Part of the skin and hair peptide hub: every topical and cosmetic peptide we cover, with its evidence grade.

Evidence: LowPeptide Research Only Cosmetic & Skin

Tetrapeptide-26

also known as: SPLQ-NH2, Ser-Pro-Leu-Gln-NH2

SPLQ-NH2, a cosmetic tetrapeptide sold for skin-care products. PubMed holds no study of it.

Tetrapeptide-26 is a synthetic tetrapeptide amide, Ser-Pro-Leu-Gln-NH2 (PubChem's record, under its INCI name). It is sold as a skin-care ingredient, but a title-and-abstract search of PubMed for its INCI name finds no study of it. It is not a drug.

No dosing data yet Details ↓

Dosing

Recommended Dosing

No dosing data yet

This page has no dosing data yet.

Mechanism of action

Not established: no published study describes its action.

Primary uses

Cosmetic skin-care formulations

Typical dosing

Not established for human use

No published study states an amount of this ingredient used on skin, and a supplier's use level is not a source on this site, so none is given.

Regulatory status

Not a drug: PubChem lists it under its INCI name as a cosmetic ingredient (CID 73507321). Drugs@FDA and the EMA medicines list hold no record for it (searched October 28, 2026).

Status as of this entry's last review, October 28, 2026. Approvals, compounding rules and sport rules change; the regulatory tracker is checked more often.

What we checked

Tetrapeptide-26 is a cosmetic peptide ingredient with little or no published literature; this section records what can be checked.

Identity, computed

Sequence	Ser-Pro-Leu-Gln-NH2 (SPLQ-NH2)
Formula	C19H34N6O6
Average mass	442.52 g/mol
Monoisotopic mass	442.254 Da
Isoelectric point	none between pH 0 and 14: no acidic group, so the peptide stays positive (net charge +0.98 at pH 7)

The sequence is the one PubChem's record gives for the INCI ingredient; the values below are computed and agree with PubChem's formula.

Regulatory status, read October 29, 2026

Drugs@FDA: 0 records for “tetrapeptide-26”. EMA medicines list: 0 records for “tetrapeptide-26”. Run for semaglutide, the same queries return 6 and 5 records (and the registry search 81 trials), so a zero here is an absence, not a broken search. Not named on the WADA 2026 and 2027 Prohibited Lists. As a substance with no current approval for human therapeutic use, it falls under section S0 (non-approved substances), which is prohibited at all times; the lists were read on October 28, 2026.

What we looked for and did not find

No published study of any kind, no registry record and no drug approval.

Source	Query	What it was
PubMed	("tetrapeptide-26"[tiab])	name matched word by word in title/abstract (a phrase search misses hyphen-numbered names)
ClinicalTrials.gov	tetrapeptide-26
Drugs@FDA (openFDA)	tetrapeptide-26
EMA medicines list	tetrapeptide-26

References

[other] PubChem CID 73507321, Tetrapeptide-26: formula C19H34N6O6, molecular weight 442.5. Read October 28, 2026. https://pubchem.ncbi.nlm.nih.gov/compound/73507321

Related peptides

Tetrapeptide-21

GEKG, a cosmetic tetrapeptide that raised collagen in skin cells and reduced skin roughness in one small 2011 placebo-controlled study; most later work is about getting it into skin.

Palmitoyl Pentapeptide-4

The palmitoylated procollagen fragment sold as Matrixyl (pal-KTTKS): in a 12-week split-face trial in 93 women a moisturiser containing it reduced wrinkles more than the same moisturiser alone. A cosmetic ingredient, not a drug.

Tripeptide-32

STP-NH2, a cosmetic tripeptide sold with circadian-rhythm claims. PubMed holds no study of it.

Acetyl Tetrapeptide-11

Ac-PPYL, a cosmetic tetrapeptide sold for skin firmness. Its one paper tests it in skin cells in combination with other peptides.

Guides & tools

Explore with tools

Glossary → Peptide Comparison → Beginner's Guide → Peptide FAQ → All Cosmetic peptides →

Disclaimer

This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.