N-ACETYL 28-MER · INN THYMALFASIN · RUO

Thymosin Alpha-1 Research Guidethymalfasin · not TB-500 · not Zadaxin

Thymosin Alpha-1 research graphic: uses, safety, research

Thymosin alpha-1 is the N-acetylated 28-residue peptide whose opened PubChem condensed sequence is Ac-Ser-Asp-Ala-Ala-Val-Asp-Thr-Ser-Ser-Glu-Ile-Thr-Thr-Lys-Asp-Leu-Lys-Glu-Lys-Lys-Glu-Val-Val-Glu-Glu-Ala-Glu-Asn-OH (INN/USAN thymalfasin; CID 16130571; UNII W0B22ISQ1C; CAS numbers 62304-98-7 and 69521-94-4 both printed on the opened PubChem page). It is not thymosin beta-4, not TB-500, not thymosin fraction 5, and not the non-U.S. brand product Zadaxin. The SRP 10 mg lyophilized vial is research-use-only. Human efficacy of a research-market vial is not established. This page does not claim that thymosin alpha-1 treats, prevents, or cures any immune, infectious, or oncologic condition. Research use only. Not medical advice. Not for human use.

Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN
CID 16130571
UNII W0B22ISQ1C
CAS 62304-98-7 / 69521-94-4
CT.gov totalCount 63
Not FDA-approved
Not TB-500
Research use only

Explore the Evidence
10 mg research vial
Identity table

Educational information only. This page describes an investigational laboratory research peptide. It is not medical advice. Simple Research Peptides (SRP) materials are for laboratory research only and are not for human or veterinary use, consumption, administration, diagnosis, treatment, or therapeutic application. Sequence, N-acetyl status, CAS, UNII, CID, and a public COA were not printed on the fetched SRP page. No human dosing, reconstitution, or administration protocol appears on this page.

Thymosin Alpha-1 peptide research infographic

01 / Identity

Sequence and chemical identity (opened registries only)

SRP product and index pages do not print CAS, UNII, PubChem CID, molecular formula, sequence, termini, salt stoichiometry, or a public COA. Identity below is taken only from opened public registries and from primary papers that name thymosin alpha-1 / thymalfasin.

01 ClassificationSynthetic N-acetyl 28-mer (INN thymalfasin)Opened PubChem / NCATS sequence Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN. Isolated historically from thymosin fraction 5; later prepared synthetically.

02 Reported sequenceAc-SDAAVDTSSEITTKDLKEKKEVVEEAENVerified on opened CID 16130571 and opened NCATS protein subunit. Goldstein 1977 (PMID 265536) established the 28-residue identity. Confirm the vial by sequence, N-acetyl, and assay.

03 Evidence profileHuman clinical evidence; context-specificSRP index tag. A large trial footprint exists under thymalfasin / thymosin alpha-1 (CT.gov intervention search totalCount 63 this session). That footprint does not convert a research-market 10 mg vial into Zadaxin or into an FDA-approved drug.

04 Regulatory statusInvestigational in the United StatesNCATS: not FDA-approved; Possibly Marketed Outside US. openFDA Drugs@FDA 404. IUPHAR ligand 404. ATC code L03AX25 exists as a WHO classification, not as a U.S. approval.

SRP listingThymosin Alpha-1 (10 mg Vial)$95.00; Immune / Longevity Research; Also Known As TA-1, Thymalfasin. product/thymosin-alpha-1-10-mg-vial.

PubChem CID16130571Title: Thymalfasin. Formula C129H215N33O55. MW 3108.3. InChIKey NZVYCXVTEHPMHE-ZSUJOUNUSA-N. Opened 16 August 2026.

CAS (both printed)62304-98-7 and 69521-94-4Do not collapse. NIAID ChemDB annotates the first as cattle and the second as unspecified. Deprecated CAS 69440-99-9 is not used.

UNIIW0B22ISQ1COpened PubChem synonym and NCATS approvalID. Identifies the substance record, not an SRP lot.

ChEBI / ChEMBL / ATCCHEBI:135915 / CHEMBL2103979 / L03AX25ATC is classification only. ChEMBL Max Phase 3 on the opened PubChem block is not a U.S. approval.

DrugBank / DSSTox / NCI / RxCUIDB04900 / DTXSID80211374 / C1253 / 38221DB05021 (EMZ702) on the same PubChem page is a related string, not the SRP lot.

ClinicalTrials.govtotalCount 63query.intr=thymalfasin. Nine NCT IDs from the first page plus one NCATS-cited ID are listed below. Remaining IDs were not individually opened. Do not invent them.

Dedicated guide URLHTTP 404/research-compound-directory/thymosin-alpha-1-research-guide/ on 16 August 2026.

Critical identity point: CID 16130571 / UNII W0B22ISQ1C is the N-acetyl 28-mer with C-terminal Asn-OH. Thymosin beta-4 is a different, much larger peptide (CID 45382195, C212H350N56O78S, MW 4963). Marketplace TB-500 resolved to CID 62707662 (title Unii-qhk6Z47gtg; C38H68N10O14; MW 889.0). An SRP Thymosin Alpha-1 10 mg lot is not automatically Zadaxin, not thymosin fraction 5, not thymosin beta-4, and not TB-500.

02 / Not analogues

How it relates to — and is not — thymosin beta-4 / TB-500, fraction 5, or Zadaxin

Catalog thymosin language does not convert a 28-residue N-acetyl peptide into thymosin beta-4, a TB-500 fragment, a bovine thymus extract, or a non-U.S. branded medicine.

Identity	What opened sources actually describe	Why it is not interchangeable
Thymosin alpha-1 / thymalfasin (this page)	Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN; 28 residues; CID 16130571; UNII W0B22ISQ1C	Yes — defined 28-mer. Isolated from thymosin fraction 5 (Goldstein 1977, {pm(265536)}); later synthetic thymalfasin.
Thymosin fraction 5	Mixed bovine thymus extract that contains several polypeptides, including alpha-1. PMID 265536: one of several present in thymosin fraction 5	Mixture, not a single sequence. Not an SRP 10 mg vial.
Thymosin beta-4	CID 45382195, title Thymosin Beta 4; C212H350N56O78S; MW 4963; InChIKey UGPMCIBIHRSCBV-UHFFFAOYSA-N; 0 defined / 47 undefined stereocenters on that record	Yes — different, longer peptide. Actin-binding / tissue-repair literature. Different molecule.
TB-500 (marketplace name)	PubChem name TB-500 resolved to CID 62707662, title Unii-qhk6Z47gtg, C38H68N10O14, MW 889.0, InChIKey ADKDNDYYIZUVCZ-ZQNQAVPYSA-N	Short peptide / fragment-scale record. Not thymosin alpha-1. Not used as TA-1 evidence.
Zadaxin (brand)	PubChem / NCATS / ChEBI synonym for thymalfasin. NCATS: SciClone / non-U.S. marketing; not FDA-approved	A different, regulated-or-regional product context. Not the SRP lyophilized research vial.

Goldstein et al. 1977 (PMID 265536; PMC392366; DOI 10.1073/pnas.74.2.725), opened abstract: thymosin alpha1 is a heat stable, highly acidic molecule composed of 28 amino acid residues isolated from calf thymus; one of several present in thymosin fraction 5. That nomenclature is why alpha-1 and beta-4 are different family members, not synonyms.

03 / Overview

What is Thymosin Alpha-1?

Thymosin alpha-1 is the N-acetylated 28-residue peptide later given the INN thymalfasin. Opened sources support four identity and research-context points — and stop short of treatment claims:

Chemical identity is unusually well documented compared with most research-market peptides: CID 16130571, NCATS UNII W0B22ISQ1C, ChEBI 135915, and the 1977 isolation paper agree on a 28-residue N-acetyl peptide.
It is a defined fragment / synthetic analogue of a thymic peptide, not the mixed extract thymosin fraction 5, and not thymosin beta-4.
A large published and registered-trial literature exists under thymalfasin / Ta1, including dendritic-cell / TLR-pathway reviews (King & Tuthill 2016, PMID 27450734) and later narrative reviews (Dominari 2020, PMID 33362999). Those reviews discuss immune-cell signaling and, in the authors own language, possible clinical uses. This educational page does not adopt those use claims.
A branded non-U.S. product (Zadaxin) is attached to the same INN in opened databases. NCATS states it is not FDA-approved. The SRP 10 mg vial is research-use-only and is not that product.

PubChem DrugBank-sourced narrative (opened 16 August 2026) describes in-vitro T-cell / dendritic-cell / TLR language and also prints indication-style sentences. Those sentences are database republishing, not a COA, not an FDA label, and not copied here as instructions or as efficacy claims for an SRP vial.

The SRP index card already states the correct boundary: regulatory status, indication, and formulation must be checked by country; research material is not equivalent to a regulated medicine. Dedicated guide URL returned HTTP 404 on 16 August 2026.

Opened SRP product (16 August 2026): http://simpleresearchpeptides.com/product/thymosin-alpha-1-10-mg-vial/. Title Thymosin Alpha-1 (10 mg Vial). Category Immune / Longevity Research. Price $95.00. Also Known As: TA-1, Thymalfasin. For Research Use Only. Not for human or veterinary use. Sequence, N-acetyl, CAS, UNII, CID, and a public COA file were not printed.

04 / Mechanism

Proposed research mechanisms (not treatment claims)

Mechanistic themes reported in experimental and review literature — not confirmed clinical effects of an SRP vial, and not treatment claims.

Identity / source. Goldstein 1977 (PMID 265536): 28 residues; acidic; isolated from calf thymus fraction 5; proposed as one member of a named polypeptide family that also includes beta peptides. That is identity, not a modern receptor-panel.

Cell signaling (as reported). King & Tuthill 2016 (PMID 27450734), opened abstract: Ta1 acts through Toll-like receptors in both myeloid and plasmacytoid dendritic cells, leading to activation and stimulation of signaling pathways and initiation of production of immune-related cytokines. Authors are SciClone-affiliated on that record. PubChem DrugBank block (opened) similarly lists TLR2/TLR9, NF-kB, and T-cell-subset language as in-vitro / database statements.

Not shown in a paper or registry opened here: FDA approval of thymalfasin / Zadaxin / an SRP vial (NCATS: not FDA-approved; openFDA 404); equivalence of a 10 mg research lyophilized vial to any branded or trial formulation; a single, universally accepted receptor Ki table on IUPHAR (ligand lookup 404); identity collapse with thymosin beta-4 or TB-500.

Do not treat as Thymosin Alpha-1 evidence: TB-500 / thymosin beta-4 tissue-repair papers; thymosin fraction 5 mixture papers that do not isolate alpha-1; vendor immune-boosting copy; any sentence that tells a reader to use this vial for infection, cancer, vaccine response, or immune optimization.

Established chemistry

N-acetyl 28-mer

PMID 265536; CID 16130571; UNII W0B22ISQ1C. Identity, not a treatment claim.

Literature theme

TLR / dendritic-cell language

PMID 27450734 review. Not adopted as a use claim.

Not transferred

Trial footprint != vial

CT.gov totalCount 63. NCATS: not FDA-approved. SRP vial is not Zadaxin.

This page maps identity and the existence of a literature/trial footprint. It does not recommend, endorse, or describe immune treatment. A research product is not a regulated medicine.

05 / Research Map

Areas of investigation

Organized by experimental question rather than consumer benefit claims. Thymosin alpha-1 != thymosin beta-4 != TB-500 != fraction 5 != Zadaxin.

01 Identity

Analytical confirmation

Sequence, N-acetyl, length 28, salt, impurities, and distinction from beta-4 / TB-500 / fraction 5.

02 Immune-cell signaling models

In-vitro endpoints

Dendritic-cell TLR pathways, T-cell-subset markers, and cytokine readouts as reported in opened reviews. These are laboratory endpoints.

03 Registered-trial landscape

Existence only

CT.gov intervention search totalCount 63. This page lists only NCT IDs that appeared on an opened first page or on the opened NCATS record. Listing a trial is not an efficacy claim and is not a protocol.

04 Regulatory-status research

Country vs research-chemical

Country-by-country approval, brand vs research-chemical distinction, and the absence of a U.S. Drugs@FDA hit.

05 Evidence translation

The gap

Formulation differences, manufacturing controls, and the gap between a branded non-U.S. product, a trial product, and a research-market vial.

06 / Snapshot

Scientific evidence snapshot

Evidence tier	Current signal	Translation confidence	Status
Chemical identity	Strong: CID, UNII, ChEBI, 1977 isolation paper, NCATS sequence	High for the defined 28-mer	ESTABLISHED IDENTITY
Cell / pathway studies	Large historical in-vitro immune-cell literature, summarized in opened reviews	Model- and context-dependent	LITERATURE EXISTS
Human / registered trials	CT.gov intervention search totalCount 63; not FDA-approved	Trial existence != SRP-vial evidence	CONTEXT-SPECIFIC; NOT TRANSFERRED
Regulatory review	NCATS: not FDA-approved; openFDA 404; IUPHAR 404; ATC L03AX25 is classification only	U.S. research-use only for this vial	INVESTIGATIONAL (US)
Distinction from TB-4 / TB-500	Different CID, formula, length	Do not collapse	SEPARATE MOLECULES

Evidence boundary: This page maps identity and the existence of a literature/trial footprint. It does not recommend, endorse, or describe immune treatment. A research product is not a regulated medicine.

Research timeline (opened pages only)

1977

Isolation and 28-residue identity

Goldstein et al., PNAS: thymosin alpha1 isolated from calf thymus; 28 amino acids; fraction-5 family nomenclature (PMID 265536).

INN / registry era

Thymalfasin as the nonproprietary name

Opened PubChem / NCATS / ChEBI print INN/USAN thymalfasin, UNII W0B22ISQ1C, CID 16130571, ATC L03AX25. Exact INN-publication year was not independently opened as a WHO PDF this session.

2016

Opened mechanism review

King & Tuthill, Vitam Horm: TLR / dendritic-cell review; SciClone affiliation on the opened record (PMID 27450734). Treatment-utility sentences in that abstract are author claims, not adopted here.

2020

Opened narrative review

Dominari et al., World J Virol: literature review that discusses historical uses and hypothesizes further antiviral research (PMID 33362999). Not used as a treatment recommendation.

2026 (this pass)

SRP listing vs missing dedicated guide

SRP sells a 10 mg RUO vial and indexes an Evidence profile. Dedicated guide URL is HTTP 404. NCATS still: not FDA-approved. CT.gov intervention search totalCount 63.

Opened NCT IDs (first API page + NCATS citation only; not a complete 63-ID dump). Listing these IDs documents that a trial footprint exists. It is not an efficacy table and not a use protocol.

NCT	How opened	Notes
NCT06821100	CT.gov first page	RECRUITING PHASE1; title names Thymalfasin (Thymosin Alpha 1; Ta1)
NCT06829355	CT.gov first page	RECRUITING PHASE2; title names Thymalfasin
NCT07103408	CT.gov first page	NOT_YET_RECRUITING PHASE2
NCT00580450	CT.gov first page	UNKNOWN PHASE1/PHASE2; Thymosin Alfa 1
NCT01943617	CT.gov first page	COMPLETED PHASE4
NCT06139419	CT.gov first page	COMPLETED PHASE2; title names Thymosin a-1
NCT02366208	CT.gov first page	COMPLETED PHASE2; PEG-Ta1 combination title
NCT06552598	CT.gov first page	RECRUITING PHASE1; KD01 title — verify before citing as thymalfasin; listed only because it appeared on the same first page
NCT02473406	NCATS W0B22ISQ1C page	PHASE4 COMPLETED; acute necrotizing pancreatitis — cited on the opened NCATS record

07 / Studies

Selected published studies (opened records only)

Inclusion does not imply clinical validation. Reviews are not used as treatment protocols. No human dosing protocol appears here.

1977 primary identity

Isolation and sequence

28 residues; thymosin fraction 5 family. PMID 265536. PMC392366. DOI 10.1073/pnas.74.2.725.

2016 review

Opened mechanism review (not a treatment protocol)

TLR / dendritic-cell language; SciClone-affiliated authors. PMID 27450734. DOI 10.1016/bs.vh.2016.04.003.

2020 review

Opened narrative review (not a treatment protocol)

Historical-use discussion; authors hypothesize further antiviral research. PMID 33362999. PMC7747025. DOI 10.5501/wjv.v9.i5.67.

Registry identity

PubChem / NCATS / ChEBI

CID 16130571; NCATS UNII W0B22ISQ1C; ChEBI 135915 — opened 16 August 2026.

08 / Lab / RUO

Study design and handling (not human-use instructions)

Identity and documentation. Confirm the 28-residue N-acetyl sequence, distinguish the lot from thymosin beta-4 / TB-500 / fraction 5, and record salt form, purity, and endotoxin if the assay is cell-based.
Controls and replication. Use sequence-matched and length-matched controls. Do not treat a TB-500 or beta-4 reagent as a TA-1 control.
Cold-chain handling. Follow the product label, batch documentation, and laboratory SOPs. Do not copy consumer reconstitution charts.
Transparent reporting. Report the actual sequence, N-acetyl status, and salt. Do not write thymosin as if it named one molecule.

Simple Research Peptides (SRP) materials are for laboratory research only and are not for human or veterinary use, consumption, administration, diagnosis, treatment, or therapeutic application. This page does not claim immune, antiviral, or oncologic efficacy.

No human dosing protocol. No reconstitution scheme. Not FDA-approved. Not Zadaxin. Not TB-500. Research use only.

09 / FAQ

Frequently asked questions

Is Thymosin Alpha-1 / thymalfasin FDA-approved?

Not on any opened U.S. registry. NCATS: Thymalfasin is not approved by the FDA. openFDA Drugs@FDA thymalfasin returned HTTP 404. A non-U.S. brand (Zadaxin) is attached to the same INN in opened databases. The SRP vial is not that product.

Is this the same as TB-500 or thymosin beta-4?

No. Different length, formula, CID, and literature. Goldstein 1977 placed alpha and beta peptides in one family, not one structure. CID 45382195 is a thymosin-beta-4 record (C212H350N56O78S). PubChem name TB-500 resolved to a different, fragment-scale CID (CID 62707662).

What is the sequence?

Opened PubChem / NCATS: Ac-SDAAVDTSSEITTKDLKEKKEVVEEAEN (28 residues). SRP does not print it. Confirm the vial.

Which CAS number is correct?

Both 62304-98-7 and 69521-94-4 are printed on the opened PubChem page. This page does not invent a single official CAS. Deprecated 69440-99-9 is not used.

Does this page recommend immune treatment?

No. Research-use only. No immune-treatment, infection-treatment, cancer-treatment, or vaccine-adjuvant claim is made for the SRP material.

Did registered trials test thymalfasin?

A CT.gov intervention search returned totalCount 63. That is a trial-footprint count, not evidence that a research vial is effective or approved.

Is UNII W0B22ISQ1C real?

Yes, on opened PubChem and opened NCATS. It identifies the active-moiety / substance record, not an SRP lot.

Can SRP vials be used as a human dose substitute?

No. SRP listings are for laboratory research only and are not for human or animal use. This page does not provide reconstitution, administration, or dosing instructions.

10 / References

Sources actually opened for this draft

Only IDs that appeared on a page opened for this draft. Do not invent the other IDs inside the totalCount 63.

Goldstein AL, et al. Thymosin alpha1: isolation and sequence analysis of an immunologically active thymic polypeptide. Proc Natl Acad Sci USA. 1977;74(2):725-729. PMID 265536. PMC392366. DOI 10.1073/pnas.74.2.725.
King R, Tuthill C. Immune modulation with thymosin alpha 1 treatment. Vitam Horm. 2016;102:151-178. PMID 27450734. DOI 10.1016/bs.vh.2016.04.003. Review; not used as a treatment claim.
Dominari A, et al. Thymosin alpha 1: a comprehensive review of the literature. World J Virol. 2020;9(5):67-78. PMID 33362999. PMC7747025. DOI 10.5501/wjv.v9.i5.67. Review; not used as a treatment claim.
PubChem CID 16130571 (Thymalfasin; C129H215N33O55; InChIKey NZVYCXVTEHPMHE-ZSUJOUNUSA-N; UNII W0B22ISQ1C; CAS 62304-98-7 and 69521-94-4). Opened 16 August 2026.
NCATS Inxight UNII W0B22ISQ1C. Sequence SDAAVDTSSEITTKDLKEKKEVVEEAEN; not FDA-approved. Opened 16 August 2026.
ChEBI CHEBI:135915 (thymalfasin). Opened 16 August 2026.
PubChem CID 45382195 (Thymosin Beta 4; C212H350N56O78S; InChIKey UGPMCIBIHRSCBV-UHFFFAOYSA-N) — distinction only.
PubChem PUG name TB-500 → CID 62707662 (Unii-qhk6Z47gtg; C38H68N10O14) — distinction only.
ClinicalTrials.gov API v2 query.intr=thymalfasin — totalCount 63 (opened 16 August 2026).
openFDA Drugs@FDA thymalfasin — HTTP 404. IUPHAR ligand API thymalfasin — HTTP 404.
SRP product page (opened 16 August 2026): product/thymosin-alpha-1-10-mg-vial. Index: compound-research-guides. Dedicated guide URL HTTP 404.

Allowed PMID list: 265536; 27450734; 33362999. Opened NCT IDs: NCT06821100; NCT06829355; NCT07103408; NCT00580450; NCT01943617; NCT06139419; NCT02366208; NCT06552598; NCT02473406. PMC: PMC392366; PMC7747025. Registry: CID 16130571; UNII W0B22ISQ1C; CAS 62304-98-7 and 69521-94-4; deprecated CAS 69440-99-9 (do not use); InChIKey NZVYCXVTEHPMHE-ZSUJOUNUSA-N; ChEBI 135915; ChEMBL CHEMBL2103979; DTXSID80211374; ATC L03AX25; DrugBank DB04900; NCI C1253; RxCUI 38221. Distinction: CID 45382195 (thymosin beta-4); CID 62707662 (TB-500 name lookup).

Educational information only. Thymosin alpha-1 is the N-acetylated 28-residue peptide (INN thymalfasin; CID 16130571; UNII W0B22ISQ1C). Two CAS numbers are printed (62304-98-7 and 69521-94-4). It is not thymosin beta-4, not TB-500, not thymosin fraction 5, and not Zadaxin. NCATS: not FDA-approved. This page does not claim immune, antiviral, or oncologic efficacy. Laboratory research use only; not for human or animal use. Not medical advice. Not for human use. No human dosing protocol. Last source review: 16 August 2026 (America/Indianapolis). For laboratory research only. Not for human or veterinary use.