Acetyl tetrapeptide-2 appears on firming creams, barrier creams and a few hair lotions. Its trade names are Thymulen 4 and Peptigravity, and the first one hints at where its sequence comes from.
The research record is two PubMed papers long. Neither tests the peptide by itself on a face.
The molecule, and where its sequence comes from
Ac-Lys-Asp-Val-Tyr-OH: lysine, aspartic acid, valine, tyrosine, acetylated at the front. PubChem CID 91936905, formula C26H39N5O9, molecular weight 565.6, CAS 757942-88-4. PubChem lists "Thymulen 4" and "Peptigravity" as synonyms of the same record.
Set that sequence beside another PubChem record, CID 451417. That compound is thymopentin, Arg-Lys-Asp-Val-Tyr, the five-residue active fragment of thymopoietin, a hormone of the thymus. Thymopentin was developed as an immune-modulating drug. Its PubChem synonyms include "Thymopoietin 32-36" and, interestingly, the cosmetic name "SH-pentapeptide-1".
Acetyl tetrapeptide-2 is thymopentin with the arginine removed and an acetyl cap added. We did not find a paper or supplier document that states this. It comes from comparing the two records directly, and it explains the trade name.
Two cautions follow. A shared sequence is not a shared action: removing the first residue and capping the end changes a peptide's binding, and nothing published tests whether this fragment does anything thymopentin does. And thymopentin's own drug literature is about the immune system, not skin. None of it can be borrowed for a face cream.
At 565.6 daltons, the molecule is above the 500-dalton line often used as a rough guide to passive skin penetration. It has no fatty tail to help it through.
What PubMed holds
Searched 5 October 2026, title and abstract, with and without the hyphen: 2 records. The trade name "Thymulen" returned none. Neither record carries the Retracted Publication type.
Kobiela and colleagues, International Journal of Peptide Research and Therapeutics 2018 (PMID 30416406). Immortalised human keratinocytes (HaCaT cells) were exposed to acetyl tetrapeptide-2 for 48 hours. Atomic force microscopy found the cells became stiffer across the concentration range tested. The peptides were supplied by Lipotec; three of the seven authors are from the research centre of the Polish cosmetics company Dr Irena Eris, and the paper declares no conflict of interest. Cell stiffness in a dish is a mechanical property of single cells, not a measure of skin firmness.
Turlier and colleagues, Journal of the European Academy of Dermatology and Venereology 2021 (PMID 34668237, registered as NCT04652232). This is the only human trial naming the peptide, and it is a hair study:
| Item | What the paper and registry state |
|---|---|
| Sponsor | Pierre Fabre Dermo-Cosmétique (all authors employed by Pierre Fabre) |
| Who | 100 women aged 19-50 with acute telogen effluvium, a temporary shedding that usually recovers in 3-6 months |
| Design | Open (not blinded), randomized, two centres |
| Arms | Lotion + mild shampoo (51) vs mild shampoo alone (49) |
| The lotion | Creatine, acetyl tetrapeptide-2 and B vitamins |
| Primary endpoint | Change in anagen-to-telogen ratio, week 1 to week 16 |
| Result | Ratio higher in both groups by week 16; the lotion group reached significance earlier (weeks 4 and 8 vs week 8). Between-group differences significant at week 8 for telogen density (P = 0.0465) and hairs shed (P = 0.0392) |
What this supports is narrow. The comparison was a three-active lotion against no lotion, so the effect cannot be assigned to the peptide, to the creatine, to the vitamins, or to the act of applying a leave-on product three times a week. The condition recovers on its own, which both arms showed.
The hair peptide with the neighbouring name, acetyl tetrapeptide-3, has the same problem: its trial tested it inside a combination.
The facial studies that mention it in passing
A Europe PMC full-text search finds the name in 7 papers. Beyond the two above:
- Liu and colleagues, Journal of Cosmetic Dermatology 2023 (PMID 35150184), sponsored by Allergan Aesthetics. Women in Chinese cities with high air pollution used a day and a night serum (the LUMIVIVE System) plus a basic moisturizer, or the basic moisturizer alone, for 84 days. The full text says both serums contain acetyl tetrapeptide-2 among many other actives, including plant cell extracts and ferment filtrates. The treatment group showed lower pigmentation and redness. The peptide was never isolated.
- A 2026 case series of three patients lists it in the ingredient list of a home-care product used after peeling and filler (PMC13611034). Three people with no control group.
- A 2026 tree-peony paper names it as an example of a widely used anti-ageing peptide. A 2020 open-label study of a two-product regimen is the seventh.
Where it turns up on this site
The Rhode Barrier Restore Cream analysis found acetyl tetrapeptide-2 declared near the middle of a 35-ingredient list, among four peptides directly above the preservative. That is a typical position for this ingredient: present, with no declared amount, after the ingredients that do the moisturising.
For barrier claims in general, peptides vs ceramides sets out which ingredient class carries the evidence.
What this file supports saying
- The compound is well characterised, and its sequence is a trimmed fragment of a known thymus hormone.
- One cell study found it stiffened cultured keratinocytes.
- One open, industry-run trial found a three-active hair lotion beat shampoo alone at week 8 in a self-resolving condition.
- No study tests acetyl tetrapeptide-2 alone on skin, and none tests it for firmness on a face.
Sources
- PubChem, CID 91936905 (acetyl tetrapeptide-2; synonyms incl. Thymulen 4, Peptigravity, CAS 757942-88-4) and CID 451417 (thymopentin, Arg-Lys-Asp-Val-Tyr; synonyms incl. Thymopoietin 32-36, SH-pentapeptide-1), read 2026-10-05.
- PubMed E-utilities searches, run 2026-10-05, with the
quotedphrasesnotfoundcheck and the Retracted Publication filter. - Kobiela T et al., Int J Pept Res Ther 2018;24(4):577-587 (PMID 30416406; PMC6208634), full text read 2026-10-05.
- Turlier V et al., J Eur Acad Dermatol Venereol 2021;35 Suppl 2:12-20 (PMID 34668237), abstract read 2026-10-05; ClinicalTrials.gov NCT04652232, record read 2026-10-05.
- Liu W et al., J Cosmet Dermatol 2023;22:245-254 (PMID 35150184; PMC10078722), full text read 2026-10-05.
- Europe PMC full-text search "acetyl tetrapeptide-2", 7 results, read 2026-10-05.