Cyclic Glycine-Proline
cGPCyclo(Gly-Pro)cyclic glycyl-prolineEvidence
Preclinical
Typical vial
10 mg
Route
Oral
Status
United States
What it is
A naturally occurring metabolite of IGF-1 that appears to regulate how much IGF-1 is available, which is the opposite of supplying more of it.
Cyclic glycine-proline is what IGF-1 becomes. The growth factor is cleaved to a tripeptide, which cyclises into cGP, and that molecule circulates in blood and cerebrospinal fluid at measurable concentrations in everybody.
Its proposed role is regulatory rather than stimulatory, and that is the whole interest of it. cGP appears to modulate the binding between IGF-1 and its binding protein, changing how much IGF-1 is *available* rather than how much exists. Where IGF-1 LR3 is engineered to escape that regulation entirely, this is the molecule that does the regulating.
The human evidence is observational. cGP concentrations in blood and cerebrospinal fluid correlate with outcomes after stroke and with cognitive measures in older adults, in work largely from one New Zealand group. Correlation in a naturally occurring metabolite is a long way from a reason to inject it, and no trial has done so.
How it works
cGP is formed from the N-terminal tripeptide of IGF-1 and is present naturally in blood and cerebrospinal fluid.
It is proposed to normalise IGF-1 function by modulating its interaction with IGF binding protein 3: raising available IGF-1 when levels are low, reducing it when they are high. A regulator, not an agonist, if the model is right.
That framing is what makes it a different proposition from every other IGF-related compound. IGF-1 LR3 is designed to defeat binding protein regulation; this is claimed to restore it.
It also has documented neuroprotective activity in animal models of brain injury, which is consistent with the observational human findings without establishing them.
What it is studied for
Each entry states the evidence behind it. We do not rank indications by effectiveness — for most compounds here, that would be a claim nobody can support.
Stroke recovery and cognitive function
Published reviewWhere the human data is, and what kind it is.
EvidenceObservational: blood and cerebrospinal fluid concentrations correlate with recovery after stroke and with cognitive measures in older adults. No interventional trial has administered it.
Neuroprotection
Published reviewThe preclinical thread.
EvidenceDemonstrated in animal models of brain injury.
Regulatory status
Last reviewed 18 Aug 2026. Positions in this category change frequently, so we date the line.
Not approved as a medicine anywhere. It occurs naturally in the body and in some foods, and is sold as a supplement in some markets and as a research chemical elsewhere. No interventional human trial has been published.
Identity and clearance
What the molecule is, and how long a dose stays measurable.
Molecule
- Class
- Cyclic dipeptide; naturally occurring IGF-1 metabolite
- Molecular weight
- 154.2 Da
- Length
- 2 amino acids
Sequence
cyclo(Gly-Pro)
Occurs naturally in human blood and cerebrospinal fluid, and is also found in some foods.
Dose protocols reported in sources
Displayed for reference only. Every row says where it came from, and a trial protocol and a community convention are not the same kind of information. None of this is fed into the calculator, and none of it is a recommendation.
| Goal | Dose | Frequency | Route | Units, 10 mg vial | Source | Start this protocol |
|---|---|---|---|---|---|---|
| Commonly described community protocol | 10 mg – 50 mg | Once daily | OralUsually taken orally, which is unusual for something filed with peptides and reflects that it is a small, stable cyclic dipeptide, not a fragile chain. No trial establishes any dose. | from 100 u | Community practice | Start this |
The doses above in syringe units, for the vial you have:
Start this copies a row into a protocol of your own, which you can then edit. Where a source gave a dose range or an ambiguous frequency, those fields arrive empty — we will not pick a number on your behalf.
CheckRows marked community practice describe what people commonly do, drawn from public discussion. They are not derived from any trial and are not evidence that a dose is safe or effective.
Safety
Reported effects, the situations that need care, and the ones that mean stop.
Reported effects
- Effects of supplementing itCommunity practice
Unknown
No interventional human trial has been published, so no adverse event has been systematically recorded.
- Consequences of altering IGF-1 availabilityPublished review
Unknown
If the regulatory model is right, this changes how much IGF-1 is active. IGF-1 availability is associated with cancer risk in population studies, and nothing establishes which direction supplementation pushes it in a given person.
When to stop
- Any new lump, unexplained weight loss or unexplained persistent pain.
- Any allergic response: rash, hives, facial swelling or difficulty breathing. Seek urgent care.
- Any new neurological symptom.
Interactions and situations that need care
- Active or previous cancerAvoid
This is claimed to alter how much IGF-1 is biologically available, and IGF-1 availability is associated with risk for several cancers in population studies. A regulator that could move availability in either direction is not something to take blind in that setting.
- Pregnancy and breastfeedingAvoid
IGF-1 signalling is central to development, and no safety data exists.
- Reading the observational data as a treatment effectUse caution
The human findings are correlations between naturally occurring concentrations and outcomes. People who recover better may simply produce more of it. No trial has given it to anyone and measured what happened.
What to expect
What the sources describe over time, and how confident anyone can be about it.
HonestlyThere is no human efficacy data for this compound, so there is no evidence-based timeline to give. Any site publishing a week-by-week schedule of expected effects has invented it.
- The human data is observational. Concentrations correlating with outcomes, not a trial of giving it to people.
- The proposed role is regulating IGF-1 availability rather than adding to it, which makes it the conceptual opposite of IGF-1 LR3.
- It occurs naturally in your blood already, and in some foods.
- No interventional human trial has been published, so what supplementing it does is genuinely unknown.
Storage and combinations
How to keep it, and what it does and does not go with.
Storage and handling
- Freeze-dried powder
- Powder at room temperature, dry and out of light.
- After mixing
- Refrigerated if made into solution, and used within days.
With other peptides
- IGF-1 LR3caution
These point in opposite directions. IGF-1 LR3 is engineered specifically to escape binding protein regulation; cGP is claimed to restore it. Taking both means deliberately driving IGF-1 availability up while adding something that modulates it, with no data on either half of that combination.
Checking your vial
Research chemicals carry no manufacturing standard, so what the vial looks like is often the only quality signal available before you use it.
White cake, clear solution
Standard for a short peptide.
Collapsed cake or cloudy solution
Heat damage or degradation. Do not use it.
Vocabulary on this page
- Concentration
- How much peptide there is in each millilitre of solution, once the vial has been reconstituted.
- Stack
- Several separate compounds run at the same time, each in its own vial and on its own schedule.
- Peptide
- A short chain of amino acids: the same building blocks as a protein, in a chain short enough to behave differently.
- Protocol
- One compound, with a dose, a frequency and a length: the plan, as opposed to what was actually taken.
Questions
- Is this the same as taking IGF-1?
- Close to the opposite. IGF-1 LR3 supplies the growth factor in a form built to escape the body's control of it. cGP is proposed to work on that control itself, normalising availability instead of raising it.
- How good is the human evidence?
- It is observational. Concentrations of a naturally occurring metabolite correlate with recovery and cognition, mostly in work from one group. Nobody has run a trial giving it to people.
References
Everything on this page that came from a source, with the source.
Cyclic glycine-proline and IGF-1 bioavailability: observational human findings and animal neuroprotection
Neuroscience and metabolism literature, 2018 · Observational human studies with supporting animal work
Humans and rodents
Blood and cerebrospinal fluid cGP concentrations correlate with recovery after stroke and with cognitive measures in older adults. Animal models show neuroprotection. No interventional human trial has been published.
Commonly reported community protocols
BioAlmanac editorial summary of public community sources, 2026 · Not a study
Records dose and route patterns described in public discussion. Carries no evidential weight about safety or effect.
Cyclic Glycine-Proline compared with
Also compared with Semax, Cerebrolysin, Dihexa, N-Acetyl Semax Amidate, Adamax, Adalank.
Related compounds
IGF-1 LR3
A modified insulin-like growth factor engineered to last far longer in the body than the natural hormone. It can cause hypoglycaemia, which makes it the most acutely dangerous compound on this site.
Semax
A seven-amino-acid peptide developed in Russia and approved there for stroke and cognitive indications. It holds no approval elsewhere and is used nasally rather than injected.
Cerebrolysin
A pig-brain peptide preparation approved as a medicine in around forty countries. Decades of trials, and systematic reviews that still cannot find a clear benefit.
Dihexa
A small peptide reported as vastly more potent than BDNF at forming new synapses in animals. No human has been studied on it, and the potency is the concern, not the selling point.
Next
What to do with Cyclic Glycine-Proline
- Keep a record of itTurn a dose and a schedule into a protocol, then log what you actually take. Cyclic Glycine-Proline is filled in for you.
- See what it costsPer-milligram prices read from vendor sites and confirmed by a person, so vial sizes compare.
- Check a combinationWhat our profiles record about Cyclic Glycine-Proline alongside each other compound — including the pairs where nothing is recorded.
Keep this page honest
If something here is wrong, out of date, or missing a source, tell us and we will fix it and say that we did.
This page is educational. It describes what published research reports, not what you should do. Peptides discussed here are largely not approved for human use, and nothing on BioAlmanac is medical advice. No clinician reviews these pages.
Page last updated 18 Aug 2026