Compare prices and buy Thymosin Alpha 1 from 34 research peptide vendors - also called suppliers or sources. Updated daily.
A synthetic N-acetylated 28-amino-acid peptide (CAS 62304-98-7) corresponding to the N-terminal end of prothymosin alpha, a protein found in many tissues and most concentrated in the thymus. Its immunostimulant effects are proposed to be mediated at least in part by Toll-like receptor 9 signaling on dendritic cells and lymphoid progenitor cells, promoting dendritic-cell activation and T-cell maturation. Marketed internationally by SciClone Pharmaceuticals as Zadaxin, chiefly for chronic hepatitis B and as a vaccine adjuvant, and holds US orphan drug designations but is not FDA-approved.
For research purposes only. Not medical advice.
Thymosin alpha-1 is a 28-residue peptide, CAS 62304-98-7, molecular formula C129H215N33O55, acetylated at its N-terminus. Its sequence is residues 2 through 29 of prothymosin alpha (UniProt P06454), a protein found in many tissues and most concentrated in the thymus. The acetyl group matches the acetylated serine that opens the processed native protein. Its INN is thymalfasin.
It was identified in 1977 in thymosin fraction 5, a partially purified calf thymus extract holding several peptides, and was synthesized two years later. That extract is the common ancestor of this category: Thymalin is a comparable extract rather than a defined sequence, and Thymogen is a dipeptide isolated as a minimal active fragment.
The name it shares with thymosin beta-4, sold as TB-500, is a historical accident of that extract. Thymosin beta-4 is a 43-residue actin-sequestering protein with no sequence relationship to thymosin alpha-1, and vendors use the TB-500 name for both it and its seven-residue 17-23 fragment.
FDA's November 2024 evaluation describes the immunostimulant effects as proposed to be mediated at least in part through Toll-like receptor 9 on dendritic cells and lymphoid progenitor cells, citing the Tuthill and King review. Through less understood, TLR-independent routes, the peptide is also described as raising surface MHC class I expression on infected and tumor cells.
FDA framed that as proposed, and said the clinical relevance of the nonclinical findings is difficult to define: doses and routes were inconsistent across studies, and the concentrations at which it prompted CD8+ T cells to release factors blocking HIV infection of macrophages in vitro were roughly 2,000 times the peak plasma level from the dose common in clinical studies. FDA identified no published nonclinical toxicity study of either form.
FDA evaluated twelve separate uses in one review and found a lack of evidence supporting effectiveness in every one.
Thymosin alpha-1 holds no US approval. It carries four US orphan drug designations, which qualify a sponsor for incentives and are separate from approval. There is no USP or National Formulary monograph for either the free base or the acetate, neither is a component of an FDA-approved drug, and it appears in neither the European nor the Japanese Pharmacopoeia.
International marketing runs under the brand Zadaxin from SciClone Pharmaceuticals. Claims about how many countries approved it trace to the company's 2014 annual report, which FDA said it could not independently verify. FDA cited regulator records in Italy (as an influenza vaccine adjuvant in immunocompromised people), India (chronic hepatitis B) and Hong Kong, plus a monograph in Singapore's national drug formulary.
Wells Pharmacy Network nominated the substance for the 503A bulk drug substances list, then withdrew the nomination, and FDA removed thymosin alpha-1 from the 503A Category 2 list in September 2024, alongside AOD-9604, CJC-1295, ipamorelin acetate and Selank acetate. FDA proceeded to the Pharmacy Compounding Advisory Committee anyway, which heard the substance on December 4, 2024 and voted against both the free base and the acetate, four in favor and seventeen against on each.
No other substance heard that day drew more than one yes vote. The removal itself followed the withdrawn nomination, not a safety finding, and FDA keeps the original safety text on the withdrawn entry, which cites significant immunogenicity risk for certain routes of administration, complexities around peptide-related impurities and characterization of the active ingredient, and inadequate safety information.
Thymosin alpha-1 is not named on the World Anti-Doping Agency's 2026 Prohibited List, while thymosin beta-4 and its derivatives, TB-500 among them, appear under S2.3 for growth factors.
Listings appear as "Thymosin Alpha 1" or the abbreviations TA-1, TA1 and bare TA, as lyophilized vials and some oral capsules. PeptideScouter indexes each mapped listing per milligram and verifies identity against the published CAS number rather than the product title.
No. It holds no marketing approval in the United States. It carries four US orphan drug designations, which qualify a sponsor for development incentives but are a separate process from approval. There is no USP or National Formulary monograph for either the free base or the acetate form, and neither is a component of any FDA-approved drug. Material sold by research vendors is research-grade and offered for laboratory use only, not for human consumption.
No, and they are catalogued as separate rows here. Thymosin alpha-1 is a 28-residue peptide corresponding to the N-terminal end of prothymosin alpha. Thymosin beta-4 is a 43-residue actin-sequestering protein from an unrelated family, and TB-500 is a name research vendors use for it and for its seven-residue 17-23 fragment. The shared name is a historical accident: both came out of the same partially purified calf thymus extract, thymosin fraction 5, with thymosin alpha-1 sequenced in 1977 and thymosin beta-4 in 1981. The World Anti-Doping Agency's 2026 Prohibited List names thymosin beta-4 and its derivatives under its growth factor section and does not name thymosin alpha-1 anywhere.
Wells Pharmacy Network nominated it for the 503A bulk drug substances list and later withdrew the nomination, and FDA removed it from the 503A Category 2 list in September 2024. FDA proceeded to the Pharmacy Compounding Advisory Committee regardless. The committee heard the substance on December 4, 2024 and voted against adding both the free base and the acetate, four in favor and seventeen against on each. No other substance heard that day drew more than one yes vote, and the summary minutes record supporters arguing the substance should remain accessible to patients and opponents finding no compelling evidence of effectiveness or safety.
The largest trial found no mortality benefit. TESTS, a double-blind, placebo-controlled Phase 3 trial published in the BMJ in 2025, randomized 1,106 adults with sepsis at 22 centers in China, and 28-day all-cause mortality was 23.4 percent with thymosin alpha-1 against 24.1 percent with placebo in its modified intention-to-treat analysis (hazard ratio 0.99). The earlier single-blind ETASS trial, published in 2013, randomized 361 patients with severe sepsis and did not meet its primary endpoint: 28-day all-cause mortality was 26 percent with thymosin alpha-1 against 35 percent in controls, a nine-point absolute difference whose confidence interval crossed zero. A 2025 systematic review pooled 11 randomized trials covering 1,927 patients and found an overall odds ratio of 0.73 for 28-day mortality, but no significant benefit once the analysis was restricted to high-quality trials or to multicenter trials, and its trial sequential analysis concluded the accumulated sample was still inadequate.
Some vendors sell oral capsules, labelled in micrograms and sold by capsule count. Per-milligram figures are computed only for vials labelled in milligrams, so capsule products appear in the listing table but are absent from every per-milligram comparison on the site.
Thymosin Alpha 1 is sold by 34 research peptide vendors indexed on PeptideScouter, with 49 tracked listings compared per vendor in the table above. Pricing is normalized and refreshed daily.
32 of the 34 indexed vendors currently have Thymosin Alpha 1 in stock. The comparison table marks out-of-stock listings, and stock state is refreshed daily.
Renova Peptides currently lists Thymosin Alpha 1 at $3.20/mg, the lowest listed price across 34 tracked research peptide vendors. With current vendor discount codes applied, the lowest effective price is $2.88/mg.
Discount codes are issued per vendor rather than per peptide, so any code applies across that vendor's whole catalog. All 34 vendors listing Thymosin Alpha 1 publish a PeptideScouter code, worth 5% to 50% off. Applied, the lowest effective price falls from $3.20/mg listed to $2.88/mg at Renova Peptides. Each vendor's code is shown beside its price in the table above.
Thymosin Alpha 1 ranges from $3.20/mg to $13.90/mg across 49 listings from 34 research peptide vendors, normalized to USD per milligram and refreshed daily.
34 research peptide vendors currently list Thymosin Alpha 1 on PeptideScouter, with 32 in stock right now. We track 49 listings across size and kit variants.
Thymosin Alpha 1's CAS Registry Number is 62304-98-7. It is also sold as TA-1, Thymosin Alpha-1 (Tα-1).
