Section 103: Neurotrophic Factor Therapies in CBS/PSP

Section 103: Neurotrophic Factor Therapies in CBS/PSP

Introduction

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">Section 103: Neurotrophic Factor Therapies in CBS/PSP</th>
</tr>
<tr>
<td class="label">Factor</td>
<td>Primary Receptor</td>
</tr>
<tr>
<td class="label">BDNF</td>
<td>TrkB (Tropomyosin receptor kinase B)</td>
</tr>
<tr>
<td class="label">NGF</td>
<td>TrkA</td>
</tr>
<tr>
<td class="label">GDNF</td>
<td>GFRα1/RET</td>
</tr>
<tr>
<td class="label">CDNF</td>
<td>GFRα1/RET (and other)</td>
</tr>
<tr>
<td class="label">CNTF</td>
<td>CNTFRα/gp130/LIFR</td>
</tr>
<tr>
<td class="label">NGF</td>
<td>TrkA</td>
</tr>
<tr>
<td class="label">Exercise Type</td>
<td>BDNF Effect</td>
</tr>
<tr>
<td class="label">Moderate aerobic (150 min/week)</td>
<td>Significant increase in peripheral BDNF</td>
</tr>
<tr>
<td class="label">High-intensity interval</td>
<td>Greater acute increases, unknown long-term</td>
</tr>
<tr>
<td class="label">Resistance training</td>
<td>Moderate increases</td>
</tr>
<tr>
<td class="label">Combined aerobic + resistance</td>
<td>Synergistic effects</td>
</tr>
<tr>
<td class="label">Agent</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">7,8-DHF (7,8-dihydroxyflavone)</td>
<td>TrkB agonist</td>
</tr>
<tr>
<td class="label">BDNF-loop peptide mimics</td>
<td>TrkB binding</td>
</tr>
<tr>
<td class="label">Gene therap

Section 103: Neurotrophic Factor Therapies in CBS/PSP

Introduction

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">Section 103: Neurotrophic Factor Therapies in CBS/PSP</th>
</tr>
<tr>
<td class="label">Factor</td>
<td>Primary Receptor</td>
</tr>
<tr>
<td class="label">BDNF</td>
<td>TrkB (Tropomyosin receptor kinase B)</td>
</tr>
<tr>
<td class="label">NGF</td>
<td>TrkA</td>
</tr>
<tr>
<td class="label">GDNF</td>
<td>GFRα1/RET</td>
</tr>
<tr>
<td class="label">CDNF</td>
<td>GFRα1/RET (and other)</td>
</tr>
<tr>
<td class="label">CNTF</td>
<td>CNTFRα/gp130/LIFR</td>
</tr>
<tr>
<td class="label">NGF</td>
<td>TrkA</td>
</tr>
<tr>
<td class="label">Exercise Type</td>
<td>BDNF Effect</td>
</tr>
<tr>
<td class="label">Moderate aerobic (150 min/week)</td>
<td>Significant increase in peripheral BDNF</td>
</tr>
<tr>
<td class="label">High-intensity interval</td>
<td>Greater acute increases, unknown long-term</td>
</tr>
<tr>
<td class="label">Resistance training</td>
<td>Moderate increases</td>
</tr>
<tr>
<td class="label">Combined aerobic + resistance</td>
<td>Synergistic effects</td>
</tr>
<tr>
<td class="label">Agent</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">7,8-DHF (7,8-dihydroxyflavone)</td>
<td>TrkB agonist</td>
</tr>
<tr>
<td class="label">BDNF-loop peptide mimics</td>
<td>TrkB binding</td>
</tr>
<tr>
<td class="label">Gene therapy (AAV-BDNF)</td>
<td>Direct BDNF expression</td>
</tr>
<tr>
<td class="label">Intervention</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">Sertraline</td>
<td>Increases BDNF expression</td>
</tr>
<tr>
<td class="label">Mementine</td>
<td>TrkB modulation</td>
</tr>
<tr>
<td class="label">Statins</td>
<td>May increase BDNF</td>
</tr>
<tr>
<td class="label">Trial</td>
<td>Delivery Method</td>
</tr>
<tr>
<td class="label">Phase 1/2 (1990s)</td>
<td>Intraparenchymal infusion</td>
</tr>
<tr>
<td class="label">Phase 2 (2003)</td>
<td>Intraparenchymal infusion</td>
</tr>
<tr>
<td class="label">Phase 1 (2019)</td>
<td>AAV-GDNF (AAV2)</td>
</tr>
<tr>
<td class="label">Sprinto trial</td>
<td>Continuous infusion</td>
</tr>
<tr>
<td class="label">Evidence Domain</td>
<td>Score</td>
</tr>
<tr>
<td class="label">Mechanistic Clarity</td>
<td>6</td>
</tr>
<tr>
<td class="label">Clinical Evidence</td>
<td>2</td>
</tr>
<tr>
<td class="label">Preclinical Evidence</td>
<td>5</td>
</tr>
<tr>
<td class="label">Replication</td>
<td>2</td>
</tr>
<tr>
<td class="label">Effect Size</td>
<td>3</td>
</tr>
<tr>
<td class="label">Safety/Tolerability</td>
<td>3</td>
</tr>
<tr>
<td class="label">Biological Plausibility</td>
<td>5</td>
</tr>
<tr>
<td class="label">Actionability</td>
<td>2</td>
</tr>
<tr>
<td class="label">Ligand</td>
<td>Receptor</td>
</tr>
<tr>
<td class="label">GDNF</td>
<td>GFRα1/RET</td>
</tr>
<tr>
<td class="label">Neurturin</td>
<td>GFRα2/RET</td>
</tr>
<tr>
<td class="label">Persephin</td>
<td>GFRα4/RET</td>
</tr>
<tr>
<td class="label">Artemin</td>
<td>GFRα3/RET</td>
</tr>
<tr>
<td class="label">Trial</td>
<td>Phase</td>
</tr>
<tr>
<td class="label">PD trial</td>
<td>Phase 1-2</td>
</tr>
<tr>
<td class="label">PD trial</td>
<td>Phase 2</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Status</td>
</tr>
<tr>
<td class="label">Intracerebral implantation</td>
<td>Historical</td>
</tr>
<tr>
<td class="label">AAV-NGF (CERE-110)</td>
<td>Phase 2 (AD)</td>
</tr>
<tr>
<td class="label">Small molecule TrkA agonists</td>
<td>Research</td>
</tr>
<tr>
<td class="label">Agent</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">CNTF (recombinant)</td>
<td>Direct CNTF action</td>
</tr>
<tr>
<td class="label">AAV-CNTF</td>
<td>Gene therapy</td>
</tr>
<tr>
<td class="label">Peptide fragments</td>
<td>Truncated CNTF</td>
</tr>
<tr>
<td class="label">Factor</td>
<td>Primary Target</td>
</tr>
<tr>
<td class="label">IGF-1</td>
<td>Multiple neurons</td>
</tr>
<tr>
<td class="label">VEGF</td>
<td>Vascular, neurons</td>
</tr>
<tr>
<td class="label">GDNF</td>
<td>Dopaminergic, motor</td>
</tr>
<tr>
<td class="label">Persephin</td>
<td>Multiple CNS</td>
</tr>
<tr>
<td class="label">Factor</td>
<td>Trial Experience</td>
</tr>
<tr>
<td class="label">GDNF</td>
<td>Extensive</td>
</tr>
<tr>
<td class="label">NGF</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">BDNF</td>
<td>Limited</td>
</tr>
<tr>
<td class="label">Factor</td>
<td>Intranasal Feasibility</td>
</tr>
<tr>
<td class="label">BDNF</td>
<td>Good</td>
</tr>
<tr>
<td class="label">GDNF</td>
<td>Good</td>
</tr>
<tr>
<td class="label">NGF</td>
<td>Good</td>
</tr>
<tr>
<td class="label">CDNF</td>
<td>Unknown</td>
</tr>
<tr>
<td class="label">Vector</td>
<td>Capacity</td>
</tr>
<tr>
<td class="label">AAV2</td>
<td>~4.7 kb</td>
</tr>
<tr>
<td class="label">AAV9</td>
<td>~4.7 kb</td>
</tr>
<tr>
<td class="label">Lentivirus</td>
<td>~8 kb</td>
</tr>
<tr>
<td class="label">Cell Type</td>
<td>Advantages</td>
</tr>
<tr>
<td class="label">Encapsulated cells</td>
<td>Contained, removable</td>
</tr>
<tr>
<td class="label">Neural stem cells</td>
<td>CNS integration</td>
</tr>
<tr>
<td class="label">Mesenchymal stem cells</td>
<td>Immunomodulatory</td>
</tr>
<tr>
<td class="label">Strategy</td>
<td>Examples</td>
</tr>
<tr>
<td class="label">TrkB agonists</td>
<td>7,8-DHF</td>
</tr>
<tr>
<td class="label">GDNF mimetics</td>
<td>Unknown</td>
</tr>
<tr>
<td class="label">Small molecule BDNF boosters</td>
<td>Various</td>
</tr>
<tr>
<td class="label">Source</td>
<td>Evidence Level</td>
</tr>
<tr>
<td class="label">Parkinson's disease trials</td>
<td>Strong (PD)</td>
</tr>
<tr>
<td class="label">ALS trials</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Preclinical tauopathy models</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Off-label use</td>
<td>Anecdotal</td>
</tr>
<tr>
<td class="label">Trial</td>
<td>Intervention</td>
</tr>
<tr>
<td class="label">AAV-GDNF (various)</td>
<td>Gene therapy</td>
</tr>
<tr>
<td class="label">CDNF (Herantis)</td>
<td>Recombinant protein</td>
</tr>
<tr>
<td class="label">Intranasal BDNF</td>
<td>Peptide</td>
</tr>
<tr>
<td class="label">AAV-NGF</td>
<td>Gene therapy</td>
</tr>
<tr>
<td class="label">Combination</td>
<td>Rationale</td>
</tr>
<tr>
<td class="label">BDNF + autophagy enhancers</td>
<td>Synaptic protection + protein clearance</td>
</tr>
<tr>
<td class="label">GDNF + MAO-B inhibitors</td>
<td>Trophic support + dopamine modulation</td>
</tr>
<tr>
<td class="label">CDNF + proteostasis modulators</td>
<td>ER stress reduction + protein clearance</td>
</tr>
<tr>
<td class="label">Multiple neurotrophic factors</td>
<td>Broader neuronal coverage</td>
</tr>
<tr>
<td class="label">Intervention</td>
<td>Rank</td>
</tr>
<tr>
<td class="label">Structured exercise</td>
<td>1</td>
</tr>
<tr>
<td class="label">Mediterranean diet</td>
<td>2</td>
</tr>
<tr>
<td class="label">Rapamycin</td>
<td>5</td>
</tr>
<tr>
<td class="label">Spermidine</td>
<td>8</td>
</tr>
<tr>
<td class="label">GDNF infusion</td>
<td>52</td>
</tr>
<tr>
<td class="label">Outcome Measure</td>
<td>Method</td>
</tr>
<tr>
<td class="label">Clinical progression</td>
<td>Standardized scales (PSPRS, CBS)</td>
</tr>
<tr>
<td class="label">Motor function</td>
<td>UPDRS, TUG</td>
</tr>
<tr>
<td class="label">Cognitive function</td>
<td>MoCA, neuropsych testing</td>
</tr>
<tr>
<td class="label">Imaging</td>
<td>DaTscan, MRI</td>
</tr>
<tr>
<td class="label">Factor</td>
<td>Consideration</td>
</tr>
<tr>
<td class="label">Surgical risk</td>
<td>Intraparenchymal delivery requires neurosurgery</td>
</tr>
<tr>
<td class="label">Device complications</td>
<td>Infusion pumps require maintenance</td>
</tr>
<tr>
<td class="label">Unknown efficacy</td>
<td>Limited CBS/PSP-specific data</td>
</tr>
<tr>
<td class="label">Cost</td>
<td>Experimental therapies may not be covered</td>
</tr>
<tr>
<td class="label">Biomarker</td>
<td>Potential Use</td>
</tr>
<tr>
<td class="label">CSF BDNF</td>
<td>Target engagement</td>
</tr>
<tr>
<td class="label">PET tracers for neurotrophic receptors</td>
<td>Receptor occupancy</td>
</tr>
<tr>
<td class="label">Serum neurotrophic factors</td>
<td>Pharmacodynamic</td>
</tr>
</table>

Neurotrophic factors are proteins that support the survival, development, and function of neurons throughout the lifespan. These molecules play critical roles in synaptic plasticity, neuronal connectivity, and neuroprotection—processes that become compromised in corticobasal syndrome (CBS) and progressive supranuclear palsy (PSP), both characterized by progressive 4R-tauopathy and prominent neurodegeneration[@aloe2023].

The concept of using neurotrophic factors as therapeutic agents for neurodegenerative diseases emerged from the observation that these proteins can protect vulnerable neurons, promote regeneration, and restore function in experimental models. However, translating this promise into effective clinical therapies has proven exceptionally challenging due to delivery limitations, safety concerns, and the complexity of CNS pathophysiology[@longo2024].

This section provides comprehensive coverage of major neurotrophic factors relevant to CBS/PSP, including their mechanisms of action, delivery challenges, clinical trial results, and emerging therapeutic strategies. The content integrates with the CBS/PSP Treatment Rankings[@neurowiki], where GDNF infusion currently ranks at position 52 with a score of 23/80 (Tier 3).

The Neurotrophic Factor Family

Classification of Neurotrophic Factors

Neurotrophic factors belong to several protein families with distinct receptor interactions and biological functions:

Neurotrophic Factor Receptors and Signaling

The therapeutic potential of neurotrophic factors depends on their ability to engage specific receptor systems on target neurons:

Why Neurotrophic Factors Matter in CBS/PSP

In CBS and PSP, multiple lines of evidence support the therapeutic potential of neurotrophic factors[@huang2001]:

Brain-Derived Neurotrophic Factor (BDNF)

Overview and Biology

BDNF is the most studied neurotrophic factor in the context of neurodegenerative diseases. It binds to TrkB receptors with high affinity, triggering downstream signaling cascades that promote neuronal survival, synaptic plasticity, and neurogenesis[@lu2014]. BDNF is widely expressed throughout the CNS, with particularly high levels in the hippocampus and cerebral cortex.

BDNF in CBS/PSP Pathogenesis

Multiple studies have investigated BDNF alterations in tauopathies:

• Reduced BDNF levels: Post-mortem studies of PSP brain tissue show decreased BDNF expression in the substantia nigra and cortex[@stocchi2018]
• TrkB signaling impairment: Tau pathology may interfere with TrkB signaling and BDNF trafficking
• Exercise-induced increases: Aerobic exercise remains the most reliable method to increase peripheral and CNS BDNF levels

Therapeutic Strategies for BDNF Modulation

Exercise-Induced BDNF

The most established method to increase endogenous BDNF is aerobic exercise:

Clinical implementation: Structured exercise programs are ranked #1 in the CBS/PSP Treatment Rankings (68/80), with BDNF elevation as one of several mechanisms[@neurowiki].

Small Molecule BDNF Mimetics

Several approaches aim to directly activate TrkB signaling:

Pharmacologic Approaches

BDNF Delivery Challenges

The major limitation of BDNF therapy is delivery to the CNS:

Emerging approaches:

• Intranasal delivery (see section below)
• BBB-penetrant small molecules
• AAV-mediated gene therapy

Glial Cell Line-Derived Neurotrophic Factor (GDNF)

Overview and Biology

GDNF was originally discovered as a survival factor for dopaminergic neurons and has since been shown to protect and regenerate multiple neuronal populations[@kotzbauer2022]. GDNF signals through a complex of the RET tyrosine receptor and GPI-anchored GFRα1 co-receptor. Alternative signaling through GFRα1 alone (RET-independent) has also been described.

GDNF in CBS/PSP

GDNF is particularly relevant to CBS/PSP for several reasons:

• Striatal protection: GDNF protects striatal medium spiny neurons, which degenerate in both conditions
• Substantia nigra support: GDNF promotes dopaminergic neuron survival in the substantia nigra pars compacta
• Motor neuron benefits: GDNF supports corticospinal motor neurons affected in CBS

Clinical Trials of GDNF

GDNF has been tested extensively in Parkinson's disease, with variable results:

CBS/PSP-specific trials: No large-scale trials have been completed in CBS/PSP. The mechanism suggests potential benefit given striatal and nigral involvement.

GDNF Ranking in Treatment List

In the CBS/PSP Treatment Rankings, GDNF infusion ranks 52/55 interventions with a score of 23/80 (Tier 3)[@neurowiki]:

Alternative GDNF Family Ligands

The GDNF family includes multiple ligands with different receptor profiles:

Cerebral Dopamine Neurotrophic Factor (CDNF)

Overview and Biology

CDNF (also known as ARMET) is a secreted protein belonging to the GDNF family with unique neuroprotective properties[@voutilainen2023]. Unlike other GDNF family members, CDNF is expressed in the endoplasmic reticulum and has both intracellular and extracellular functions. CDNF signals through GFRα1/RET but may also act through additional, less characterized receptors.

CDNF Mechanism of Action

CDNF has several distinctive mechanisms:

CDNF in Neurodegeneration

CDNF has shown promise in multiple neurodegeneration models:

• Parkinson's disease models: CDNF protects dopaminergic neurons and improves behavioral outcomes
• Amyotrophic lateral sclerosis (ALS): Shows protection of motor neurons
• Ischemia: Reduces infarct size in stroke models
• Tauopathies: Emerging evidence of benefit in tauopathy models

Clinical Development

CDNF (manufactured as Lu ET1900 by Herantis Pharma) has undergone clinical testing:

CBS/PSP potential: CDNF's mechanism suggests relevance to CBS/PSP given:

• Protection of dopaminergic and cortical neurons
• ER stress reduction (relevant to tauopathy)
• Potential for improved safety profile vs GDNF

Nerve Growth Factor (NGF)

Overview and Biology

NGF was the first discovered neurotrophic factor and primarily targets TrkA-expressing neurons, particularly basal forebrain cholinergic neurons (BFNs)[@sofroniew2022]. These neurons are important for memory and cognition and degenerate in multiple neurodegenerative conditions.

NGF in CBS/PSP

While CBS/PSP are primarily movement disorders, cognitive impairment occurs in many patients:

• Cognitive decline: CBS often presents with asymmetric cortical dysfunction, including language and executive deficits
• Cholinergic involvement: Some patients show cholinergic dysfunction
• Potential benefit: NGF could potentially support remaining cholinergic neurons

Clinical Approaches

NGF delivery has been attempted through:

NGF and Basal Forebrain Cholinergic System

The basal forebrain cholinergic system is particularly vulnerable in several neurodegenerative conditions:

• Anatomic vulnerability: BFNs project to hippocampus and cortex
• TrkA dependence: These neurons require NGF for survival
• Tau involvement: Cholinergic neurons can be affected by tau pathology

Ciliary Neurotrophic Factor (CNTF)

Overview and Biology

CNTF signals through a tripartite receptor complex (CNTFRα/gp130/LIFR) and activates JAK/STAT and MAPK pathways[@stahl2024]. CNTF is expressed primarily by astrocytes and has broad neuroprotective effects on motor neurons, dopaminergic neurons, and oligodendrocytes.

CNTF in CBS/PSP

CNTF has several features relevant to CBS/PSP:

• Motor neuron protection: CNTF supports corticospinal motor neurons
• Oligodendrocyte support: Potential to address myelin dysfunction in CBS
• Anti-inflammatory: May modulate neuroinflammation

CNTF Clinical Development

MANF and Other Emerging Neurotrophic Factors

MANF (Mesencephalic Astrocyte-Derived Neurotrophic Factor)

MANF (also known as ARMETL1) is an ER-resident neurotrophic factor with unique properties[@glembotski2022]:

• ER stress protection: MANF is upregulated during ER stress and protects neurons from ER stress-induced death
• Secreted and intracellular forms: Both have neuroprotective properties
• Broad neuronal protection: Affects dopaminergic, motor, and cortical neurons

Other Neurotrophic Factors

Delivery Methods

The central challenge in neurotrophic factor therapy is achieving sufficient CNS delivery while minimizing peripheral side effects.

Intraparenchymal Infusion

Direct brain infusion bypasses the BBB but requires surgery:

Intranasal Delivery

The nasal route provides a non-invasive pathway to the CNS:

• Olfactory pathway: Direct nose-to-brain transport via olfactory epithelium
• Trigeminal pathway: Transport via trigeminal nerve
• Advantages: Non-invasive, bypasses BBB
• Limitations: Variable absorption, limited to rostral brain regions

Gene Therapy (Viral Vectors)

Viral vector-mediated expression provides sustained delivery:

AAV-GDNF trials: Several trials have tested AAV-mediated GDNF delivery:

• AAV2-GDNF: Safety established, efficacy ongoing
• AAV9-GDNF: Entering clinical testing

Cell-Based Delivery

Cellular vehicles can produce neurotrophic factors in situ:

BBB-Penetrant Small Molecules

Small molecule agonists offer oral availability:

Clinical Trial Landscape for CBS/PSP

Current Neurotrophic Factor Trials

No large-scale Phase 3 trials of neurotrophic factors have been completed specifically in CBS/PSP. Current evidence comes from:

Barriers to CBS/PSP Trials

Ongoing Trials with Potential CBS/PSP Relevance

Combination Strategies

Rationale for Combination Therapy

Neurotrophic factors may work synergistically with other interventions:

Integration with Treatment Rankings

Neurotrophic factor therapies should be considered in the context of evidence-ranked interventions:

The low ranking of GDNF reflects the challenges of delivery and limited CBS/PSP-specific evidence rather than lack of mechanistic rationale.

Patient Counseling and Clinical Implementation

Patient Selection

Consider neurotrophic factor approaches for patients who:

• Have confirmed CBS/PSP diagnosis
• Show progressive disease despite standard care
• Have realistic expectations about experimental approaches
• Are able to participate in clinical trials or access specialized centers

Monitoring and Outcomes

Risk-Benefit Considerations

Research Directions

Promising Avenues

Biomarker Development

Challenges to Address

Conclusion

Neurotrophic factor therapies represent a mechanistically compelling approach to neuroprotection in CBS/PSP. The rationale is strong—vulnerable neurons require trophic support, and neurotrophic factors can provide this support. However, the translation from promising mechanisms to clinical benefit has been hampered by delivery challenges, limited CBS/PSP-specific data, and the complexity of neurodegenerative pathophysiology.

Current evidence places GDNF infusion at rank 52/55 in the Treatment Rankings (23/80, Tier 3), reflecting the gap between mechanistic promise and clinical proof. The highest-ranked interventions that influence neurotrophic signaling remain lifestyle approaches (exercise, diet) and pharmacological interventions already available (rapamycin, spermidine).

Future progress will require:

• Improved delivery systems that achieve adequate CNS distribution
• CBS/PSP-specific clinical trials rather than extrapolation from PD
• Biomarker development to confirm target engagement
• Combination approaches that address multiple aspects of neurodegeneration

See Also

• [CBS/PSP Treatment Rankings](/diseases/corticobasal-degeneration)
• [Section 102: Proteostasis Network Dysregulation in CBS/PSP](/therapeutics/section-102-proteostasis-network-cbs-psp)
• [BDNF and Neurodegeneration](/therapeutics/bdnf-therapy)
• [GDNF for Parkinson's Disease](/therapeutics/gdnf-parkinsons)
• [Intranasal Drug Delivery for Neurodegeneration](/therapeutics/intranasal-drug-delivery)
• [Exercise and Neurodegeneration](/therapeutics/exercise-neurodegeneration)
• [TrkB Modulators](/therapeutics/trkb-modulators)
• [Stem Cell Therapy for Parkinsonism](/therapeutics/stem-cell-therapy-parkinsons)
• [Gene Therapy for Neurodegeneration](/therapeutics/gene-therapy-neurodegeneration)

Related Hypotheses

From the [SciDEX Exchange](/exchange) — scored by multi-agent debate

• [Bacterial Enzyme-Mediated Dopamine Precursor Synthesis](/hypothesis/h-7bb47d7a) — <span style="color:#ffd54f;font-weight:600">0.44</span> · Target: TH, AADC
• [Hippocampal CA3-CA1 circuit rescue via neurogenesis and synaptic preservation](/hypothesis/h-856feb98) — <span style="color:#81c784;font-weight:600">0.73</span> · Target: BDNF
• [Vagal Afferent Microbial Signal Modulation](/hypothesis/h-ee1df336) — <span style="color:#81c784;font-weight:600">0.71</span> · Target: GLP1R, BDNF
• [Vocal Cord Neuroplasticity Stimulation](/hypothesis/h-e0183502) — <span style="color:#ffd54f;font-weight:600">0.48</span> · Target: CHR2/BDNF

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