LL-37 vs Thymosin Alpha-1
LL-37 belongs to innate immunity — the first-line antimicrobial defence. Thymosin alpha-1 acts mainly on adaptive immunity, supporting T-cell maturation.
LL-37
The only human cathelicidin antimicrobial peptide — a 37-residue host-defence peptide with antimicrobial, anti-biofilm and immune-signalling activity.
BEST STUDIED FOR
Repair & immune
Read the cited profile →
Thymosin Alpha-1
A 28-amino-acid thymic peptide that modulates T-cell and dendritic-cell function, registered as a medicine in a number of countries.
BEST STUDIED FOR
Repair & immune
Read the cited profile →
SIDE BY SIDE
| LL-37 | Thymosin Alpha-1 | |
|---|---|---|
| The key difference | Innate-immunity antimicrobial | Adaptive-immunity modulator |
| Class | Repair & immune | Repair & immune |
| Mechanism | LL-37 disrupts bacterial membranes and biofilms, binds and neutralises endotoxin, and acts as an immune signal (chemotaxis, wound angiogenesis). | Thymosin α1 acts on innate and adaptive immunity — reported to signal through Toll-like receptors on dendritic cells and to promote T-cell maturation — which is why it is studied as an immune "modifier" in infections, vaccines and oncology. |
| Status | Extensively studied in vitro and in animal models; LL-37-based topical therapeutics remain in development. | Approved (thymalfasin) in over 30 countries, mainly for hepatitis B/C and as an immune adjuvant; not registered in South Africa. Ongoing trials in oncology. |
| Reported safety signals | Reviews note cytotoxicity at higher concentrations and a role in some inflammatory skin conditions — the reason translation has been slow. | Reviews describe a favourable tolerability record in clinical use; injection-site discomfort is the most cited effect. |
| A key study | Reviews LL-37 as the sole human cathelicidin and its antimicrobial and immunomodulatory activities. (Pharmacol Rep 2016, PMID 27117377) | A comprehensive review of thymosin α1 in immunocompromised states, malignancy and vaccine response. (World J Virol 2020, PMID 33362999) |
WHEN TO RESEARCH WHICH
They model two different arms of the immune system. Both are discussed here strictly as research compounds; nothing on this page is medical advice or a dosing guide.
REFERENCES (PUBMED)
- [LL-37] LL-37: Cathelicidin-related antimicrobial peptide with pleiotropic activity — Pharmacol Rep 2016. PMID 27117377
- [LL-37] Antibiofilm properties of cathelicidin LL-37: an in-depth review — World J Microbiol Biotechnol 2023. PMID 36781570
- [LL-37] Human antimicrobial/host defense peptide LL-37 may prevent the spread of a local infection through multiple mechanisms: an update — Inflamm Res 2025. PMID 40063262
- [Thymosin Alpha-1] Thymosin alpha 1: A comprehensive review of the literature — World J Virol 2020. PMID 33362999
- [Thymosin Alpha-1] Historical review of thymosin α 1 in infectious diseases — Expert Opin Biol Ther 2015. PMID 26098768
- [Thymosin Alpha-1] Aging and Thymosin Alpha-1 — Int J Mol Sci 2025. PMID 41373628
FREQUENTLY ASKED
What is the difference between LL-37 and Thymosin Alpha-1?
LL-37 belongs to innate immunity — the first-line antimicrobial defence. Thymosin alpha-1 acts mainly on adaptive immunity, supporting T-cell maturation.
What is the regulatory status of LL-37 and Thymosin Alpha-1?
LL-37: Extensively studied in vitro and in animal models; LL-37-based topical therapeutics remain in development. Thymosin Alpha-1: Approved (thymalfasin) in over 30 countries, mainly for hepatitis B/C and as an immune adjuvant; not registered in South Africa. Ongoing trials in oncology.
What safety signals have been reported?
LL-37: Reviews note cytotoxicity at higher concentrations and a role in some inflammatory skin conditions — the reason translation has been slow. Thymosin Alpha-1: Reviews describe a favourable tolerability record in clinical use; injection-site discomfort is the most cited effect.
Which studies is this comparison based on?
For LL-37: “LL-37: Cathelicidin-related antimicrobial peptide with pleiotropic activity” (PMID 27117377); “Antibiofilm properties of cathelicidin LL-37: an in-depth review” (PMID 36781570); “Human antimicrobial/host defense peptide LL-37 may prevent the spread of a local infection through multiple mechanisms: an update” (PMID 40063262). For Thymosin Alpha-1: “Thymosin alpha 1: A comprehensive review of the literature” (PMID 33362999); “Historical review of thymosin α 1 in infectious diseases” (PMID 26098768); “Aging and Thymosin Alpha-1” (PMID 41373628).
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