TB-500 + PE-22-28
Tissue Repair, Regenerative Biology & Neurological Signaling Research
PRECLINICAL / LIMITED DIRECT HUMAN EVIDENCE
PRECLINICAL ONLY
NOT ESTABLISHED
What Is TB-500 + PE-22-28?
TB-500 is the common name used for a synthetic seven-amino-acid fragment related to thymosin beta-4. FDA describes TB-500 free base as an N-terminally acetylated fragment corresponding to amino acids 17–23 of thymosin beta-4. FDA also warns that the common name “TB-500” has been applied to multiple forms and derivatives, making exact compound identity particularly important.
PE-22-28, sometimes described as a shortened spadin analog or “mini-spadin,” is a separate seven-amino-acid experimental peptide developed from the spadin/TREK-1 research program. It has primarily been investigated for its ability to influence the TREK-1 potassium channel, which is involved in neuronal excitability and has been studied as a potential target in mood-related research.
These peptides belong to very different research areas. TB-500 research centers largely on tissue repair, wound biology, angiogenesis and regeneration. PE-22-28 research centers largely on TREK-1 signaling, neurobiology, neurogenesis and antidepressant-like effects in animal models.
Important: TB-500 and PE-22-28 are two distinct experimental peptides being discussed together for educational purposes. They are not the same compound, they are not studied in the same research areas, and there is no established scientific evidence that combining them is safe or effective.
What The Research Suggests
TB-500 Is Not the Same Molecule as Full-Length Thymosin Beta-4
Much of the human research sometimes cited in discussions of TB-500 actually involved full-length thymosin beta-4, not the seven-amino-acid TB-500 fragment.
A 2026 scoping review found that most of the literature involved thymosin beta-4 rather than TB-500 specifically, and direct evidence involving musculoskeletal tissues was much more limited than online discussions often imply.
FDA's own 2026 review reported that it did not identify studies in which TB-500 itself had been administered to humans.
Tissue Repair & Regenerative Biology
The broader thymosin beta-4 research field provides a biological rationale for studying processes involving cell migration, actin regulation, angiogenesis, wound repair, tissue remodeling, inflammatory signaling, and regenerative biology.
The important limitation is that findings involving full-length thymosin beta-4 cannot simply be transferred to TB-500. The compounds are related, but they are not interchangeable evidence.
PE-22-28 — TREK-1 Channel Research
TREK-1 is a two-pore-domain potassium channel involved in regulation of neuronal electrical activity. Preclinical research has investigated whether blocking TREK-1 could influence pathways associated with mood and neuroplasticity.
PE-22-28 demonstrated greater TREK-1 inhibitory potency than its parent peptide spadin in the original laboratory experiments. In the principal 2017 study, PE-22-28 showed potent TREK-1 inhibition in laboratory cells and produced antidepressant-like behavioral effects in mice. Researchers also examined neurogenesis-related effects.
PE-22-28 — Animal Mood Research
Researchers reported antidepressant-like behavioral changes in mouse experiments involving PE-22-28. These experiments used animal behavioral models associated with antidepressant drug discovery.
That does not mean PE-22-28 has been shown to treat depression in people.
Evidence At A Glance
TB-500 — Tissue Repair Biology
There is substantial related research involving full-length thymosin beta-4, but much less direct evidence involving TB-500 itself.
TB-500 — Human Clinical Evidence
FDA reported no identified human administration studies of the TB-500 fragment in its 2026 evaluation.
PE-22-28 — TREK-1 & Neurological Research
Laboratory and mouse research supports biological activity at TREK-1, but clinical translation remains unknown.
PE-22-28 — Human Clinical Evidence
No registered or published human clinical trials were identified.
TB-500 + PE-22-28 Combination
We found no scientific research establishing the safety, effectiveness, or biological advantage of this specific combination.
Safety & Limitations
This combination presents an especially important evidence issue because uncertainties from two experimental compounds cannot simply be assumed to cancel each other out.
TB-500 has unresolved questions involving human safety, exact compound identity, peptide impurities and potential immunogenicity. FDA specifically notes that multiple substances have been marketed under the TB-500 name.
PE-22-28 has even less human information. Its published evidence remains preclinical, leaving human pharmacology, interactions and long-term effects unknown.
There also appears to be no scientific evidence evaluating interactions between TB-500 and PE-22-28. That should be considered a significant unknown, not evidence that combining them is harmless.
Regulatory Status
Neither TB-500 nor PE-22-28 has an FDA-approved therapeutic indication. Both remain experimental compounds discussed here for educational purposes only.
TB-500 — Under FDA Review
In July 2026, FDA's Pharmacy Compounding Advisory Committee considered TB-500 free base and TB-500 acetate for potential inclusion on the 503A Bulks List, with wound healing as the use evaluated by FDA.
On July 23, 2026, the independent Pharmacy Compounding Advisory Committee voted 8–6, with one abstention, to recommend TB-500 for inclusion on the 503A Bulks List. That recommendation was contrary to FDA staff's recommendation.
The committee vote is advisory. It is not FDA approval and does not itself place TB-500 on the 503A Bulks List. FDA still must make the regulatory determination through its applicable process.
PE-22-28 — Experimental / Preclinical
PE-22-28 remains an experimental research peptide. No FDA-approved drug containing PE-22-28, established FDA-approved indication, or human clinical evidence demonstrating safety or effectiveness was identified.
Unlike TB-500, PE-22-28 was not part of the July 2026 FDA peptide compounding advisory review. The FDA meeting addressed BPC-157, KPV, TB-500, MOTS-c, emideltide/DSIP, Semax and Epitalon.
Regulatory Status — TB-500: Under FDA Review. TB-500 is not FDA-approved. In July 2026, FDA's Pharmacy Compounding Advisory Committee recommended TB-500-related bulk substances for inclusion on the 503A Bulks List despite FDA staff recommending against inclusion. The advisory recommendation does not constitute FDA approval or final placement on the Bulks List. | Regulatory Status — PE-22-28: Experimental / Preclinical. PE-22-28 is not FDA-approved and has not been established as a treatment for depression, mood disorders, cognitive conditions, or other human medical uses. Published research remains preclinical.
Why These Two Peptides Should Not Share Evidence
This is an important educational distinction. Research supporting one of these compounds does not provide evidence for the other, and research on either compound individually does not establish the safety or effectiveness of combining them.
TB-500
Research focus: Tissue biology • wound repair • regeneration • angiogenesis. Related to thymosin beta-4, but the seven-amino-acid fragment is not the same molecule and the evidence is not interchangeable.
PE-22-28
Research focus: TREK-1 signaling • neurobiology • mood-related animal models • neuroplasticity. A separate experimental peptide with no established human clinical evidence.
Research & Publications
FDA — TB-500 2026 Scientific Review
U.S. Food and Drug Administration
FDA's official briefing materials evaluating TB-500 free base and TB-500 acetate for potential inclusion on the 503A Bulks List. FDA reviewed wound healing and raised concerns involving compound identity, evidence, safety and human exposure.
View FDA TB-500 ReviewFDA — July 2026 Pharmacy Compounding Advisory Committee
U.S. Food and Drug Administration
Official FDA meeting materials covering TB-500, BPC-157, KPV, MOTS-c and other peptide-related substances.
View FDA Meeting Materials2026 Scoping Review — Thymosin Beta-4 & TB-500
Applied Sciences — 2026
Reviews the scientific literature involving thymosin beta-4 and TB-500 in tissue healing, regeneration and musculoskeletal repair. One of its most useful features for this website is that it explicitly distinguishes full-length thymosin beta-4 evidence from TB-500 evidence.
Read the Scoping Review (DOI)Full Article — Applied Sciences
MDPI — 2026
The complete 2026 scoping review examining thymosin beta-4 and TB-500 evidence in tissue healing and musculoskeletal repair.
Read Full ArticleFDA — Potential Safety Concerns for TB-500
U.S. Food and Drug Administration
FDA discusses potential immunogenicity, aggregation, peptide impurities and the absence of identified human exposure data for TB-500 drug products.
View FDA Safety InformationPE-22-28 — Original 2017 Research
Frontiers in Pharmacology — 2017
The primary publication describing shortened spadin analogs, including PE-22-28, TREK-1 inhibition, improved experimental stability and antidepressant-like effects in mice.
View on PubMedPE-22-28 — Full Research Article
PubMed Central (PMC)
The complete 2017 article is available through PubMed Central.
Read Full Article on PMCTREK-1 in Health & Disease
Frontiers in Pharmacology — 2019
A broader review of TREK-1 biology and the development of spadin and related analogs, including PE-22-28.
Read Full ReviewTB-500 and PE-22-28 are two distinct experimental peptides being investigated in very different areas of biological research.
TB-500-related research focuses primarily on regenerative and tissue-repair biology, while PE-22-28 research focuses primarily on TREK-1 signaling and neurological pathways.
Human clinical evidence is extremely limited for TB-500 itself and absent for PE-22-28. No established scientific evidence was identified demonstrating that TB-500 and PE-22-28 are safer, more effective, or therapeutically advantageous when used together.
Neither peptide should be presented as an established treatment on this website. This page is provided for educational purposes only. TB-500 and PE-22-28 are not offered for sale, prescription, or distribution through this website.