participants also continued their standard lung medications during the trial, another factor that could influence protein levels.
Conflicts of interest also apply. Insilico founder Alex Zhavoronkov is the first author, several co-authors are affiliated with the company, and Insilico supplied the drug.
In short, this was an exploratory biomarker analysis of 42 patients from a company-sponsored Phase 2a trial. It found lower predicted biological age on six clocks. It did not measure lifespan, health span, or any clinical aging outcome, and it offers no basis for using the drug outside a trial.
A Phase 3 Test Focused on Lungs, Not Longevity
Insilico says rentosertib has entered Phase 3 development for idiopathic pulmonary fibrosis in China. That lung disease program, not the aging analysis, will determine whether the drug reaches patients.
The authors propose a stepwise path for aging research: collect aging biomarkers as exploratory measures in disease trials, test promising drugs in older adults without the target disease, and pursue formal biomarker qualification or composite clinical endpoints with regulators. They note that under current FDA frameworks, such studies would not be run as trials for an aging indication, and any clinical claim would require conventional clinical outcomes or a qualified biomarker.
People with idiopathic pulmonary fibrosis who are interested in trials can ask a pulmonologist and search ClinicalTrials.gov. The disease often causes a persistent dry cough and shortness of breath with activity, and anyone with those symptoms lasting weeks should see a clinician.
Consumers should be cautious with at-home biological age tests and supplements marketed with references to aging clocks. These tests have not been validated to guide individual medical care, and no drug is approved to slow aging itself. For now, the best-supported steps for healthy aging remain regular exercise, not smoking, blood pressure control, and recommended screenings.
Key Questions Answered
What is rentosertib?
It is an experimental pill from Insilico Medicine that blocks a protein called TNIK. It is being developed to treat idiopathic pulmonary fibrosis, a disease that scars the lungs.
Did the drug slow aging?
The study cannot say. Six blood-protein clocks predicted lower biological age in treated patients, but the authors state that the clocks cannot separate aging effects from improvement in lung disease.
How many people were studied?
The aging analysis included 42 of the 71 patients in a 12-week Phase 2a trial conducted in China.
What is a proteomic aging clock?
It is a statistical model that estimates biological age from patterns of proteins in the blood. These tools are new and have had limited validation in clinical settings.
Who conducted the study?
Insilico's founder is the first author, several co-authors are affiliated with the company, and the company supplied the drug. Academic collaborators also contributed.
Can I get rentosertib?
No. It is not approved and is available only through clinical trials for idiopathic pulmonary fibrosis.
Should I buy a biological age test?
Consumer biological age tests have not been shown to guide medical care. Regular exercise, not smoking, and blood pressure control remain the best-supported ways to protect long-term health.
