Senolytics: revision 3 to 4 — Future Human Wiki

Revision 3

Revision 4

categories: ["longevity"]

tags: ["cellular senescence", "aging", "sasp", "clinical trials", "drug repurposing", "apoptosis"]

summary: "Drugs that selectively kill senescent cells, an approach that reduces age-related pathology in mice but has so far produced modest or null results in humans."

summary: "Drugs that selectively kill senescent cells, an approach that reduces age-related pathology in mice but has so far produced modest or null results in humans."

updated: "2026-10-28"

updated: "2026-10-29"

humanEvidence: "Human data are small open-label pilots of nine to fourteen patients, one showing reduced senescent-cell markers in fat and skin, plus two randomized failures; every lifespan result is from mice."

humanEvidence: "Human data are small open-label pilots of nine to fourteen patients, one showing reduced senescent-cell markers in fat and skin, plus two randomized failures; every lifespan result is from mice."

access: "No senolytic is approved for any aging indication; dasatinib is an approved cancer drug available only on prescription, and fisetin and quercetin are sold over the counter as supplements at doses taken from mouse studies."

access: "No senolytic is approved for any aging indication; dasatinib is an approved cancer drug available only on prescription, and fisetin and quercetin are sold over the counter as supplements at doses taken from mouse studies."

reversibility: "partly-reversible"

{ "label": "Mechanism", "value": "Blocking anti-apoptotic pathways" },

{ "label": "Term coined", "value": "2015" },

{ "label": "Lead candidates", "value": "Dasatinib + quercetin, fisetin, navitoclax" },

{ "label": "Clinical stage", "value": "Phase 1–2" },

{ "label": "Clinical stage", "value": "Phase 1-2" },

{ "label": "Approved for aging", "value": "No" },

{ "label": "Readiness", "value": "TRL 5" }

]

factors known as the senescence-associated secretory phenotype (SASP), characterized in the 2000s by

groups including those at the [[buck-institute]]. The SASP is what makes senescent cells plausible

drivers of aging rather than inert debris, and its paracrine spread links the process to

[[inflammaging]] and to [[stem-cell-exhaustion]]. Cells reach the state by several routes —

[[inflammaging]] and to [[stem-cell-exhaustion]]. Cells reach the state by several routes:

[[telomeres-and-telomerase|telomere attrition]] in replicative senescence, DNA damage, oncogene

activation, severe [[mitochondrial-dysfunction|mitochondrial stress]] — which is one reason the

activation, and severe [[mitochondrial-dysfunction|mitochondrial stress]]. The variety of routes is

resulting populations are not biochemically uniform. [[cellular-senescence]] treats the cell state

one reason the resulting populations are not biochemically uniform. [[cellular-senescence]] covers

itself, including its triggers, markers, and useful roles; this article treats the drugs. Senescence

the cell state itself, including its triggers, markers, and useful roles; this article covers the

appears in its own right as one of the [[hallmarks-of-aging]].

drugs. Senescence appears in its own right as one of the [[hallmarks-of-aging]].

```figure

{"key": "senescent-mefs-sabg", "caption": "The target, in mouse cells: late-passage fibroblasts grow large and flat and stain for SA-β-galactosidase, the standard senescence marker. The stain identifies the cells senolytics aim to kill; it does not harm them."}

{"key": "senescent-mefs-sabg", "caption": "The target, in mouse cells: late-passage fibroblasts grow large and flat and stain for SA-β-galactosidase, the standard senescence marker. The stain identifies the cells senolytics aim to kill; it does not harm them."}

```

Resistance to apoptosis is the drugging opportunity. Senescent cells depend on what the field calls

senescent cell anti-apoptotic pathways: members of the BCL-2 family, PI3K–AKT signalling, p53–p21

senescent cell anti-apoptotic pathways: members of the BCL-2 family, PI3K-AKT signalling, p53-p21

regulation, HIF-1α, and heat-shock protein 90. Crucially, different senescent cell types depend on

regulation, HIF-1α, and heat-shock protein 90. Different senescent cell types depend on different

different pathways. Senescent human preadipocytes are killed by dasatinib, an approved kinase

pathways. Senescent human preadipocytes are killed by dasatinib, an approved kinase

inhibitor; senescent endothelial cells are killed by the flavonoid quercetin. Neither alone covers

both, which is why the founding paper proposed the combination.

The pharmacology has an unusual feature. Because senescent cells do not divide, a drug does not need

Because senescent cells do not divide, a drug does not need to maintain steady-state exposure. It

to maintain steady-state exposure — it needs only to be present long enough to trigger apoptosis, and

needs only to be present long enough to trigger apoptosis, and the cleared population takes weeks to

the cleared population takes weeks to months to rebuild. This licenses "hit-and-run" intermittent

months to rebuild. This unusual pharmacology licenses "hit-and-run" intermittent dosing, typically a

dosing, typically a few days every few weeks, which in principle limits cumulative toxicity from

few days every few weeks, which in principle limits cumulative toxicity from drugs that would be

drugs that would be intolerable continuously.

intolerable continuously.

> [!note] Terminology

> A *senolytic* kills the cell. A *senomorphic* (or senostatic) leaves it alive but suppresses the

**Fisetin**, another flavonoid, showed senolytic activity and healthspan effects in aged mice and has

attracted disproportionate consumer interest because it is sold as a

[[dietary-supplements|supplement]]. Its human evidence

[[dietary-supplements|supplement]]. Its human evidence base is thin, and the bioavailability

base is thin, and the bioavailability problem is worse than quercetin's.

problem is worse than quercetin's.

**Navitoclax (ABT-263)** inhibits BCL-2, BCL-xL, and BCL-W, and clears senescent cells efficiently in

mice, including in aged haematopoietic stem cells.[^chang2016] Its dose-limiting thrombocytopenia

because platelets lack the machinery to execute targeted protein degradation.

**Unity Biotechnology** pursued locally injected senolytics to avoid systemic exposure. UBX0101, an

MDM2–p53 interaction inhibitor for knee osteoarthritis, failed its randomized phase 2. The company's

MDM2-p53 interaction inhibitor for knee osteoarthritis, failed its randomized phase 2. The company's

subsequent lead, UBX1325 (foselutoclax), a BCL-xL inhibitor injected into the eye for diabetic

macular edema, has produced phase 2 data the company describes as favourable; an independent

confirmatory trial had not been published as of 2026.

lifespan in male progeroid mice; a vaccine against CD153 reduced senescent T cells in the fat of

obese mice.[^suda2021]

The appeal is durability: one treatment rather than repeated drug courses. The same property is the

The appeal is durability: one treatment rather than repeated drug courses. The same property is also

main concern. Engineered T cells that persist, or an antibody response that lasts months, cannot be

the main concern. Engineered T cells that persist, or an antibody response that lasts months, cannot

withdrawn the way a short drug course can; CAR T therapy carries the cytokine-release toxicity known

be withdrawn the way a short drug course can; CAR T therapy carries the cytokine-release toxicity

from its cancer use; and neither uPAR nor GPNMB is unique to senescent cells, so normal cells

known from its cancer use; and neither uPAR nor GPNMB is unique to senescent cells, so normal cells

carrying the target are exposed too. Every result above is from mice, and no immune-based senolytic

had reported data in people as of October 2026. Immorta Bio said in October 2026 that it had

completed preclinical studies of SenoMune-0257, a synthetic nine-amino-acid peptide it identified using

completed preclinical studies of SenoMune-0257, a synthetic nine-amino-acid peptide it identified

[[ai-drug-discovery|artificial intelligence]] to stimulate cytotoxic T cells against senescent

using [[ai-drug-discovery|artificial intelligence]] to stimulate cytotoxic T cells against senescent

cells, and that it

cells, and that it expected initial human evaluation before the end of the year; no peer-reviewed

expected initial human evaluation before the end of the year; no peer-reviewed data on the peptide

data on the peptide had been published as of October 2026.[^immorta2026]

had been published as of October 2026.[^immorta2026]

## Human evidence

The human record is short and must be read carefully. The idiopathic pulmonary fibrosis pilot

The human record is short, and each study has to be read for its design. The idiopathic pulmonary

enrolled fourteen patients with no control group and reported improvements in walking-based physical

fibrosis pilot enrolled fourteen patients with no control group and reported improvements in

function measures, which in an open-label study of a symptomatic population cannot be separated from

walking-based physical function measures, which in an open-label study of a symptomatic population

expectation and practice effects.[^justice2019] The diabetic kidney disease study, with nine

cannot be separated from expectation and practice effects.[^justice2019] The diabetic kidney disease

participants, is more informative on mechanism than on benefit: adipose and skin biopsies showed

study, with nine participants, is more informative on mechanism than on benefit: adipose and skin

reduced senescent-cell markers days after dosing, establishing target engagement in at least one

biopsies showed reduced senescent-cell markers days after dosing, establishing target engagement in

tissue.[^hickson2019] A pilot in Alzheimer's disease established that the drugs are tolerated in that

at least one tissue.[^hickson2019] A pilot in Alzheimer's disease established that the drugs are

population and that dasatinib reaches cerebrospinal fluid, without addressing efficacy.

tolerated in that population and that dasatinib reaches cerebrospinal fluid, without addressing

efficacy.

The most rigorous test to date is a randomized trial of intermittent D+Q in postmenopausal women with

bone-turnover endpoints, which did not meet its primary endpoint; the authors reported signals in

prespecified subgroups, which is hypothesis-generating rather than confirmatory.[^farr2024] Combined

prespecified subgroups, which is hypothesis-generating rather than confirmatory.[^farr2024] Taken

with the UBX0101 failure, the pattern is a field whose animal data are strong and whose human data

together with the UBX0101 failure, these results describe a field whose animal data are strong and

are, so far, unpersuasive.

whose human data are, so far, unpersuasive.

> [!caution] The missing measurement

> No validated assay reports senescent-cell burden in a living human across tissues. Without one,

The marker problem runs deeper than assay development. There is no single molecular signature of

senescence, and the cells that carry the usual markers differ by tissue, inducing stimulus, and time

since induction, so a drug that kills one senescent population may leave another untouched — the

since induction, so a drug that kills one senescent population may leave another untouched. This is

[[cellular-senescence|heterogeneity problem]] in its therapeutic form. The NIH-funded Cellular

the [[cellular-senescence|heterogeneity problem]] in its therapeutic form. The NIH-funded Cellular

Senescence Network was established in part to build the tissue atlases it requires.

Mouse-to-human translation carries the field's usual discount. Many striking results come from

marketing claims that far outrun the evidence, at doses chosen from mouse studies with no human

pharmacokinetic basis. This is the recurring pattern in longevity medicine, shared with

[[nad-precursors]] and with off-label mTOR-inhibitor use: a plausible mechanism, an unregulated

product, and no outcome data. Against that background it is worth noting the comparator. The

product, and no outcome data. For the functional endpoints senolytic trials target, among them

best-supported intervention for the functional endpoints senolytic trials target, among them

mobility, frailty, and cardiorespiratory capacity, the best-supported intervention is

mobility, frailty, and cardiorespiratory capacity, is [[exercise-and-aging|structured exercise]],

[[exercise-and-aging|structured exercise]], and dietary approaches such as [[caloric-restriction]]

and dietary approaches such as [[caloric-restriction]] have a far longer animal record than any

have a far longer animal record than any senolytic. A drug that cannot add to those has little claim

senolytic. A drug that cannot add to those has little claim on healthy people.

on healthy people.

## Outlook

Three developments would change the picture. The first is a validated, tissue-resolved measure of

senescent-cell burden, which would convert trials from guesswork into pharmacology. The second is a

randomized trial with a functional endpoint such as mobility, frailty, or visual acuity, run in a

population with a high senescent-cell load, powered properly and controlled. The third is targeting: prodrugs

population with a high senescent-cell load, powered properly and controlled. The third is targeting:

activated by senescence-associated enzymes, antibody-directed delivery of the kind developed for

prodrugs activated by senescence-associated enzymes, antibody-directed delivery of the kind

[[targeted-drug-delivery|tumour-directed payloads]], or engineered immune clearance would let the

developed for [[targeted-drug-delivery|tumour-directed payloads]], or engineered immune clearance

field escape the systemic toxicity ceiling that limits current compounds.

would let the field escape the systemic toxicity ceiling that limits current compounds.

Senolytics remain among the most advanced tests of the [[geroscience-hypothesis]] — the claim that

Senolytics remain among the most advanced tests of the [[geroscience-hypothesis]], the claim that

hitting a shared upstream driver of aging beats treating diseases one at a time. Competitions such as

[[xprize-healthspan]], which reward measured restoration of muscle, cognitive, and immune function in

older adults, are structured to reward exactly that kind of demonstration, and senolytics are among