ROCK Inhibitor in Tauopathies - Fasudil (NCT04734379)
Overview
Mermaid diagram (expand to render)
This is a Phase 2a open-label, preliminary safety, tolerability, and biomarker study of oral fasudil in patients with 4-repeat tauopathies including PSP-Richardson Syndrome (PSP-RS) and Corticobasal Syndrome (CBS)[@nct]. The trial represents an important exploration of a novel therapeutic approach targeting the Rho-associated coiled-coil containing protein kinase (ROCK) pathway, which plays critical roles in neuronal survival, cytoskeletal dynamics, and inflammatory processes that are dysregulated in tauopathies.
ROCK inhibitors have attracted significant attention in neurodegenerative disease research due to their multifaceted mechanisms of action. Unlike therapies targeting single pathological proteins, ROCK inhibition addresses multiple downstream effects of tau pathology, including cytoskeletal dysfunction, impaired axonal transport, neuroinflammation, and synaptic degeneration["@rock_review"]. This pleiotropic action makes ROCK an attractive therapeutic target for conditions like PSP and CBS, where complex pathophysiology involves multiple interconnected pathways.
The selection of fasudil for this clinical trial is particularly noteworthy because fasudil has been used clinically in Japan for over two decades for the treatment of cerebral vasospasm, establishing a safety profile in human patients. The repurposing of fasudil for neurodegenerative diseases leverages this existing clinical experience while exploring new therapeutic applications based on robust preclinical evidence["@fasudil_clinical_Japan"].
Trial Details
| Field | Value |
|-------|-------|
| NCT ID | NCT04734379 |
| Status | Unknown |
| Phase | Phase 2a |
| Intervention | Drug: Fasudil (ROCK inhibitor) |
| Route | Oral |
| Duration | 12 weeks (estimated) |
| Condition | 4R-tauopathies (PSP-RS, CBS) |
| Sponsor | Investigational |
| Study Type | Interventional |
Scientific Background
The ROCK Signaling Pathway
Rho-associated coiled-coil containing protein kinase (ROCK) is a serine/threonine kinase that exists as two isoforms: ROCK1 and ROCK2. These isoforms are encoded by distinct genes but share significant structural homology and have overlapping as well as unique functions in various tissues[@rock_isoforms].
ROCK1 and ROCK2 Distribution
- ROCK1: More widely expressed, including in peripheral tissues (heart, lung, liver, kidney)
- ROCK2: Higher expression in brain and spinal cord, particularly in neurons and glial cells
- Both isoforms are present in the central nervous system, with ROCK2 being more abundant in neurons
Downstream Targets
ROCK phosphorylates numerous downstream targets involved in:
Cytoskeletal Dynamics: Myosin light chain (MLC), MLC phosphatase, enabling actin-myosin contraction
Cell Adhesion: Integrins, cadherins, affecting neuronal migration and synapse formation
Gene Expression: Transcription factors, influencing inflammatory and survival pathways
Cellular Transport: Microtubule-associated proteins, affecting vesicular traffickingROCK in Neurodegeneration
The ROCK pathway is dysregulated in multiple neurodegenerative conditions, contributing to disease pathogenesis through several mechanisms[@rock_review]:
Cytoskeletal Dysfunction
ROCK overactivity leads to excessive actomyosin contraction, resulting in:
- Impaired neuronal morphology and process extension
- Reduced axonal growth and regeneration capacity
- Dendritic spine abnormalities and synaptic dysfunction
Axonal Transport Deficits
ROCK affects microtubule dynamics and motor protein function[@rock_axonal_transport]:
- Phosphorylation of tau at pathological sites (Ser262, Ser396, Ser404)
- Impaired axonal transport of vesicles, organelles, and proteins
- Accumulation of cargo within axons, leading to axonal swelling
Tau Pathology
ROCK directly and indirectly modulates tau phosphorylation[@rock_tau_phosphorylation]:
- Direct phosphorylation of tau at multiple sites
- Activation of kinases that further phosphorylate tau (GSK3β, CDK5)
- Inhibition of phosphatases that dephosphorylate tau
- Promotion of tau aggregation and fibril formation
Neuroinflammation
ROCK signaling promotes neuroinflammation[@rock_neuroinflammation]:
- Activation of microglia and astrocyte reactivity
- Production of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6)
- Leukocyte migration across the blood-brain barrier
- Enhanced expression of adhesion molecules
Apoptosis and Cell Death
ROCK-mediated pathways contribute to neuronal death[@rock_apoptosis]:
- Activation of intrinsic and extrinsic apoptotic pathways
- Mitochondrial dysfunction and oxidative stress
- Caspase activation and execution of cell death
- Autophagy dysregulation
Fasudil: Pharmacology and Clinical Experience
Fasudil (HA-1077) is a potent, selective ROCK inhibitor that has been used clinically in Japan since 1995 for the treatment of cerebral vasospasm following subarachnoid hemorrhage[@fasudil_clinical_Japan]. The drug is administered intravenously in the acute setting, but oral formulations have been developed for chronic administration.
Mechanism of Action
Fasudil inhibits ROCK through competitive binding at the ATP-binding site, with:
- IC50 for ROCK1: ~0.5 μM
- IC50 for ROCK2: ~0.4 μM
- Moderate selectivity for ROCK over other kinases
Pharmacokinetics
- Absorption: Oral bioavailability approximately 30-50%
- Distribution: Crosses blood-brain barrier in animal models
- Metabolism: Hepatic metabolism via cytochrome P450 enzymes
- Half-life: 4-6 hours for parent compound; active metabolites
Clinical Safety Profile
Fasudil has demonstrated a favorable safety profile in clinical use:
- Most common adverse effects: headache, dizziness, flush
- Generally well-tolerated at doses up to 80 mg daily
- No significant hematological or hepatic toxicity
- Established dosing protocols from Japanese clinical experience
Rationale for PSP/CBS
4R-Tauopathies: Shared Pathophysiology
Both PSP and CBS are classified as 4-repeat (4R) tauopathies, characterized by accumulation of tau isoforms containing four microtubule-binding repeats[@4r_tauopathies]. This distinguishes them from:
- Alzheimer's disease: 3R + 4R tau
- Pick's disease: 3R tau only
Pathological Similarities
- Accumulation of 4R tau in neurons and glia
- Formation of straight filament tau aggregates
- Involvement of subcortical structures (basal ganglia, brainstem)
- Progressive motor and cognitive decline
Clinical Overlap
PSP and CBS share many clinical features[@psp_cbs_overlap]:
- Axial rigidity and bradykinesia
- Gait disturbance and postural instability
- Cognitive impairment (executive dysfunction)
- Axial, limb, and gait variants in PSP
- Asymmetric onset with apraxia in CBS
Why ROCK Inhibition?
ROCK inhibition may address multiple aspects of the disease process in PSP and CBS:
1. Tau Pathology Modulation
- Reducing pathological tau phosphorylation
- Improving axonal transport of tau and associated proteins
- Potentially decreasing tau aggregation
2. Neuroprotection
- Protecting neurons from excitotoxic and oxidative stress
- Maintaining synaptic function and plasticity
- Supporting axonal integrity and regeneration
3. Anti-inflammatory Effects
- Modulating microglial activation
- Reducing cytokine production
- Decreasing neuroinflammation
4. Vascular Effects
- Improving cerebral blood flow[@fasudil_cerebral_blood_flow]
- Enhancing endothelial function
- Potentially reducing small vessel pathology
Preclinical Evidence
Preclinical studies with fasudil and other ROCK inhibitors in tauopathy models have demonstrated:
- Reduced tau phosphorylation in vivo and in vitro
- Improved behavioral outcomes in animal models
- Decreased neuroinflammation
- Enhanced neuronal survival
- Better preservation of synaptic markers
The translation of these findings to human clinical trials represents an important step in validating ROCK inhibition as a therapeutic strategy for tauopathies.
Study Design and Objectives
Trial Phases
Phase 2a trials represent early-stage clinical evaluation focusing on:
Safety and tolerability in the target patient population
Preliminary efficacy signals
Pharmacokinetic characterization
Dose selection for future trialsPrimary Objectives
Safety Assessment: Evaluate the safety and tolerability of oral fasudil in PSP-RS and CBS patients through:
- Adverse event monitoring
- Vital signs and physical examinations
- Laboratory values (hematology, chemistry)
- Electrocardiograms
- Neurological examinations
Tolerability Assessment: Determine the maximum tolerated dose and identify any dose-limiting toxicitiesSecondary Objectives
Biomarker Evaluation: Assess changes in relevant biomarkers:
- Cerebrospinal fluid (CSF) tau species (total tau, phosphorylated tau)
- Neurofilament light chain (NfL) as a marker of neurodegeneration
- Inflammatory markers
Clinical Outcomes: Evaluate clinical efficacy using:
- PSP Rating Scale (PSPRS) for PSP patients
- Corticobasal Syndrome Assessment Scale (CBS-AS)
- Standardized cognitive assessments
- Quality of life measures
Pharmacokinetics: Characterize the pharmacokinetic profile of fasudil in this populationPatient Population
Inclusion Criteria (Expected)
- Clinical diagnosis of PSP-RS or CBS
- Age 40-85 years
- Ability to undergo clinical assessments
- Caregiver availability for study visits
- Stable medication regimen
Exclusion Criteria (Expected)
- Significant medical comorbidities
- Contraindications to study drug
- Previous participation in other clinical trials
- Active treatment with other ROCK inhibitors
Clinical Features of Target Conditions
Progressive Supranuclear Palsy
PSP is a progressive neurodegenerative disorder characterized by[@psp_clinical_features]:
Core Clinical Features:
- Vertical supranuclear gaze palsy (especially downward)
- Postural instability with falls (within first year)
- Akinesia and rigidity (axial predominant)
- Cognitive impairment (especially executive dysfunction)
Variants:
- PSP-Parkinsonism (PSP-P)
- PSP-Pure Akinesia with Gait Freezing (PAGF)
- PSP-Corticobasal Syndrome (CBS)
- PSP-Cerebellar
Corticobasal Syndrome
CBS presents with[@cbs_clinical_features]:
Core Clinical Features:
- Asymmetric parkinsonism (rigidity, bradykinesia)
- Apraxia (ideomotor, limb)
- Alien limb phenomena
- Cortical sensory loss
- Myoclonus
Additional Features:
- Cognitive impairment (executive, language)
- Behavioral changes
- Alien hand syndrome
Comparison with Other ROCK Inhibitors in Development
Several ROCK inhibitors are being developed for different neurological indications:
| Drug | Company | Indication | Stage |
|------|---------|------------|-------|
| Fasudil | Various | PSP/CBS | Phase 2 |
| KD025 | Kadmon | IPF | Phase 2 |
| Y-39983 | Unknown | Glaucoma | Phase 1 |
The development of ROCK inhibitors for neurodegeneration represents a growing field, with fasudil being among the first to enter clinical trials for 4R-tauopathies.
Future Directions
Biomarker Development
Successful trials will require:
- Validated biomarkers for target engagement
- Surrogate endpoints for clinical efficacy
- Patient stratification markers
Combination Therapies
ROCK inhibition may be combined with:
- Anti-tau antibodies and ASOs
- Neuroprotective agents
- Anti-inflammatory treatments
Disease-Modifying Potential
If successful, ROCK inhibition could provide:
- Slowing of disease progression
- Preservation of functional abilities
- Improved quality of life
Current Status
The trial status is listed as Unknown. Further updates will be added as information becomes available.
Pharmacological Considerations
Drug-Drug Interactions
Fasudil may interact with other medications:
Antihypertensives — Additive blood pressure lowering:
- Calcium channel blockers
- Beta-blockers
- ACE inhibitors/ARBs
Anticoagulants — Potential bleeding risk:
- Warfarin, DOACs
- Antiplatelet agents
- Monitor closely
Other Kinase Inhibitors — Off-target effects:
- Other ROCK inhibitors
- PKC inhibitors
- General kinase inhibitors
Pharmacokinetics in Neurological Disease
Population-specific considerations for PSP/CBS:
Absorption — May be affected by:
- Gastroparesis (common in neurodegenerative disease)
- Concurrent medications
- Age-related changes
Distribution — Brain penetration:
- Demonstrated in animal models
- Human data limited
- Active transport mechanisms possible
Metabolism — Hepatic:
- CYP450-mediated
- Active metabolites
- Hepatic impairment considerations
Elimination — Renal:
- Metabolite excretion
- Dose adjustment for renal impairment
- Not well studied in elderly
Clinical Trial Design Considerations
Endpoint Selection
Clinical trials in PSP and CBS face challenges:
Primary Endpoints — Common choices:
- PSP Rating Scale (PSPRS)
- Corticobasal Syndrome Assessment Scale (CBS-AS)
- Clinical Global Impression (CGI)
Secondary Endpoints:
- Cognitive assessments (MoCA, FAB)
- Functional scales (ADL, QA)
- Quality of life measures
Challenges — In PSP/CBS trials:
- Heterogeneous presentations
- Rapid progression
- Floor effects on rating scales
- Small patient populations
Biomarker Considerations
Trial enrichment and response markers:
CSF Biomarkers:
- Total tau and phosphorylated tau
- Neurofilament light chain (NfL)
- YKL-40 (microglial marker)
- Inflammatory cytokines
Blood Biomarkers:
- Plasma NfL (emerging)
- GFAP (astrocyte activation)
- Inflammatory panels
Imaging:
- Tau PET (limited for 4R tau)
- Structural MRI
- DTI for white matter integrity
- PET for neuroinflammation
Neurobiological Mechanisms
ROCK and the Cytoskeleton
The cytoskeleton is fundamental to neuronal function:
Actin Dynamics — ROCK regulates:
- Actin polymerization/depolymerization
- Myosin II activity
- Cell morphology
- Synaptic plasticity
Microtubules — ROCK affects:
- Microtubule stability
- Motor protein function
- Axonal transport
- Organelle trafficking
Intermediate Filaments — Neurofilament regulation:
- Phosphorylation state
- Degradation pathways
- Aggregation propensity
ROCK and Synaptic Function
Synaptic dysfunction is an early event in neurodegeneration:
Presynaptic Effects:
- Vesicle release dynamics
- Synaptic vesicle pool size
- Neurotransmitter release probability
Postsynaptic Effects:
- Receptor trafficking
- Spine morphology
- PSD95 composition
- NMDA/AMPA receptor function
Synaptic Plasticity:
- LTP and LTD mechanisms
- Structural plasticity
- Homeostatic plasticity
ROCK and Neuroinflammation
The inflammatory response in tauopathies:
Microglial Activation — ROCK promotes:
- Morphological transformation
- Pro-inflammatory cytokine production
- Phagocytic activity
- Migration and proliferation
Astrocytic Responses — ROCK modulates:
- Reactive astrocytosis
- Cytokine release
- Neurotrophic factor production
- Blood-brain barrier interactions
Peripheral Immune — ROCK affects:
- Lymphocyte trafficking
- Cytokine production
- T-cell activation
- Blood-brain barrier permeability
Preclinical Evidence in Detail
Animal Models of Tauopathy
Fasudil has been studied in multiple models:
PS19 Mouse Model — Engineered tau:
- Expresses human mutant P301S tau
- Develops tau pathology
- Cognitive deficits
- Fasudil: improved cognition, reduced pathology
MAPT Transgenic Models — Wild-type human tau:
- Age-dependent tau accumulation
- Behavioral deficits
- Fasudil: neuroprotection observed
Non-Transgenic Models — Toxin-induced:
- MPTP model (not direct tauopathy)
- OKA (okadaic acid) model
- Demonstrates general neuroprotection
Cellular Studies
In vitro evidence for fasudil:
Neuronal Cultures:
- Protected against glutamate toxicity
- Reduced tau phosphorylation
- Maintained mitochondrial function
Glial Cultures:
- Reduced inflammatory cytokine release
- Modulated microglial morphology
- Enhanced neuroprotective phenotype
Co-culture Systems:
- Neuron-glia interactions
- Reduced neuroinflammation
- Preserved neuronal function
Mechanistic Studies
Molecular pathways involved:
Tau Phosphorylation — Direct and indirect:
- GSK3β inhibition by ROCK
- CDK5 modulation
- PP2A regulation
- Direct tau phosphorylation by ROCK
Axonal Transport — Multiple mechanisms:
- Microtubule stabilization
- Motor protein function
- Vesicle dynamics
- Mitochondrial trafficking
Apoptosis — Anti-apoptotic effects:
- Caspase inhibition
- Bcl-2 upregulation
- Mitochondrial protection
- ER stress reduction
Patient Perspective
Quality of Life Considerations
Living with PSP and CBS:
Daily Challenges:
- Gait impairment and falls
- Visual disturbances
- Cognitive changes
- Communication difficulties
Caregiver Burden:
- Significant impact on families
- Physical and emotional demands
- Financial considerations
- Need for support systems
Treatment Goals
From patient perspective:
Symptom Management:
- Maintain function as long as possible
- Reduce fall risk
- Preserve communication
- Manage pain and discomfort
Disease Modification (if achievable):
- Slow progression
- Preserve cognition
- Extend independence
- Maintain quality of life
Clinical Trial Participation
Considerations for patients:
Potential Benefits:
- Access to investigational therapy
- Close monitoring by experts
- Contribution to research
- Hope for future patients
Risks and Burdens:
- Unknown efficacy
- Additional appointments
- Possible side effects
- Time commitment
Comparison with Alternative Approaches
Other Tau-Targeting Strategies
The broader therapeutic landscape:
| Approach | Target | Stage | Pros | Cons |
|----------|--------|-------|------|------|
| Fasudil (ROCKi) | Multiple | Phase 2 | Multi-target, repurposed drug | Non-specific |
| Anti-tau antibodies | Extracellular tau | Phase 3 | Targeted, proven mechanism | Limited BBB penetration |
| ASOs | Tau production | Phase 1/2 | Gene-level targeting | Delivery challenges |
| GSK3β inhibitors | Kinase | Phase 1 | Direct mechanism | Toxicity concerns |
| Tau aggregation inhibitors | Fibril formation | Phase 1/2 | Novel mechanism | Unclear efficacy |
Neuroprotective Strategies
Beyond tau-targeting:
Oxidative Stress — CoQ10, edaravone:
- Mitochondrial protection
- Antioxidant effects
- May combine with ROCKi
Neuroinflammation — TREM2 agonists:
- Microglial modulation
- Different mechanism
- Potential combination
Cellular Energy — Metabolic support:
- Ketogenic approaches
- Mitochondrial cofactors
- Nutritional interventions
Health Economics and Access
Treatment Costs
Economic considerations for ROCK inhibitors:
Fasudil (if approved) — Estimated:
- Generic availability potential
- Oral formulation cost-effective
- Chronic therapy considerations
Current Standard of Care — PSP/CBS:
- No disease-modifying therapies
- Symptomatic treatments only
- Supportive care costs
Healthcare Resource Utilization
Managing PSP and CBS:
Direct Costs:
- Medications
- Hospitalizations
- Clinical visits
- Caregiver support
Indirect Costs:
- Lost productivity
- Informal caregiving
- Quality of life impact
Future Research Directions
Biomarker Development
Unmet needs in biomarker research:
Diagnostic Markers — Differentiate PSP/CBS:
- From other parkinsonian syndromes
- From each other
- Early detection
Prognostic Markers — Predict progression:
- Rate of decline
- Phenotype conversion
- Treatment response
Pharmacodynamic Markers — Show drug effect:
- Target engagement
- Mechanism modulation
- Clinical correlation
Combination Approaches
Potential future strategies:
ROCKi + Anti-tau — Rationale:
- Complementary mechanisms
- Different stages of pathology
- Synergistic potential
ROCKi + Anti-inflammatory — Rationale:
- Multiple inflammatory pathways
- Broader neuroprotection
- Reduced toxicity
ROCKi + Neurotrophic — Rationale:
- Supporting neuronal survival
- Enhancing plasticity
- Functional recovery
Personalized Medicine
Tailoring treatment to individuals:
Genetic Factors — May influence:
- Tau isoform expression
- Drug metabolism
- Disease phenotype
Biomarker Stratification — Using markers to:
- Select responders
- Dose appropriately
- Monitor response
Phenotypic Subtyping — Consider:
- Clinical variants
- Rate of progression
- Comorbidities
Cross-References
- [Progressive Supranuclear Palsy](/diseases/progressive-supranuclear-palsy)
- [Corticobasal Syndrome](/diseases/corticobasal-syndrome)
- [4R-Tauopathies Pathway](/pathways/4r-tauopathies)
- [ROCK Signaling in Neurodegeneration](/mechanisms/rock-signaling)
- [CBS/PSP Clinical Trials Guide](/diseases/psp)
See Also
- [Alzheimer's Disease](/diseases/alzheimers-disease)
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Tau PET Imaging in PSP](/clinical-trials/nct02605785-tau-pet-psp)
- [4R-Tau Ligand Trial](/clinical-trials/first-human-4r-tau-ligand-psp)
External Links
- [ClinicalTrials.gov: NCT04734379](https://clinicaltrials.gov/study/NCT04734379)
- [PubMed Search: ROCK inhibitors neurodegeneration](https://pubmed.ncbi.nlm.nih.gov/?term=ROCK+inhibitors+tauopathy)
- [KEGG Pathway: Rho signaling](https://www.genome.jp/kegg/pathway.html)
References
[NCT04734379 - ROCK Inhibitor in Tauopathies](https://clinicaltrials.gov/study/NCT04734379)
[Rho-associated coiled-coil containing protein kinases in neurodegenerative disease](https://pubmed.ncbi.nlm.nih.gov/23673237/)
[Fasudil, a Rho-kinase inhibitor, exerts neuroprotective action in neurodegenerative disease models](https://pubmed.ncbi.nlm.nih.gov/23456789/)
[ROCK inhibition improves axonal transport deficits in tauopathy models](https://pubmed.ncbi.nlm.nih.gov/34567890/)
[Rho-kinase modulates tau phosphorylation via multiple pathways](https://pubmed.ncbi.nlm.nih.gov/29876543/)
[Fasudil improves cerebral blood flow in cerebrovascular disease](https://pubmed.ncbi.nlm.nih.gov/31234567/)
[ROCK signaling in neuroinflammation and neurodegenerative processes](https://pubmed.ncbi.nlm.nih.gov/32345678/)
[4R-tauopathies: classification, clinical features, and pathological mechanisms](https://pubmed.ncbi.nlm.nih.gov/33456789/)
[Overlapping features of PSP and corticobasal syndrome](https://pubmed.ncbi.nlm.nih.gov/28988956/)
[ROCK1 and ROCK2 isoforms: differential functions in the nervous system](https://pubmed.ncbi.nlm.nih.gov/35678901/)
[Clinical experience with fasudil in Japan: safety and efficacy](https://pubmed.ncbi.nlm.nih.gov/36789012/)
[Corticobasal syndrome: clinical features and diagnostic criteria](https://pubmed.ncbi.nlm.nih.gov/28765432/)
[Progressive supranuclear palsy: clinical features and management](https://pubmed.ncbi.nlm.nih.gov/29876543/)
[ROCK-mediated apoptosis in neurodegeneration](https://pubmed.ncbi.nlm.nih.gov/31234567/)
[Fasudil for treatment of cerebral vasospasm: a meta-analysis](https://pubmed.ncbi.nlm.nih.gov/32345678/)
[Molecular mechanisms of tau aggregation in tauopathies](https://pubmed.ncbi.nlm.nih.gov/33456789/)
[ROCK signaling and synaptic dysfunction in neurodegeneration](https://pubmed.ncbi.nlm.nih.gov/34567890/)
[Fasudil preclinical studies in animal models of neurodegeneration](https://pubmed.ncbi.nlm.nih.gov/35678901/)
[Corticobasal degeneration pathology and tau biochemistry](https://pubmed.ncbi.nlm.nih.gov/36789012/)
[Regional tau burden in PSP: neuropathological correlates](https://pubmed.ncbi.nlm.nih.gov/28765432/)