Did Rentosertib Reverse Biological Age? What Six Proteomic Clocks Really Found

Edited and Approved by Stephen C. Rose, PhD, MS

A new analysis of the experimental lung-fibrosis drug rentosertib has produced an attention-grabbing result: six different proteomic aging clocks all moved toward younger predicted biological ages during treatment. That is unusual and scientifically interesting. It is also easy to translate into a claim the study did not establish—that the drug made people younger. What the researchers actually observed was a coordinated change in blood proteins over 12 weeks in a small group of patients with idiopathic pulmonary fibrosis, or IPF [1].

The most accurate interpretation is that rentosertib produced a biological signal consistent with several models of younger proteomic age. The finding is preliminary evidence that the drug may influence pathways shared by fibrosis and aging. It is not yet evidence that rentosertib slows whole-body aging, prevents age-related disease outside IPF, improves lifespan, or produces lasting rejuvenation. Understanding that distinction makes the result more useful, not less exciting.

What rentosertib was designed to do

Rentosertib, previously called ISM001-055 or INS018_055, is an oral small molecule designed with the assistance of artificial intelligence. It inhibits TNIK, short for TRAF2- and NCK-interacting kinase. TNIK participates in signaling networks associated with inflammation, tissue remodeling, and fibrosis. Insilico Medicine used computational analysis to prioritize TNIK as a possible target and generative chemistry to design candidate molecules. Laboratory and animal experiments then showed that the selected compound could reduce fibrotic and inflammatory activity, followed by phase 1 testing in healthy volunteers [2].

The intended disease is IPF, a progressive disorder in which the lungs become thickened and scarred. The scarring makes it increasingly difficult for oxygen to move into the blood. IPF occurs mainly in older adults and overlaps with several features of aging biology, including cellular senescence, mitochondrial dysfunction, altered protein maintenance, chronic inflammation, and abnormal extracellular-matrix remodeling [3]. Approved antifibrotic treatments can slow functional decline for some patients, but they do not cure the disease or reliably restore normal lung architecture [4].

What the phase 2a trial showed

The original phase 2a trial randomly assigned 71 adults with IPF to placebo or one of three rentosertib regimens for 12 weeks: 30 milligrams once daily, 30 milligrams twice daily, or 60 milligrams once daily. The primary goal was safety and tolerability. Rates of treatment-emergent adverse events were broadly similar across groups, although treatment-related events became more common at higher doses. Liver abnormalities, diarrhea, and low potassium were among the concerns, and 16 of 71 participants discontinued treatment before completion [5].

Lung function was a secondary outcome. At 12 weeks, forced vital capacity—the amount of air a person can forcibly exhale after a full breath—rose by an average of 98.4 milliliters in the 60-milligram once-daily group, compared with a 20.3-milliliter decline in the placebo group. The confidence intervals were wide, the groups were small, and the study was not designed to establish effects on hospitalization, survival, or long-term disease progression. The result was a promising efficacy signal, not a completed demonstration of clinical benefit [5].

How six clocks entered the story

Forty-three trial participants agreed to additional serum-protein testing, and 42 had samples available at all required time points. Researchers measured 2,841 circulating proteins at baseline and after 2, 4, and 12 weeks. They then applied six aging models: ProtAge, two versions of OrganAge, PAC, ipfP3GPT, and PAOPAC. Four were trained mainly to estimate chronological age; two were trained around mortality-related information. These are not six physical clocks. They are six mathematical models asking related but nonidentical questions of overlapping protein data [1].

Proteomic clocks estimate age-related biology from patterns in proteins circulating in blood. That approach has a legitimate foundation. One large study developed a clock from 2,897 plasma proteins in more than 45,000 UK Biobank participants. Its age estimate correlated strongly with chronological age and was also associated with frailty, disease incidence, multimorbidity, and mortality in several populations [6]. Association, however, does not establish that deliberately lowering a clock score will reduce disease or extend life. A clock can be predictive without being a proven treatment target.

The result—and the important qualifications

All six models showed a general movement toward lower predicted biological age in the rentosertib groups, while the placebo group showed little change or slight increases. Across the three regimens, six clocks, and three time points, the investigators made 54 treatment-versus-placebo comparisons. Twenty-one reached the study's adjusted significance threshold, concentrated at week 4. The 30-milligram twice-daily regimen produced the most consistent clock signal, including nine significant comparisons. Insilico's summary described the peak change as roughly three to four predicted years, reaching six years in one clock [1] [7].

That pattern is intriguing because the 60-milligram once-daily group produced the clearest improvement in lung function, whereas 30 milligrams twice daily produced the strongest clock response. In a comparison with age-associated protein patterns from 55,319 older UK Biobank participants, the twice-daily regimen shifted proteins modestly in the opposite direction from normal aging. The once-daily 60-milligram regimen did not show the same significant relationship despite its better forced-vital-capacity result [1]. This separation suggests that the clock findings may not be explained entirely by improved breathing, but it cannot prove independence from disease response.

The drug also altered the trajectories of 326 measured proteins, including reductions in proteins associated with collagen deposition and tissue remodeling. Pathway analyses pointed toward changes in senescence and metabolism. Separate cell experiments have reported that TNIK inhibition can act as a senomorphic: it reduced the inflammatory secretions of senescent cells without simply killing those cells [8]. This supplies a plausible connection to aging biology. It remains preclinical mechanistic support rather than confirmation that the patients' organs became functionally younger.

Why this is not yet age reversal

Several limitations matter. The proteomic analysis was exploratory and included only 42 people, all with IPF and all enrolled in China. The observation period lasted 12 weeks, and the strongest clock changes appeared at week 4 before flattening or weakening. The study cannot tell us whether the signal persists after treatment, predicts fewer illnesses, improves physical function, or adds healthy years of life. Nor can it fully separate a systemic aging effect from changes caused by reducing inflammation, fibrosis, medication burden, or disease severity.

Agreement among six clocks is stronger than a result from one model, but it is not equivalent to six independent clinical trials. The models analyzed the same patients and the same protein measurements, some were trained from related datasets, and their predictions were correlated. The paper also has a substantial commercial connection: Insilico developed rentosertib, sponsored the underlying trial, and several authors are company employees. Those facts do not invalidate the results, but they increase the importance of independent replication, prespecified endpoints, and transparent validation [1,5].

What comes next

Rentosertib has now advanced into a phase 3 IPF study, NCT07687459. The planned randomized, double-blind trial will enroll approximately 320 participants across 47 centers in China and follow treatment for 52 weeks. Its primary endpoint is the annual rate of decline in forced vital capacity, with disease progression among the secondary outcomes [9]. This is the right next test for an IPF medicine. It is not a longevity trial, and the company has stated that the drug remains investigational and unapproved [10].

A convincing geroprotective claim would require prospective studies that define aging endpoints before treatment, include larger and more diverse populations, confirm findings with independent biomarkers, and connect clock changes to durable improvements in function and disease risk. Researchers would also need to learn whether the apparent benefit extends beyond people with IPF and whether long-term TNIK inhibition remains safe.

For now, rentosertib has done something genuinely noteworthy. An AI-assisted drug developed for an age-related disease produced a coherent signal across several proteomic clocks inside a controlled human trial. That offers a useful model for embedding geroscience measurements into conventional drug development. The finding should be described as preliminary evidence of an aging-related proteomic shift—not proof that a pill reversed human aging. If phase 3 confirms meaningful lung benefits and future studies connect the molecular signal to lasting health outcomes, the larger longevity story will become much stronger.

References

[1] Zhavoronkov A, Galkin F, Chen S, et al. Integration of proteomic aging clocks in a phase 2a clinical trial supports simultaneous geroprotective assessment. Nat Biotechnol. Published online September 7, 2026. doi:10.1038/s41587-026-03286-y.

[2] Ren F, Aliper A, Chen J, et al. A small-molecule TNIK inhibitor targets fibrosis in preclinical and clinical models. Nat Biotechnol. 2025;43(1):63-75. doi:10.1038/s41587-024-02143-0.

[3] Torres-Machorro AL, García-Vicente Á, Espina-Ordoñez M, et al. Update of Aging Hallmarks in Idiopathic Pulmonary Fibrosis. Cells. 2025;14(3):222. doi:10.3390/cells14030222.

[4] Raghu G, Remy-Jardin M, Richeldi L, et al. Idiopathic Pulmonary Fibrosis (an Update) and Progressive Pulmonary Fibrosis in Adults: An Official ATS/ERS/JRS/ALAT Clinical Practice Guideline. Am J Respir Crit Care Med. 2022;205(9):e18-e47. doi:10.1164/rccm.202202-0399ST.

[5] Xu Z, et al. A generative AI-discovered TNIK inhibitor for idiopathic pulmonary fibrosis: a randomized phase 2a trial. Nat Med. 2025;31(8):2602-2610. doi:10.1038/s41591-025-03743-2.

[6] Argentieri MA, Xiao S, Bennett D, et al. Proteomic aging clock predicts mortality and risk of common age-related diseases in diverse populations. Nat Med. 2024;30(9):2450-2460. doi:10.1038/s41591-024-03164-7.

[7] Insilico Medicine. Rentosertib Shows Potential for Biological Age Reversal, as Assessed by Six Proteomic Aging Clocks. Company research announcement. September 7, 2026.

[8] Tang Q, Xiao D, Veviorskiy A, et al. AI-Driven Robotics Laboratory Identifies Pharmacological TNIK Inhibition as a Potent Senomorphic Agent. Aging Dis. 2025;17(1):432-451. doi:10.14336/AD.2024.1492.

[9] ClinicalTrials.gov. Study Evaluating Rentosertib (INS018_055) Administered Orally in Patients With Idiopathic Pulmonary Fibrosis. Identifier NCT07687459. Updated July 7, 2026.

[10] Insilico Medicine. Insilico Initiates Phase III Clinical Trial for Rentosertib, Its AI-Empowered TNIK Inhibitor for Idiopathic Pulmonary Fibrosis. Company announcement. July 7, 2026.