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Not FDA approved
This peptide is not FDA approved for human use, and because peptides are often incompletely studied you should not use or self-experiment with it outside qualified medical supervision.
Overview
Cyclic glycine-proline (cGP) is an endogenous cyclic dipeptide and an IGF-1 metabolite. The reviewed source set supports real mechanistic work showing that cGP can alter IGF-1 interaction with IGFBP-3, plus animal studies and a small set of human biomarker or nutrition-intervention papers.
What it does not support is a clinically established purified-cGP oral protocol or a broad approved therapeutic program.
Reported benefits
- Clear endogenous IGF-1-metabolite identity with a real mechanistic literature base.
- Published work supports IGFBP-3 / IGF-1 homeostasis as the main evidence-backed mechanism.
- Animal studies extend into stroke, developmental, obesity, and neural-cell contexts.
- Human evidence exists, but it is limited and often indirect rather than a purified-cGP drug program.
Mechanism of action
The strongest direct mechanism paper in the reviewed source set is the 2014 Scientific Reports study showing that cGP alters IGFBP-3 binding to IGF-1, which can change the balance between more and less bioavailable IGF-1. That supports an IGF-1-modulator framing.
It does not justify stacking on extra receptor claims like AMPA, GABA-A, or broad BDNF (a protein involved in brain cell growth and maintenance) effects unless those are tied to direct cGP data rather than downstream speculation or version programs.
Reported Use
No FDA dosing guidance
This peptide is not covered by FDA-labeled dosing guidance on this page. Peptides are often investigational or incompletely studied. Do not self-experiment; use only with a doctor or qualified clinician.
Typical dose
No validated purified-cGP consumer dose was identified in the reviewed source set
Frequency
Not established
Administration sites
One small human study used blackcurrant anthocyanin supplementation rather than purified cGP, and animal studies have used oral cGP; those are not the same as a validated supplement label
Best timing
Not established
Effects timeline
Not established as a reliable consumer expectation schedule
Storage
Follow product-specific handling only; do not treat generic supplement advice as proof of efficacy
Cycle length
Not established
Break between
Not established
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Quick Signals
At A Glance
A faster read on evidence, focus, structure, and status.
Evidence
Emerging human evidence
The reviewed source set includes direct IGFBP-3 / IGF-1 mechanism work, several animal studies, observational human bio…
22 indexed studiesCurrent level
Mixed human
Scale: low evidence to established use
Safety
Side Effects And Safety
Switch between common side-effect notes and stop criteria to keep safety context visible.
Key cautions
- Direct purified-cGP human safety data are limited.
- A small human study using blackcurrant anthocyanin supplementation did not create a broad safety signal, but that is not the same as a formal purified-cGP safety program.
- Oral supplement or food-derived products can still cause gastrointestinal intolerance, allergy, or ingredient-quality issues.
- Because cGP intersects with IGF-1 biology, endocrine or metabolic context still matters even if the molecule is endogenous.
- Do not treat natural or endogenous as meaning automatically safe in all settings.
Molecule
Molecular Information
Core structure fields that help explain what kind of peptide this is and how much sequence detail is available.
Molecular weight
154.17 Da
Chain length
2 amino acids (cyclic)
Sequence type
Cyclic dipeptide (2,5-diketopiperazine)
Derived from
Endogenous IGF-1 metabolite context
Amino acid sequence source string
cyclo(Gly-Pro)
Cyclized glycine-proline dipeptide ring
Context
Important Context
The main context that changes how confidently this peptide should be interpreted.
Research status
The reviewed source set includes direct IGFBP-3 / IGF-1 mechanism work, several animal studies, observational human biomarker papers in stroke and Parkinson disease, and a small blackcurrant anthocyanin intervention study rather than a broad purified-cGP therapeutic program.
Regulatory and sport status
FDA review shows it is not FDA approved. Source: openFDA drugsfda API. Sport review: Not specifically named by WADA; athlete-specific review advised.
Use extra caution if
- • No formal FDA-labeled contraindication set was identified; caution is mainly about product identity, oral tolerance, IGF-1-related biology, and anti-doping interpretation.
Route Notes
Route-Specific Notes
Only shown when the source material adds route-specific details beyond the quick-start guide.
Oral
- Administration: Human intervention evidence in the reviewed source set involves blackcurrant anthocyanin supplementation rather than purified cGP.
- Absorption: Oral relevance is suggested by animal work and a blackcurrant anthocyanin intervention, but direct purified-cGP human PK remains limited.
- Cycle: Not established.
- Additional: Animal studies include oral cGP, but that is not the same as a validated consumer-use supplement label.
Compare
How Well Documented Is It?
A quick five-point snapshot of how visible and well-documented this peptide is. Higher values mean more coverage or clearer status in that area, not better medical performance.
Research
How much published research coverage this peptide has in the linked sources, with an approval-context floor for clearly established drug products.
Source: PubMed
Regulatory
How clearly the approval or regulatory status is documented for this entry.
Source: openFDA drugsfda API
Sport
How clearly sports or competition status is documented in the linked review sources.
Source: 2026 WADA Prohibited List PDF
Breadth
How broadly this peptide appears across discussion topics and use-case groupings in the catalog.
Source: Curated site taxonomy
Sequence
How much structure or residue-sequence detail is available for this entry.
Source: Catalog seed
Protocols
Research Protocols
Common protocol-style rows shown in a consistent table layout so every peptide page is easy to compare.
| Goal | Dose | Route | Frequency |
|---|---|---|---|
| IGF-1 / IGFBP-3 mechanism studies | Model-specific | Cell, ex vivo, or animal systems | Study-specific |
| Human nutrition-intervention context | The reviewed human intervention study used blackcurrant anthocyanin supplementation rather than purified cGP | Oral | Study-specific |
Research
What It Has Been Studied For
Plain-language summaries of the main health areas where this peptide shows up in the linked research.
Stacking
What People Commonly Stack It With
A plain-language view of compounds that are commonly discussed alongside this peptide in the source material.
Practical
Preparation, Quality, And Expectations
Operational checklist blocks designed for quick scanning and repeatable page structure.
How to reconstitute
- •No reconstitution is needed for a finished oral product.
- •No validated injectable or compounded reconstitution protocol was identified for exact cGP.
- •Do not convert nutrition-study context into generic vial-mixing guidance.
Quality indicators
Good signs
- Exact cGP content is disclosed rather than implied.
- Analytical testing distinguishes purified cGP from blackcurrant extract or mixed dietary products.
- Source material and labeling are traceable.
Avoid
- Blackcurrant anthocyanin data being presented as if they prove a purified cGP protocol.
- Generic oral dose claims without a direct source trail.
- Vague supplement labeling or no analytical documentation.
- Marketing that implies settled anti-doping permissibility.
What to expect
No reliable purified-cGP consumer expectation timeline was established from the reviewed source set.
Human biomarker and nutrition-intervention papers should not be turned into a polished therapeutic timeline.
References
Research And Source List
Structured reference cards with source metadata and a direct link so users can inspect the original study/source.
Guan et al. 2014
Scientific Reports
Foundational mechanism paper supporting the IGFBP-3 / IGF-1 homeostasis claim.
Fan et al. 2019
Annals of Clinical and Translational Neurology
Human observational stroke paper; biomarker association, not an interventional therapy trial.
Fan et al. 2018
Nutrients
Small human nutrition-intervention study using blackcurrant anthocyanins rather than purified cGP.
Kaneko et al. 2022
Behavioural Brain Research
Oral animal study relevant to neurologic preclinical claims.
Murotomi et al. 2023
Journal of Cellular Physiology
Human neural-stem-cell paper, not a clinical efficacy trial.
Guan et al. 2023 review
Molecules
Review used to frame the broader literature while keeping mechanism and human-evidence limits clear.
PubChem compound record
Technical
Registry support for molecular identity.
2026 WADA Prohibited List PDF
WADA
Official anti-doping source used for athlete-status review.