Where to Buy Thymosin Alpha-1: 7 Purity and Identity Checks for a Defined 28-Mer Where Mass Spectrometry Actually Works

Thymosin alpha-1 has a clean mass target at 3,108.3 daltons, which puts it ahead of most of this market on verifiability. The risk sits elsewhere: an acetyl group worth 42 daltons, a wrong database identifier, and an 18.8% fill shortfall on record.

This page is the sourcing walkthrough. Thymosin alpha-1 sits in the immune support and longevity peptides category, vendor listings and per-milligram pricing sit on the thymosin alpha-1 compound page, and the evidence picture — the 1,106-patient double-blind trial that came back null, the meta-analysis that dissolves in its own subgroups, the Cochrane review that was never completed — is in thymosin alpha-1 and sepsis. Read that one for whether it works. Read this one before you pay.

What is thymosin alpha-1, and why does source quality matter?

Thymosin alpha-1 is a defined 28-residue peptide, Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN, N-terminally acetylated, with the formula C₁₂₉H₂₁₅N₃₃O₅₅ and a molecular weight of 3,108.3 g/mol. Source quality matters in a narrower way here than for most of this market, because the mass target is clean and mass spectrometry against it works. The specific risk is the acetyl group: it is part of the molecule rather than decoration, a non-acetylated version would be 42 daltons lighter and a different compound, and HPLC purity will not distinguish it.

One verification trap is worth naming before anything else, because it is the fastest check on this page. PubChem CID 16130265 is not thymosin alpha-1 — it is a 14-residue peptide, C₈₁H₁₁₄N₁₆O₃₀, auto-titled "Tyifevefqkeedd". If a certificate of analysis or a vendor page cites that CID for Tα1, it is wrong, and a reader can confirm that in about thirty seconds. The correct record is CID 16130571.

The reason the mass check carries so much weight here is that it is a check that actually resolves. Mass spectrometry confirms identity by comparing a measured mass against an authoritative expected one, and for this compound the expected value is established, published and consistent across sources — which is not true of every compound sold beside it. The method is in mass spectrometry for peptides, and on this molecule it delivers what it promises.

What is the regulatory status of thymosin alpha-1?

Thymosin alpha-1 is not FDA-approved — a query of FDA's drug application database for thymalfasin returns no matches, verified against a working control query — and as of August 2026 it is not legally compoundable in the United States, because it is not on the 503A bulks list, not on the 503B list and has no USP monograph, so it satisfies none of the three statutory routes. It holds US and European orphan drug designation, which is not approval. WADA's 2026 Prohibited List does not name it.

On the FDA bulk drug substances page current 22 April 2026, thymosin alpha-1 sits in the second table, "Bulk drug substances nominated but withdrawn," rather than in active Category 2. That control query on the database search matters as well, because a negative result from a search tool you have not tested is not a finding.

Orphan designation is not approval, and it is the most commonly inverted fact about this compound. SciClone's own SEC filing records US and European orphan drug designation for hepatocellular carcinoma. Designation is granted at the development stage, carries tax credits and market exclusivity if a drug is later approved, involves no finding of efficacy, and is routinely presented in marketing as though it were an approval.

The ex-US approvals are real, and the number attached to them is dated. SciClone's 2005 annual report states that ZADAXIN was "currently approved for sale in over 30 countries internationally, primarily in Asia, the Middle East and Latin America," principally for hepatitis B, with additional approvals in some countries for hepatitis C, as a vaccine adjuvant, or as a chemotherapy adjuvant. That is a twenty-year-old filing. We could not verify a current country-by-country list, and the specific figures circulating online are not traceable to any current source.

Those two facts are usually distorted in opposite directions, and the gap between them is why this page has no compounded-thymosin-alpha-1 section. An approval in another jurisdiction does not create a US compounding route, and compounding pharmacy versus research peptide sets out what a route would require. FDA's retained language on that page states it directly:

"Compounded drugs containing thymosin-alpha-1 (Ta1) may pose significant risk for immunogenicity for certain routes of administration and may have complexities with regard to peptide-related impurities and API characterization. The safety-related information is inadequate for the agency to sufficiently understand the extent of any safety issues raised by the proposed compounded drug."

Thymosin alpha-1 was not reviewed at the July 2026 advisory committee meeting. That meeting covered BPC-157, KPV, TB-500 and MOTS-c on 23 July, and DSIP, Semax and Epitalon on 24 July; this compound was not on the agenda, which matters because cluster coverage of that round can leave the impression that every peptide was assessed. The full sequence of determinations is in our FDA peptide regulation timeline, and the jurisdiction-by-jurisdiction picture is in are peptides legal.

Note the shape of those errors. Five are misread regulatory documents, three are misread statistics, and one cites a review that was never completed. None of them requires a conspiracy — they require nobody having opened the source.

Which "thymosin" are you buying: alpha-1, beta-4 or thymalin?

Three different substances are sold under the word thymosin, and confusing them has consequences in both directions. Thymosin alpha-1 is a defined 28-mer at 3,108.3 daltons. Thymosin beta-4 and its fragment TB-500 are entirely different molecules, and WADA section S2.3 names "Thymosin-β4 and its derivatives e.g. TB-500". Thymalin is an undefined calf thymus extract with no single mass to confirm. Content treating thymosin as one substance gets this wrong both ways.

The doping asymmetry is the sharp end of it. An athlete told "thymosin is banned" may avoid a compound the 2026 list does not name; an athlete told "thymosin is fine" may inject one the list names explicitly at S2.3, which is a named entry rather than an S0 catch-all inference. We verified name-absence for thymosin alpha-1 only, and did not assess whether S0 could apply, so absence from the list is not a statement that Tα1 is permitted — the practical consequences for tested athletes are in do peptides show up on drug tests.

Thymalin is the instructive contrast for a buyer, because it shares an organ of origin and a therapeutic story with thymosin alpha-1 and shares almost nothing else. It is an undefined extract, which means there is no mass to check, no sequence to print on a certificate and no specification a laboratory could hold a batch against. Being a defined molecule is what made a definitive answer possible for thymosin alpha-1 on the trial bench, and it is the same property that makes a vial checkable at the point of purchase.

7 things to check before ordering thymosin alpha-1

Seven checks cover thymosin alpha-1, and the first is a mass spectrum at 3,108.3 daltons read specifically for the N-terminal acetyl, since a des-acetyl form is 42 daltons lighter. After that come the correct PubChem CID, the CAS and UNII identifiers, third-party HPLC against the platform's 99.51% average, fill quantity as its own line, an LAL endotoxin result answering FDA's stated concern, and the product page read against the trial record.

1. A batch-matched mass spectrum at 3,108.3 daltons, read for the acetyl group. This is the check that catches the compound's identity-critical defect, because a des-acetyl form is 42 daltons lighter and a certificate reporting an HPLC purity figure and nothing else has not confirmed identity at all. Insist the result is tied to your lot rather than a specimen certificate from an earlier batch, which is among the standard problems in red flags in peptide certificates of analysis.

2. The correct PubChem CID on the paperwork: 16130571. CID 16130265 is a different 14-residue peptide, C₈₁H₁₁₄N₁₆O₃₀, auto-titled "Tyifevefqkeedd", and it is cited for Tα1 often enough to be worth checking directly. A vendor quoting it has copied an identifier from another page rather than verified one, which is a documentation failure that tells you what the rest of the file is likely to be worth.

3. CAS 62304-98-7 or 69521-94-4, UNII W0B22ISQ1C, and thymalfasin recognised as the same substance. Two CAS numbers are legitimate here, so a page listing either is not wrong. What matters is whether the vendor knows that thymalfasin and ZADAXIN name this compound, because a listing that treats them as separate products, or that cannot produce any identifier at all, was assembled from other listings rather than from a specification.

4. Third-party HPLC from a named laboratory, with the acetyl limit stated alongside it. The Purity Index records 99.51% average across 217 independent tests with the most recent returning 99.95% on 31 July 2026 (verified August 2026), so the bar is high and a vendor should be able to meet it with a named laboratory's document rather than their own, as third-party peptide testing labs sets out. Then hold the ceiling: purity is a proportion, and it will not tell you the acetyl group is there.

5. Fill quantity as its own line, because this is where the variance lives. Measured content on this compound runs −18.8% to +14.6% against label, with most results within ±5%, and one vendor's product labelled 13 mg tested at 10.56 mg. Purity is a proportion and net content is a quantity, the distinction net peptide content exists to make, so ask for a quantitative content figure separately rather than accepting the purity percentage as an answer to both questions.

6. An LAL endotoxin result on the batch, which answers the regulator's own objection. FDA named immunogenicity and peptide-related impurities as its stated concerns for this substance in writing, which makes an LAL result the test that speaks to the specific issue on the record rather than a generic box to tick. Endotoxin results appear sporadically rather than routinely on this compound, with compliant samples passing at ≤0.05 EU/mL, so an absent result means untested rather than passed.

7. The product page read against the trial record, plus shop record and price. A page selling sepsis benefit is selling a claim that TESTS refuted at HR 0.99 and P = 0.93; a page citing Cochrane is citing a protocol with no conclusions; a page saying "FDA orphan status" without the word designation has overstated it. Screen the vendor with what to look for in a peptide shop, read community-verified shop reviews alongside the documents, and check price against a $6.80/mg median across 59 shops (verified 10 August 2026).

Two of those rows are specific to this compound rather than generic advice, and one is specific to this cluster. The acetyl row is the identity-critical feature nothing else on a certificate reaches. The endotoxin row answers the exact issue FDA named in writing. And unlike the compounds in this cluster whose reference mass cannot be established, every row here is answerable — which means a vendor who declines to answer has made a choice rather than met a limit.

Where does thymosin alpha-1 rank on Peptigrity's lab test database?

The Purity Index records thymosin alpha-1 at 99.51% average HPLC purity across 217 independent tests from Kovera Labs, Janoshik, Freedom Diagnostics and others, across 224 verified shops (verified August 2026), with the most recent test returning 99.95% on 31 July 2026. Those purity figures are among the strongest on the platform. Measured content is the weaker axis, running −18.8% to +14.6% against label, and price data shows 59 shops in stock, a median of $6.80/mg and a low of $2.50/mg on a 10 mg vial (verified 10 August 2026).

Strong purity is what you would expect for a synthetically straightforward peptide with an established pharmaceutical version behind it, and that is exactly why the risk has migrated. Most quantity results sit within ±5%, but one vendor's product labelled 13 mg tested at 10.56 mg, an 18.8% shortfall, and two others returned roughly +14% overages. A buyer auditing this compound on its purity figure alone is auditing the axis that is already solved.

Read the third row against the first two. A price per milligram is only meaningful if the milligrams are in the vial, and the one documented shortfall on this compound was 18.8% — which turns an apparently cheap listing into a differently priced one. The full spread across in-stock vendors is on the thymosin alpha-1 price data page. Those figures exclude shipping, taxes and customs, coupon codes, bulk tiers, multi-vial kits and account-gated pricing.

Every result behind those averages is browsable in the independent lab tests database, batch by batch. Trust scores weight community reviews and independently verified HPLC purity equally, at 50% each, with no financial relationship influencing the ranking, and those figures sit inside a platform tracking 530 shops and 11,852 independent lab tests across 118 peptides, with 1,283 community reviews (verified August 2026).

The trial that would settle this is not a sepsis trial, because that question is closed.

For a buyer, the first row is the one that changes a purchase. Sepsis does not remain open, and no amount of secondary citation will reopen it — so a vendor page selling this compound on sepsis data is selling a result that a 1,106-patient double-blind trial has already reported as null.

Frequently Asked Questions

What purity standard should thymosin alpha-1 meet?

High, and higher than most of this market: the platform average is 99.51% across 217 independent tests, with the most recent test returning 99.95% on 31 July 2026. Treat that as the benchmark for the HPLC line. Then treat the HPLC line as answering only one question, because purity reports the proportion of a sample that is a single species and will not tell you the N-terminal acetyl group is present. A des-acetyl form is 42 daltons lighter and a different compound.

How much does thymosin alpha-1 cost?

Price data shows 59 shops in stock at a median of $6.80/mg and a low of $2.50/mg on a 10 mg vial (verified 10 August 2026). Compare within a single vial-size band, since fixed per-vial costs push per-milligram figures down as fill size rises and make larger vials look like better products rather than simply bigger ones. Then remember what the price assumes: measured content on this compound runs from −18.8% to +14.6% against label.

Is thymosin alpha-1 legal to buy, and is it banned in sport?

It is not FDA-approved — a query of FDA's drug application database for thymalfasin returns no matches — and as of August 2026 it is not legally compoundable in the United States, because it is not on the 503A bulks list, not on the 503B list and has no USP monograph, so it satisfies none of the three statutory routes. It is approved in a number of other countries, primarily in Asia, the Middle East and Latin America, mainly for hepatitis B. WADA's 2026 Prohibited List does not name it, though we verified name-absence only.

How do I know my vial is really thymosin alpha-1?

Mass spectrometry at 3,108.3 daltons on a certificate matched to your batch, read specifically for the acetyl group, because a des-acetyl form is 42 daltons lighter and HPLC purity alone will not distinguish it. This is one of the few compounds in this market where the identity check genuinely resolves: the expected mass is established and consistent across sources. Check the identifiers as well — CAS 62304-98-7 or 69521-94-4, UNII W0B22ISQ1C, and PubChem CID 16130571 rather than 16130265.

What dose has actually been used in trials?

TESTS dosed subcutaneously every 12 hours for seven days in 1,106 adults with sepsis and found no mortality benefit. ETASS dosed 1.6 mg subcutaneously twice daily for five days, then once daily for two, in 361 patients, and was non-significant on its primary analysis at P = 0.062. Those are hospital protocols in critically ill inpatients rather than community regimens, and neither produced a positive result. The peptide dosing calculator and reconstitution calculator convert a chosen dose into a syringe volume; they are arithmetic, not a recommendation.

If it is approved in other countries, why is it not compoundable in the US?

Because US compounding runs on three statutory routes and an overseas approval is not one of them. Thymosin alpha-1 clears none of the three: it is not on the 503A bulks list — on the page current 22 April 2026 it sits in the "nominated but withdrawn" table — it is not on the 503B list, and it has no USP monograph. FDA's retained language states the safety information "is inadequate for the agency to sufficiently understand the extent of any safety issues."

Browse the immune support and longevity peptides category, or our complete peptide guide with 118 compounds (verified August 2026). For reconstitution and per-injection volume, use the peptide dosing calculator alongside the reconstitution calculator. Compare shops through independent lab tests and community-verified shop reviews.

This article is for educational and informational purposes only and does not constitute medical advice. Peptides discussed may be investigational compounds not approved by the FDA (or equivalent regulators in your jurisdiction) for human use. Always consult a qualified healthcare provider before using any peptide or research compound. Peptigrity is an independent review platform and does not sell, endorse, or recommend specific products or vendors.