Brain-protein-mimicking antidepressant peptide (GSB-106)
A lab-made peptide that mimics a brain growth protein (BDNF) to produce antidepressant and anxiety-reducing effects in animal studies; experimental, not yet an approved drug.
- Class
- BDNF mimetic dipeptide
- Status
- Not approved as a medicine in any major jurisdiction; research compound only
- Best-supported effect
- Antidepressant-like and anxiolytic activity in rodent behavioral models; neuroprotection in ischemia and neurodegeneration rodent models (preclinical)
- Main caveat
- No published completed human trial for any indication; almost all efficacy data comes from one research group at the Zakusov Institute with limited independent Western replication
A researcher, an agent, or an algorithm wrote down the sequence and picked a target to hit.
An AI model like OpenFold3 or AlphaFold built a 3D structure and scored how well it fits the binding site.
A second contributor repeated the computation on their own hardware and the scores matched.
A chemistry service or a researcher ordered the sequence, it was manufactured, and mass spectrometry confirmed the right molecule was produced.
A binding or activity measurement confirmed that it actually does what the computer predicted — or didn't.
Snapshot
Class: BDNF mimetic dipeptide
Evidence tier: Animal-only evidence
Status: Not approved as a medicine in any major jurisdiction; research compound only
Best-supported effect: Antidepressant-like and anxiolytic activity in rodent behavioral models; neuroprotection in ischemia and neurodegeneration rodent models (preclinical)
Main caveat: No published completed human trial for any indication; almost all efficacy data comes from one research group at the Zakusov Institute with limited independent Western replication
What this is
GSB-106 is a synthetic dimeric dipeptide designed to mimic the fourth beta-turn loop of brain-derived neurotrophic factor (BDNF) — the region of the full-length neurotrophin implicated in binding to the TrkB receptor. Its chemical structure is a bis-(N-monosuccinyl-L-seryl-L-methionine) hexamethylenediamide: two L-Ser–L-Met units linked through a hexamethylenediamine spacer via succinyl groups, forming a symmetric dimer. The dimerization is deliberate, reflecting the homodimeric geometry of native neurotrophins.
GSB-106 was designed and studied at the V.V. Zakusov Research Institute of Pharmacology in Moscow (Russian Academy of Medical Sciences) by the group of Tatiana A. Gudasheva and Sergey B. Seredenin. The design goal was a low-molecular-weight, orally active molecule that could engage TrkB and reproduce part of BDNF's neurotrophic signaling — something full-length BDNF (a 27 kDa protein that does not cross the blood-brain barrier after peripheral administration) cannot do as a systemic drug. GSB-106 is the BDNF-counterpart to GK-2, the same group's TrkA-targeting NGF-loop mimetic. It is a preclinical drug candidate, not an approved medicine, and it is not interchangeable with BDNF itself or with BDNF-upregulating interventions such as exercise, SSRIs, or ketamine.
Evidence map
| Evidence layer | Grade | What it supports |
|---|---|---|
| Human | None identified | No published completed human clinical trial for any indication found |
| Animal | Moderate | Antidepressant-like activity in forced-swim and tail-suspension tests; anxiolytic effects in open-field and elevated-plus-maze assays; neuroprotection in focal cerebral ischemia, Alzheimer's-type, and MPTP Parkinson's-type rodent models — published primarily by the Gudasheva and Seredenin group; independent Western replication is limited |
| In vitro | Moderate | TrkB activation and downstream PI3K/Akt, MAPK/ERK, and PLC-γ phosphorylation in cultured neurons at sub-micromolar concentrations; neuroprotection against glutamate excitotoxicity; protection from beta-amyloid-induced neuronal damage |
| Computational | None identified | No computational prediction data identified |
| Mechanism | Plausible | TrkB is a well-characterized receptor-tyrosine kinase; the loop-4 mimicry design rationale is rational; whether the small-molecule mimetic reproduces the full native BDNF-TrkB signaling signature in vivo remains unresolved |
A large share of the published efficacy evidence originates from the Gudasheva and Seredenin group at the Zakusov Institute. Independent replication by unaffiliated laboratories is limited and is a key constraint on interpreting the animal evidence base.
Claim check
| Claim | Verdict | Evidence layer | Confidence |
|---|---|---|---|
| Antidepressant-like activity in rodent behavioral models | Supported (animal) | Animal | Medium — single research program; limited independent replication |
| Anxiolytic-like activity in rodent models | Supported (animal) | Animal | Medium — same single-program caveat applies |
| Neuroprotection in ischemia and neurodegeneration rodent models | Supported (animal) | Animal | Medium — preclinical models; human translation not established |
| Human antidepressant or anxiolytic efficacy | Not established | Human | High confidence in absence — no completed human RCT found in available literature |
| Neuroprotection or cognitive benefit in humans | Not established | Human | High confidence in absence — no completed human trial found in available literature |
| TrkB agonism and downstream Akt/ERK activation | Supported (in vitro) | In vitro | Medium — reported in cultured neurons; in vivo receptor selectivity and signaling fidelity not fully confirmed |
| Oral bioavailability in humans | Not established | None | Low — oral activity reported in rodents; human pharmacokinetics uncharacterized in any peer-reviewed source |
Experimental exposure
This section reports exposure used in animal experiments. It does not establish human dosing.
| Context | System | Experimental exposure | Duration | Endpoint | Limitation |
|---|---|---|---|---|---|
| Rodent antidepressant models | Mice and rats (forced-swim test, tail-suspension test, chronic social defeat stress) | Oral administration; study-specific doses (low mg/kg range reported in preclinical publications) | Acute and sub-chronic dosing per individual study designs | Immobility duration; behavioral despair markers; stress-induced depressive-like behavior | Rodent behavioral despair assays translate imperfectly to human depression; no human pharmacokinetic data available |
| Rodent anxiolytic models | Mice and rats (open-field test, elevated-plus-maze) | Oral administration; study-specific doses | Per individual study designs | Open-field locomotion and anxiety markers; maze exploration behavior | No human translation established; same single-program caveat |
| Rodent neuroprotection models | Rats (focal cerebral ischemia — middle cerebral artery occlusion; Alzheimer's-type; MPTP Parkinson's-type) | Oral or experimental administration; study-specific doses | Per individual study designs | Infarct volume, neurological deficit, behavioral recovery, lesion markers | Preclinical models; species-to-human translation uncertain; no clinical safety data |
| In vitro neuroprotection | Cultured neurons | Sub-micromolar concentration range | Assay-specific timepoints | TrkB phosphorylation; Akt/ERK activation; protection from glutamate excitotoxicity and beta-amyloid-induced damage | Cell assay; does not establish in vivo exposure or systemic tolerability |
Preclinical safety signals
| Signal | System | Notes |
|---|---|---|
| Human adverse events | Not identified | No published human clinical trial; no human safety data identified |
| Chronic TrkB activation | Theoretical concern | Sustained TrkB activation has theoretical implications for cell proliferation and neurotrophin receptor desensitization; long-duration animal toxicology at clinically relevant exposures has not been characterized |
| Long-term rodent toxicology | Not extracted | available literature does not report formal toxicology studies; safety in chronic animal exposure is not established |
| Research-chemical sourcing | Product quality unknown | No pharmaceutical-grade formulation exists; research-chemical-channel identity and purity are unverified |
Regulatory status
| Region / body | Status | Notes |
|---|---|---|
| US | Not approved | Not FDA-approved for any indication; not a controlled substance; not a recognized dietary supplement ingredient under DSHEA; not a legitimate compounding ingredient; Per available sources, availability only through research-chemical channels not authorized for human use |
| EU / UK / Canada / Australia | Not approved | Per available sources, GSB-106 is not approved by EMA, MHRA, Health Canada, or TGA |
| Russia | Not identified as registered drug | Per available sources, the Gudasheva / Seredenin group at the Zakusov Institute has published extensively on preclinical pharmacology, but source does not identify GSB-106 as a registered medicine approved by Russia's Ministry of Health for marketing |
| WADA | per available sources S0 concern | GSB-106 is not currently named on the WADA Prohibited List per source; however, WADA S0 prohibits any substance not approved by any governmental regulatory health authority for human therapeutic use, which source states applies to GSB-106 in most jurisdictions; current list status not independently refreshed in this card |
Mechanism
GSB-106 is a symmetric dimeric dipeptide built to copy the bioactive conformation of the fourth beta-turn loop of BDNF — the loop implicated by crystallographic and mutagenesis work in direct contact with the TrkB receptor. Native neurotrophins are homodimers that engage their Trk receptors as dimers; the dimeric dipeptide architecture of GSB-106 attempts to recapitulate that receptor-engagement geometry at molecular weights compatible with oral bioavailability.
In preclinical work from the Gudasheva and Seredenin group, GSB-106 is reported to activate TrkB and its canonical downstream cascades in cultured neurons: PI3K/Akt (cell survival), MAPK/ERK (synaptic plasticity and neuronal growth), and PLC-γ. Reported downstream effects include restoration of hippocampal BDNF-related signaling markers after chronic stress, neuroprotection against glutamate excitotoxicity, reduction of beta-amyloid-induced neuronal damage in Alzheimer's-type models, and functional recovery in ischemic and MPTP Parkinson's-type rodent models.
The mechanistic rationale is coherent. TrkB is one of the better-characterized receptor-tyrosine-kinase systems in neuroscience. However, whether a small-molecule loop mimetic reproduces the full temporal and spatial pattern of native BDNF-TrkB signaling in vivo — including the specific receptor trafficking and sustained signaling dynamics that distinguish endogenous neurotrophin responses from synthetic ligand engagement — has not been resolved in the published literature identified.
Chemistry
| Field | Value |
|---|---|
| Full chemical name | Bis-(N-monosuccinyl-L-seryl-L-methionine) hexamethylenediamide |
| Abbreviation / code | GSB-106 |
| Type | Dimeric dipeptide mimetic |
| Monomer unit | N-succinyl-L-seryl-L-methionine |
| Linker | Hexamethylenediamine spacer |
| Topology | Symmetric dimer (linear backbone, non-cyclic) |
| Design basis | Fourth beta-turn loop of BDNF |
| Molecular weight | Not individually extracted from source |
| Formula | Not individually extracted from source |
| CAS | Not individually extracted from source |
| Sequence confidence | Not applicable (non-standard dipeptide conjugate; structural descriptor is the defining identifier) |
Open questions
- Human translation: No published completed randomized controlled trial has tested GSB-106 for depression, anxiety, stroke, Alzheimer's, or any other indication. Human efficacy is entirely unestablished. This is the most consequential gap in the evidence record.
- Human pharmacokinetics: Oral bioavailability, plasma exposure, CNS penetration, half-life, and metabolism in humans have not been characterized in any peer-reviewed source identified.
- Independent preclinical replication: The efficacy record comes almost entirely from the Gudasheva and Seredenin program at the Zakusov Institute. Independent reproduction of the antidepressant-like, anxiolytic, and neuroprotective findings by unaffiliated Western laboratories is limited and represents a critical weakness in interpreting the animal evidence.
- Signaling fidelity vs. native BDNF: Whether the small-molecule TrkB loop mimetic reproduces the full repertoire of native BDNF-TrkB signaling in vivo — including receptor trafficking, internalization dynamics, and sustained vs. transient signaling patterns — remains unresolved and has implications for which BDNF-associated effects should and should not be expected.
- Chronic TrkB-activation safety: Sustained TrkB agonism has theoretical implications for cell proliferation and receptor desensitization. Long-duration toxicology at doses relevant to proposed human exposure has not been characterized in any species.
- Comparative efficacy: GSB-106 has not been compared head-to-head with established antidepressants (SSRIs, SNRIs, ketamine) or with other BDNF-upregulating interventions (exercise, antidepressants) in any human context. Relative efficacy and safety relative to existing treatments are unknown.
- Product quality in non-pharmaceutical supply: Research-chemical-channel GSB-106 lacks the identity, purity, and chain-of-custody verification required to characterize the actual compound being used.
Research directions for this peptide, selected from the current sources — hypotheses you can explore and model. None of it is proven yet; tap any one to see the full thinking.
Does the symmetric double structure of GSB-106 allow it to grip both sides of the brain growth-factor receptor at once, and is that grip what makes it work?
If true, drug designers would know that any future antidepressant built on this template must be a mirror-image dimer, preventing years of wasted effort on simpler single-arm versions. This could accelerate development of oral antidepressants that mimic BDNF for people who do not respond to current medications.
Does GSB-106 trigger only one of several signals from the TrkB receptor, specifically the one linked to mood improvement, while leaving other pathways quiet?
If true, GSB-106 could offer the antidepressant benefits of boosting BDNF signaling without some of the risks of fully activating the receptor, such as abnormal memory effects. This would make it a safer candidate for long-term depression treatment.
Does GSB-106 activate brain survival signals strongly enough to protect neurons in the 1-3 day window after a stroke, when no approved drugs currently help?
If true, stroke patients who miss the narrow window for clot removal could still benefit from a neuroprotective pill or injection started within the first day or two. This could reduce disability for millions of people worldwide each year.
Would replacing the stiff 6-carbon spacer connecting GSB-106's two active arms with a more flexible chain allow the molecule to grip its brain receptor more effectively?
If the flexible-linker version is significantly more potent, it could work at much lower doses, reducing the amount of drug needed and potentially lowering the risk of side effects for patients. This kind of engineering insight can guide the design of an entire generation of improved BDNF-mimicking antidepressants.
Does GSB-106 also act on the p75NTR brain receptor, which is active in regions linked to treatment-resistant depression?
If GSB-106 activates p75NTR, it could help people whose TrkB receptors have been worn down by chronic stress, a group that often fails to respond to existing antidepressants. This would open a new patient group for this class of drugs.
▸3-letter notation
▸citationbibtex
@peptide{pep10958,
sequence = {HSFSDK},
target = {},
author = {peptidemodel},
year = {2026},
status = {designed}
}