LL-37 vs Thymosin Alpha-1
A neutral, side-by-side comparison of two healing & recovery peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
LL-37
LL-37 is the only human cathelicidin — a host defense peptide produced by neutrophils, epithelial cells, and macrophages in response to infection and inflammation. It functions simultaneously as a broad-spectrum antimicrobial agent and an immune-modulatory signaling molecule. Research interest has expanded dramatically since COVID-19 studies linked low LL-37 levels to severe outcomes, and gut health research identified it as a key regulator of intestinal barrier integrity.
Full profileThymosin Alpha-1
Thymosin Alpha-1 (Tα1) is a 28-amino acid peptide naturally derived from the thymus gland. It plays a central role in regulating immune function — specifically in the maturation and differentiation of T-cells. Unlike most research peptides, Thymosin Alpha-1 has approved clinical use in multiple countries (China, Italy, and others) for hepatitis B, hepatitis C, and as an immune adjuvant in cancer patients undergoing chemotherapy. In the US it is sold as Zadaxin and used as a research compound.
Full profile| LL-37 | Thymosin Alpha-1 | |
|---|---|---|
| Category | Healing & Recovery | Healing & Recovery |
| Also known as | Cathelicidin LL-37, hCAP-18 C-terminal fragment, CRAMP (murine equivalent) | Tα1, Thymalfasin, Zadaxin |
| Evidence | Research-stage | Research-stage |
| Dosing range | 100mcg–500mcg mcg, Daily or 3–5x weekly | 900mcg–3.2mg mg, 2–3 times per week subcutaneously |
| Administration | Subcutaneous injection, Intranasal (for respiratory applications), Topical (wound care) | Subcutaneous injection |
| Key side effects | Injection site redness and irritation (common — pro-inflammatory at injection site), Transient flu-like symptoms (immune activation), Local induration, High doses may be cytotoxic — dose-response curve is non-linear | Generally very well tolerated, Mild injection site reactions (most common), Transient fatigue in initial doses, Flu-like symptoms (rare) |
| Cited sources | 3 references | 4 references |
Key differences
- Administration: LL-37 — Subcutaneous injection, Intranasal (for respiratory applications), Topical (wound care); Thymosin Alpha-1 — Subcutaneous injection.
- Dosing units differ: LL-37 is dosed in mcg, Thymosin Alpha-1 in mg — they operate at different scales.
- Frequency: LL-37 is typically Daily or 3–5x weekly; Thymosin Alpha-1 is 2–3 times per week subcutaneously.
- Research depth: this profile cites 3 sources for LL-37 vs 4 for Thymosin Alpha-1.
How each works
LL-37
LL-37 exerts antimicrobial activity by disrupting bacterial membranes via electrostatic interaction with negatively charged lipopolysaccharide — effective against gram-positive and gram-negative bacteria, fungi, and enveloped viruses including SARS-CoV-2 in vitro. Beyond direct antimicrobial action, LL-37 modulates innate immunity through TLR4 signaling, promotes wound healing via EGFR and FPRL1 receptor activation, and has demonstrated anti-biofilm activity against P. aeruginosa and S. aureus. Vitamin D is the primary driver of endogenous LL-37 production.
Thymosin Alpha-1
Extensive human clinical research documents Tα1's immune-modulating effects. It increases T-cell counts, enhances NK cell activity, and promotes Th1 cytokine balance. Multiple randomized trials have shown efficacy in treating chronic hepatitis B and C, reducing infection severity in critically ill patients, and improving outcomes in sepsis. More recent research investigates its role in long COVID immune dysregulation. It is considered one of the best-studied peptides in immunology.
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.