AAV-LRRK2 Gene Therapy IND-Enabling Study Design

Overview

This page outlines the IND-enabling preclinical development plan for AAV-[LRRK2](/entities/lrrk2) gene therapy in [Parkinson's disease](/diseases/parkinsons-disease). Building on the serotype comparison studies that identified optimal vectors for delivering LRRK2 knockdown constructs to the substantia nigra, this program details the studies required to support an Investigational New Drug (IND) application with the FDA.

Background

The preceding serotype comparison study identified AAV-PHP.B as the optimal serotype for delivering LRRK2 shRNA to dopaminergic [neurons](/entities/neurons) in the substantia nigra, achieving 78% transduction efficiency in mouse models and 65% in non-human primates (NHP) [1]. The IND-enabling studies outlined here will advance the lead candidate (AAV-PHP.B-U6-shRNA-LRRK2) toward clinical trials.

GLP Toxicology Studies

Single-Dose Toxicity Study (GLP)

Study Design:

• Species: Sprague-Dawley rats (n=80, 40 male/40 female)
• Dose groups: Vehicle control, 1×10¹³ GC/kg, 3×10¹³ GC/kg, 1×10¹⁴ GC/kg
• Administration: Single intravenous (IV) infusion via tail vein
• Observation period: 6 months (with necropsies at 2 weeks, 1 month, 3 months, 6 months)

Overview

This page outlines the IND-enabling preclinical development plan for AAV-[LRRK2](/entities/lrrk2) gene therapy in [Parkinson's disease](/diseases/parkinsons-disease). Building on the serotype comparison studies that identified optimal vectors for delivering LRRK2 knockdown constructs to the substantia nigra, this program details the studies required to support an Investigational New Drug (IND) application with the FDA.

Background

The preceding serotype comparison study identified AAV-PHP.B as the optimal serotype for delivering LRRK2 shRNA to dopaminergic [neurons](/entities/neurons) in the substantia nigra, achieving 78% transduction efficiency in mouse models and 65% in non-human primates (NHP) [1]. The IND-enabling studies outlined here will advance the lead candidate (AAV-PHP.B-U6-shRNA-LRRK2) toward clinical trials.

GLP Toxicology Studies

Single-Dose Toxicity Study (GLP)

Study Design:

• Species: Sprague-Dawley rats (n=80, 40 male/40 female)
• Dose groups: Vehicle control, 1×10¹³ GC/kg, 3×10¹³ GC/kg, 1×10¹⁴ GC/kg
• Administration: Single intravenous (IV) infusion via tail vein
• Observation period: 6 months (with necropsies at 2 weeks, 1 month, 3 months, 6 months)

• Clinical observations (daily)
• Body weight and food consumption (weekly)
• Clinical pathology (hematology, clinical chemistry, urinalysis)
• Toxicokinetics (blood collection at 0, 4, 24, 72 hours, 1, 2, 4 weeks)
• Biodistribution (qPCR for vector genome copies)
• Histopathology (full tissue panel including brain, spinal cord, liver, kidney, heart, lung, spleen, gonads)

Repeat-Dose Toxicity Study (GLP)

Study Design:

• Species: Cynomolgus monkeys (n=24, 12 male/12 female)
• Dose groups: Vehicle control, 1×10¹² GC/kg, 3×10¹² GC/kg, 1×10¹³ GC/kg
• Administration: Single IV infusion
• Observation period: 12 months

• Neurological examinations
• CSF collection for biomarkers
• Immune response monitoring (anti-AAV antibodies, T-cell responses)
• Electrophysiological assessments
• Detailed neuropathology including stereological neuron counts in substantia nigra

Biodistribution Studies

Tissue Distribution Analysis

Study Design:

• Species: Rats and NHPs
• Timepoints: 2 weeks, 1 month, 3 months, 6 months, 12 months
• Tissues: Brain (16 regions), spinal cord, liver, kidney, heart, lung, spleen, lymph nodes, gonads, muscle, adipose, blood

• qPCR for vector genome copies
• ddPCR for sensitivity verification
• RNAscope for mRNA expression in target brain regions
• Immunohistochemistry for LRRK2 knockdown validation

Vector Shedding Study

Design:

• Collect urine, feces, saliva, tears, and blood from dosed animals
• Quantify vector DNA/RNA at multiple timepoints
• Assess shedding duration and potential for environmental transmission

Dose Escalation Studies

Pre-Clinical Dose Range Finding

Rationale for Dose Selection:

• Efficacy threshold: Based on mouse studies, ≥50% LRRK2 knockdown required for phenotypic benefit
• Safety margin: 10× the efficacious dose should show no severe adverse effects

Efficacy Readouts:

• LRRK2 protein levels (Western blot, IHC)
• Phospho-Ser1292 LRRK2 activity marker
• Dopamine levels in striatum
• Tyrosine hydroxylase-positive neuron counts
• Behavioral assessments (cylinder test, stepping test, gait analysis)

Non-Human Primate Safety Studies

12-Month Chronic Safety Study

Design:

• Species: Cynomolgus macaques (n=30)
• Groups: Vehicle control, low dose, mid dose, high dose (as above)
• Administration: Single IV infusion

• Weekly neurological examinations
• CSF analysis (cell count, protein, cytokines)
• MRI at baseline, 3, 6, 12 months
• PET for neuroinflammation (TSPO ligand)

• Full clinical pathology
• Cytokine/chemokine panel (IL-6, TNF-α, IL-1β, IFN-γ)
• Anti-drug antibody (ADA) development
• T-cell ELISpot for cellular immune response

• Ophthalmologic examinations
• Cardiovascular telemetry
• Reproductive toxicity assessment (dedicated study)

Immunogenicity Assessment

Key Questions:

• Pre-existing immunity: Screen all NHPs for anti-AAV antibodies
• ADA development: Characterize titer, neutralizing capacity, impact on efficacy
• Cellular immunity: Monitor T-cell responses to transgene and capsid
• Mitigation strategies: Corticosteroid preconditioning protocol

Manufacturing Scale-Up

Production Platform

Cell Line: HEK293 cells grown in suspension culture

Upstream Process:

• Triple transfection in 50L bioreactors
• Harvest 72 hours post-transfection
• Yield target: ≥1×10¹⁶ GC per batch

• Benzonase treatment for nucleic acid clearance
• Chromatographic purification (affinity + ion exchange)
• Tangential flow filtration for concentration
• 0.2μm filtration for sterility

Fill-Finish

• Formulation: PBS + 5% sorbitol
• Fill volume: 10 mL
• Container: Glass vials
• Storage: -80°C, stability data to support 24-month shelf life

IND-Stage Manufacturing Requirements

| Attribute | Specification |
|-----------|---------------|
| Purity | ≥95% full particles (AUC) |
| Identity | qPCR, sequencing |
| Potency | In vitro transduction (HEK293) |
| Safety | Endotoxin <5 EU/mL, sterility, mycoplasma |
| Stability | 24 months at -80°C |

Regulatory Strategy

Pre-IND Meeting Package

Timeline: Submit 6 months before projected IND filing

Content:

Clinical Trial Design (Phase 1)

Population: Early-stage PD patients (Hoehn & Yahr 1-2)

Dosing:

• Single ascending dose cohorts: 3+3 design
• Dose levels: 1×10¹², 3×10¹², 1×10¹³ GC/kg
• Route: Intrathecal or intraventricular (to maximize CNS delivery)

• Primary: Safety and tolerability (12 months)
• Secondary: LRRK2 activity (phospho-Ser1292 in CSF), motor scores (MDS-UPDRS), PET biomarkers
• Exploratory: Gene expression profiling, immune biomarkers

Regulatory Pathways

• FDA: IND via Center for Biologics Evaluation and Research (CBER)
• EU: CTA via EMA (simultaneous submission recommended)
• Fast Track Designation: Request based on unmet need in PD

Budget and Timeline

| Phase | Duration | Estimated Cost |
|-------|----------|----------------|
| GLP Toxicology | 18 months | $2.5M |
| NHP Safety | 18 months | $3.2M |
| Manufacturing | 12 months | $1.8M |
| Regulatory | 6 months | $0.5M |
| Total | ~30 months | $8.0M |

Risk Mitigation

| Risk | Probability | Impact | Mitigation |
|------|-------------|--------|------------|
| Preexisting immunity | Medium | High | Screen patients; alternative serotypes |
| Neuroinflammation | Medium | High | Steroid preconditioning; monitoring |
| Manufacturing yield | Low | Medium | Scale-up studies early |
| Regulatory delays | Low | Medium | Pre-IND meeting; parallel tracking |

See Also

• [AAV Serotype Comparison Experiment](/experiments/lrrk2-aav-gene-therapy-comparison)](/experiments)
• [LRRK2 Gene Therapy Approaches](/therapeutics/lrrk2-gene-therapy)](/therapeutics)
• [Parkinson's Disease Gene Therapy](/therapeutics/parkinsons-gene-therapy)

References

[@standaert2023]: [Standaert DG, et al. AAV-LRRK2 preclinical toxicology. Mol Ther. 2023](https://doi.org/10.1016/j.ymthe.2023.02.015)
[@volpatti2023]: [Volpatti JR, et al. AAV serotype comparison for CNS gene delivery. Nat Methods. 2023](https://doi.org/10.1038/s41592-023-01950-8)
[@hudry2022]: [Hudry E, et al. AAV biodistribution in non-human primates. Mol Ther. 2022](https://doi.org/10.1016/j.ymthe.2022.09.021)
[@weberadrian2023]: [Weber-Adrian D, et al. AAV manufacturing scale-up. Nat Biotechnol. 2023](https://doi.org/10.1038/s41587-023-01842-4)