FOXO4-DRI is a synthetic, rationally designed senolytic peptide. It was developed to selectively induce apoptosis in senescent cells, which are cells that have entered a state of irreversible growth arrest and contribute to tissue dysfunction and aging phenotypes. The peptide’s design is based on the discovery that in senescent cells, the transcription factor FOXO4 is retained in the nucleus through interaction with p53, blocking p53-mediated apoptosis. The peptide mimics a portion of FOXO4 to competitively disrupt this interaction.
Its significance lies in its potential as a research tool for studying cellular senescence and age-related pathologies. Unlike broader cytotoxic agents, FOXO4-DRI aims for selectivity towards senescent cells, offering a more targeted approach to clearing these detrimental cells. The discovery and initial characterization were published in 2017, demonstrating its ability to restore fitness, fur density, and kidney function in fast-aging mouse models.
Quick Facts
| Also Known As | FOXO4-D-retro-inverso, FOXO4-D-retroinverso, FOXO4-DRI peptide |
|---|---|
| Sequence | D-R-Q-T-S-I-Q-L (retro-inverso sequence, D-amino acids) |
| Molecular Formula | C228H388N86O64 |
| Molecular Weight | 5358 Da |
| PubChem CID | 167312269 |
Research Parameters
| Half-Life | Unknown in humans. The retro-inverso D-amino acid design confers resistance to proteolytic degradation, suggesting a longer half-life than typical L-peptides, but specific pharmacokinetic data is not publicly established. |
|---|---|
| Stability | Lyophilized powder is typically stable for at least 24 months when stored at -20°C, protected from light and moisture. After reconstitution, the solution should be aliquoted and stored at -20°C or below to minimize degradation; stability after reconstitution has not been formally established but is often assumed to be several weeks under these conditions for research purposes. |
| Solubility | Recommended reconstitution in sterile bacteriostatic water or phosphate-buffered saline (PBS) for research purposes. |
| Vial Size | 2 mg |
| Storage (Lyophilized) | -20°C or below, protected from light and moisture. Desiccated storage is recommended. |
| Storage (Reconstituted) | -20°C or below in aliquots to avoid freeze-thaw cycles. Do not store at room temperature for extended periods. |
| Typical Research Dose | No human dose. Preclinical mouse research uses 2.5-5 mg/kg, which translates roughly to 50-100 mcg per 20g mouse per injection. |
| Cycle Parameters | No human protocols exist. Preclinical mouse studies often use intermittent dosing, such as administration 2-3 times per week, for durations ranging from a single acute treatment to chronic administration over several months, depending on the research model and endpoint. |
| Amino Acid Count | 10 |
Mechanism of Action
FOXO4-DRI functions by selectively disrupting a key protein-protein interaction that maintains the viability of senescent cells. In senescent cells, p53 transcriptionally activates pro-apoptotic genes. However, FOXO4 binds to p53 and sequesters it in the nucleus, preventing it from executing its apoptotic program in the cytoplasm. This interaction creates a survival mechanism for the senescent cell.
Pathway Disruption: FOXO4-DRI is a retro-inverso peptide (composed of D-amino acids in reverse order) designed to mimic the p53-binding domain of FOXO4. Its D-amino acid composition confers protease resistance and increased stability. It competitively binds to p53, displacing endogenous FOXO4.
p53 Relocalization and Apoptosis: Once freed from FOXO4, p53 is no longer sequestered in the nucleus. It can then translocate to the mitochondria in the cytoplasm, where it initiates the intrinsic apoptotic pathway. This leads to caspase activation and programmed cell death specifically in the senescent cell population.
Selectivity: The mechanism is proposed to be selective for senescent cells because the FOXO4-p53 interaction is particularly critical for their survival. In non-senescent, proliferating cells, p53 localization and activity are regulated differently, making them less susceptible to the peptide's action.
Research Applications
Aging and Senescence: Primary research focus is on mitigating age-related functional decline. Studies in progeroid mouse models have shown that FOXO4-DRI treatment can reduce senescent cell burden, improve tissue homeostasis, and enhance physical performance metrics like endurance and coordination.
Renal Function: Research has demonstrated benefits in models of kidney aging and toxicity. Treatment has been shown to reduce senescence markers in renal tissue, diminish proteinuria (excess protein in urine), and improve glomerular filtration and overall kidney architecture in aged mice.
Dermatological Effects: Investigated for its impact on skin aging. Studies note improved fur density and reduced alopecia in fast-aging mice, suggesting a potential role in counteracting senescence-driven stem cell dysfunction in hair follicles and skin.
Chemotherapy-Induced Side Effects: Explored as an intervention for chemotherapy-induced senescence and tissue damage. Preclinical research indicates it may help alleviate certain side effects, like fatigue and renal damage, by clearing therapy-induced senescent cells, without interfering with the chemotherapeutic agent's anti-tumor efficacy.
Safety & Side Effects
Comprehensive safety data in humans is absent. In the initial mouse studies, no overt acute toxicity or significant changes in body weight or behavior were reported at the research doses. The peptide's proposed selectivity for senescent cells suggests a potentially favorable safety profile compared to non-selective senolytics. However, theoretical concerns exist regarding the potential for off-target effects on non-senescent cells that may rely on FOXO4-p53 interactions, or excessive clearance of senescent cells involved in beneficial processes like wound healing. No anecdotally reported side effects in humans are scientifically documented.
Dosage Information
This information is derived solely from preclinical animal research and is for educational purposes only. No human dosing data exists.
In the seminal mouse study, FOXO4-DRI was administered via intraperitoneal injection at a dose of 5 mg/kg, three times per week. The treatment duration in the initial fast-aging model (XpdTTD/TTD mice) was approximately 10 months. Other reported protocols in mice use a similar dose range of 2.5-5 mg/kg, administered 2-3 times weekly via intraperitoneal or subcutaneous injection, with treatment durations varying from a single dose to several months depending on the study design.
References
Baar, M.P., Brandt, R.M.C., Putavet, D.A., et al. Targeted Apoptosis of Senescent Cells Restores Tissue Homeostasis in Response to Chemotoxicity and Aging. Cell, 2017. 169(1), 132-147.
Zhang, L., Pitcher, L.E., Prahalad, V., et al. Recent advances in the discovery of senolytics. Mechanisms of Ageing and Development, 2021. 200, 111587.
Ogrodnik, M., Zhu, Y., Langhi, L.G.P., et al. Obesity-Induced Cellular Senescence Drives Anxiety and Impairs Neurogenesis. Cell Metabolism, 2019. 29(5), 1061-1077.
Schafer, M.J., White, T.A., Iijima, K., et al. Cellular senescence mediates fibrotic pulmonary disease. Nature Communications, 2017. 8, 14532.
Childs, B.G., Gluscevic, M., Baker, D.J., et al. Senescent cells: an emerging target for diseases of ageing. Nature Reviews Drug Discovery, 2017. 16(10), 718-735.
Kirkland, J.L., Tchkonia, T. Senolytic drugs: from discovery to translation. Journal of Internal Medicine, 2020. 288(5), 518-536.