Endogenous dipeptide / noopept metabolite

Plain-language summaryIntrigue 60 / 100

Cycloprolylglycine (CPG) is a cyclic dipeptide your body produces naturally and stores in spinal fluid. It is the active metabolite of noopept; when you take noopept your body converts it to CPG, which does most of the work. Researchers study it on its own to understand brain mechanisms. Not stocked by Kodiac. This monograph is provided for research and educational reference.

Intrigue 0–100 blends mechanism novelty, evidence strength, and translational potential. Kodiac editorial, not peer-reviewed.

Our opinion on this compoundNiche research probe

48/100

Endogenous noopept metabolite with real probe value but thin, consortium-concentrated evidence

Look, CPG sits in an unusual position. It’s not a synthetic nootropic with an invented mechanism; it’s an endogenous cyclic dipeptide that shows up in human CSF and brain tissue, which immediately gives it biological legitimacy that most research peptides don’t have. The story here is that noopept, a compound with real but messy pharmacology, gets hydrolyzed in vivo, and what the body actually does with it is partly form CPG. So if you want to understand what noopept is actually doing at the receptor level, CPG is the probe that lets you ask that question cleanly, without the prodrug pharmacology confounding the read.

The mechanism overlaps substantially with noopept: BDNF and NGF upregulation, modulation of NMDA and AMPA receptor expression, some antioxidant activity, modest cholinergic facilitation. None of these are individually paradigm-shifting. Neurotrophin upregulation is a crowded mechanism space, and glutamate receptor modulation has been worked from every direction for decades. What’s interesting is the combination, and particularly the idea that an endogenous molecule is doing this at all. That raises a real question: is CPG part of a broader endogenous regulatory loop for synaptic plasticity? Thats a legitimate thing to want to know.

Here’s the problem though: the evidence base is thin and geographically concentrated. The foundational work comes from Voronina, Gudasheva, and collaborators at the Zakusov Institute, the same group that developed noopept. That’s not inherently disqualifying, they’re serious pharmacologists with peer-reviewed output, but independent replication of the CPG-specific findings is sparse. We’re largely in single-consortium territory, which is exactly where you have to be cautious about effect size inflation and publication bias. The rodent data is real, but the human-relevant story for CPG as a standalone is essentially absent. You can extrapolate cautiously from the noopept clinical literature, but that’s not the same thing.

What we actually like about CPG is the bench value proposition. If your lab is studying endogenous cyclic dipeptide signaling in the CNS, or running noopept mechanism work and want to separate prodrug effects from active metabolite effects, CPG is the compound you need. Thats a real use case, even if its narrow. The translational arrow is weak right now, there’s no serious human program for CPG as a standalone compound, but as a tool for investigators who already have a reason to care about this mechanism space, it earns a spot in a serious research library.

We see CPG as a legitimate niche probe with an interesting endogenous angle, modest but real mechanism, weak evidence base, and genuine utility for a small set of investigators. Don’t prioritize it unless noopept mechanism work or endogenous cyclic dipeptide biology is central to your program. If it is, it belongs on your list.

Novelty: 62
Mechanism promise: 58
In-category differentiation: 48
Evidence quality: 30
Translational signal: 25
Research bench value: 60

Rationale CPG earns points on novelty (endogenous CNS dipeptide recently characterized as an independent research entity) and bench probe value (isolates active-metabolite pharmacology from noopept prodrug effects), but the evidence base is heavily concentrated in the Gudasheva/Zakusov Institute group with minimal independent replication and essentially no human-specific efficacy data.

Endogenous dipeptide / noopept metabolite

An endogenous dipeptide present in mammalian CSF; the principal active metabolite of noopept and a research probe for endogenous nootropic mechanisms.

Abstract

Cycloprolylglycine (CPG; cyclic Pro-Gly dipeptide) is an endogenous cyclic dipeptide identified in human cerebrospinal fluid and brain tissue. The compound is the principal active metabolite of noopept (formed by enzymatic cyclization after the parent compound’s hydrolysis) and has been investigated as an independent research probe. Pharmacology overlaps with noopept: BDNF and NGF upregulation, antioxidant effects, modulation of NMDA and AMPA receptor expression, modest cholinergic facilitation. CPG itself is sold as a research peptide for investigators studying the noopept mechanism without the parent compound’s prodrug pharmacology. Pharmacokinetics: plasma half-life ~2 hours; oral bioavailability presumed adequate. Doses are not formally established; rodent doses scale to micrograms per kilogram.

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The full reference document covers compound identification, discovery and developmental history, mechanism of action, pharmacokinetics, sourcing and quality verification, and a curated reference list. Embedded inline below; download for offline reading.

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FOR RESEARCH USE ONLY. Not for medical, diagnostic, or therapeutic purposes. Not for human consumption. All information is provided for research and educational purposes only.

Tag: Endogenous dipeptide / noopept metabolite

Cycloprolylglycine (CPG)

Abstract

Read the full monograph