FOXO4-DRI Research Guide — Senolytic Peptide, FOXO4–p53 Protein-Protein Interaction Disruption & Senescent Cell Clearance (2026)
- FOXO4-DRI (FOXO4-p53-Disrupting Retro-Inverso peptide; also written FOXO4 DRI) is a 29-amino acid D-retro-inverso synthetic peptide designed by Baar et al. to selectively induce apoptosis in senescent cells by disrupting the FOXO4–p53 protein-protein interaction (PPI) that maintains senescent cell viability. The landmark characterization was published in Cell in 2017 (Baar et al., PMID: 28340347) and established FOXO4-DRI as one of the first mechanistically targeted senolytic peptides. YPB offers research-grade FOXO4 as YPB.255 10mg (Research Use Only).
- Mechanism: In senescent cells, FOXO4 protein is upregulated and sequesters p53 in the nucleus, preventing p53 from executing its pro-apoptotic function and allowing senescent cells to persist despite irreversible cell cycle arrest. FOXO4-DRI mimics the FOXO4 domain that binds the p53 transactivation domain (p53TAD), competitively displacing endogenous FOXO4 from p53. This disruption releases p53 from FOXO4 sequestration, allowing p53 to translocate to mitochondria where it activates the intrinsic apoptosis pathway. The selectivity basis: FOXO4 is elevated in senescent cells but not in normal proliferating cells, so the FOXO4–p53 axis is predominantly active in senescent cells — FOXO4-DRI preferentially affects cells where this axis is engaged.
- Baar et al. (2017, Cell) published mouse data demonstrating that FOXO4-DRI treatment of naturally aged mice restored fur density, improved renal function, increased physical fitness (grip strength, treadmill performance), and extended median lifespan by 24.8% in fast-aging XFE progeroid mice. Selective clearance of p21-positive (senescent) cells was confirmed; no significant damage to normal cells was documented.
- The D-retro-inverso (DRI) structural modification is the pharmacokinetic engineering: the 29-amino acid sequence is both reversed in order and synthesized using all-D amino acids. This produces a peptide that is resistant to all natural proteases (which recognize only L-amino acid substrates in the standard sequence orientation), extending plasma half-life to 48+ hours vs. minutes for unmodified L-peptides of equivalent length.
- Important evidence caveat: FOXO4-DRI data is predominantly from in vitro and mouse models; no published Phase 1 or Phase 2 human clinical trial as of April 2026. SASP heterogeneity across cell types means FOXO4-DRI may not be universally effective in all senescent cell populations. YPB.255 is Research Use Only. Updated April 2026.
What Is FOXO4-DRI and Why Is It a Research Priority in Aging Biology?
Landmark 2017 Cell Paper
First Targeted Senolytic Peptide
FOXO4-DRI is a 29-amino acid D-retro-inverso synthetic senolytic peptide designed to selectively clear senescent cells through targeted disruption of the FOXO4–p53 protein-protein interaction. Updated April 2026. Its significance in longevity and aging biology research stems from its mechanistic novelty: rather than broadly inhibiting pro-survival pathways in all cell types (as earlier senolytics like dasatinib and quercetin do), FOXO4-DRI exploits a senescent-cell-specific protein complex — the FOXO4–p53 axis — to drive apoptosis selectively in the cell population most implicated in tissue aging and age-related dysfunction.
Cellular senescence — the state of irreversible cell cycle arrest with persistent metabolic activity — was initially understood as a tumor-suppressive mechanism that prevents damaged cells from replicating. The discovery that senescent cells accumulate with age and secrete a pro-inflammatory signal cocktail (the SASP: senescence-associated secretory phenotype) linked cellular senescence directly to tissue aging, organ dysfunction, and age-related pathology. Clearing senescent cells became a primary target in aging research. FOXO4-DRI (Baar et al. 2017, Cell) provided the first mechanistically targeted peptide approach to senescent cell clearance, distinguishing it from small-molecule senolytics by its protein-protein interaction specificity.
Key Characteristics
| Parameter | Value |
|---|---|
| Full Name | FOXO4-DRI (FOXO4-p53-Disrupting Retro-Inverso peptide); also written FOXO4 DRI |
| Peptide Length | 29 amino acids (all D-amino acids; reversed sequence vs. native FOXO4 forkhead domain segment) |
| Structural Modification | D-retro-inverso (DRI): both (1) all-D amino acids + (2) reversed amino acid sequence. Produces proteolysis-resistant peptide that mimics the binding geometry of the original L-sequence. |
| Target | FOXO4–p53 protein-protein interaction (PPI); specifically: FOXO4 forkhead domain binding to p53 transactivation domain 2 (p53TAD2) |
| Mechanism | Competitive displacement of endogenous FOXO4 from p53TAD2 → p53 nuclear exclusion → p53 mitochondrial translocation → intrinsic apoptosis activation selectively in senescent cells |
| Selectivity Basis | FOXO4 is upregulated in senescent cells but not in normal proliferating cells; the FOXO4–p53 sequestration axis is predominantly active in senescent cells, so disruption preferentially targets the senescent population |
| Half-Life | ~48+ hours in vivo (vs. minutes for equivalent unmodified L-peptide); D-amino acid configuration resists all natural proteases (which recognize L-amino acid substrates) |
| Landmark Publication | Baar et al. (2017) Cell 169(1):132–147. PMID: 28340347 |
| FDA Status | Not research-grade. No Phase 1 or Phase 2 human clinical trial published as of April 2026. Research Use Only (RUO). |
| WADA Status | Not listed on WADA Prohibited List 2025 |
| Storage | Lyophilized: −20°C. Reconstituted: 2–8°C, use within 14 days. Excellent stability due to D-amino acid protease resistance; reconstituted half-life substantially longer than standard L-peptides |
How Does FOXO4-DRI Work? The FOXO4–p53 Senescent Cell Survival Axis
Understanding FOXO4-DRI’s mechanism requires understanding why senescent cells survive despite irreversible cell cycle arrest — and the specific molecular machinery that FOXO4-DRI disrupts.
The Senescent Cell Survival Problem: FOXO4 Sequesters p53
Normal cells undergoing severe DNA damage, oncogenic stress, or replicative exhaustion activate p53 — the “guardian of the genome” — which drives either cell cycle arrest or apoptosis. In cellular senescence, p53 drives cell cycle arrest (via p21/CDKN1A) rather than apoptosis. The question is: what prevents p53 from executing apoptosis in senescent cells? Baar et al. (2017) identified FOXO4 — a forkhead box transcription factor — as the key p53-sequestering protein in senescent cells. FOXO4 is upregulated in senescent fibroblasts and directly binds the p53 transactivation domain 2 (p53TAD2), retaining p53 in the nucleus in a transcriptionally active but pro-apoptotically suppressed state. The FOXO4–p53 nuclear complex is the molecular mechanism by which senescent cells maintain viability despite persistent DNA damage signaling. Blocking this interaction releases p53 to execute its apoptotic function.
FOXO4-DRI: Competitive Disruption of the FOXO4–p53 Complex
FOXO4-DRI was designed as a D-retro-inverso analogue of the FOXO4 forkhead domain segment that directly contacts the p53TAD2 region. In the DRI design strategy: (1) the amino acid sequence is reversed (retro) to maintain the correct C-→N backbone orientation when all amino acids are inverted; (2) all amino acids are synthesized as D-enantiomers (inverso), which produces a mirror-image peptide that binds the same target surface as the original L-sequence despite the backbone reversal. The result: FOXO4-DRI mimics the FOXO4 binding surface for p53TAD2 and competitively displaces endogenous FOXO4 from the p53TAD2 binding site.
p53 Nuclear Exclusion and Mitochondrial Apoptosis
Once displaced from FOXO4 sequestration, free p53 undergoes nuclear exclusion — it leaves the nucleus and translocates to mitochondria. At mitochondria, p53 interacts with anti-apoptotic Bcl-xL and Bcl-2 family proteins, antagonizing their survival function and activating the intrinsic apoptosis pathway via cytochrome c release, apoptosome formation, and caspase cascade execution. This is cell-intrinsic apoptosis — the senescent cell’s own apoptotic machinery directed against itself once the FOXO4 survival brake is removed.
What Research Applications Has FOXO4-DRI Been Studied For?
Aging Biology and Tissue Rejuvenation Research
The primary research application from the Baar et al. (2017, Cell) publication is senescent cell clearance in naturally aged mice and progeroid (fast-aging) mouse models. IP administration of FOXO4-DRI in naturally aged mice produced: restoration of fur density (a senescence-associated phenotype); improved renal function markers; improved physical fitness including grip strength and treadmill performance. In XFE progeroid mice (fast-aging model with impaired DNA repair), FOXO4-DRI extended median lifespan by 24.8% and restored hair follicle cycling. These outcomes are attributed to clearance of FOXO4-positive senescent cells confirmed by reduction in p21-positive cell populations.
Chemotherapy-Induced Senescence (CISR) Research
Chemotherapy compound induce senescence in both tumor cells and normal bystander cells, contributing to therapy-related accelerated aging phenotypes and potentially to tumor recurrence (via SASP-driven re-awakening of dormant cancer cells). FOXO4-DRI has been studied as a research tool for clearing therapy-induced senescent cells (TIS) in chemotherapy models, with published data in Cancer Discovery (2017) demonstrating that FOXO4-DRI limits chemotoxicity in mice by eliminating senescent normal cells generated during doxorubicin treatment.
Osteoarthritis and Cartilage Research
Senescent chondrocytes accumulate in articular cartilage with age and after joint injury, contributing to cartilage degradation and osteoarthritis pathology through SASP-mediated matrix metalloproteinase upregulation. Published data in PMC (2021) demonstrated that FOXO4-DRI selectively removes senescent chondrocytes from in vitro expanded human chondrocytes used in autologous chondrocyte implantation (ACI) procedures, improving the quality of implantable cell populations.
Cancer Senescence Research
Tumor cells can enter a senescent state in response to oncogene activation or chemotherapy, where their SASP contributes to immunosuppression and metastasis facilitation. Le et al. (2021, EBioMedicine) published molecular modeling and in vitro data extending FOXO4-DRI analogue design for senolytic activity in senescent cancer cells, demonstrating that the FOXO4–p53 axis in senescent cancer cells is targetable with optimized peptides.
What Does the Research Data Show?
| Study | Model / N | Key Finding & Adverse Events | Year |
|---|---|---|---|
| Baar et al. — Landmark senolytic characterization | In vitro (fibroblasts) + in vivo (naturally aged mice; XFE progeroid mice) | FOXO4-DRI selectively induces apoptosis in senescent fibroblasts (p21-positive); spares normal proliferating cells. Naturally aged mice: restored fur density, improved renal function, physical fitness (grip, treadmill). XFE progeroid mice: 24.8% median lifespan extension; hair follicle cycling restored. p21-positive cell reduction confirmed. No significant adverse events in normal tissue at doses studied. (Cell, 2017 — PMID: 28340347) | 2017 |
| FOXO4-DRI in chemotoxicity — Cancer Discovery | In vivo (chemotherapy-treated mice) | FOXO4-DRI limits accelerated aging phenotypes and tissue toxicity induced by doxorubicin chemotherapy in mice by clearing therapy-induced senescent (TIS) normal cells. Tumor cell senescence also addressed. Well tolerated at studied doses. | 2017 |
| Senescent chondrocyte clearance (PMC) | In vitro / expanded human chondrocytes | FOXO4-DRI selectively removes senescent chondrocytes from in vitro expanded human chondrocytes for ACI, improving cell quality. Selectivity for senescent vs. non-senescent chondrocytes confirmed. Well tolerated in non-senescent chondrocyte population. | 2021 |
| Human clinical trial | No published trial as of April 2026 | No published Phase 1 or Phase 2 human clinical trial for FOXO4-DRI as of April 2026. All human-relevant data is extrapolated from in vitro and mouse model research. Chronic dosing safety in non-senescent cells and theoretical p53 pathway interference at tissue-wide scale remains an active research question. | N/A |
How Does FOXO4-DRI Compare to Other Longevity and Senolytic Research Approaches?
| Parameter | FOXO4-DRI | Epitalon (AEDG) | SS-31 (Elamipretide) | NAD+ |
|---|---|---|---|---|
| Longevity Mechanism | Senolytic: targeted elimination of senescent cells via FOXO4–p53 PPI disruption → selective apoptosis | Epigenetic/telomere: telomerase activation (hTERT), AANAT/melatonin, circadian gene regulation | Mitochondrial membrane: cardiolipin stabilization, mitochondrial ROS reduction, ATP production preservation | Sirtuin activation, NAD+/NADH redox, PARP substrate, energy metabolism |
| Level of Action | Cell-level: eliminates entire senescent cells (cytocidal; permanent for targeted cells) | Nuclear/epigenetic: modulates gene expression and telomere biology without eliminating cells | Organelle-level: mitochondrial inner membrane | Metabolic: cellular energy and signaling pathways |
| Selectivity | Senescent cells (FOXO4-elevated): mechanistically selective; normal cells spared in published data | No cell-type selectivity claimed | All cells with mitochondria (broad) | All cells (universal metabolic substrate) |
| Landmark Publication | Baar et al. (2017) Cell (PMID: 28340347); 24.8% lifespan extension in progeroid mice; tissue rejuvenation | Khavinson group (single-institute; telomerase data in human somatic cells) | FDA accelerated approval (Forzinity™, Sep 2025, Barth syndrome); Phase 2/3 data | Extensive NMN/NR precursor literature; aging biology well-established |
| D-Amino Acid Modified? | Yes — all-D amino acids + reversed sequence (DRI); 48+ hour half-life; protease resistant | No (L-amino acids; standard tetrapeptide) | No (contains Dmt: synthetic residue, not D-amino acid) | Not a peptide (adenine dinucleotide) |
| Human Clinical Data | None published as of April 2026 | Small-N single-institute (Khavinson) | research-grade (Barth syndrome); Phase 2/3 cardiac data | Extensive NMN/NR human RCTs |
| YPB SKU | YPB.255 — 10mg | YPB.253/254 — see guide | YPB.245/246 — see guide | YPB._ — see guide |
FOXO4-DRI occupies a unique longevity research position: it is the only compound in the YPB catalog with a senolytic (cell-elimination) mechanism. Epitalon, SS-31, and NAD+ all operate within existing cells to improve cellular function; FOXO4-DRI selectively eliminates the specific cell population — senescent cells — that drives SASP-mediated tissue aging. The two research strategies are complementary: removing the senescent burden (FOXO4-DRI) while preserving mitochondrial function in surviving cells (SS-31) and maintaining energy metabolism (NAD+) represent convergent multi-mechanism approaches to cellular aging research. See the SS-31 Research Guide and Epitalon Research Guide for the complementary mechanisms.
What Should Researchers Know About FOXO4-DRI Stability and Handling?
D-Retro-Inverso: Exceptional Stability Profile
The DRI modification that defines FOXO4-DRI provides an unusually robust stability profile compared to standard research peptides. All natural proteases (serine proteases, metalloproteases, cysteine proteases, aspartyl proteases) recognize L-amino acid substrates in the forward sequence orientation. FOXO4-DRI presents an all-D-amino acid, reverse-sequence backbone that is not recognized as a substrate by any natural protease. In practice: plasma half-life is extended to approximately 48 hours or longer; reconstituted solutions are stable for extended periods compared to standard peptides; cell culture medium stability is dramatically improved, enabling long-duration (24–96 hour) in vitro senolytic experiments without the degradation variability that would affect equivalent L-peptides.
COA Verification
HPLC purity (≥98%) and MS confirmation at the correct 29-residue DRI molecular weight is standard. The DRI modification (all-D amino acids + reversed sequence) cannot be confirmed by MS alone — all-D and all-L peptides of the same sequence have identical molecular weights. Chiral amino acid analysis is the definitive method for confirming D-amino acid content. At minimum, researchers should confirm that the COA specifies “D-retro-inverso” or “all-D amino acids” explicitly, as an L-amino acid version of the same sequence would lack the protease resistance and may have different binding geometry. All YPB FOXO4-DRI batches include lot-traceable COA documentation through the COA Library.
Research Protocol Considerations
Effective FOXO4-DRI concentrations in published in vitro senolytic studies are typically in the low micromolar range (1–10 µM) for selective senescent cell killing. At these concentrations, specificity for senescent vs. normal cells depends on the FOXO4 elevation in the senescent population. Researchers should include appropriate senescence markers (p21/CDKN1A, p16/CDKN2A, SA-β-gal, SASP cytokines) to confirm senescent cell presence in their model system, and non-senescent cell viability controls to confirm selectivity of any cytotoxic effects observed.
Key Research Findings
- Landmark 2017 Cell paper (Baar et al., PMID: 28340347): FOXO4-DRI selectively induces apoptosis in senescent fibroblasts; restored fur density, renal function, and physical fitness in naturally aged mice; 24.8% median lifespan extension in XFE progeroid mice. Cited 500+ times.
- Mechanism: FOXO4–p53 PPI disruption: FOXO4 sequesters p53 in senescent cells; FOXO4-DRI competitively displaces FOXO4 from p53TAD2; free p53 translocates to mitochondria; intrinsic apoptosis activated selectively in senescent cells.
- Selectivity basis: FOXO4 upregulation in senescent cells: FOXO4 is elevated in senescent but not normal proliferating cells; the FOXO4–p53 sequestration complex is a senescent-cell-specific survival mechanism. FOXO4-DRI preferentially targets cells where this axis is active.
- D-retro-inverso engineering: All-D amino acids + reversed sequence = protease-resistant; 48+ hour half-life; cell culture medium stable for extended incubations. Enables intermittent dosing in mouse protocols impossible with equivalent L-peptides.
- SASP context: Senescent cells drive aging via SASP — constitutive secretion of IL-6, IL-8, MMPs, TGF-β, and other pro-inflammatory cytokines. FOXO4-DRI addresses aging by eliminating the SASP source cells rather than blocking individual SASP components.
- No human clinical trial published as of April 2026: All data from in vitro and mouse models; chronic dosing safety and theoretical p53 pathway interference in non-senescent cells at tissue-wide scale are active research questions.
- D-amino acid confirmation required in COA: DRI modification cannot be distinguished from L-peptide by MS alone; chiral analysis or explicit DRI notation required in quality documentation.
- Heterogeneous SASP selectivity: FOXO4-DRI effectiveness varies by senescent cell type; some senescent immune cells (macrophages, T cells) may upregulate alternative anti-apoptotic pathways (BCL-2, BCL-xL) that reduce FOXO4-DRI efficacy.
Browse the Full Research Catalog
Market Demand and Research Interest
| Demand Indicator | FOXO4-DRI Data Point |
|---|---|
| Monthly US searches | ~3,600/mo (growing rapidly with aging biology research interest) |
| Landmark citation | Baar et al. (2017) Cell (PMID: 28340347) — 500+ citations; among the most cited aging biology papers of the past decade |
| Research field context | Cellular senescence and senolytics are one of the top-funded areas in aging biology research (NIH, NIA); multiple clinical trials for senolytic compounds ongoing |
| Unique mechanism | Only senolytic compound in YPB catalog; only cell-elimination (cytocidal) longevity mechanism; only PPI-disrupting peptide in catalog |
| DRI design precedent | D-retro-inverso peptide engineering is an established compound strategy; FOXO4-DRI is one of the best-characterized DRI research compounds in the literature |
| Keyword difficulty range | Low-medium (KD <15) |
How Can Researchers Offer FOXO4-DRI Under Their Own Brand?
Wholesale Pricing & Margin Analysis
| SKU | Compound | Premier ($497/mo) | Core ($297/mo) | Suggested MSRP | Premier Margin |
|---|---|---|---|---|---|
| YPB.255 (RUO) | FOXO4 (FOXO4-DRI) 10mg | TBC Premier | TBC Core | $120.00 | TBC at Premier tier |
Contact the YPB team for confirmed Premier and Core tier pricing. Use the YPB Profit Calculator to model projected revenue. White-label brands offering FOXO4-DRI alongside Epitalon, SS-31, and NAD+ create the most mechanistically comprehensive cellular aging research catalog available, covering all four major cellular aging mechanisms: senescent cell elimination (FOXO4-DRI), telomere/epigenetic regulation (Epitalon), mitochondrial membrane integrity (SS-31), and energy/sirtuin metabolism (NAD+). Download the full catalog for all longevity category pricing.
Methodology & Data Sources
Methodology & Data Sources
Scientific literature: PubMed searched for “FOXO4-DRI,” “FOXO4 p53 senolytic,” “senolytic peptide,” and “senescent cell apoptosis peptide.” Search conducted through April 2026.
Key sources: Baar et al. (2017) Cell 169(1):132–147 (PMID: 28340347; landmark FOXO4-DRI characterization); Cancer Discovery (2017) chemotoxicity data; Le et al. (2021) EBioMedicine 73:103646 (PMID: 34689087; senolytic peptide modeling); PMC 8116695 (senescent chondrocyte clearance); Nature Communications 2025 (NMR structural model of FOXO4-DRI–p53TAD2 complex).
Limitations: All published FOXO4-DRI data is from in vitro models and rodents; no human Phase 1 or Phase 2 clinical trial published as of April 2026. FOXO4-DRI effectiveness varies by senescent cell type; not all senescent cell populations equally respond (heterogeneous FOXO4 expression). Chronic dosing safety and theoretical p53 pathway concerns remain unresolved at the preclinical level. This article is for educational purposes only.
References
- Baar, M. P., Brandt, R. M. C., Putavet, D. A., Klein, J. D. D., Derks, K. W. J., Bourgeois, B. R. M., Stryeck, S., Rijksen, Y., van Willigenburg, H., Feijtel, D. A., van der Pluijm, I., Essers, J., van Cappellen, W. A., van IJcken, W. F., Houtsmuller, A. B., Pothof, J., de Bruin, R. W. F., Madl, T., Hoeijmakers, J. H. J., … de Keizer, P. L. J. (2017). Targeted apoptosis of senescent cells restores tissue homeostasis in response to chemotoxicity and aging. Cell, 169(1), 132–147. PMID: 28340347
- Le, H. H., Cinaroglu, S. S., Manalo, E. C., Ors, A., Gomes, M. M., Duan Sahbaz, B., Bonic, K., Origel Marmolejo, C. A., Quentel, A., Plaut, J. S., Kawashima, T. E., Ozdemir, E. S., Malhotra, S. V., Ahiska, Y., Sezerman, U., Bayram Akcapinar, G., Saldivar, J. C., Timucin, E., & Fischer, J. M. (2021). Molecular modelling of the FOXO4-TP53 interaction to design senolytic peptides for the elimination of senescent cancer cells. EBioMedicine, 73, 103646. PMID: 34689087
- Bourgeois, B., Madl, T., et al. (2025). The disordered p53 transactivation domain is the target of FOXO4 and the senolytic compound FOXO4-DRI. Nat Commun. (NMR structural characterization of FOXO4-DRI–p53TAD2 complex.)
- van Deursen, J. M. (2014). The role of senescent cells in aging. Nature, 509(7501), 439–446. (Cellular senescence and aging context.)
- Coppé, J. P., Patil, C. K., Rodier, F., Sun, Y., Muñoz, D. P., Goldstein, J., Nelson, P. S., Desprez, P. Y., & Campisi, J. (2008). Senescence-associated secretory phenotypes reveal cell-nonautonomous functions of oncogenic RAS and the p53 tumor suppressor. PLoS Biol, 6(12), 2853–2868. (SASP characterization foundational paper.)
- Baker, D. J., Wijshake, T., Tchkonia, T., LeBrasseur, N. K., Childs, B. G., van de Sluis, B., Kirkland, J. L., & van Deursen, J. M. (2011). Clearance of p16Ink4a-positive senescent cells delays aging phenotypes. Nature, 479(7372), 232–236. (INK-ATTAC senolytic mouse model; precursor context.)
- Chondrocyte clearance study. (2021). Senolytic peptide FOXO4-DRI selectively removes senescent cells from in vitro expanded human chondrocytes. Front Bioeng Biotechnol. PMC8116695.
- Di Micco, R., Krizhanovsky, V., Baker, D., & d’Adda di Fagagna, F. (2021). Cellular senescence in aging: from mechanisms to therapeutic opportunities. Nat Rev Mol Cell Biol, 22(2), 75–95.
- Kirkland, J. L., & Tchkonia, T. (2020). Senolytic compound: from discovery to translation. J Intern Med, 288(5), 518–536. (Senolytic landscape context including FOXO4-DRI.)
Frequently Asked Questions
FOXO4-DRI (29 amino acids; all-D amino acids; reversed sequence; D-retro-inverso peptide) is a senolytic compound that selectively induces apoptosis in senescent cells by disrupting the FOXO4–p53 protein-protein interaction. Mechanism: FOXO4 is upregulated in senescent cells and sequesters p53 in the nucleus, preventing pro-apoptotic p53 function. FOXO4-DRI competitively displaces endogenous FOXO4 from p53TAD2, releasing p53 to translocate to mitochondria and activate intrinsic apoptosis. Selectivity: FOXO4 elevation is specific to senescent cells; normal proliferating cells are spared in published data. Landmark publication: Baar et al. (2017) Cell (PMID: 28340347) — restored fur density, renal function, and physical fitness in naturally aged mice; 24.8% lifespan extension in progeroid mice. No human clinical trial as of April 2026. Research Use Only (RUO). Updated April 2026.
D-retro-inverso (DRI) is a two-part structural modification strategy for peptides: (1) “retro” = the amino acid sequence is reversed (C-to-N becomes N-to-C); (2) “inverso” = all amino acids are synthesized as D-enantiomers (mirror images of natural L-amino acids). The combined effect: the DRI peptide presents the same side chains in the same spatial arrangement as the original L-sequence, allowing it to bind the same protein target (p53TAD2) while being made from D-amino acids in reverse order. All natural proteases recognize L-amino acid substrates in the standard sequence orientation; DRI peptides are therefore invisible to proteolysis. For FOXO4-DRI specifically, the DRI modification extends plasma half-life to 48+ hours (vs. minutes for an equivalent L-peptide), enabling the intermittent subcutaneous dosing schedule used in Baar et al. (every other day for three weeks). Without the DRI modification, continuous IV infusion would be required to maintain effective concentrations for FOXO4–p53 PPI disruption — making the published mouse longevity experiments impractical.
The selectivity is mechanistically based on FOXO4 expression level, not on a receptor or cell surface marker that researchers artificially target. In normal proliferating cells, FOXO4 expression is low; the FOXO4–p53 nuclear complex is not significantly active; p53 functions through normal cell cycle regulation and its standard pro-apoptotic response to severe damage is intact. When FOXO4-DRI is used, it competes for p53TAD2 binding, but in normal cells there is insufficient endogenous FOXO4–p53 complex to meaningfully disrupt — p53 is not being sequestered, so displacing FOXO4 from p53 has minimal functional consequence for cells where p53 is already operating normally. In senescent cells, FOXO4 is markedly upregulated and actively sequesters p53 in a pro-arrest, anti-apoptotic nuclear complex. FOXO4-DRI disruption of this complex has a major functional consequence: it removes the specific survival mechanism that allows senescent cells to evade p53-mediated apoptosis. This differential functional consequence based on FOXO4 expression level is the mechanistic basis for FOXO4-DRI’s senescent-cell selectivity.
Several important limitations should be documented in FOXO4-DRI research protocols. First, no human clinical trial data exists as of April 2026; all functional rejuvenation data comes from mouse models. Translating mouse longevity effects to human contexts is not validated. Second, FOXO4-DRI is not a universal senolytic: its efficacy depends on FOXO4 upregulation in the target senescent cell population. Some senescent immune cells (macrophages, T cells) upregulate alternative anti-apoptotic pathways (BCL-2, BCL-xL) that can maintain viability even after FOXO4–p53 disruption; FOXO4-DRI may be less effective in these cell types. Third, theoretical safety concerns exist for chronic dosing: FOXO4–p53 interaction is present at low levels in non-senescent tissues, and chronic disruption at tissue-wide scale raises questions about tumor suppressor pathway interference that have not been fully resolved in long-term safety studies. Fourth, D-amino acid configuration verification by chiral analysis is required beyond standard MS; an L-amino acid batch would have the same MW but lack protease resistance and may have different binding geometry.
FOXO4-DRI and Epitalon address aging from mechanistically non-overlapping cellular levels. FOXO4-DRI is a senolytic: it eliminates entire senescent cells (cytocidal; permanent for targeted cells) by disrupting the specific FOXO4–p53 survival axis that keeps senescent cells alive. The mechanism removes the source of SASP pro-inflammatory signaling from tissues. Epitalon is an epigenetic/telomere modulator: it operates within existing cells to activate telomerase (hTERT), modulate AANAT/melatonin synthesis, and regulate circadian gene expression. It preserves and supports cell function without targeting or eliminating any specific cell population. Conceptually: FOXO4-DRI addresses aging by clearing the dysfunctional “zombie cells” that accumulate; Epitalon addresses aging by preserving the genomic and circadian function of surviving cells. A longevity research catalog including both provides researchers studying cellular aging with tools that address the two major senescence-related aging hypotheses: burden reduction (senolytic clearance) and functional preservation (telomere/epigenetic support).
Yes. YourPeptideBrand.com provides white-label dropship for research-grade FOXO4-DRI in a 10mg configuration (YPB.255; Research Use Only). White-label storefronts include pre-built RUO-compliant product pages with senolytic mechanism descriptions, Baar et al. 2017 context (clearly framed as mouse model research, not human clinical data), DRI structure notes, and COA library links. Contact the YPB team for confirmed Premier and Core pricing at $120 MSRP, and use the profit calculator to model projected revenue.
Every FOXO4-DRI batch includes a lot-specific COA: HPLC purity (≥98%), MS confirmation at the correct 29-residue DRI molecular weight, explicit D-retro-inverso or all-D amino acid notation (critical: an L-amino acid batch has the same MW but lacks protease resistance and may have different binding geometry), endotoxin (<1 EU/mg), TAMC, and TYMC. The explicit D-amino acid configuration notation in the COA is the most critical quality parameter for FOXO4-DRI research applications: the DRI modification is the compound’s primary pharmacokinetic advantage and its identity-defining feature, and it cannot be verified by MS molecular weight alone. Chiral amino acid analysis is the definitive confirmation method. All lots are traceable through the batch-specific COA library.
In published in vitro senolytic research, FOXO4-DRI is typically used at 1–10 µM concentrations for selective senescent cell clearance (specific concentrations vary by cell type and senescence induction method). The selectivity window — the concentration range where senescent cells are eliminated while non-senescent cells remain viable — should be determined empirically for each cell model. Researchers must confirm that their model contains a meaningful senescent cell population (verified by p21, p16, SA-β-gal, or SASP marker expression) before interpreting FOXO4-DRI effects. In vivo mouse protocols in published literature used IP administration; specific dosing details are in the Baar et al. 2017 Cell supplementary methods. The 48+ hour half-life of the DRI form means that dosing intervals for in vivo protocols can be substantially longer than for standard L-peptides. All YPB FOXO4-DRI is designated Research Use Only.
Key Takeaways
Research Takeaways
- Only senolytic compound in YPB catalog: Cell-elimination (cytocidal) mechanism targeting senescent cells via FOXO4–p53 PPI disruption; qualitatively distinct from all other longevity mechanisms in the catalog (telomere, mitochondrial, metabolic).
- Landmark Baar et al. 2017 Cell (PMID: 28340347): Restored fur density, renal function, physical fitness in naturally aged mice; 24.8% median lifespan extension in XFE progeroid mice; 500+ citations.
- Selectivity mechanism: FOXO4 upregulated in senescent cells → FOXO4–p53 nuclear sequestration; FOXO4-DRI displaces FOXO4 from p53TAD2 → p53 mitochondrial translocation → intrinsic apoptosis in senescent cells specifically.
- DRI modification = 48+ hour half-life: All-D amino acids + reversed sequence = protease-resistant; enables intermittent SC dosing; cell culture medium stable for extended incubations.
- D-amino acid COA verification: MS alone cannot confirm D vs. L; chiral analysis or explicit DRI notation required. An L-amino acid batch has the same MW but lacks protease resistance.
- No human clinical trial published (April 2026): All functional data from in vitro and mouse models; heterogeneous SASP cell type response; theoretical chronic dosing p53 pathway concerns remain active research questions.
Business Takeaways
- $120 MSRP — contact YPB for confirmed wholesale pricing at Premier tier.
- ~3,600 monthly searches; growing — accelerating with NIA-funded senolytic research investment and public interest in cellular aging mechanisms.
- Only senolytic in catalog — unique mechanism with zero overlap with any other longevity guide; positions the catalog as covering the full cellular aging spectrum.
- FOXO4-DRI + Epitalon + SS-31 + NAD+ longevity quad covers senolysis, telomere/epigenetic, mitochondrial, and metabolic aging dimensions from a single longevity research buyer audience.
Ready to add FOXO4-DRI to your research catalog? Book a consultation with the YPB team.
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