Longevity · 9 min read · Published September 8, 2026

Senolytics in 2026: Dasatinib plus Quercetin, Fisetin, and What Human Trials Have Shown

Every human senolytic trial that has read out as of September 2026: Kirkland's dasatinib plus quercetin pilots in lung fibrosis and diabetic kidney disease, the still-unfinished fisetin trials, foselutoclax in the eye, RLS-1496 on skin, and why the capsules sold as senolytics have nothing to do with any of it.

Do senolytics work in humans?

Not proven. As of September 2026 no senolytic is approved for aging, and the three randomized trials that have read out (D+Q in lung fibrosis, n=12, 2023; fisetin in knee osteoarthritis, n=75, 2024; foselutoclax in macular edema, n=52, 2025) showed no benefit over their controls on clinical endpoints. The positive human data are biomarker and open-label pilot results.

Senolytics are drugs meant to kill senescent cells, the damaged cells that stop dividing but keep secreting inflammatory signals. The idea has strong animal support: clearing senescent cells in mice improves function and extends lifespan in several models (animal evidence). The human story is smaller, slower and more honest than the marketing around it. This article walks through every human result that exists, with its size and duration, so the gap between what is sold and what is known is visible. Dasatinib is an FDA-approved leukemia drug used off-label in these trials; quercetin and fisetin are dietary supplements with no drug approval; foselutoclax and RLS-1496 are investigational and cannot be legally sold.

What did the dasatinib plus quercetin trials show?

Five small studies since 2019. The open-label IPF pilot (n=14, 3 weeks) improved 6-minute walk distance by 21.5 meters. The diabetic kidney pilot (n=9) reduced p16 and p21 positive cells in fat biopsies 11 days after three days of dosing. The randomized IPF follow-up (n=12, 2023) was feasible but found no meaningful functional difference versus placebo.

Two things stand out. First, the drugs do something measurable: the Hickson biopsy data remain the clearest evidence that a senolytic reduces senescent cell burden in human tissue (EBioMedicine, 2019). Second, the one placebo-controlled comparison did not reproduce the walking improvement of the open-label pilot, and the treated group had three times as many minor adverse events, with sleep disturbance and anxiety over-represented (EBioMedicine, 2023). Twelve people cannot settle the question either way, which is exactly the point: after seven years, the total randomized D+Q evidence in humans is 12 people for 3 weeks.

Where are the fisetin trials?

Still running. AFFIRM (older women, NCT03430037, started February 2018) and AFFIRM-LITE (adults 70 to 90, NCT03675724, started November 2018), both 40-person Mayo Clinic Phase 2 trials of fisetin 20 mg/kg/day for two days, were listed as enrolling by invitation in May 2026 with primary completion pushed to November 2026 and no results posted.

Fisetin became the internet's favorite senolytic because it is a flavonoid you can buy, and because mouse data suggested it was the most potent of a panel of natural compounds tested. In humans the record is thin. The Mayo trials above are the ones the field is waiting on (ClinicalTrials.gov NCT03675724). The only fisetin trial with posted results is a Phase 1/2 study in knee osteoarthritis (Steadman Philippon Research Institute, n=75, 34 on fisetin and 40 on placebo). It used 100 mg capsules to reach about 20 mg/kg/day on two consecutive days, repeated after 28 days off. Results posted in September 2024 showed no significant differences from placebo in C-reactive protein, the cartilage marker COMP, physical function, pain or MRI cartilage measures, and no safety difference (ClinicalTrials.gov NCT04210986). Evidence tier: human RCT, negative.

What happened to foselutoclax (UBX1325) in the eye?

It came close and fell short. In the Phase 2b ASPIRE trial (n=52, diabetic macular edema, randomized against aflibercept every 8 weeks for 6 months), UBX1325 gained 5.2 letters at 24 weeks and 5.5 at 36 but missed the primary non-inferiority endpoint at an 88 percent confidence interval versus the 90 percent required (March 24, 2025).

Foselutoclax is the most rigorously tested senolytic in humans: a BCL-xL inhibitor injected into the eye, where senescent cells are thought to drive leaky vessels. Unity Biotechnology's ASPIRE design was bold, an active comparison against the standard biologic rather than placebo. The drug was non-inferior at 9 of 10 time points and statistically non-inferior at week 36, and it outperformed aflibercept in a prespecified subgroup with thinner retinas at baseline, but the primary analysis missed. On May 5, 2025 Unity announced a workforce reduction affecting all employees, moved its executives to consulting roles and began exploring a sale, license or merger for the program (Unity Biotechnology, May 2025). Evidence tier: human RCT, primary endpoint missed. As of September 2026 no partner has been announced.

What is RLS-1496 and what did its first human trial show?

RLS-1496 is Rubedo Life Sciences' topical GPX4 modulator, designed to push senescent skin cells into ferroptosis. Its Phase 1 (single-center, ascending-dose, randomized, vehicle-controlled, 4 weeks, roughly 70 subjects across psoriasis, atopic dermatitis and photo-aged skin) met its safety endpoint on March 26, 2026, with a 20 percent average reduction in epidermal thickness in psoriasis.

The efficacy signals were exploratory: 25 percent of atopic dermatitis subjects on drug reached a 4-point itch improvement versus none on vehicle, and skin biopsies showed rising collagen gene expression and falling inflammatory and SASP markers over the month (Rubedo, March 2026). A Phase 1b/2a in actinic keratosis is running in the United States. Evidence tier: human pilot, safety primary. It is a skin cream in early trials, not an anti-aging pill, and it is not available outside those trials.

Senolytic supplements versus what the trials actually used

The products sold as 'senolytic activators' or 'senolytic complexes' usually contain fisetin, quercetin or both, sometimes with other flavonoids, in capsules meant to be taken every day. Compare that with the trials:

• Quercetin was never tested alone. In every D+Q study it was paired with dasatinib, a prescription chemotherapy drug. A quercetin capsule is not half of a senolytic regimen; quercetin has no human senolytic data on its own.
• Fisetin trial parameters were pulses, not daily use. AFFIRM-LITE and the knee OA trial gave about 20 mg/kg/day for two consecutive days, roughly 1,400 mg a day for a 70 kg adult, then nothing for weeks. The knee OA trial needed about 14 of its 100 mg capsules per day to reach that. A daily capsule delivers a small fraction of the trial exposure on a pattern no trial has tested.
• The one fisetin trial with results was negative. The trial pulse did not beat placebo on pain, function or cartilage in 75 people.
• Blood tests marketed as 'senescence panels' are not validated endpoints. The trials measured p16 and p21 in tissue biopsies and SASP factors in blood as exploratory markers, not as proof of benefit.

The bottom line

Senolytics are one of the best-supported ideas in aging biology and one of the least-proven in aging medicine. Human D+Q data show target engagement in tissue but no controlled functional benefit. Fisetin's key trials are eight years old and unfinished, and its one completed RCT was negative. The best-designed senolytic trial to date, ASPIRE, missed by a hair and its company is winding down. RLS-1496 is the newest entrant and has a safety result on skin. If you see a capsule sold as a senolytic in 2026, the accurate label is: an ingredient from a trial that has not reported, at a dose and schedule no trial used. Related reading: what the FDA changed for peptides in 2026, klotho and the new compounds of 2026.