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Peptide Science

Peptide Science

Structure and molecular mechanism for the peptides on the FDA’s July 2026 compounding-review list — each figure generated directly from the peptide’s amino-acid sequence, each mechanism tied to a primary citation.

Research use only
How peptides are built: the peptide bond
Residue i Residue i+1 …Cα C O peptide bond NH Cα… + H₂O released (condensation: –CO–NH– amide linkage)
Adjacent amino-acid residues are joined by a peptide (amide) bond (–CO–NH–) formed by condensation, releasing one water molecule per bond. An N-residue peptide contains N–1 such bonds.
BPC-157

Body Protection Compound-157 — a synthetic pentadecapeptide (partial sequence of a human gastric-juice protein).

Sequence (1-letter)
GEPPPGKPADDAGLV
Sequence (3-letter)
Gly–Glu–Pro–Pro–Pro–Gly–Lys–Pro–Ala–Asp–Asp–Ala–Gly–Leu–Val
Length
15 residues (pentadecapeptide)
Molecular formula
C₆₂H₉₈N₁₆O₂₂
Molecular weight
1419.6 g/mol
Origin / class
Partial sequence of a human gastric-juice protein
The amino-acid chain
Gly1Glu2Pro3Pro4Pro5Gly6Lys7Pro8Ala9Asp10Asp11Ala12Gly13Leu14Val15H₂N––COOH
nonpolarprolinepolaracidicbasic
The 15 residues of BPC-157. Note the three consecutive prolines (positions 3–5), which give the backbone an unusually rigid, protease-resistant kink.
Full chemical structure
BPC-157 structure
Two-dimensional structure generated directly from the published sequence. Formula C₆₂H₉₈N₁₆O₂₂, MW 1419.6.
What the research describes

Angiogenesis via the VEGFR2 pathway

Research reports that BPC-157 promotes the formation of new blood vessels (angiogenesis) in association with activation and up-regulation of vascular endothelial growth factor receptor 2 (VEGFR2), the principal receptor driving endothelial-cell growth and migration.[2]

Interaction with the nitric-oxide (NO) system

Reviews describe BPC-157 as an active modulator of the nitric-oxide system — the eNOS/NO signaling axis governing vascular tone and cytoprotection — proposed to underlie much of its reported cytoprotective activity.[1]

Cell migration via the FAK–paxillin pathway

In cultured tendon fibroblasts, BPC-157 has been reported to increase cell survival, outgrowth, and migration through the focal-adhesion-kinase (FAK)–paxillin signaling pathway that controls cell attachment and movement across the extracellular matrix.[3]

Growth-factor signaling & cytoprotection

Literature and patent reviews describe modulation of several growth-factor and receptor pathways and a broad cytoprotective/stress-response profile, alongside notable stability in gastric juice.[1][4]

Research status & open questions

The evidence base is predominantly preclinical (in-vitro and animal-model studies); large controlled human trials are lacking, and BPC-157 is not an FDA-approved drug. In July 2026 an FDA advisory committee (PCAC) recommended it be considered for pharmacy compounding — advisory, not yet rule. Reviewers also flag an open safety question: the same pro-angiogenic activity in its reported mechanism warrants careful study in the context of tumor biology.[5]

References
  1. Sikiric P, et al. Stable Gastric Pentadecapeptide BPC 157 and Wound Healing. Front Pharmacol. 2021;12:627533. doi:10.3389/fphar.2021.627533
  2. Hsieh MJ, Liu HT, Wang CN, et al. Therapeutic potential of pro-angiogenic BPC157 is associated with VEGFR2 activation and up-regulation. J Mol Med (Berl). 2017;95(3):323–333. doi:10.1007/s00109-016-1488-y
  3. Chang CH, Tsai WC, Lin MS, Hsu YH, Pang JS. The promoting effect of pentadecapeptide BPC 157 on tendon healing involves tendon outgrowth, cell survival, and cell migration. J Appl Physiol. 2011;110(3):774–780. doi:10.1152/japplphysiol.00945.2010
  4. Józwiak M, et al. Multifunctionality and Possible Medical Application of the BPC 157 Peptide. Pharmaceuticals (Basel). 2025;18(2):185. doi:10.3390/ph18020185
  5. Regeneration or Risk? A Narrative Review of BPC-157 for Musculoskeletal Healing. Curr Rev Musculoskelet Med. 2025. doi:10.1007/s12178-025-09990-7
TB-500

A synthetic peptide based on the actin-binding domain of thymosin β4.

Sequence (1-letter)
LKKTETQ
Sequence (3-letter)
Leu–Lys–Lys–Thr–Glu–Thr–Gln
Length
7 residues (actin-binding domain)
Molecular formula
C₃₆H₆₆N₁₀O₁₃
Molecular weight
847.0 g/mol
Origin / class
Synthetic actin-binding domain (LKKTETQ) of thymosin β4
The amino-acid chain
Leu1Lys2Lys3Thr4Glu5Thr6Gln7H₂N––COOH
nonpolarprolinepolaracidicbasic
The actin-binding heptapeptide LKKTETQ. The two adjacent lysines (positions 2–3) form the positively charged surface that contacts monomeric (G) actin.
Full chemical structure
TB-500 structure
Two-dimensional structure generated directly from the published sequence. Formula C₃₆H₆₆N₁₀O₁₃, MW 847.0.
What the research describes

G-actin sequestration

Thymosin β4 is the major intracellular G-actin–sequestering protein; the LKKTETQ motif on which TB-500 is based binds monomeric actin and regulates the pool available for filament assembly, influencing cytoskeletal remodeling.[1]

Cell migration & tissue repair

In wound-repair models, thymosin β4 is reported to promote endothelial and keratinocyte migration and angiogenesis — activities attributed to its actin-regulating, cell-motility role, and mapped in part to short active sequences including the actin-binding domain.[1][2]

Modulation of inflammatory signaling

Reviews describe additional reported activities of thymosin β4 and its fragments, including modulation of inflammatory signaling in injury models.[2]

Research status & open questions

The evidence base is predominantly preclinical (in-vitro and animal models of injury and wound repair); TB-500 is not an FDA-approved drug, and its exact composition varies by supplier (the actin-binding fragment versus full-length thymosin β4). In July 2026 an FDA advisory committee (PCAC) recommended it be considered for pharmacy compounding — an advisory recommendation, not yet rule.

References
  1. Goldstein AL, Hannappel E, Kleinman HK. Thymosin β4: actin-sequestering protein moonlights to repair injured tissues. Trends Mol Med. 2005;11(9):421–429. doi:10.1016/j.molmed.2005.07.004
  2. Sosne G, Qiu P, Goldstein AL, Wheater M. Biological activities of thymosin β4 defined by active sites in short peptide sequences. FASEB J. 2010;24(7):2144–2151. doi:10.1096/fj.09-142307
KPV

Lysine–Proline–Valine — the C-terminal tripeptide of α-melanocyte-stimulating hormone (α-MSH).

Sequence (1-letter)
KPV
Sequence (3-letter)
Lys–Pro–Val
Length
3 residues (tripeptide)
Molecular formula
C₁₆H₃₀N₄O₄
Molecular weight
342.4 g/mol
Origin / class
C-terminal tripeptide of α-MSH
The amino-acid chain
Lys1Pro2Val3H₂N––COOH
nonpolarprolinepolaracidicbasic
A three-residue peptide — lysine, proline, valine. Its small size allows uptake by peptide transporters, letting it act inside the cell.
Full chemical structure
KPV structure
Two-dimensional structure generated directly from the published sequence. Formula C₁₆H₃₀N₄O₄, MW 342.4.
What the research describes

NF-κB pathway inhibition

Research reports that KPV reduces pro-inflammatory signaling by interfering with the NF-κB pathway — the central transcriptional switch controlling inflammatory gene expression — after entering the cell.[1]

PepT1-mediated uptake

In intestinal epithelial and immune cells, KPV is reported to enter via the peptide transporter PepT1 and act intracellularly to downregulate inflammatory cytokines, a mechanism studied in models of intestinal inflammation.[1]

Melanocortin-derived activity

As an α-MSH fragment, KPV is described as retaining anti-inflammatory activity attributed to the parent hormone while lacking its pigmentary action.[2]

Research status & open questions

Reported activity is drawn from preclinical cell and animal studies (including models of intestinal inflammation); KPV is not an FDA-approved drug. It was among the six peptides an FDA advisory committee (PCAC) recommended for compounding consideration in July 2026 — an advisory recommendation, not yet rule.

References
  1. Dalmasso G, Charrier-Hisamuddin L, Nguyen HTT, Yan Y, Sitaraman S, Merlin D. PepT1-mediated tripeptide KPV uptake reduces intestinal inflammation. Gastroenterology. 2008;134(1):166–178. doi:10.1053/j.gastro.2007.10.026
  2. Brzoska T, Luger TA, Maaser C, Abels C, Böhm M. α-Melanocyte-stimulating hormone and related tripeptides: biochemistry, antiinflammatory and protective effects in vitro and in vivo. Endocr Rev. 2008;29(5):581–602. doi:10.1210/er.2007-0027
MOTS-c

A mitochondrial-derived peptide encoded within the mitochondrial 12S rRNA.

Sequence (1-letter)
MRWQEMGYIFYPRKLR
Sequence (3-letter)
Met–Arg–Trp–Gln–Glu–Met–Gly–Tyr–Ile–Phe–Tyr–Pro–Arg–Lys–Leu–Arg
Length
16 residues (mitochondrial-derived)
Molecular formula
C₁₀₁H₁₅₂N₂₈O₂₂S₂
Molecular weight
2174.6 g/mol
Origin / class
Mitochondrial-derived peptide (encoded in 12S rRNA)
The amino-acid chain
Met1Arg2Trp3Gln4Glu5Met6Gly7Tyr8Ile9Phe10Tyr11Pro12Arg13Lys14Leu15Arg16H₂N––COOH
nonpolarprolinepolaracidicbasic
Sixteen residues encoded inside the mitochondrial genome — one of the few peptides written in mitochondrial rather than nuclear DNA.
Full chemical structure
MOTS-c structure
Two-dimensional structure generated directly from the published sequence. Formula C₁₀₁H₁₅₂N₂₈O₂₂S₂, MW 2174.6.
What the research describes

AMPK activation

MOTS-c is reported to activate AMP-activated protein kinase (AMPK), the cell’s central energy sensor, promoting glucose uptake and metabolic homeostasis in preclinical models.[1]

Nuclear translocation & stress-response genes

Under metabolic stress, MOTS-c has been reported to translocate to the nucleus and, with transcription factors such as NRF2, regulate antioxidant and stress-response gene programs — a rare case of a mitochondrial-encoded peptide acting on nuclear DNA.[2]

Metabolic / exercise-associated signaling

It is described in the literature as an exercise-associated metabolic signal, linked to the folate–methionine and AMPK pathways.[1]

Research status & open questions

Findings are predominantly preclinical (cell and rodent metabolic models); MOTS-c is not an FDA-approved drug. It was among the six peptides an FDA advisory committee (PCAC) recommended for compounding consideration in July 2026 — an advisory recommendation, not yet rule.

References
  1. Lee C, Zeng J, Drew BG, et al. The mitochondrial-derived peptide MOTS-c promotes metabolic homeostasis and reduces obesity and insulin resistance. Cell Metab. 2015;21(3):443–454. doi:10.1016/j.cmet.2015.02.009
  2. Kim KH, Son JM, Benayoun BA, Lee C. The mitochondrial-encoded peptide MOTS-c translocates to the nucleus to regulate nuclear gene expression in response to metabolic stress. Cell Metab. 2018;28(3):516–524. doi:10.1016/j.cmet.2018.06.008
Epitalon

Alanine–Glutamate–Aspartate–Glycine — a synthetic analog of the pineal peptide epithalamin.

Sequence (1-letter)
AEDG
Sequence (3-letter)
Ala–Glu–Asp–Gly
Length
4 residues (tetrapeptide)
Molecular formula
C₁₄H₂₂N₄O₉
Molecular weight
390.3 g/mol
Origin / class
Synthetic pineal tetrapeptide (Ala-Glu-Asp-Gly)
The amino-acid chain
Ala1Glu2Asp3Gly4H₂N––COOH
nonpolarprolinepolaracidicbasic
Four residues — alanine, glutamate, aspartate, glycine — among the shortest bioactive “regulatory” peptides studied.
Full chemical structure
Epitalon structure
Two-dimensional structure generated directly from the published sequence. Formula C₁₄H₂₂N₄O₉, MW 390.3.
What the research describes

Telomerase induction

Research from Khavinson and colleagues reports that Epitalon can induce telomerase activity and telomere elongation in cultured human somatic cells.[1]

Gene-expression / pineal signaling

It is described as a short regulatory peptide proposed to interact with DNA and modulate expression of specific genes, and is studied in the context of pineal and melatonin signaling.[2]

Research status & open questions

The evidence base is limited and largely originates from a single research group (Khavinson and colleagues); independent replication is sparse, and Epitalon is not an FDA-approved drug. It was among the six peptides an FDA advisory committee (PCAC) recommended for compounding consideration in July 2026 — an advisory recommendation, not yet rule. Claims in this area should be read with appropriate caution.

References
  1. Khavinson VKh, Bondarev IE, Butyugov AA. Epithalon peptide induces telomerase activity and telomere elongation in human somatic cells. Bull Exp Biol Med. 2003;135(6):590–592. doi:10.1023/A:1025493705728
  2. Overview of Epitalon — Highly Bioactive Pineal Tetrapeptide with Promising Properties (review). PubMed PMID 40141333.
Semax

A synthetic analog of the ACTH(4–10) fragment, with a C-terminal Pro-Gly-Pro extension.

Sequence (1-letter)
MEHFPGP
Sequence (3-letter)
Met–Glu–His–Phe–Pro–Gly–Pro
Length
7 residues (heptapeptide)
Molecular formula
C₃₇H₅₁N₉O₁₀S
Molecular weight
813.9 g/mol
Origin / class
Synthetic ACTH(4–10) analog
The amino-acid chain
Met1Glu2His3Phe4Pro5Gly6Pro7H₂N––COOH
nonpolarprolinepolaracidicbasic
Seven residues; the C-terminal Pro-Gly-Pro (positions 5–7) protects the peptide from rapid breakdown by peptidases.
Full chemical structure
Semax structure
Two-dimensional structure generated directly from the published sequence. Formula C₃₇H₅₁N₉O₁₀S, MW 813.9.
What the research describes

BDNF / TrkB regulation

Research reports that Semax binds in the basal forebrain and increases levels of brain-derived neurotrophic factor (BDNF) and its receptor TrkB in the hippocampus — key regulators of neuronal survival and plasticity.[1][2]

Neurotrophic & neuromodulatory signaling

It is described as influencing neurotrophin systems and monoaminergic signaling, and as being enzymatically stabilized by its C-terminal Pro-Gly-Pro against rapid peptidase degradation.[1]

Research status & open questions

Reported activity comes largely from preclinical studies; Semax is registered as a medicine in Russia but is not an FDA-approved drug in the United States. It was among the six peptides an FDA advisory committee (PCAC) recommended for compounding consideration in July 2026 — an advisory recommendation, not yet rule.

References
  1. Dolotov OV, Karpenko EA, Inozemtseva LS, et al. Semax, an analog of ACTH(4-10) with cognitive effects, regulates BDNF and trkB expression in the rat hippocampus. Brain Res. 2006;1117(1):54–60. doi:10.1016/j.brainres.2006.07.108
  2. Dolotov OV, Karpenko EA, Seredenina TS, et al. Semax, an analogue of adrenocorticotropin (4-10), binds specifically and increases levels of BDNF protein in rat basal forebrain. J Neurochem. 2006;97(Suppl 1):82–86. doi:10.1111/j.1471-4159.2006.03658.x
Structure and chain figures were generated programmatically from each peptide’s published amino-acid sequence, so they are chemically accurate rather than artistic approximations. For research purposes only. Mechanisms are described as reported in the cited literature and do not constitute medical advice or any claim of effect in humans. This section will expand with more peptides and citations as research becomes available. © 2026 Synthalab.