Healing & Recovery

Thymosin Beta-4

TB4 · Tβ4 · Full-length thymosin beta-4

Thymosin β4 is the endogenous 43-amino-acid G-actin-sequestering peptide (CAS 77591-33-4, ~4963 Da). That is not TB-500. Commercial TB-500 is usually the 7-mer Ac-LKKTETQ. Human trial programs (ophthalmic, dermal, cardiac) used formulated 43-mer; several late-stage readouts missed primary endpoints. Research-chem vials labeled TB4 are often the fragment. Confirm the COA before you math a dose.

Not FDA-approved - research chemical

Reviewed by CalcMyPeptide Editorial Team

·Last updated: August 2026·Evidence: Moderate·1 peer-reviewed citation

Typical research dose

750-2000 mcg/day

Frequency

1× daily for 10-20 days

Half-life

Hours-class in some models; SKU PK unpublished. Do not print a 12–24 h fragment figure here.

Common vials

5 mg

CAS

77591-33-4

Molecular weight

4963.4 g/mol

Use-case scores

0–10 against the evidence we have, not a gym ranking. Hidden domains do not apply here.

Injury & tissue4.5/10
Parent protein has multi-lab animal repair models plus human programs in eye, skin, and heart. Haircut because several late-stage trials missed primary endpoints, and research-chem vials are often the 7-mer mislabeled.
Recovery & sleep3.5/10
Used in recovery conversations because of the parent’s repair story. Not a sleep peptide. Confirm the SKU before scoring a protocol.

Compound card

Sequence: 43-aa parent (Ac-SDKP…AGES). Not Ac-LKKTETQ.
Class: Endogenous G-actin-sequestering peptide (full-length Tβ4)
Formula: C212H350N56O78S
Status: Not FDA-approved · research use

Dose it

5 mg + 2 mL BAC water → 2.5 mg/mL · 750 mcg ≈ 30 units (U-100)

Open in calculator

How it works

Thymosin β4 is a conserved 43-amino-acid peptide and the main G-actin sequestering molecule in human cells. CAS 77591-33-4, about 4963 Da. That is not TB-500. TB-500 as sold is usually Ac-LKKTETQ (residues 17–23, ~889 Da).

The parent has the human trial record: topical/ophthalmic programs (RGN-259 and related), dermal, and cardiac. Several late-stage readouts missed primary endpoints. Actin biochemistry is solid. “It heals tendons in people at 2–5 mg twice weekly” is the fragment folklore, not a 43-mer label.

If the COA says 7 residues, you are on the TB-500 leaf.

Source: PMID: 20514133

Confirm 43 residues before you math a vial

Full Tβ4 is ~4963 Da, CAS 77591-33-4. TB-500 is Ac-LKKTETQ, ~889 Da, CAS 885340-08-9. Many bottles labeled “TB4” are the fragment. Use the TB-500 leaf if that is what you have.

Background & History

Thymosin β4 is the 43-aa G-actin-sequestering peptide (CAS 77591-33-4, ~4963 Da). TB-500 as sold is usually the 7-mer Ac-LKKTETQ, not a 17-aa fragment. Human trial programs used formulated 43-mer; several late-stage readouts missed primary endpoints. Research-chem “TB4” is often the fragment. Confirm the COA.

Research Use Cases

✓Full-length 43-mer identity (vs TB-500)
✓Not a 2–5 mg twice-weekly fragment calendar

Dosing

Phase	Dose	Frequency	Notes
Research 43-mer (if COA matches)	750–2000 mcg	Daily SubQ	Matches this leaf’s typical range. Not the TB-500 2–5 mg twice-weekly calendar.

Administration

Route / form

Subcutaneous injection from a reconstituted 43-mer vial. Abort if the COA is Ac-LKKTETQ.

Timing

No PK mandate. Daily research range is the typical 43-mer calendar, not twice-weekly fragment loading.

Empty stomach?

No - Food timing is not critical.

Timeline

Human programs (eye, skin, heart)

Those calendars belong to formulated 43-mer trials, not a research-chem loading week. Several late-stage readouts missed primary endpoints.

Research-chem 43-mer (if that is actually in the vial)

No honest consumer healing timeline. Do not copy TB-500 4–6 week folklore onto this leaf.

Who it is for

Need the parent molecule

Moderate

This is the 43-mer with the human trial record. Confirm CAS 77591-33-4.

Need the fragment SKU

Low

That is TB-500 (Ac-LKKTETQ). Do not dual-count.

Reconstitution

Vial	Water	Concentration	Example dose
5 mg (43-mer)	2.0 mL BAC	2.5 mg/mL	1 mg = 0.40 mL = 40 units. Abort if the COA is Ac-LKKTETQ.

Change vial size or water volume? Open the reconstitution calculator.

Safety & Considerations

Research compound in many jurisdictions. Do not use in individuals with active malignancy, as it promotes angiogenesis and cell migration (which could theoretically aid tumor metastasis).

Regulatory & Legal Status

FDA Status (US)

Research Only

WADA Status (2026)

Not Listed

Not currently on the WADA 2026 Prohibited List. Policies may change - verify before competition.

Classification

Research Chemical

US Compounding: Not eligible / not available

⚠️ This information is for educational purposes only and may not reflect the most current regulatory updates. Always verify with official FDA, WADA, and jurisdiction-specific sources before use.

Limits of current evidence

Human programs used full-length Tβ4 (or topical formulations), not Ac-LKKTETQ.
Several late-stage Tβ4 trials missed pre-specified primary endpoints. Do not advertise them as wins.
Community 2–5 mg twice-weekly calendars are fragment folklore. This leaf’s typical research range is 750–2000 mcg/day when the vial is actually 43-aa.

Verdict

This leaf is the 43-mer. TB-500 is the loop fragment. Human trials, such as they are, belong here. Research-chem loading calendars usually belong on the TB-500 page. Read the COA.

Interactions & Contraindications

Cell-migration and angiogenesis signaling is the theoretical caution in active malignancy. Research compound. No established drug-interaction file for gray-market 43-mer lots.

Synergies & Common Stacks

+ TB-500 →

Parent vs fragment. Do not dual-count. If the COA is Ac-LKKTETQ, use the TB-500 leaf.

+ BPC-157 →

Common pair. Complementary marketing (actin vs gastric 15-mer) is not a synergy RCT.

Frequently Asked Questions

Is thymosin β4 the same as TB-500?▼

No. This leaf is the 43-mer (CAS 77591-33-4, ~4963 Da). TB-500 as sold is usually Ac-LKKTETQ (CAS 885340-08-9, ~889 Da). Read the COA.

Does TB-500 have a longer half-life than Tβ4?▼

We do not print that. Fragment vs parent PK is not a sourced head-to-head we will treat as fact. See the TB-500 leaf for what is actually published (equine detection work, not a human t½ table).

Why is the research range 750–2000 mcg/day here?▼

That is this leaf’s typical 43-mer band. The 2–5 mg twice-weekly calendar is fragment folklore and lives on the TB-500 page.

How do I reconstitute a 5 mg 43-mer vial?▼

Add 2.0 mL bacteriostatic water for 2.5 mg/mL. A 1 mg dose is 0.40 mL (40 units on a U-100). If the COA is Ac-LKKTETQ, stop and use the TB-500 math instead.

Did human trials use this peptide?▼

Formulated full-length Tβ4 (and topical/ophthalmic programs) had human trials. Several late-stage readouts missed primary endpoints. Research-chem vials are often the 7-mer mislabeled.

Can I stack it with BPC-157?▼

People do. Complementary marketing (actin motility vs gastric 15-mer) is not a synergy RCT. Confirm you do not already have TB-500 in the other vial.

Is it FDA-approved?▼

No approved US drug for “heal my tendon.” Ophthalmic and cardiac programs were development paths, not a research-chem label.

What about cancer risk?▼

Cell-migration and angiogenesis signaling is the theoretical caution. Active malignancy is a reason to stay out. There is no human oncology indication either direction.

References

Goldstein AL et al. “"Thymosin beta4: actin-sequestering protein moonlights to repair injured tissues".” Trends in Molecular Medicine (2012). PMID: 22115354

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