Thymosin Alpha-1

Immune support Investigational (in clinical trials)

Synthetic 28-amino-acid thymic peptide · also known as Tα1, Thymalfasin, Zadaxin

For reference only — not medical advice. Figures are commonly reported values compiled from published sources and may be wrong or out of date. Many compounds listed are not approved for human use. Talk to a licensed clinician before using any compound.

Thymosin alpha-1 is a synthetic version of a naturally occurring thymic peptide. It has been evaluated in clinical studies of viral hepatitis, sepsis and as a vaccine adjuvant, and a brand product is marketed in a number of countries outside the US. It is categorized here as immune because nearly all of its research concerns immune-system modulation rather than tissue repair.

Commonly reported dosing (5 mg vial)

Reconstituted with 3 mL → 1.667 mg/mL.

Also sold in 10 mg vials.

Phase	Dose	Volume	U-100 units
Starting	300 mcg	0.18 mL	18
Standard	500 mcg	0.3 mL	30

Frequency: Once daily, subcutaneous · Half-life: About 2 hours after subcutaneous administration

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Commonly reported reconstitution steps

Vials are usually brought to room temperature (about 15-20 minutes) first.
3 mL of bacteriostatic water is added slowly down the inside wall of the 5 mg vial.
The vial is swirled gently until clear, not shaken.
This gives 1.67 mg/mL. Mixed vials are typically labeled with the date and refrigerated.

Storage

Before mixing: Sealed vials are commonly stored refrigerated (2-8 °C) and protected from light, or frozen (about -20 °C) for long-term storage.

After mixing: Reconstituted solution is commonly kept refrigerated (2-8 °C), protected from light, and not frozen.

Commonly used within 28 days of mixing.

How it works

It is reported to signal through Toll-like receptors (notably TLR9 and TLR2) on dendritic cells and other immune cells, which is associated with enhanced Th1-type responses, natural killer cell activity and T-cell maturation in laboratory and clinical studies.

Researched for

Studied in chronic viral hepatitis, where it has been used alongside standard antiviral care.
Investigated as an immunomodulatory add-on in sepsis, with mixed trial results.
Examined as a vaccine adjuvant and in immune function in older or immunocompromised populations.
Studied in several cancer-supportive and infection settings in small to mid-sized trials.

Notes

Figures shown (about 300-500 mcg daily) are those commonly reported in peptide-protocol charts; they differ from the 1.6 mg twice-weekly schedule used in many published clinical studies.
A large phase 3 sepsis trial reported no clear reduction in 28-day mortality versus placebo, so evidence for that use is inconclusive.
Approved as a prescription product in some countries outside the US; it is not an FDA-approved drug.

Sources

Last reviewed 2026-10-05.

LL-37

Human cathelicidin antimicrobial peptide

LL-37 is the active fragment of the only human cathelicidin, an antimicrobial peptide that also signals to immune and epithelial cells.

5 mg vial · Once daily, subcutaneous (sometimes 5 days on, 2 off)

KPV

Tripeptide fragment of α-MSH

KPV is the three-amino-acid C-terminal sequence of alpha-MSH, studied mainly for anti-inflammatory activity in gut and skin models.

10 mg vial · Once daily, subcutaneous

BPC-157

Synthetic pentadecapeptide

BPC-157 is a synthetic peptide derived from a sequence found in gastric juice.

5 mg vial · Once daily, subcutaneous (some reports split it into two injections)

TB-500

Thymosin beta-4 fragment

TB-500 is a synthetic version of a region of the naturally occurring protein thymosin beta-4.

5 mg vial · Once daily, subcutaneous (a weekly loading pattern is also reported)

ARA-290

Erythropoietin-derived innate repair receptor agonist peptide

Derived from a region of erythropoietin, ARA-290 (cibinetide) is a short synthetic peptide built to engage tissue-protective receptors without stimulating red-cell production.