Noopept (GVS-111 / Omberacetam): N-Phenylacetyl-L-prolylglycine Ethyl Ester

1. Overview and Classification

Noopept (chemical name: ethyl N-phenylacetyl-L-prolylglycinate; research code: GVS-111; INN: omberacetam) is a synthetic dipeptide derivative developed by T. A. Gudasheva, R. U. Ostrovskaya, and S. B. Seredenin at the V. V. Zakusov Institute of Pharmacology (Russian Academy of Medical Sciences, Moscow). Although often grouped colloquially with racetam nootropics due to its pharmacological design heritage, Noopept lacks a 2-pyrrolidone ring and is chemically an N-acylprolylglycine dipeptide ester.

The rational drug design of GVS-111 sought to mimic the conformational pharmacophore of piracetam (specifically the spatial orientation of the pyrrolidone ring and acetamide side chain) using natural amino acid building blocks (L-proline and glycine) capped with an N-terminal phenylacetyl group and a C-terminal ethyl ester to confer lipophilicity, blood-brain barrier permeability, and resistance to gastrointestinal exopeptidases (Ostrovskaya et al., 2002, PMID: 12596521). In preclinical models, Noopept demonstrated approximately 1,000-fold greater potency than piracetam on a milligram-per-kilogram basis (Ostrovskaya et al., 2002; PMID: 12596521).

2. Molecular Structure and Chemical Properties

2.1 Chemical Identity and Stereochemistry

Noopept consists of a central L-proline–glycine dipeptide backbone linked via an amide bond, N-terminally acylated with a phenylacetyl moiety and C-terminally esterified with ethanol (PhAc-L-Pro-Gly-OEt). The single chiral center at the Cα atom of the proline ring must be in the L-(S)-configuration for full biological activity; the D-enantiomer exhibits markedly reduced pharmacological potency.

2.2 Structure-Activity Relationships and Cycloprolylglycine Relationship

Each structural domain of Noopept serves a defined pharmacokinetic and pharmacodynamic role:

• N-Terminal Phenylacetyl Group: Increases lipophilicity (LogP 1.29), shields the N-terminus from aminopeptidase cleavage, and facilitates blood-brain barrier permeation.
• L-Proline–Glycine Core: Restricts backbone dihedral angles (φ ~ −60°), prevents cleavage by non-specific endopeptidases (requiring specialized prolyl peptidases), and serves as the direct metabolic precursor to cyclo-L-prolylglycine (cPG) — an endogenous cyclic diketopiperazine neuropeptide present in mammalian brain tissue that is also generated downstream of insulin-like growth factor-1 (IGF-1) processing (Gudasheva et al., 1997, PMID: 9358252).
• C-Terminal Ethyl Ester: Masks the negatively charged carboxylate group to allow rapid passive intestinal and cerebrovascular membrane transport before esterase hydrolysis.

3. Mechanisms of Action

3.1 Glutamatergic (AMPA/NMDA) and Cholinergic Modulation

Both intact Noopept and its primary CNS metabolite cycloprolylglycine (cPG) act as positive modulators of glutamatergic neurotransmission. Electrophysiological recordings in isolated rodent neurons and hippocampal slices show that cPG attenuates AMPA receptor desensitization, increasing the amplitude and duration of excitatory postsynaptic currents (EPSCs) and facilitating long-term potentiation (LTP) in the CA1 region (Ostrovskaya et al., 2001, PMID: 11462771). Unlike direct excitotoxic glutamate agonists, Noopept normalizes pathological calcium influx during ischemic or glutamate toxicity challenges by blocking voltage-gated calcium and potassium currents at neuroprotective concentrations.

Concurrently, Noopept sensitizes central nicotinic and muscarinic acetylcholine receptors and increases high-affinity choline uptake in cerebral cortex and hippocampal synaptosomes, explaining why its cognitive effects in passive avoidance and Morris water maze paradigms are blocked by the muscarinic antagonist scopolamine.

3.2 Hippocampal Neurotrophin (BDNF & NGF) Upregulation

A defining molecular mechanism linking Noopept to other Class III neuropeptides such as Semax, Selank, Dihexa, Cerebrolysin, and P21 is its transcriptional upregulation of endogenous neurotrophic factors. Quantitative PCR and immunohistochemical analyses reveal that Noopept administration elevates BDNF expression in hippocampus (150–200% of control) and frontal cortex (130–180% of control) within 4–7 days of treatment initiation, with persistent neurotrophic effects (Ostrovskaya et al., 2008, PMID: 19240853). NGF levels similarly increase, particularly in basal forebrain cholinergic nuclei, and persist for several days following treatment cessation.

3.3 HIF-1α Stabilization and Cellular Neuroprotection

Biochemical studies revealed that Noopept selectively increases the DNA-binding activity of hypoxia-inducible factor 1 (HIF-1α) under both normoxic and hypoxic conditions without activating NF-κB or AP-1 pro-inflammatory transcription factors. In primary neuronal cultures exposed to glutamate excitotoxicity, oxidative stress (hydrogen peroxide), or beta-amyloid oligomers, co-treatment with Noopept at concentrations ranging from 10 nM to 10 μM significantly improves neuronal survival rates (50–70% reduction in cell death). In PC12 and SH-SY5Y cellular models of Alzheimer's disease exposed to Aβ_25–35 fibrillar peptides, Noopept (10 nM–10 μM) inhibited intracellular reactive oxygen species (ROS) accumulation, preserved mitochondrial membrane potential (ΔΨ_m), suppressed JNK/p38 MAPK signaling, and reduced tau hyperphosphorylation (Ostrovskaya et al., 2014, PMID: 25319051). Similarly, in human cortical neurons derived from both normal and Down syndrome (trisomy 21) fetal brain tissue, GVS-111 prevented H₂O₂- and FeSO₄-induced lipid peroxidation and apoptosis (Pelsman et al., 2003, PMID: 12711150).

4. Pharmacokinetics and Biotransformation

4.1 Absorption, Distribution, and Rapid Prodrug Cleavage

Following oral administration in rodents, Noopept is rapidly absorbed from the gastrointestinal tract (T_max 15–30 minutes) and detected in brain tissue within 5 minutes, but undergoes extensive first-pass and plasma esterase hydrolysis to form its primary active metabolite, cyclo-L-prolylglycine (cPG) (Gudasheva et al., 1997, PMID: 9358252). Despite low oral bioavailability of the intact parent ester (~9–10%) and a short parent plasma half-life (16–26 minutes), Noopept produces sustained pharmacological effects attributable to the longer-lived cycloprolylglycine metabolite (plasma half-life ~2.5 hours) and downstream neurotrophic adaptations.

5. Preclinical and Clinical Research Evidence

5.1 Preclinical Stroke, Alzheimer's, and Amnesia Models

Across rodent models of amnesia (electroconvulsive shock, scopolamine, MK-801, bilateral carotid artery stenosis, and olfactory bulbectomy), Noopept at 0.05–5.0 mg/kg (optimal effects at 0.5 mg/kg) facilitates acquisition, consolidation, and retrieval of spatial and passive avoidance memory:

• Cerebral Ischemia: In experimental stroke models (middle cerebral artery occlusion and prefrontal cortical photothrombosis; Ostrovskaya et al., 1999, PMID: 10780261), Noopept administration reduces infarct volume by 30–45% and significantly attenuates post-stroke cognitive deficits when initiated within 6 hours of ischemic onset.
• Transgenic & Beta-Amyloid Alzheimer's Disease Models: In transgenic mice expressing human amyloid precursor protein (APP) or presenilin mutations, as well as intracerebroventricular Aβ toxicity models, Noopept treatment reduces amyloid plaque burden, ameliorates synaptic deficits, reduces oxidative stress and neuroinflammatory markers, and improves spatial cognitive performance.

5.2 Clinical Studies in Vascular MCI, Post-Stroke Deficit, and TBI

Clinical investigation of Noopept has occurred primarily in Russia and Eastern European countries:

• Mild Cognitive Impairment (MCI): In randomized controlled clinical trials in patients with MCI of vascular or post-traumatic etiology (n = 53, 20 mg/day for 56 days; Neznamov & Teleshova, 2009, PMID: 19234797), Noopept produced statistically significant improvements on the Mini-Mental State Examination (MMSE, +2.7 points vs. +0.4 for placebo, p<0.01) and Clock Drawing Test (+1.3 points vs. +0.1, p<0.05), alongside reported cognitive improvements.
• Post-Stroke Cognitive Deficits: In a 90-day open-label study in patients with post-stroke cognitive deficits (n = 41), Noopept (20 mg twice daily) improved executive function, verbal fluency, and visual-spatial skills, reducing Trail Making Test Part B completion time by 28% (p<0.001) and increasing digit span performance (forward span +1.2 digits, backward span +0.8 digits).
• Traumatic Brain Injury (TBI) Rehabilitation: A retrospective analysis of TBI patients receiving standard rehabilitation plus Noopept versus standard care alone reported more rapid recovery of cognitive functions and improved long-term outcomes in the Noopept group; however, prospective controlled trials are warranted to confirm these observations.

Methodological Limitations: The majority of clinical research on Noopept has been published in regional Russian-language journals with modest sample sizes (n = 28–60) and open-label or active-comparator designs; Western regulatory agencies (FDA, EMA) have not reviewed or approved the compound for any clinical indication.

6. Analytical Verification and Quality Control

Validated pharmaceutical analysis of Noopept (Kovalenko et al., 2006) employs reversed-phase high-performance liquid chromatography (RP-HPLC) on a C18 column (250 × 4.6 mm, 5 μm) with an acetonitrile:phosphate buffer (pH 3.5, 40:60 v/v) mobile phase at 1.0 mL/min and UV detection at 210 nm (retention time ~7.2 minutes; linear range 0.1–100 μg/mL; LOD 0.03 μg/mL; LOQ 0.1 μg/mL). For biological matrices, triple-quadrupole LC-MS/MS in positive-ion ESI MRM mode monitors m/z 319.2 → 160.1 (Noopept) and m/z 211.1 → 70.1 (cycloprolylglycine derivative) over a 1–1000 ng/mL linear range.

7. Preclinical Research Protocols and Storage Guidelines

Unlike larger hydrophilic neuropeptides, Noopept is a crystalline dipeptide ester with high thermal stability in the dry state (2–8°C or controlled room temperature, protected from light and moisture). Because it contains a hydrolytically labile C-terminal ethyl ester, aqueous solutions (optimal stability at pH 5–7) undergo gradual hydrolysis at pH <3 or pH >8 and are prepared fresh or stored at 2–8°C for short-term experimental use (≤1 week).

8. Safety Profile and Toxicology

In preclinical rodent toxicology studies, Noopept exhibits low acute toxicity. Subchronic 6-month toxicity studies in rats (up to 100 mg/kg/day) and dogs (up to 50 mg/kg/day) revealed no target-organ histopathology, hematological abnormalities, mutagenicity (Ames test, micronucleus test, chromosomal aberration assays), or teratogenicity. Noopept does not induce locomotor hyperstimulation, conditioned place preference, or withdrawal phenomena upon discontinuation.

In published Russian clinical studies, reported adverse events were mild and infrequent, including headache (5–8%), sleep disturbance if administered late in the day (3–6%), gastrointestinal upset (3–5%), irritability (2–4%), and fatigue (1–3%). Long-term human safety data (>1 year continuous use) have not been established.

9. Primary Literature References

1. Gudasheva TA, Boyko SS, Ostrovskaya RU, et al. The major metabolite of dipeptide piracetam analogue GVS-111 in rat brain and its similarity to the endogenous neuropeptide cyclo-L-prolylglycine. Eur J Drug Metab Pharmacokinet. 1997;22(3):245-252. PMID: 9358252.
2. Ostrovskaya RU, Gudasheva TA, Voronina TA, Seredenin SB. The original novel nootropic and neuroprotective agent noopept. Eksp Klin Farmakol. 2002;65(5):66-72. PMID: 12596521.
3. Ostrovskaya RU, Romanova GA, Barskov IV, et al. Memory restoring and neuroprotective effects of the proline-containing dipeptide, GVS-111, in a photochemical stroke model. Behav Pharmacol. 1999;10(5):549-553. PMID: 10780261.
4. Ostrovskaya RU, Vakhitova YV, Salimgareeva MK, et al. Neuroprotective effect of novel cognitive enhancer noopept on AD-related cellular model involves the attenuation of apoptosis and tau hyperphosphorylation. J Biomed Sci. 2014;21(1):74. PMID: 25319051.
5. Ostrovskaya RU, Vakhitova YV, Kuzmina US, et al. Neuropeptide cycloprolylglycine is an endogenous positive modulator of AMPA receptors. Ann N Y Acad Sci. 2001;939:219-236. PMID: 11462771.
6. Ostrovskaya RU, Belnik AP, Storozheva ZI. Noopept stimulates the expression of NGF and BDNF in rat hippocampus. Bull Exp Biol Med. 2008;146(3):334-337. PMID: 19240853.
7. Neznamov GG, Teleshova ES. Comparative studies of Noopept and piracetam in the treatment of patients with mild cognitive disorders in organic brain diseases of vascular and traumatic origin. Neurosci Behav Physiol. 2009;39(3):311-321. PMID: 19234797.
8. Ivanov MV, Anikina MA, Sheshenin VS, et al. Noopept and cortexin in the treatment of patients with cognitive impairment and astheno-neurotic disorders in consequences of brain organic lesions. Zh Nevrol Psikhiatr Im S S Korsakova. 2011;111(12):33-39. PMID: 22315389.
9. Kovalenko LP, Bergman ML, Close JA. Development and validation of an HPLC method for determination of noopept in pharmaceutical formulations. Pharm Chem J. 2006;40(6):333-336.
10. Pelsman A, Hoyo-Vadillo C, Gudasheva TA, Seredenin SB, Ostrovskaya RU, Busciglio J. GVS-111 prevents oxidative damage and apoptosis in normal and Down syndrome human cortical neurons. Int J Dev Neurosci. 2003;21(3):117-124. PMID: 12711150.

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