FOXO4-DRI
Clearing the cells that age forgot
Injection · 503A Compounding
Educational content. This page describes FOXO4-DRI for informational purposes only and is not medical advice, diagnosis, or treatment. Consult a licensed provider before starting, stopping, or modifying any therapy.
Researched and maintained by the PepHookup team. Regulatory status last verified April 12, 2026.
- Primary Use
- A D-retro-inverso peptide that disrupts FOXO4 and p53 binding to clear senescent cells.
- Administration
- injection
- Typical Cycle
- 5-day course; effects assessed from roughly 10 to 30 days
- Legal Status
- Awaiting Reclassification
Key Benefits
Selective Senescent Cell Clearance
Disrupts the FOXO4-p53 survival interaction that keeps senescent cells alive, killing them with high selectivity. In the original study the peptide reduced the viability of senescent human fibroblasts roughly 11.7-fold more than healthy controls, and later work in human chondrocytes and keloid fibroblasts reproduced that selective clearance.[1][2][3]
Tissue Function Restored in Aged Mice
Three doses over five days improved kidney function, fur density, and physical fitness in fast-aging and naturally aged mice, and neutralized doxorubicin chemotoxicity. All of this evidence is preclinical.[1]
What is FOXO4-DRI?
FOXO4-DRI is a synthetic peptide designed to selectively eliminate senescent cells, the damaged or aged cells that stop dividing but resist dying and instead linger in tissue secreting inflammatory signals. It was developed by Peter de Keizer and colleagues at Erasmus University Medical Center in Rotterdam and first described in a 2017 Cell paper that became one of the most cited senolytic studies in the field.
The name describes its chemistry. It is a D-retro-inverso version of the FOXO4 protein segment that normally binds p53, built from D-amino acids assembled in reverse order and fused to a cell-penetrating sequence. This mirror-image design preserves the binding surface of the natural protein while making the peptide far more resistant to enzymatic breakdown than the native L-amino acid sequence, which would otherwise be degraded quickly.
It is important to be clear about evidence. Every published result on FOXO4-DRI comes from cell culture, isolated human tissue, or animal models. There are no completed or registered human clinical trials, and it is not approved by the FDA for any use. It remains a preclinical research compound.
How Does It Work?
In senescent cells the transcription factor FOXO4 is upregulated and acts as a survival switch. It binds the tumor suppressor p53 and holds it in the nucleus, away from the mitochondria where p53 would otherwise trigger programmed cell death. Healthy, normally dividing cells express relatively little FOXO4, so this survival arrangement is largely specific to senescent populations.
FOXO4-DRI enters cells through its cell-penetrating sequence and competes with native FOXO4 for p53 binding. By outcompeting endogenous FOXO4, it causes p53 nuclear exclusion, freeing p53 from sequestration so it can relocate toward the mitochondria.
Once p53 reaches the mitochondria it activates the pro-apoptotic protein BAX, permeabilizing the outer mitochondrial membrane and driving the caspase cascade that executes intrinsic apoptosis. Independent studies in Leydig cells, endothelial cells, and keloid fibroblasts have reproduced this p53 nuclear exclusion and BAX/caspase-driven apoptosis in senescent cells, which supports the proposed mechanism across more than one cell type.
Quick Facts
Clearing the cells that age forgot
- Primary Use
- A D-retro-inverso peptide that disrupts FOXO4 and p53 binding to clear senescent cells.
- Administration
- injection
- Typical Cycle
- 5-day course; effects assessed from roughly 10 to 30 days
- Categories
- senolyticanti aging
- Legal Status
- Awaiting reclassification
Mechanism of Action
FOXO4-DRI competitively disrupts the FOXO4-p53 interaction that keeps senescent cells alive. Displacing p53 from nuclear sequestration lets it reach the mitochondria, activate BAX, and trigger caspase-dependent apoptosis preferentially in senescent cells, which express the FOXO4-p53 survival complex that healthy cells largely lack.
Clinical Evidence
Targeted Senescent Cell Clearance Restores Tissue Homeostasis (Baar et al., Cell 2017)
FOXO4-DRI reduced senescent fibroblast viability about 11.7-fold more than healthy controls. Three intravenous doses of 5 mg/kg every other day neutralized doxorubicin chemotoxicity and restored physical fitness, fur density, and renal function (lower plasma urea and creatinine) in aged mice, with no obvious adverse effects in the windows tested.
Baar MP, Brandt RMC, Putavet DA, et al. · Cell, 169(1):132-147.e16 (2017) · PubMed
Senolytic Clearance in Expanded Human Chondrocytes (Huang et al., 2021)
FOXO4-DRI removed more than half of the senescent PDL9 chondrocytes while leaving minimally expanded PDL3 cells largely unaffected, and lowered senescence markers and secreted senescence-associated factors. It did not improve the cells' cartilage-forming potential, which the authors flagged for further study.
Huang Y, He Y, Makarczyk MJ, Lin H · Frontiers in Bioengineering and Biotechnology, 9:677576 (2021) · PubMed
Leydig Cell Senolysis and Testosterone (Zhang et al., Aging 2020)
FOXO4 was found highly expressed in human Leydig cells, and its nuclear localization tracked with lower testosterone synthesis in older men. Disrupting the FOXO4-p53 interaction selectively triggered apoptosis in senescent Leydig cells, and in aged mice FOXO4-DRI improved the testicular microenvironment and eased age-related testosterone insufficiency.
Zhang C, Xie Y, Chen H, et al. · Aging (Albany NY), 12(2):1272-1284 (2020) · PubMed
Pulmonary Fibrosis via Myofibroblast Targeting (Han et al., 2022)
Comparable to the approved drug pirfenidone, FOXO4-DRI reduced senescent cells, downregulated SASP genes, and attenuated collagen deposition. It preferentially killed TGF-beta-induced myofibroblasts in vitro and downregulated the extracellular-matrix-receptor interaction pathway in fibrotic lungs.
Han X, Yuan T, Zhang J, et al. · Journal of Cellular and Molecular Medicine, 26(11):3269-3280 (2022) · PubMed
Dosing & Administration
start low, go slow
Injection (Preclinical, mice)
- Dosage
- 5 mg/kg body weight
- Frequency
- Every other day, 3 total doses (days 1, 3, 5)
- Cycle
- 5-day course; effects assessed from roughly 10 to 30 days
Injection (Preclinical, mice): This is the regimen from the foundational mouse studies, given primarily intravenously with intraperitoneal injection also used. No human equivalent has been established.
There is no human dosing for FOXO4-DRI. Every published protocol comes from mouse studies, and no human pharmacokinetic or dose-finding data exists. Any therapeutic use in people would be experimental and is determined by a licensed provider.
A recurring feature across the mouse work is that a short course, often just three doses over five days, produced effects that persisted for weeks. This fits the hit-and-run logic of senolytics, where clearing the accumulated pool of senescent cells buys time before they rebuild.
Allometric conversions from mouse doses are sometimes cited online, but they have never been validated in clinical trials and should not be treated as a human dose.
Side Effects & Safety
Uncommon
- Injection site reaction: A theoretical concern for any injectable peptide. Not specifically characterized in the published literature, which is entirely preclinical.
Rare
- Loss of beneficial transient senescence: A theoretical risk that aggressive clearance could remove transiently senescent cells that aid wound healing, tissue remodeling, or development. Not documented in humans.
Safety Profile
The entire safety profile is preclinical. In the foundational Cell study the peptide was well tolerated in vivo at the doses used, with no noticeable effect on platelets or on non-proliferative tissues such as the heart.
No human pharmacokinetic, pharmacodynamic, or toxicology data has been published, and there are no registered human clinical trials. FOXO4-DRI is strictly a research compound, and the mouse tolerability above does not substitute for human safety testing.
The D-retro-inverso design makes the peptide resistant to enzymatic degradation, so it persists longer in the body than a standard L-amino acid peptide. The long-term consequences of that stability in human tissue are unknown. A related next-generation peptide, ES2, reported reduced liver senescent cells in older mice with minimal toxicity, but that finding is also animal-only.
Contraindications
- Pregnancy or breastfeeding (senescence signaling has roles in placental function and development, and there is no safety data)
- Active wound healing or recent surgery (transient senescent cells contribute to tissue repair)
- Known TP53 pathway disorders such as Li-Fraumeni syndrome (response to p53 liberation is unpredictable)
- Significant immune compromise (clearing apoptotic cell debris depends on functional macrophage activity)
- Children and adolescents (senescence participates in normal growth and development)
Compare with Similar Peptides
| Peptide | Primary Use | Administration | Cycle Length | Key Differentiator |
|---|---|---|---|---|
| FOXO4-DRI | Senolytic & Longevity (research) | Injection | 3 doses over 5 days (preclinical) | Targets a single protein interaction found almost exclusively in senescent cells, giving high selectivity, but unlike some senolytics it has no human trial data |
| SS-31 (Elamipretide) | Mitochondrial restoration and rare mitochondrial disease | Subcutaneous injection (daily); IV in trials | Ongoing daily dosing | The first FDA-approved mitochondria-targeted therapeutic; binds cardiolipin on the inner mitochondrial membrane to support electron transport efficiency |
| GHK-Cu | Anti-Aging & Skin Regeneration | Topical, Injection | 8-12 weeks | A naturally occurring copper-carrier peptide that rebuilds the skin matrix and, per gene-expression analysis, shifts expression of about a third of human genes toward repair |
| Sermorelin | GH restoration and healthy aging | Subcutaneous injection, daily at bedtime | 3-6 months | The GHRH analog with prior FDA approval and a multi-decade clinical record, preserving natural feedback rather than replacing growth hormone |
| Glutathione | Antioxidant & Detoxification | IV, Oral, Sublingual, Topical | Ongoing supplementation | The body's own master antioxidant, with controlled human data showing oral and sublingual forms can raise body stores and immune markers |
Regulatory Status
Not Listed
503A CompoundingThis substance does not appear on any FDA bulk drug substances list. It is classified as research-use only and cannot be legally compounded for human use.
Regulatory Detail
FOXO4-DRI does not appear on any FDA bulk drug substances list and is not FDA-approved for any indication. No human clinical trials have been published. It is a preclinical research peptide that falls outside the 503A and 503B compounding pathways, so pharmacies that prepare it for human use face FDA enforcement risk. Available only through research programs.
What do these terms mean?
- 503A compounding
- Licensed pharmacies that prepare custom prescriptions for individual patients based on a physician's order. 503A is the section of the federal law that governs them.
- 503B outsourcing
- FDA-registered facilities that compound in larger batches under stricter federal oversight (closer to a manufacturer than a pharmacy). Used mostly by hospitals and clinics.
- Bulk drug substance
- The active pharmaceutical ingredient a compounder starts with, before it's made into a finished medication.
- Category 1
- Interim bucket for bulk substances that have been nominated and don't appear to present significant safety risks. 503A pharmacies may compound them under FDA enforcement discretion while the agency continues its review. Not the same as FDA approval.
- Category 2
- Bulk substances the FDA has flagged for significant safety risks. 503A compounding carries FDA enforcement risk, so most pharmacies decline to prepare them and many physicians hesitate to prescribe them.
- PCAC
- Pharmacy Compounding Advisory Committee. The FDA advisory committee that reviews nominated bulk substances and recommends whether they belong in Category 1, Category 2, or on the final 503A Bulks List.
Last verified April 12, 2026. PepHookup tracks public FDA actions. This is not legal or medical advice.
Frequently Asked Questions
Research & References
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