Thymosin Alpha-1 vs TB-500
How Thymosin Alpha-1 and TB-500 differ on mechanism, dosing, and the strength of the evidence behind each.
How this is graded
Every compound below carries a REGEN research grade, from S (regulatory approval behind the use it is bought for) down to F (no clinical evidence). Ordering follows that grade rather than search volume, so the compound at the top is the one with the most evidence, not the one most often sold. Doses are those reported in published protocols and are not recommendations.
Thymosin Alpha-1
Thymosin Alpha-1 is a naturally occurring 28-amino-acid peptide fragment of prothymosin alpha, produced by the thymus gland and involved in T-cell maturation and innate immune signaling (notably through TLR9). Under the brand name Zadaxin, it's an approved drug in more than 35 countries — including Italy and China — for chronic hepatitis B and C and as a general immune-modulating agent. It has never been FDA-approved in the United States; as of a February 2026 reclassification, it holds FDA 503A Category 2 status, meaning US patients can access it only by prescription through licensed compounding pharmacies.
TB-500
TB-500 is a synthetic version of the active region of Thymosin Beta-4, a naturally occurring protein involved in cell migration, blood vessel formation, and tissue repair. It works systemically rather than locally, making it popular for whole-body recovery, muscle and tendon healing, and reducing stiffness. It upregulates actin, a protein central to cell movement and wound healing. TB-500 is most commonly paired with BPC-157 in healing blocks, where the two are seen as complementary — BPC-157 acting more locally and TB-500 systemically. Most evidence is preclinical or anecdotal.
Evidence compared
| Thymosin Alpha-1 | TB-500 | |
|---|---|---|
| Research grade | Agrade | Dgrade |
| Reported dose | 1.6 mg | 2–5 mg |
| Frequency | 2x weekly | 2x weekly (loading), then 1x weekly |
| Half-life | ~2 hours | ~2-3 days |
| Routes | subcutaneous | subcutaneous, intramuscular |
| Tracked outcomes | — | Joint & Tendon Health |
| Contraindications | pregnancy, organ transplant recipients on immunosuppressive therapy, known hypersensitivity | active malignancy, pregnancy |
Which has more behind it
Thymosin Alpha-1 carries the stronger evidence grade (A) against TB-500 at D, which means more of what is claimed for Thymosin Alpha-1 has been tested in humans. Both entries link through to the full reference, where the trial list and citations for each claim are set out in full.
Full Thymosin Alpha-1 reference · Full TB-500 reference
At a glance
| Compound | Grade | Reported dose | Half-life |
|---|---|---|---|
| Thymosin Alpha-1 | Agrade | 1.6 mg · 2x weekly | ~2 hours |
| TB-500 | Dgrade | 2–5 mg · 2x weekly (loading), then 1x weekly | ~2-3 days |
Frequently asked questions
Thymosin Alpha-1 or TB-500, which has better evidence?
Thymosin Alpha-1 carries the stronger evidence grade (A) against TB-500 at D, which means more of what is claimed for Thymosin Alpha-1 has been tested in humans.
Can Thymosin Alpha-1 and TB-500 be used together?
The catalog does not list Thymosin Alpha-1 and TB-500 as a common pairing. Combining compounds does not combine their evidence.
What doses are reported for Thymosin Alpha-1?
Published protocols report 1.6 mg, 2x weekly. This is what the literature describes, not a recommendation.
References
- Thymosin-α1 for people with chronic hepatitis B (Cochrane Review CD014610) · Htet NH, et al. · 2022
- Thymosin beta4 and tissue regeneration · Goldstein AL, et al. · 2012
- Goldstein AL, Kleinman HK. Minireview: Crosstalk between thymosin β4 and the chemokine network. Ann N Y Acad Sci. 2015. · Martinez JO, Evangelopoulos M, Bhavane R, Acciardo S, Salvatore F, Liu X, Ferrari M, Tasciotti E · 2015
- Thymosin β4 Promotes Dermal Healing. · Kleinman HK, Sosne G · 2016
- Gene ResultTMSB4X thymosin beta 4 X-linked [ (human)] - NCBI
- Philp D, Kleinman HK. Animal studies with thymosin β4, a multifunctional tissue repair and regeneration peptide. Ann N Y Acad Sci. 2012. · Meyer M, Elmer S, Jäncke L · 2012
- Intra-Articular Injection of BPC 157 for Multiple Types of Knee Pain. · Lee E, Padgett B · 2021
- Biological activities of thymosin beta4 defined by active sites in short ... · Sosne G, Qiu P, Goldstein AL, Wheater M · 2010
- Malinda KM, et al. Thymosin beta4 accelerates wound healing. J Invest Dermatol. 1999. · Pinto B, Pierotti R, Canale G, Reali D · 1999
- Identification of glutamine as a potential therapeutic target in dry eye disease. · Chen X, Zhang C, Peng F et al. · 2025
- Thymosin Beta-4 - an overview | ScienceDirect Topics
- Smart N, et al. Thymosin beta4 induces adult epicardial progenitor mobilization and neovascularization. Nature. 2007. · Lindholm P, Voutilainen MH, Laurén J, Peränen J, Leppänen VM, Andressoo JO, Lindahl M, Janhunen S, Kalkkinen N, Timmusk T, Tuominen RK, Saarma M · 2007
- Thymosin beta-4 denotes new directions towards developing prosperous anti-aging regenerative therapies. · Bock-Marquette I, Maar K, Maar S et al. · 2023