AB-1005 (also known as AAV2-GDNF) is an adeno-associated virus serotype 2 (AAV2)-based gene therapy developed by a consortium of researchers, designed to deliver the Glial Cell Line-Derived Neurotrophic Factor (GDNF) gene directly to the putamen of patients with Parkinson's disease. This approach represents a novel disease-modifying strategy that aims to protect and potentially restore dopaminergic neurons through continuous local GDNF expression.
Unlike previous GDNF delivery methods that required continuous infusion devices, AB-1005 provides sustained GDNF expression through a single surgical procedure, potentially offering long-term neuroprotective effects with a favorable safety profile.
| Property |
Value |
| Phase |
Phase 2 |
| Status |
Active, recruiting |
| Drug |
AB-1005 (AAV2-GDNF) |
| Sponsor |
Clinical consortium / Research institutions |
| ClinicalTrials.gov Identifier |
NCT04815625 (REGENERATE-PD) |
| Study Name |
REGENERATE-PD |
| Indication |
Parkinson's Disease |
| Target Enrollment |
Approximately 40-60 patients |
AB-1005 utilizes a recombinant AAV2 capsid to deliver the human GDNF transgene:
- Vector Construction: The AAV2 genome has been engineered to carry the human GDNF gene under the control of a constitutive promoter
- Serotype Selection: AAV2 was chosen for its well-characterized safety profile and ability to transduce neurons effectively in the brain
- Promoter: Strong neuronal promoter ensures GDNF expression primarily in neuronal cells within the target region
¶ GDNF Expression and Signaling
Once delivered, the transduced cells produce and secrete GDNF protein:
- GDNF Secretion: Transduced cells in the putamen continuously secrete GDNF into the extracellular space
- Receptor Binding: GDNF binds to GFRα1 (GDNF Family Receptor Alpha 1) on the surface of nearby dopaminergic nerve terminals
- RET Activation: GFRα1 recruitment triggers RET (Rearranged during Transfection) receptor tyrosine kinase dimerization and autophosphorylation
- Downstream Signaling: Multiple protective pathways are activated:
- PI3K/Akt pathway (anti-apoptotic, cell survival)
- MAPK/ERK pathway (neuronal differentiation, outgrowth)
- PLCγ pathway (calcium homeostasis)
The GDNF signaling cascade produces several beneficial effects:
- Dopaminergic Neuron Survival: Promotes survival of degenerating dopaminergic neurons in the substantia nigra
- Axonal Protection: Protects striatal nerve terminals from degeneration
- Functional Restoration: May restore dopamine release capacity in surviving neurons
- Oxidative Stress Protection: Enhances cellular defenses against oxidative damage
AB-1005 is delivered via stereotactic neurosurgery:
- Pre-operative Planning: High-resolution MRI used to map target coordinates for bilateral putamen
- Anesthesia: Patient under general anesthesia for the procedure
- Craniotomy: Small burr hole created bilaterally
- Cannula Placement: Precision cannulas positioned in the posterior putamen
- Convection-Enhanced Delivery: Slow infusion using convection to improve distribution
- Bilateral Administration: Both hemispheres treated in a single procedure
| Parameter |
Specification |
| Target |
Bilateral posterior putamen |
| Injection Volume |
Approximately 2-4 mL per hemisphere |
| Infusion Rate |
Slow convection-enhanced delivery |
| Procedure Duration |
Approximately 4-6 hours |
The REGENERATE-PD trial is designed as a Phase 2, open-label study with the following components:
- Screening Period: Comprehensive evaluation to confirm eligibility
- Surgical Procedure: Single AAV2-GDNF administration
- Acute Phase: Immediate post-operative monitoring (2-4 weeks)
- Follow-up Phase: Long-term assessment up to 2-5 years
- Safety: Incidence and severity of adverse events (primary)
- Tolerability: Assessment of surgical and vector-related complications
- Motor Function: Change in Unified Parkinson's Disease Rating Scale (UPDRS) Part III "Off" medication scores
- Quality of Life: PDQ-39 scores
- Biomarkers: CSF and blood biomarkers including:
- Imaging: DaTscan (dopamine transporter SPECT) to assess striatal integrity
- Levodopa Response: Assessment of levodopa responsiveness
- Age 40-75 years
- Diagnosis of idiopathic Parkinson's disease
- Disease duration 4-15 years
- Hoehn & Yahr stage 2-3 in "On" state
- Positive levodopa response (≥30% improvement in UPDRS Part III)
- Stable antiparkinsonian medication for ≥4 weeks
- MMSE score ≥26 (no significant cognitive impairment)
- Capable of undergoing neurosurgical procedure
- Atypical parkinsonism (PSP, MSA, CBD)
- Significant cognitive impairment (MoCA <24)
- Psychiatric contraindications (active psychosis, severe depression)
- Previous brain surgery (DBS, lesioning)
- Active infection or inflammatory condition
- Immunosuppressive therapy
- Prior AAV vector exposure
- Contraindications to MRI or anesthesia
- Active malignancy
The REGENERATE-PD trial is being conducted at leading movement disorder centers:
- United States: Major academic medical centers with expertise in gene therapy and movement disorders
- Additional sites: International centers with established PD research programs
For current site information, please refer to ClinicalTrials.gov (NCT04815625).
| Feature |
Historical GDNF Infusion |
AB-1005 Gene Therapy |
| Delivery |
Continuous external pump |
Single surgical procedure |
| Duration |
Requires device maintenance |
Long-term expression |
| Distribution |
Limited by diffusion |
CED improves distribution |
| Safety |
Device-related risks |
No external hardware |
| Patient Burden |
High (device, frequent visits) |
Lower (one-time procedure) |
AB-1005 represents a potentially disease-modifying approach because it:
- Targets Root Cause: Addresses dopaminergic neuron degeneration, not just symptoms
- Continuous Therapy: Provides sustained neurotrophic support rather than intermittent dosing
- Neuroprotection + Potential Rescue: May protect remaining neurons while potentially restoring function
- Novel Mechanism: Different from all current symptomatic treatments (dopamine replacement, DBS)
| Trial |
Approach |
Outcome |
| 1995 (Intraventricular) |
Direct brain infusion |
Mixed results, discontinued |
| 2002-2004 (Phase I) |
Putaminal infusion |
Improved motor scores |
| 2006-2008 (Phase II) |
Continuous putaminal infusion |
Did not meet primary endpoint |
- Gene Therapy vs. Protein Delivery: Single procedure vs. continuous infusion
- Modern Delivery: Convection-enhanced delivery for better distribution
- Targeted Approach: Precision stereotactic placement
- Sustained Expression: Long-term GDNF production from transduced cells
- Surgical Risks: Intracranial hemorrhage, infection
- Vector-Related: Immune response to AAV2 capsid or GDNF protein
- Off-Target Effects: GDNF expression outside target region
- Immunogenicity: Pre-existing antibodies to AAV2
- Long-Term Safety: Unknown effects of sustained GDNF overexpression
- Regular neurological examinations
- MRI imaging at specified intervals
- CSF biomarker sampling
- Immunogenicity assessments
The REGENERATE-PD trial represents a critical proof-of-concept for GDNF gene therapy in Parkinson's disease. Success could pave the way for:
- Expanded Trials: Larger Phase 2b/3 studies
- Earlier Intervention: Testing in early-stage PD patients
- Combination Approaches: GDNF gene therapy with other neuroprotective strategies
- Next-Generation Vectors: AAV capsid variants with improved neuronal tropism