rock-inhibitor-fasudil-psp-cbs-nct04734379

ROCK Inhibitor in Tauopathies - Fasudil (NCT04734379)

Overview

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.

ROCK Inhibitor in Tauopathies - Fasudil (NCT04734379)

Overview

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:

ROCK 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

Study Design and Objectives

Trial Phases

Phase 2a trials represent early-stage clinical evaluation focusing on:

Primary Objectives

• Adverse event monitoring
• Vital signs and physical examinations
• Laboratory values (hematology, chemistry)
• Electrocardiograms
• Neurological examinations

Secondary Objectives

• Cerebrospinal fluid (CSF) tau species (total tau, phosphorylated tau)
• Neurofilament light chain (NfL) as a marker of neurodegeneration
• Inflammatory markers

• PSP Rating Scale (PSPRS) for PSP patients
• Corticobasal Syndrome Assessment Scale (CBS-AS)
• Standardized cognitive assessments
• Quality of life measures

Patient 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)

• 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

• 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

• Warfarin, DOACs
• Antiplatelet agents
• Monitor closely

• 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

• Demonstrated in animal models
• Human data limited
• Active transport mechanisms possible

• CYP450-mediated
• Active metabolites
• Hepatic impairment considerations

• 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)

• Cognitive assessments (MoCA, FAB)
• Functional scales (ADL, QA)
• Quality of life measures

• 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

• Plasma NfL (emerging)
• GFAP (astrocyte activation)
• Inflammatory panels

• 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

• Microtubule stability
• Motor protein function
• Axonal transport
• Organelle trafficking

• 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

• Receptor trafficking
• Spine morphology
• PSD95 composition
• NMDA/AMPA receptor function

• 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

• Reactive astrocytosis
• Cytokine release
• Neurotrophic factor production
• Blood-brain barrier interactions

• 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

• Age-dependent tau accumulation
• Behavioral deficits
• Fasudil: neuroprotection observed

• 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

• Reduced inflammatory cytokine release
• Modulated microglial morphology
• Enhanced neuroprotective phenotype

• 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

• Microtubule stabilization
• Motor protein function
• Vesicle dynamics
• Mitochondrial trafficking

• 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

• 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

• 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

• 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

• Microglial modulation
• Different mechanism
• Potential combination

• 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

• 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

• 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

• Rate of decline
• Phenotype conversion
• Treatment response

• Target engagement
• Mechanism modulation
• Clinical correlation

Combination Approaches

Potential future strategies:

ROCKi + Anti-tau — Rationale:

• Complementary mechanisms
• Different stages of pathology
• Synergistic potential

• Multiple inflammatory pathways
• Broader neuroprotection
• Reduced toxicity

• Supporting neuronal survival
• Enhancing plasticity
• Functional recovery

Personalized Medicine

Tailoring treatment to individuals:

Genetic Factors — May influence:

• Tau isoform expression
• Drug metabolism
• Disease phenotype

• Select responders
• Dose appropriately
• Monitor response

• 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