Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Head-to-head comparison of LL-37 and Thymosin Alpha-1 — mechanism, side effects, legal status, and pricing.
LL-37 is the only human cathelicidin antimicrobial peptide — a 37-amino-acid peptide (starting with two leucines) cleaved from the hCAP-18 precursor. It has broad-spectrum antimicrobial activity and immunomodulatory roles, but is also implicated in the pathogenesis of autoimmune and inflammatory skin diseases including psoriasis, rosacea, and lupus. Not FDA-approved; research-use only.
Thymosin Alpha-1 (Tα1) is a 28-amino-acid acetylated peptide (Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN) corresponding to the N-terminus of prothymosin α. Marketed as Zadaxin / thymalfasin and approved in 35+ countries for chronic hepatitis B/C and as an immune adjuvant, but NOT FDA-approved in the US — Phase 3 HCV trials ended without approval. Outside the US it is one of the most clinically validated immune-modulating peptides.
LL-37
Thymosin Alpha-1
Category
Legal Status
Mechanism
Half-life
Side Effects
COA-verified vendors · trust score ≥70 required · single-vial price — bulk/bundle deals may be lower
LL-37
Thymosin Alpha-1
COA corpus from Disclosed Labs — independently tested batches only.
LL-37
31
COAs
99.2%
Avg purity
8
Labs
Thymosin Alpha-1
69
COAs
99.6%
Avg purity
12
Labs
LL-37 was characterized in the mid-1990s as the processed antimicrobial product of hCAP-18 (Gudmundsson et al., 1996). Dürr et al. (2006, Biochim Biophys Acta, PMID 16716248) provided a foundational review of its structure and activity as the sole human cathelicidin. Overhage et al. (2008, Infection and Immunity, PMID 18591225) showed LL-37 prevents Pseudomonas aeruginosa biofilm formation at 0.5 µg/mL — far below its MIC. A randomized, placebo-controlled Phase 1/2 trial (Grönberg et al., 2014, Wound Repair and Regeneration, PMID 25041740) found topical LL-37 safely accelerated healing of hard-to-heal venous leg ulcers at low doses. Its dual role in autoimmunity is well established: Lande et al. (2014, Nature Communications, PMID 25470744) identified LL-37 as a T-cell autoantigen in two-thirds of moderate-to-severe plaque psoriasis patients. No FDA approval exists for any indication. Injectable grey-market protocols for Lyme, biofilm, or mold illness lack controlled clinical evidence and carry theoretical autoimmune risk given LL-37's role in psoriasis, lupus, and rosacea pathogenesis.
Key references
Thymosin alpha-1 has been studied in 90+ clinical trials. A meta-analysis by Yang et al. (Antiviral Research 2008, PMID 18078676) in chronic hepatitis B found antiviral efficacy comparable to interferon-alpha. Tuthill, Rios & McBeath (Ann N Y Acad Sci 2010, PMID 20536460) reviewed the global Zadaxin program across HBV, HCV, melanoma, HCC, and vaccine adjuvancy. Romani et al. (Blood 2006, PMID 16741252) established the TLR9 / IDO dendritic-cell mechanism that underlies Ta1's dual pro-inflammatory / tolerogenic effects. During the COVID-19 pandemic, Liu et al. (Clin Infect Dis 2020, PMID 32442287) reported reduced mortality (11.11% vs 30.00%, p=0.044) in severe lymphopenic COVID-19 patients via restoration of exhausted T cells. A 2024 systematic review by Dinetz & Lee (Altern Ther Health Med, PMID 38308608) covering 30+ trials and 11,000+ subjects concluded Ta1 is a well-tolerated and effective immune modulator, and argued the FDA's 2023 restriction appeared unfounded given the clinical evidence. US regulatory status: NOT FDA-approved; removed from 503A Category 2 in September 2024 after nominator withdrawal; PCAC voted AGAINST inclusion on the 503A Bulks List on December 4, 2024.
LL-37 and Thymosin Alpha-1 are both in the Immune category and may have overlapping mechanisms. Researchers should review both profiles carefully, understand the mechanisms of action, and monitor the relevant biomarkers when combining compounds in the same class. As always, consult a licensed healthcare provider before making any decisions about combining research compounds.
This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.
Contraindications
Lab Testing
Key references
Disclosed Labs