Semax vs Cycloprolylglycine
Both are Russian-research-programme cognitive peptides, but they sit at very different points on the evidence-and-development spectrum. Semax is a registered Russian product (Vidal.ru) with an extensive post-stroke and cognitive-endpoint evidence base. Cycloprolylglycine (CPG) is the endogenous cyclic dipeptide that emerges from Noopept metabolism and serves primarily as the mechanistic bridge that explains Noopept's neurochemical effects.
At a glance
| Semax | Cycloprolylglycine | |
|---|---|---|
| Structural class | ACTH(4-10) heptapeptide analogue | Endogenous cyclic dipeptide |
| Primary route | Intranasal | Oral (as N-Phenylacetylprolylglycine ethyl ester → CPG metabolite) |
| Regulatory status (Russia) | Registered (Vidal.ru) — post-stroke, cognitive support | Not assessed as a separate product; parent Noopept is registered (Vidal.ru) |
| UK status | No emc entry found (checked 17 October 2026) | No emc entry found (checked 17 October 2026) |
| Primary mechanism | BDNF/NGF induction, enkephalinase inhibition, monoaminergic modulation | BDNF induction, anxiolytic-adjacent mechanisms |
| Clinical evidence base | Substantial Russian post-stroke and cognitive-endpoint trial body | Preclinical characterisation predominantly; positioned as Noopept's active metabolite |
| Evidence tier | B | C |
| Signature indication research angle | Post-stroke rehabilitation, ADHD-adjacent research, cognitive support | Endogenous cognitive modulation research, Noopept mechanism understanding |
Evidence-base positioning
Mature clinical compound versus endogenous metabolite
Semax's positioning in the cognitive-peptide research field is that of a mature clinical compound with the strongest single-peptide Russian evidence base for cognitive-endpoint indications. It is a registered Russian product (Vidal.ru) used in post-stroke rehabilitation, cognitive-support, and ADHD-adjacent indications. The evidence base includes multiple multicentre Russian post-stroke trials, cognitive-endpoint studies in healthy volunteer populations, and substantial mechanism-of-action characterisation.
Cycloprolylglycine (CPG) sits at a very different point on the same research spectrum. It was not assessed as a separate registered product for this article; it is the endogenous cyclic dipeptide that emerges when Noopept (a registered Russian product, per Vidal.ru) is metabolised in the body. The mechanism-of-action framing for Noopept treats CPG as the active metabolite responsible for a substantial fraction of the parent compound's cognitive effects, particularly the BDNF-induction and anxiolytic components.
This positioning has implications for how researchers interpret CPG data. Findings from CPG-specific preclinical work are simultaneously a characterisation of CPG's own pharmacology and a mechanism-of-action characterisation of Noopept. Semax findings, by contrast, stand alone as a characterisation of a discrete clinical compound.
Mechanism overlap and divergence
Where these peptides meet — and where they don't
Both compounds engage BDNF induction as a shared cognitive-plasticity mechanism-of-action angle. Semax's BDNF induction was characterised in the Dolotov laboratory work in the 2000s; CPG's BDNF-induction contribution has been characterised in the parallel Noopept mechanism-of-action literature. This shared angle provides research-tool complementarity for BDNF-mediated cognitive-plasticity research questions.
Beyond the shared BDNF angle, the mechanism-of-action framing diverges. Semax's monoaminergic modulation and enkephalinase inhibition provide additional research-tool angles unshared by CPG. CPG's endogenous cyclic-dipeptide nature and the metabolite-of-Noopept context provide distinct research-tool angles unshared by Semax.
Route-of-administration differences are substantial. Semax's licensed intranasal route provides direct nose-to-brain delivery bypassing peripheral metabolism. CPG's context as Noopept's metabolite means most CPG research applications use Noopept as the oral pro-drug, relying on the endogenous CPG production for cognitive-effect delivery.