Most ingredient entries begin with how many papers exist. This one begins with the fact that the number is zero.
PubMed, searched on 2026-09-11 across every field and in both hyphenations, returns no record naming biotinoyl tripeptide-1. Nor does a search for biotinyl tripeptide. Search instead for Procapil, the trade name of the blend the peptide is sold inside, and six records come back.
That gap is the whole story of this ingredient. Its scientific record exists, but it is filed under a supplier's brand name, and it belongs to a mixture.
What it actually is
PubChem CID 11534242: biotin joined through a glycine to a histidine to a lysine. Formula C24H38N8O6S, molecular weight 566.7.
The arithmetic is clean enough to check by hand. Glycyl-histidyl-lysine is C14H24N6O4. Biotin is C10H16N2O3S. Join them with an amide bond, releasing one water molecule, and the result is C24H38N8O6S — the registered formula exactly.
So this is GHK carrying a vitamin. The copper peptide entry deals with the version of the same tripeptide that carries a metal instead. It is worth noticing how much of a scalp-serum ingredient list can consist of one tripeptide wearing different attachments, and how little of the evidence for any of them transfers to the others.
What the six papers are
Procapil is biotinyl-GHK plus apigenin, a flavonoid found in citrus and chamomile, plus oleanolic acid, a triterpene from olive leaf. Every indexed study is a study of that trio.
The largest is Khoso and Fahim, Journal of Ayub Medical College Abbottabad, 2024 (PMID 39609969). One hundred and sixty men with androgenetic alopecia, split into two groups of eighty: four sessions of platelet-rich plasma four weeks apart, or the same four sessions plus twice-daily topical 5% Procapil, assessed at six months.
The paper's own words for its design are quasi-experimental. There is no randomisation and no blinding, and the outcome measures are a seven-point patient satisfaction scale and a dermatologist evaluation score. No hair count, no hair diameter, no standardised photographic grading. The reported result — a greater proportion of the combination group achieving better scores, P below 0.05 — is therefore a difference in how a treatment looked to people who knew which treatment they had received, after six months of clinic visits.
The remaining five are smaller or further from the question: a brief clinical assessment of a caffeine-plus-Procapil formulation in male pattern hair loss (J Cosmet Dermatol 2024, three pages, no structured abstract), an observational study of a different branded serum added to minoxidil, a study of a different branded infusion, a comparison against a redensyl and saw palmetto stack, and a review of topical alternatives for hair loss.
An honest summary: the blend has been looked at repeatedly by clinicians who found it worth adding to something else, and never once tested against a vehicle in a blinded trial of its own.
The 2026 mouse study, and what it does and does not add
The newest primary work is Zheng et al., European Journal of Pharmacology, September 2026 (PMID 42575238), from a joint laboratory at China Pharmaceutical University with authors from a biotech company. It tests a three-part combination — EGCG from green tea, biotin, and Pal-GHK — in a mouse model of stress-induced alopecia.
The mechanistic numbers are specific: BMP2 up 2.77-fold in the high-dose group, TGF-beta1 down to 35.7% and phosphorylated Smad2 to 65.9% of the model group, with improvements in follicle morphology and regrowth.
Two things should be said plainly about it. It is a mouse study, so it establishes a pathway and not a human result. And the GHK derivative in it is the palmitoyl form, not the biotinyl form — the tail is different, which is precisely the variable that decides whether a peptide of this size gets through skin at all. The palmitoyl tripeptide-1 entry covers that molecule, which is also sold under the retired name palmitoyl oligopeptide. A study of one GHK derivative is read here as background for the family, not as evidence for this ingredient.
Whose literature is it borrowing?
Two comparisons put the six records in proportion, both searched the same day on the same database.
| Indexed records | |
|---|---|
| Platelet-rich plasma in androgenetic alopecia | 256 |
| GHK-Cu and copper tripeptide, all fields | 143 |
| Procapil, all fields | 6 |
| Biotinoyl tripeptide-1, all fields | 0 |
The first line matters because the blend's largest study is a platelet-rich plasma study. PRP in this condition has its own 256-record literature and its own contested effect; a trial in which every participant receives four PRP sessions, and half also apply a topical, is measuring the topical's contribution on top of an active background. If the eighty men in the combination arm were more satisfied, the treatment they were more satisfied with was PRP plus a serum, applied twice daily for six months, in an unblinded trial scored by questionnaire.
The second line is the one that explains the ingredient's presence on labels at all. The tripeptide at its core has a literature of 143 records under its copper name. The biotinylated version has none. The copper peptide entry sets out what that 143 actually contains, including how much of it is authored by people selling the ingredient.
Products and labels
It appears in scalp serums, lash and brow serums, and shampoos, and it is usually the blend name that is marketed while the INCI name sits in the list. Where a percentage is given at all it is the percentage of the blend — the 3% and 5% figures in the two clinical reports are Procapil concentrations, not peptide concentrations, and the peptide is a minor fraction of the blend by weight.
That distinction is the single most common misreading of this ingredient. A serum described as 5% Procapil is not a 5% peptide serum, and no public document states what fraction of the blend the peptide is.
No Cosmetic Ingredient Review safety assessment naming this peptide could be located; the panel's published peptide reviews cover protein-derived and plant-derived material rather than the numbered synthetic actives.
What the evidence does not show
There is no published trial of biotinoyl tripeptide-1 against a vehicle. No penetration study of the biotinylated form through human scalp or eyelid skin that could be located. No measurement of whether the biotin is released once the peptide is applied, which is the implicit premise of the name. No dose-response curve, and no concentration on any label — products name the blend, not the percentage.
For lashes and brows, where this ingredient is also sold, there is not even a blend-level trial; that category's evidence is discussed in the myristoyl pentapeptide-17 entry, and it is mostly a story about a different class of molecule entirely.
Sources and dates
Opened 2026-09-11: PubMed E-utilities searches for biotinoyl tripeptide-1 and biotinyl tripeptide (zero records, all fields, both hyphenations) and for Procapil (six records, all retrieved and read by title and abstract); full abstracts of PMID 39609969, PMID 37990760 and PMID 42575238; PubChem compound record CID 11534242 for structure, formula and molecular weight. The GHK-plus-biotin formula arithmetic was carried out for this entry and can be checked against the PubChem record. The comparison table was produced by two further PubMed counts run in the same session: platelet-rich plasma with androgenetic alopecia in a title or abstract (256 records) and GHK-Cu, copper tripeptide or copper peptide across all fields (143). Both are raw database counts and are cited as a measure of how much has been published, not of how well. Corrections go to the contact page; the review standard is on the testing notes page.