Most fisetin human research is small, short, and aimed at slow outcomes such as frailty or biological age. There is one exception, and it is aimed at something that kills people in days.
STOP-Sepsis is a phase 2, multicenter, randomized, double-blinded trial testing whether fisetin can prevent clinical deterioration in elderly patients who have already been diagnosed with sepsis [1]. It is registered as NCT05758246, sponsored by the University of Minnesota, and as of August 2026 it is still recruiting toward its enrollment target of 220.
Key Takeaways
- STOP-Sepsis randomizes patients over 65 with a clinical diagnosis of sepsis to one oral 20 mg/kg dose of fisetin, two 20 mg/kg doses a day apart, or placebo [1].
- The primary outcome is the change at 7 days in a composite of cardiovascular, respiratory and renal SOFA scores, the same organ-failure scoring used at the bedside [1].
- A secondary outcome directly counts senescent CD3-positive T cells at 7 days, which makes this a test of the senolytic hypothesis and not just of a flavonoid [1].
- 20 mg/kg is about 1,400 mg for a 70 kg adult, in a single dose, given in hospital. Retail fisetin capsules are typically 100 to 500 mg.
- The animal work behind it is genuinely strong and structurally mismatched: the key mouse study injected fisetin half an hour before inducing sepsis [2].
Why senolytics and sepsis
Sepsis is the body’s own response to infection turning destructive, damaging organs faster than the infection itself would. It is heavily age-skewed: older patients get sepsis more often and die from it more often, and that pattern is not fully explained by comorbidity.
The hypothesis behind this trial is that senescent immune cells are part of the reason. Senescent cells accumulate with age, show altered gene expression, and resist apoptosis, and the trial protocol argues that senescence-associated maladaptive signaling may contribute to sepsis and septic shock [1]. If that is right, clearing those cells should blunt the response, and fisetin is the senolytic with the best safety record for human dosing.
This sits next to the same reasoning covered in our articles on fisetin and immunosenescence and fisetin and post-viral senescence, and the COVID-FIS trial was the same logic applied to a different acute infection.
What the trial actually does
Two hundred and twenty patients aged over 65 with a clinical diagnosis of sepsis are randomized three ways: a single oral dose of fisetin at 20 mg/kg, two oral doses of 20 mg/kg each spaced one day apart, or placebo. It is double-blinded and uses adaptive allocation, meaning the randomization ratio can shift during the trial as data accumulates [1].
The primary endpoint is the change in a composite of cardiovascular, respiratory and renal sequential organ failure assessment scores at 7 days from enrollment. SOFA is not a research-only instrument; it is what intensivists use to track how many organ systems are failing and how badly. A trial that moves SOFA is speaking the language of critical care rather than the language of supplement marketing.
Secondary outcomes include quantification of senescent CD3-positive cells at 7 days, plus 28-day organ-failure-free days, ICU days, and all-cause mortality [1]. That CD3 measurement is the part that makes this scientifically interesting beyond the clinical question: if fisetin improves outcomes without reducing senescent T cells, the senolytic explanation is wrong even if the drug works.
The registry lists the trial as recruiting, with a start date of August 2023 and a primary completion date of August 2026. Results have not been published. Anyone wanting the current status should check NCT05758246 on ClinicalTrials.gov directly rather than trust a date in an article.
The dose is a hospital dose
Twenty milligrams per kilogram is roughly 1,400 mg for a 70 kg adult, taken at once. Retail fisetin capsules are typically 100 to 500 mg, and the daily-use protocols discussed in our dosage article sit well below this.
The 20 mg/kg figure comes from the same lineage as the Mayo Clinic senolytic protocols, and it is a supervised inpatient dose given to people already under continuous monitoring for organ failure. The human pharmacokinetic data helps explain why the number is so large: a 1000 mg dose of unformulated fisetin peaks at only about 10 ng/ml in plasma [3], so reaching a concentration with any chance of clearing senescent cells requires either a very large dose or an engineered formulation.
Nothing about this is a template for home use. Sepsis is a medical emergency where every hour of delayed antibiotics measurably raises mortality. The trial gives fisetin alongside standard sepsis care, not instead of it.
The animal evidence, and the way it does not match
The preclinical case is unusually broad for a fisetin indication.
The most cited study used cecal ligation and puncture in mice, the standard model of polymicrobial sepsis. Fisetin at 10 mg/kg significantly reduced lung, liver and kidney injury and lowered IL-6, TNF-alpha and IL-1beta in bronchoalveolar lavage fluid. In LPS-treated bone marrow derived macrophages, fisetin at 3 to 10 micromolar dose-dependently suppressed those same cytokines plus iNOS, by inhibiting phosphorylation of p38 MAPK, MK2 and TAK1 and weakening the TAK1 to TAB1 interaction [2].
Separate work found fisetin reduced kidney inflammation and apoptosis in sepsis through Src-mediated NF-kappaB p65 and MAPK signaling [4], improved cognitive impairment in rats with sepsis-associated encephalopathy by activating mitophagy and suppressing neuroinflammation [5], and decreased endotoxic shock by activating beta-catenin [6].
Now the mismatches, which are the parts worth holding onto. The mouse study injected fisetin intraperitoneally, bypassing the absorption problem entirely, and did so 30 minutes before inducing sepsis [2]. Real patients arrive after sepsis has started, and swallow the drug. A pretreatment study answers a different question from the one the trial is asking.
None of the animal studies measured senescent cell clearance either. They reported cytokine suppression and kinase inhibition, which are anti-inflammatory mechanisms rather than senolytic ones. So the strongest preclinical evidence supports fisetin as an acute anti-inflammatory, while the trial is built on a senolytic rationale, and the CD3 secondary endpoint is where those two stories get tested against each other.
How to read this if you are not a critical care physician
The honest summary is that a serious, well-designed trial is asking a serious question, and it has not answered it yet.
What the trial’s existence does tell you is that fisetin has cleared enough safety review to be given at 1,400 mg to acutely ill 70-year-olds across multiple hospitals, which is a meaningful signal about tolerability even before any efficacy result. What it does not tell you is that fisetin helps with infections, that taking fisetin will protect you from sepsis, or that a daily capsule does anything comparable. Phase 2 trials frequently fail, and the protocol paper says plainly that the intent is to inform the design of a larger phase 3 study [1].
If someone you know has sepsis, the intervention that matters is prompt antibiotics and fluids in a hospital. Nothing in this literature changes that.
Common questions
Can fisetin treat sepsis?
Unknown. A phase 2 trial is testing exactly that in 220 patients over 65 and has not reported results [1]. Mouse studies show reduced organ injury and cytokine levels, but the key one dosed by injection before sepsis was induced rather than orally after [2].
Should I take fisetin when I get an infection?
There is no evidence supporting that, and the trial dose is roughly 1,400 mg given under hospital monitoring rather than anything sold as a daily supplement. Ordinary infections do not call for it, and serious ones call for medical care.
How is this different from the COVID trial?
Both apply the senolytic hypothesis to acute infection in older adults, and both use fisetin. The COVID-FIS trial studied skilled nursing facility residents with COVID-19, while STOP-Sepsis studies hospitalized patients with sepsis from any cause and uses organ failure scores as its primary outcome. Our COVID article covers that trial in detail.
When will results be available?
The registry lists a primary completion date in August 2026, and results were not published as of this writing. Trials routinely run past their listed dates and analysis takes months afterward. NCT05758246 on ClinicalTrials.gov is the authoritative source.
References
- Senolytics To slOw Progression of Sepsis (STOP-Sepsis) in elderly patients: Study protocol for a multicenter, randomized, adaptive allocation clinical trial. Trials (2024). PMID 39434114
- Fisetin alleviates sepsis-induced multiple organ dysfunction in mice via inhibiting p38 MAPK/MK2 signaling. Acta Pharmacol Sin (2021). PMID 32661350
- Enhanced bioavailability and pharmacokinetics of a novel hybrid-hydrogel formulation of fisetin orally administered in healthy individuals. J Nutr Sci (2022). PMID 36304817
- Flavonoid fisetin alleviates kidney inflammation and apoptosis via inhibiting Src-mediated NF-kappaB p65 and MAPK signaling pathways. Biomed Pharmacother (2020). PMID 31918290
- Fisetin ameliorates cognitive impairment by activating mitophagy and suppressing neuroinflammation in rats with sepsis-associated encephalopathy. CNS Neurosci Ther (2022). PMID 34837343
- Fisetin inhibits lipopolysaccharide-induced inflammatory response by activating beta-catenin, leading to a decrease in endotoxic shock. Sci Rep (2021). PMID 33863923
These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Content is for informational purposes only and is not medical advice; consult a qualified healthcare provider before starting any supplement. As an Amazon Associate we earn from qualifying purchases.
