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Not FDA approvedMostly animal or lab research

Plain-English fact sheet

Thymosin beta-4

Also known as Tβ4, TB4, full-length thymosin beta-4, TB-500 (fragment marketed online)

Recovery and tissue repairSkin and hair

Thymosin beta-4 and fragments marketed as TB-500 are not FDA-approved medicines, and evidence for popular recovery claims remains limited.

Quick answer

Thymosin beta-4 is a naturally occurring peptide involved in cell movement and tissue processes. Experimental full-length products and the TB-500 fragment marketed online should not be treated as proven or interchangeable therapies.

By the PeptideFactSheets Editorial Team. Use the source links to verify status, evidence, risks, and unknowns; our editorial policyexplains the boundaries. Clinician review appears only when a named reviewer is shown.

What is Thymosin beta-4?

Thymosin beta-4 is present in many tissues and has roles involving actin, cell movement, inflammation, and repair signaling.

TB-500 commonly refers to a shorter fragment marketed online. Evidence about full-length thymosin beta-4 cannot automatically be applied to that fragment or to an unverified product.

Why are people interested in it?

It is discussed for injury recovery, wound healing, heart repair, eye conditions, and athletic performance.

Much of the enthusiasm comes from mechanistic or preclinical research rather than proven clinical outcomes.

Current regulatory status

Not FDA approved

No thymosin beta-4 or TB-500 product is FDA approved for consumer recovery or performance uses. FDA has specifically described evidence gaps and potential risks for the thymosin beta-4 fragment used in compounding.

What is it approved for?

No FDA-approved use. This matters because clinical-trial participation and products marketed online are not the same as an approved medicine.

FDA approval path

Phase 3

Ophthalmic Phase 3 studies completed

RGN-259, a thymosin beta-4 ophthalmic product candidate, has completed Phase 3 dry-eye studies. No thymosin beta-4 or TB-500 product is FDA approved.

Step 5 of 7

  1. DiscoveryBasic research
  2. PreclinicalLab and animal work
  3. Phase 1Initial human testing
  4. Phase 2Condition-focused trials
  5. Phase 3Confirmatory trials
  6. FDA reviewApplication review
  7. ApprovedLabel-specific use

Timeline source basis

ClinicalTrials.gov: RGN-259 ARISE-2 dry eye studyClinicalTrials.gov: RGN-259 ARISE-3 dry eye studyFDA: bulk substances that may present significant safety risks

What is it being studied for?

Tissue and wound repair
Corneal healing
Cardiac repair
Inflammation
Cell migration

Investigational areas

  • Topical and systemic tissue-repair applications in research settings

Evidence snapshot

Mostly animal or lab research

There are early human studies in selected areas, but the broad recovery claims seen online are supported mainly by preclinical evidence.

Potential benefits being researched

  • Preclinical research suggests roles in cell migration, blood-vessel formation, and tissue repair.
  • Early studies do not establish a general injury-recovery or athletic-performance treatment.

Potential does not mean proven. Study design, population, endpoint, and regulatory review matter.

Known or possible risks

  • FDA notes potential immune reactions, aggregation, peptide impurities, and a lack of identified human exposure data for the TB-500 fragment in drug products.
  • Systemic effects and long-term consequences are insufficiently understood.
  • Online products add identity, purity, sterility, and labeling uncertainty.

What we still do not know

  • Whether effects in models translate into improved human recovery
  • How full-length thymosin beta-4 differs clinically from marketed fragments
  • Long-term safety and effects on abnormal blood-vessel or cell growth
  • Reliable dosing, product identity, and manufacturing quality—topics this site does not provide instructions for

Plain-English takeaway

Thymosin beta-4 is scientifically interesting, but online recovery claims run ahead of clinical proof. Full-length peptide, fragments, and marketed products are not automatically equivalent.

Research and reference links

Use these primary and reputable sources to verify status and read beyond this summary. Trial registries may list studies without proving a benefit.

  1. 1
    fdaFDA: bulk substances that may present significant safety risks

    FDA summaries of safety concerns and evidence gaps for selected bulk substances used in compounding.

  2. 2
    clinical trialsClinicalTrials.gov: RGN-259 ARISE-2 dry eye study

    Registry record for an ophthalmic thymosin beta-4-related study.

  3. 3
    clinical trialsClinicalTrials.gov: RGN-259 ARISE-3 dry eye study

    Registry record for an additional ophthalmic thymosin beta-4-related study.

  4. 4
    pubmedThymosin beta-4 and corneal inflammation review

    Peer-reviewed review discussing thymosin beta-4 in corneal wound healing and inflammation.