Gathering the record
Relay is organizing the evidence and source boundaries.
Endogenous 43-amino-acid actin-sequestering peptide
Thymosin beta-4 is a naturally occurring 43-amino-acid peptide involved in actin regulation. Several investigational formulations have reached human studies, but results are early, route- and condition-specific, and do not apply to the seven-amino-acid TB-500 fragment.
60-Second Overview
Start with what it is, why it matters, what research has shown, and what remains unknown. The science follows after the orientation.
Start here. These four answers explain why the compound matters before the page introduces the deeper science.
Thymosin beta-4 is a naturally occurring 43-amino-acid peptide involved in organizing actin, a structural protein inside cells. Several finished investigational formulations have reached early human studies.
Its repair-related biology led researchers to test intravenous, eye-drop, and cardiac programs. Each formulation asks a different question, so route and product identity are central to interpreting the evidence.
Short Phase 1 studies described pharmacokinetics and early tolerability. A nine-patient eye study reported signals in severe dry eye. In a 96-person heart-attack trial, the overall infarct-area comparison was not significant, although an earlier-treatment subgroup showed a signal.
Larger replication, durable clinical benefit, uncommon harms, and long-term safety remain unknown. Full-length thymosin beta-4 is not interchangeable with TB-500, a much shorter fragment, and one route cannot validate another.
The research depth, routes, studies, and primary sources below explain how Relay knows—and where the evidence stops.
Research context
Published research has investigated this compound using the following study designs.
These records explain what researchers did. They are not instructions, recommendations, or a transferable protocol.
A randomized controlled study investigated a recombinant full-length thymosin beta-4 product after reperfusion treatment for acute heart attack.
Reported study administration—not a recommendation.
Research at a glance
Evidence depth, confidence, and route context explain how Relay knows—not what anyone should do.
Controlled human studies exist for full-length synthetic or recombinant products, but they remain small, formulation-specific, and outcome-limited.
Research depth describes how large and mature the overall record is. It does not tell you whether the results were positive.
IV exposure and short-term tolerability are documented; clinical benefit remains preliminary, mixed, or confined to very small studies.
Confidence describes how reliable and consistent the conclusions are. It can be high for one outcome and low for another.
The strongest evidence type shows what the best-supported conclusions are actually based on.
Human findings are more directly relevant than animal or laboratory results, but they still apply only to the populations and outcomes studied.
Route-specific record
These are exposures used in cited research for a specific route and population—not an instruction for an individual.
Half-life describes how long it takes the measured amount in the body to fall by half. It is not a dosing recommendation.
Evidence can change by administration method. Findings from one route should not automatically be applied to another.
Evidence boundary: The overall 96-person infarct-area comparison was not significant; the positive signal depended on treatment timing and subgroup interpretation. This product and study do not establish systemic repair effects or any finding for the seven-amino-acid TB-500 fragment. Amounts shown describe cited research exposure—not a dosage recommendation.
Detailed evidence
Start with the strongest supported conclusion and its main uncertainty. Claim-level records below show how the evidence changes by question, population, route, formulation, and study design.
Multiple controlled studies exist, but each is limited: short Phase 1 IV safety studies, a nine-patient ophthalmic Phase 2 trial, and a 96-person STEMI trial with a timing-dependent subgroup result but no significant overall infarct-area difference.
This is the strongest supported conclusion in the current human evidence—not a summary of every claim made about the compound.
Which formulation-specific findings replicate in larger trials, long-term safety, whether any benefit generalizes beyond the studied route and condition, and how investigational products differ.
Keeping the main uncertainty visible prevents an early or promising finding from looking more settled than it is.
Questions people bring to the evidence
Research questions—not promises of benefit.
TB-500 contains only an N-acetylated seven-amino-acid segment from residues 17-23.
Human programs include short IV safety studies, a very small ophthalmic dry-eye trial, wound programs, and a 96-person recombinant-product cardiac trial.
Two early studies reported no dose-limiting toxicity or serious adverse events over short observation periods.
A nine-patient Phase 2 study reported improvements after 0.1% thymosin beta-4 eye drops.
A smaller infarct area was reported in the subgroup first treated within eight hours, while the overall 96-person comparison was not significant.
Its human evidence comes from research formulations and trial protocols rather than an approved label.
Mechanisms
Full-length thymosin beta-4 sequesters globular actin and has been studied in cell migration, wound repair, ophthalmic disease, and cardiac injury. Controlled human evidence spans short IV safety/PK studies, a very small topical-eye Phase 2 trial, and a 96-person recombinant-product STEMI trial whose overall infarct-area comparison was not significant.
A plausible mechanism can explain why a study was attempted. It does not prove that the compound improves a human outcome.
Studies
Study arms are reported for transparency. They describe what researchers did in a defined record and do not transfer across identities, routes, formulations, or populations.
A later trial phase can ask a more mature question, but it does not guarantee a positive result, regulatory approval, or relevance outside the studied population.
Randomized, double-blind, placebo-controlled trial after PCI for acute STEMI
Adults with acute ST-segment elevation myocardial infarction after reperfusion
The overall infarct-area difference was not significant. A reported subgroup first treated within eight hours after PCI showed a smaller infarcted area at 90 days.
Study administration: Protocol-defined recombinant human thymosin beta-4 or placebo after PCI
Limitations: The positive finding depended on treatment timing and subgroup interpretation, while the overall 96-person comparison was not significant. Replication is needed and the study is not evidence for TB-500.
Randomized, double-blind, placebo-controlled single- and multiple-ascending-dose study
Healthy Chinese volunteers
Reported adverse events were mild to moderate, with no dose-limiting toxicity or serious adverse events. Exposure increased with dose and no obvious accumulation was reported.
Study administration: Protocol-defined intravenous recombinant human thymosin beta-4 NL005 or placebo
Limitations: Short Phase 1 study in healthy volunteers. It does not establish clinical efficacy, long-term safety, non-IV use, or any result for TB-500.
Multicenter, randomized, double-masked, vehicle-controlled ophthalmic trial
Nine patients with severe dry eye, including graft-versus-host-associated disease
The small trial reported improvements in discomfort and corneal staining at several time points, including day 56.
Study administration: RGN-259 0.1% thymosin beta-4 eye drops or vehicle under the trial protocol
Limitations: Only nine patients and 18 eyes at two sites. This topical eye formulation does not establish systemic effects, injection benefits, or TB-500 activity.
Randomized, placebo-controlled, single- and multiple-ascending-dose study
Healthy volunteers in four cohorts
Adverse events were infrequent and mild or moderate, with no dose-limiting toxicities or serious adverse events reported during the short study. Exposure increased with dose.
Study administration: Protocol-defined intravenous synthetic full-length thymosin beta-4 or placebo
Limitations: Small, short safety and PK study in healthy volunteers. It did not test healing, recovery, or long-term benefit and is not evidence for TB-500.
Safety snapshot
Short intravenous studies support tolerability and pharmacokinetic characterization, not broad clinical benefit.
Controlled human evidenceSmall samples and short follow-up cannot resolve rare events, long-term safety, effectiveness, or other routes.
Open sourceThe current record does not support a reliable common-versus-uncommon frequency split.
Evidence boundaryUnder-detected or under-reported events must not be described as rare.
No source-qualified compound-specific warning or contraindication is encoded in the current record.
Evidence boundaryInvestigational; no FDA-approved thymosin beta-4 product was located. WADA prohibits thymosin beta-4 and its derivatives. Which formulation-specific findings replicate in larger trials, long-term safety, whether any benefit generalizes beyond the studied route and condition, and how investigational products differ.
The current record does not identify a reliable compound-specific pattern of events that caused study discontinuation.
Evidence boundaryThis is an evidence gap, not proof that discontinuations did not occur.
No compound-specific patient-facing urgent-action threshold is established in the current Relay record.
Evidence boundaryRelay does not infer emergency guidance from study discontinuations, mechanism, or incomplete adverse-event reporting.
Community
Built by the community
Every structured report adds useful context about research setup, outcomes, and unwanted effects as the community dataset grows.
Publicly anonymous by default. Your account keeps reports editable and helps reduce duplicate submissions.Sources
2026-07-21
2026-01-01
2025-12-31 · PMID 41229390 · NCT05485818 · DOI 10.1093/cvr/cvaf223
2021-08-02 · PMID 34346165 · DOI 10.1111/jcmm.16693
2015-05-01 · PMID 25826322 · NCT01393132 · DOI 10.1097/ICO.0000000000000379
2012-10-01 · PMID 23050815 · DOI 10.1111/j.1749-6632.2012.06717.x
2010-04-01 · PMID 20536472 · DOI 10.1111/j.1749-6632.2010.05474.x