Senolytics in 2026: Inside the Clinical Trials Targeting Zombie Cells to Extend Healthy Lifespan

In the late 1990s, a mouse pathologist at the Mayo Clinic named Jan van Deursen began noticing something peculiar in the tissues of animals engineered to age prematurely. Scattered throughout their lungs, kidneys, and skeletal muscle were cells that refused to die. They had stopped dividing years ago, yet they persisted, quietly spewing inflammatory cytokines, proteases, and growth factors into the tissue around them. Van Deursen and his protege Darren Baker began calling them "zombie cells." In 2011, in a landmark paper published in Nature, the team showed that selectively clearing these senescent cells from progeroid mice delayed the onset of age-related dysfunction across multiple organ systems.

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Fifteen years later, the field van Deursen and Baker helped launch has grown into one of the most heavily capitalized and clinically active frontiers in longevity medicine. As of early 2026, more than 30 clinical trials investigating senolytic or senomorphic interventions are enrolling or have recently reported data, spanning indications from diabetic macular edema and idiopathic pulmonary fibrosis to osteoarthritis, Alzheimer’s disease, and frailty in older adults. The question the field is now asking is no longer whether senescent cells drive aging pathology. The question is which compounds, at which doses, in which patients, can safely clear those cells without collateral damage.

What Senescent Cells Actually Do

Cellular senescence was first described in 1961 by Leonard Hayflick, who observed that normal human fibroblasts in culture would divide roughly 50 times before ceasing to replicate. For decades, senescence was understood as a simple endpoint: a tumor-suppressive mechanism that kept damaged or stressed cells from propagating. What van Deursen, Judith Campisi at the Buck Institute, and others began documenting in the 2000s was far more unsettling. Senescent cells are not inert. They secrete a complex cocktail of bioactive molecules known as the senescence-associated secretory phenotype, or SASP, which includes interleukin-6, interleukin-8, matrix metalloproteinases, and various chemokines that drive chronic low-grade inflammation in surrounding tissue.

The SASP is evolutionarily useful in the short term. It recruits immune cells to clear damaged tissue and promotes wound healing. But in older organisms, senescent cells accumulate faster than the immune system can remove them, and their persistent inflammatory signaling becomes a driver of pathology. Studies in both mice and humans have now linked senescent cell burden to atherosclerosis, osteoarthritis, pulmonary fibrosis, type 2 diabetes, sarcopenia, neurodegeneration, and age-related macular degeneration. The Mayo Clinic group’s 2016 follow-up paper in Nature, which used a genetic system called INK-ATTAC to selectively kill p16-positive senescent cells in naturally aging mice, demonstrated lifespan extensions of roughly 25 percent and significant improvements in healthspan markers.

The First-Generation Senolytics

The pharmacological effort to replicate these genetic results began in earnest in 2015, when James Kirkland and Laura Niedernhofer published work identifying dasatinib and quercetin as the first small-molecule senolytic combination. Dasatinib, a tyrosine kinase inhibitor originally approved for chronic myeloid leukemia, targets senescent preadipocytes and endothelial cells. Quercetin, a naturally occurring flavonoid, hits a different subset including senescent mesenchymal stem cells. Together, the combination exploits the fact that senescent cells become dependent on specific pro-survival pathways, what the field now calls senescent cell anti-apoptotic pathways, or SCAPs, to resist programmed cell death.

Subsequent work added fisetin, another flavonoid found in strawberries and apples, which Kirkland’s group at the Mayo Clinic reported in 2018 to be more potent and better tolerated than quercetin in animal models. Navitoclax, a BCL-2 family inhibitor originally developed for oncology, was identified as a broad-spectrum senolytic targeting the BCL-2 and BCL-xL anti-apoptotic proteins upregulated in many senescent cell types. FOXO4-DRI, a cell-penetrating peptide developed in the laboratory of Peter de Keizer in the Netherlands, disrupts the interaction between FOXO4 and p53 to selectively trigger apoptosis in senescent cells.

These first-generation compounds have now been tested in small pilot trials in humans. In 2019, a team led by Jamie Justice at Wake Forest and Kirkland at Mayo published the first clinical results using dasatinib plus quercetin in a small cohort of patients with idiopathic pulmonary fibrosis, a devastating age-related lung disease. After a short intermittent dosing regimen, patients showed measurable improvements in physical function metrics including gait speed and chair stand tests, though the trial was too small to establish disease-modifying effects. A follow-up study in patients with diabetic kidney disease, published in 2019 in EBioMedicine, demonstrated that the combination could reduce senescent cell burden in human adipose and skin biopsies, providing the first proof of pharmacodynamic target engagement in humans.

The Clinical Trial Landscape in 2026

The clinical pipeline has expanded dramatically since those early pilots. Unity Biotechnology, the publicly traded senolytics company cofounded by Judith Campisi, Nathaniel David, and Leonard Guarente, has pivoted its lead asset UBX1325 from an earlier osteoarthritis program to ophthalmology. UBX1325 is a small-molecule inhibitor of BCL-xL designed for intravitreal injection, and data from the ASPIRE and BEHOLD trials have shown durable improvements in best-corrected visual acuity in patients with diabetic macular edema. The company’s ENVISION trial, which read out preliminary data in late 2025, compared UBX1325 against aflibercept in age-related macular degeneration, with results suggesting non-inferior efficacy at extended dosing intervals.

BioAge Labs has taken a different approach, focusing on what the company calls aging biomarker-driven drug discovery. Rather than starting with senolytic activity, BioAge mines longitudinal human aging cohorts to identify molecular targets associated with exceptional healthspan, then develops compounds against those targets. The company’s lead asset, azelaprag, an apelin receptor agonist, entered Phase 2 trials in 2024 for obesity in older adults, with a secondary hypothesis that apelin signaling modulates senescence and inflammaging.

Cleara Biotech, spun out of Peter de Keizer’s Utrecht laboratory, is advancing a next-generation FOXO4-targeting peptide and associated small molecules toward oncology and fibrotic disease indications. Rubedo Life Sciences, founded by Marco Quarta, a former Stanford researcher, has developed a proprietary computational platform to identify cell-type-specific senolytic targets and recently nominated its lead clinical candidate RLS-1496 for skin aging indications, with a first-in-human trial initiated in 2025.

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Perhaps the most clinically advanced effort outside UBX1325 is the ongoing trial landscape for fisetin. The Mayo Clinic’s AFFIRM-LITE study, a Phase 2 trial enrolling adults over 70 with frailty, and a parallel study in COVID-19 survivors with persistent pulmonary dysfunction, are testing whether intermittent high-dose fisetin dosing can improve functional and biomarker outcomes. Full results from AFFIRM-LITE are expected in 2026 and will provide one of the first rigorous placebo-controlled readouts of a senolytic intervention in a general aging population.

Senomorphics: The Other Strategy

Not all of the field is chasing outright cell killing. A parallel effort focuses on what Manuel Serrano at the Institute for Research in Biomedicine in Barcelona has termed senomorphics, drugs that do not eliminate senescent cells but instead suppress their inflammatory secretory phenotype. The logic is straightforward. If most of the damage senescent cells cause is mediated by the SASP, then silencing the SASP may achieve similar benefits with a lower risk of tissue disruption.

Rapamycin, the mTOR inhibitor originally isolated from Easter Island soil bacteria in 1972, remains the most widely studied senomorphic. Rapamycin suppresses SASP factor production through inhibition of mTORC1-dependent translation, and its effect on lifespan in mice has been replicated across more than a dozen laboratories since the 2009 NIA Interventions Testing Program publication. Metformin, similarly, appears to reduce SASP signaling indirectly through AMPK activation, and the long-delayed TAME (Targeting Aging with Metformin) trial, led by Nir Barzilai at the Albert Einstein College of Medicine, aims to test whether metformin can delay the onset of age-related diseases as a category.

Newer senomorphic candidates include JAK inhibitors such as ruxolitinib, which blocks the JAK-STAT signaling downstream of many SASP cytokines, and inhibitors of the NLRP3 inflammasome, which mediates IL-1 beta production in senescent cells. A 2024 paper in Nature Aging from Vishwa Deep Dixit’s laboratory at Yale demonstrated that NLRP3 inhibition in aged mice preserved thymic function and improved immune response to vaccination, suggesting that senomorphic interventions may be particularly valuable for immunosenescence.

The Specificity Problem

The principal technical challenge confronting senolytic drug development is specificity. Senescent cells are heterogeneous across tissues, and the SCAPs they rely on for survival differ by cell type, stress signal, and microenvironment. A drug that effectively clears senescent endothelial cells in the vasculature may leave senescent neurons untouched, or worse, may cause off-target toxicity in non-senescent cells that share the same pro-survival pathway. Navitoclax, for example, causes dose-limiting thrombocytopenia because platelets depend on BCL-xL for survival.

The field has responded with increasingly sophisticated targeting strategies. Proteolysis-targeting chimeras, or PROTACs, are being developed to degrade BCL-xL selectively in senescent cells while sparing platelets. Antibody-drug conjugates targeting the senescence-associated cell surface marker B2M are in preclinical development. A 2023 paper in Cell from Manuel Serrano’s group demonstrated that CAR T cells engineered to recognize uPAR, a surface protein expressed on many senescent cell types, could selectively eliminate senescent cells in mouse models of liver fibrosis and osteoarthritis, raising the possibility of a cell-based senolytic therapy.

Biomarker development has lagged behind therapeutic development, which is a significant problem for the field. Unlike oncology, where tumor burden can be measured directly through imaging or circulating tumor DNA, there is no validated blood or imaging biomarker for senescent cell burden in living humans. Most clinical trials rely on surrogate measures such as serum SASP factor panels, adipose tissue biopsy, or skin biopsy, none of which fully capture the systemic senescent cell load. Several groups, including teams at the Buck Institute and the Translational Gerontology Branch at the NIA, are working on imaging agents and liquid biopsy panels that could make senescent cell burden a measurable clinical endpoint.

The Skeptics

Not everyone in the aging research community is convinced the senolytic thesis will translate as cleanly into human medicine as animal data suggest. Joao Pedro de Magalhaes at the University of Birmingham has written critically about the risk that long-term senescent cell clearance could impair wound healing and tumor suppression. The tumor-suppressive role of senescence is well established, and several groups have shown that elimination of senescent cells in certain contexts can accelerate tumor progression by removing immune recruitment signals.

Matt Kaeberlein, formerly of the University of Washington and now leading the Dog Aging Project and running the biotech Optispan, has argued publicly that rapamycin and other senomorphic interventions may ultimately prove more clinically useful than senolytic cell-killing strategies, given the specificity challenges and the strong translational data for rapamycin in multiple mammalian species. Kaeberlein is also a frequent skeptic of overhyped longevity claims from commercial supplement vendors selling fisetin and quercetin without the intermittent high-dose protocols shown to work in rodent studies.

Companies, Capital, and the Next Wave

The commercial landscape has matured considerably. In addition to Unity Biotechnology, BioAge, Cleara, and Rubedo, the space now includes companies such as Oisin Biotechnologies, which is developing a lipid nanoparticle delivery system that triggers apoptosis specifically in p16- or p53-expressing cells, and Gerostate Alpha, founded by University of Michigan researchers to pursue novel small-molecule senolytics identified through high-throughput screens. Retro Biosciences, backed by Sam Altman with a reported 180 million dollar seed funding in 2022, is pursuing multiple longevity modalities including partial cellular reprogramming, which may produce rejuvenation effects partly through clearance of senescent-like states.

Funding into the broader geroscience sector has totaled billions of dollars over the past five years, with sovereign wealth funds, tech billionaires, and specialty biotech investors all participating. Altos Labs, launched in 2022 with reported initial capitalization of 3 billion dollars from investors including Jeff Bezos and Yuri Milner, has focused primarily on partial reprogramming rather than senolytics, but the scientific overlap between these programs is significant, and the talent flow between the subfields continues.

What This Means For You

For readers wondering how to act on the current state of senolytics research, the honest answer is that it is still too early for most of these interventions to be ready for routine use. Fisetin and quercetin are widely available as supplements, but the intermittent high-dose protocols used in research settings (typically 20 milligrams per kilogram of body weight for two consecutive days, repeated monthly) are very different from the daily low-dose regimens most supplement vendors market. The safety profile of such high-dose intermittent regimens in humans is still being characterized in ongoing trials, and self-administration without medical supervision is not advised.

Dasatinib is a prescription drug with known hematologic and cardiovascular side effects, and its use as a senolytic outside a clinical trial is not standard medical practice. Rapamycin and metformin are being prescribed off-label by some physicians for longevity indications, but the evidence for healthspan benefits in healthy adults remains inconclusive, and both drugs carry real side effect profiles that require clinical monitoring.

The most evidence-based actions an individual can take while senolytic clinical trials mature are the lifestyle interventions that reduce the underlying stressors that drive senescent cell accumulation in the first place. Regular exercise, particularly resistance training and zone 2 cardiovascular work, has been shown in human studies to reduce markers of cellular senescence in skeletal muscle. Caloric restriction and time-restricted eating activate many of the same mTOR-suppressing pathways that rapamycin targets pharmacologically. Sleep of sufficient duration and quality reduces oxidative stress, one of the primary drivers of senescence induction. Avoiding smoking, excessive alcohol, and prolonged UV exposure reduces the DNA damage that triggers senescence in multiple cell types.

For those interested in participating in the clinical research, ClinicalTrials.gov lists current enrolling senolytic studies, and centers including Mayo Clinic, Wake Forest, and several academic medical centers associated with the Translational Geroscience Network are actively recruiting for age-related disease studies. As the AFFIRM-LITE and ENVISION trials read out over the next 12 to 24 months, the field should have its most rigorous evidence yet about whether the remarkable results seen in genetically engineered mice can translate into meaningful healthspan extension in human beings.

The zombie cells Jan van Deursen first noticed in aging mouse tissue two decades ago have turned out to be a far more consequential biological target than anyone anticipated. Whether the pharmacology catches up to the biology in a form that reaches patients at scale is the question the next few years will answer.

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