PTD-DBM
PTD-DBM, protein transduction domain-Dishevelled binding motif peptide, CXXC5-Dvl disrupting peptide
PTD-DBM is a cell-penetrating decoy peptide designed to block the interaction between CXXC5 and Dishevelled, releasing a brake on Wnt/beta-catenin signalling in skin. In mice it accelerates wound healing and hair regrowth, particularly when combined with valproic acid. Its exact amino acid sequence is not disclosed in the primary publications, and it has never been tested in humans.
Mechanism
Wnt/beta-catenin signalling drives hair follicle development, entry into the anagen growth phase, and wound-induced hair follicle neogenesis. CXXC-type zinc finger protein 5 (CXXC5) is a negative-feedback regulator of that pathway. It binds the PDZ domain of Dishevelled, the cytoplasmic transducer immediately downstream of the Frizzled receptor, and prevents Dishevelled from relaying the Wnt signal, so beta-catenin continues to be degraded rather than accumulating in the nucleus. Because CXXC5 is itself a Wnt target gene, the loop is self-limiting: Wnt signalling switches on its own inhibitor. The 2015 wound-healing paper reports that CXXC5 protein levels are reduced in epidermal keratinocytes and dermal fibroblasts of acute human wounds, consistent with the brake being lifted during normal repair, and the 2017 hair paper reports that CXXC5 is upregulated in the miniaturised follicles and arrector pili muscles of human balding scalp. That second observation is what made it a target for hair loss.
PTD-DBM is a competitive decoy against that inhibitor. The DBM portion is the Dishevelled-binding motif, and it occupies the Dishevelled PDZ domain so that endogenous CXXC5 cannot, releasing the brake and permitting beta-catenin to accumulate. A protein transduction domain is fused on because the target is intracellular and the peptide must cross the membrane to reach it. In the published work the peptide is applied topically and typically combined with valproic acid, a GSK-3beta inhibitor that stabilises beta-catenin from the opposite direction. The two act at different nodes of the same pathway, which is why the 2015 paper describes the combination as synergistic. A later paper from the same group connected CXXC5 to dihydrotestosterone-driven androgenetic alopecia via prostaglandin D2.
What the research shows
Two papers carry nearly all of the evidence, both from Kang-Yeol Choi's laboratory at Yonsei University. The 2015 Journal of Experimental Medicine paper established CXXC5 as a negative-feedback regulator of Wnt/beta-catenin signalling via Dishevelled, reported that CXXC5 protein was reduced in epidermal keratinocytes and dermal fibroblasts of acute human wounds, showed CXXC5-knockout mice healed faster, and demonstrated that the competitor peptide, named PTD-Dvl-binding motif (PTD-DBM), activated beta-catenin and collagen production and, combined with valproic acid, synergistically accelerated cutaneous wound healing in mice. The 2017 Journal of Investigative Dermatology paper extended this to hair: CXXC5 was upregulated in miniaturised follicles and arrector pili muscles of human balding scalp, CXXC5-knockout mice showed accelerated hair regrowth which valproic acid enhanced further, and disrupting the CXXC5-Dishevelled interaction with the competitor peptide accelerated both hair regrowth and wound-induced hair follicle neogenesis in mice. The inhibitory effect of CXXC5 on alkaline phosphatase activity and proliferation was demonstrated in human hair follicle dermal papilla cells. A 2023 paper linked CXXC5 to androgenetic alopecia through prostaglandin D2.
Two structural problems should temper how this is read. First, and verified directly against the primary sources: neither the 2015 nor the 2017 paper discloses the amino acid sequence of PTD-DBM. The 2015 paper describes the construct only as comprising a protein transduction domain for delivery, a flexible linker, the Dishevelled-binding motif, and a lysine conjugated to FITC for visualisation. A sequence circulates on vendor websites, but it cannot be checked against the literature, which means anyone buying material under this name has no way to confirm it is the compound that was studied. Second, the published effect depends on co-administration of valproic acid, so the peptide's standalone efficacy is not well characterised even in mice. There are no clinical trials, and the corresponding author declares an affiliation with a spin-out biotechnology company.
Evidence assessment
Preclinical only
All published data are mouse models, human scalp tissue expression and human dermal papilla cell culture, from a single research group; there are no registered clinical trials and no published human efficacy or safety data.
Tiers are applied consistently across the library and re-checked when new trials read out. Read the grading method.
Key studies
The Dishevelled-binding protein CXXC5 negatively regulates cutaneous wound healing Preclinical only
CXXC5 binds Dishevelled and suppresses Wnt/beta-catenin signalling in skin, with CXXC5 protein reduced in keratinocytes and fibroblasts of acute human wounds; PTD-DBM, a competitor peptide blocking the CXXC5-Dvl interaction, activated beta-catenin and collagen production and, combined with valproic acid, synergistically accelerated wound healing in mice.
Targeting of CXXC5 by a Competing Peptide Stimulates Hair Regrowth and Wound-Induced Hair Neogenesis Preclinical only
CXXC5 was upregulated in miniaturised hair follicles and arrector pili muscles of human balding scalp; knockout mice regrew hair faster, and the competing peptide accelerated hair regrowth and wound-induced follicle neogenesis in mice.
CXXC5 Mediates DHT-Induced Androgenetic Alopecia via PGD2 Preclinical only
Links CXXC5 to androgenetic alopecia through prostaglandin D2 signalling downstream of dihydrotestosterone.
Adhesive Hydrogel Patch-Mediated Combination Drug Therapy Induces Regenerative Wound Healing through Reconstruction of Regenerative Microenvironment Preclinical only
Combination delivery via an adhesive hydrogel patch promoted regenerative rather than fibrotic wound healing in mice.
Safety
No human data. The mechanistic concern is specific rather than generic: this compound works by de-repressing Wnt/beta-catenin signalling in skin. Constitutive activation of that pathway is oncogenic in several tissues and is specifically implicated in pilomatricoma and other follicular tumours, so chronic unsupervised pathway activation is not a trivial intervention. The published regimen also pairs it with valproic acid, which is a well-documented human teratogen subject to pregnancy prevention programmes in the UK and elsewhere; it is not a benign topical adjunct and should not be treated as one. Finally, because the sequence is undisclosed, the identity and purity of any material sold under this name are unverifiable.
Regulatory status
| Jurisdiction | Status |
|---|---|
| United Kingdom | No MHRA authorisation. Not an authorised medicine or permitted cosmetic active with therapeutic claims. Note separately that valproate, with which it is typically combined in the published work, is subject to strict MHRA safety controls including pregnancy prevention requirements. |
| United States | Not FDA-approved. No investigational new drug programme or registered clinical trial. Sold online and through some compounding channels as a research chemical or topical preparation with no regulatory review. |
| WADA (sport) | Not individually named on the Prohibited List. As a substance with no regulatory approval for human therapeutic use it would fall within S0, prohibited at all times. |
Questions
It is not published. We checked the two primary papers directly. The 2015 Journal of Experimental Medicine paper describes the construct only as a protein transduction domain, a flexible linker, the Dishevelled-binding motif and an FITC-conjugated lysine, and gives no sequence; the 2017 hair paper does not supply one either. A sequence circulates on vendor sites but cannot be verified against the literature, so material sold under this name cannot be confirmed to be the studied compound.
No. There are no registered clinical trials and no published human treatment data. The hair regrowth findings are from mice, supported by expression studies in human balding scalp tissue and experiments on cultured human dermal papilla cells. That is a reasonable basis for pursuing a trial, not a substitute for one.
They act at different points in the same pathway. PTD-DBM removes the CXXC5 brake at the level of Dishevelled; valproic acid inhibits GSK-3beta, which otherwise marks beta-catenin for degradation. Pushing from both ends produced more effect than either alone, which the 2015 paper describes as synergistic. Note that valproate is an established human teratogen with strict regulatory controls, which matters for anyone considering topical use.
Potentially, and this deserves to be stated plainly. Wnt/beta-catenin is a developmental growth pathway, and its constitutive activation is oncogenic in several tissues, with specific implication in pilomatricoma and other follicular tumours. Short-term experimental activation in mice tells you little about years of unsupervised use in people. No long-term safety study of any kind exists.