Neurotrophic factors (GDNF, CDNF, BDNF, neurturin) are among the most promising payloads for CNS gene therapy because they address the fundamental problem of neuronal survival. Unlike small molecules that modulate pathways, gene therapy can provide sustained local production of these proteins at therapeutic concentrations in target brain regions — overcoming the key limitation of protein infusion (poor tissue distribution, catheter complications, immune responses).
This page tracks all active gene therapy programs delivering neurotrophic factors for neurodegenerative diseases.
| Program | Company/Lab | Vector | Route | Indication | Phase | Status |
|---|---|---|---|---|---|---|
| AB-1005 | AskBio/Bayer | AAV2-GDNF | Bilateral putaminal | PD | Phase 2 | REGENERATE-PD enrolling |
| AAV2-GDNF (NIH) | NIH/NINDS | AAV2-GDNF | Intraputaminal | PD | Phase 1 | Completed — long-term f/u |
| AAV9-GDNF | Academic | AAV9-GDNF | ICM/IV | PD | Preclinical | BBB-crossing capsid |
Key findings:
Deep dive: GDNF Therapy for PD | GDNF Signaling Pathway | GDNF Protein
| Program | Company/Lab | Vector | Route | Indication | Phase | Status |
|---|---|---|---|---|---|---|
| AAV2-CDNF | Herantis Pharma | AAV2-CDNF | Intraputaminal | PD | Phase 1-2 | NCT01362994 (protein completed, gene therapy follow-on) |
| CDNF protein | Herantis | Recombinant protein | Intraputaminal CED | PD | Phase 1-2 | Completed |
Key findings:
Deep dive: CDNF Therapy | ER Stress in Neurodegeneration
| Program | Company/Lab | Vector | Route | Indication | Phase | Status |
|---|---|---|---|---|---|---|
| CERE-120 | Ceregene/Sangamo | AAV2-NRTN | Intraputaminal | PD | Phase 2 | Failed (2013) |
| Next-gen NRTN | Academic | AAV9/PHP.eB-NRTN | IV/ICM | PD | Preclinical | Enhanced capsids |
Lessons from CERE-120 failure:
Deep dive: Neurturin Therapy | Neurturin Protein
| Program | Company/Lab | Vector | Route | Indication | Phase | Status |
|---|---|---|---|---|---|---|
| AAV-BDNF | Multiple academic | AAV9-BDNF | Various | AD, HD | Preclinical | Active research |
| TrkB agonist gene therapy | Academic | AAV-TrkB-agonist | Intrahippocampal | AD | Preclinical | Alternative approach |
Key considerations:
Deep dive: BDNF | Exercise-Induced BDNF
| Factor | Mechanism | Advantage over GDNF/BDNF | Programs |
|---|---|---|---|
| MANF | ER stress/UPR, immune modulation | Dual neuroprotective + immunomodulatory | Academic (Finland, China) |
| Artemin (ARTN) | GFRα3/RET signaling | Pain + neuroprotection | Academic |
| CNTF | JAK/STAT, gp130 signaling | Motor neuron support (ALS) | Historical (Regeneron, failed) |
| FGF2/FGF20 | FGFR signaling | DA neuron specification | Academic |
| VEGF | Neuroprotection, angiogenesis | Dual vascular + neuronal | Academic (ALS) |
| Delivery Method | Vector | Coverage | Redosing | Invasiveness | Clinical Stage |
|---|---|---|---|---|---|
| Intraputaminal CED | AAV2 | Focal (putamen) | No (one-time) | High (stereotactic surgery) | Phase 2 |
| Intracisternal (ICM) | AAV9 | Broad CNS | No | Moderate (LP-like) | Phase 1 (other payloads) |
| Intrathecal | AAV9/rh10 | Spinal + brainstem | No | Low | Phase 1-2 (SMA) |
| IV with engineered capsid | PHP.eB/CAP-B10 | Broad CNS | No | Low (IV) | Preclinical |
| FUS + AAV | Any serotype | Targeted region | Potentially | Moderate | Phase 1 |
| Ex vivo cell therapy | Encapsulated cells | Local secretion | Retrievable | High | Phase 1-2 (NT-501) |
Neurotrophic factor gene therapy has potential relevance to CBS/PSP through:
Key gap: No neurotrophic gene therapy trials specifically in CBS/PSP or 4R-tauopathies. All current programs target PD or AD. The cure roadmap should track when these programs could expand to atypical parkinsonism indications.
Gene therapy for neurotrophic factors requires careful patient selection to maximize benefit-risk:
| Criterion | Rationale | Clinical Use |
|---|---|---|
| Age 40-70 | Surgical risk increases >75; younger patients may have more residual neurons | REGENERATE-PD inclusion |
| Disease duration 4-12 years | Enough degeneration to benefit; too advanced = insufficient target | Most trials |
| Hoehn & Yahr 2-3 | Preserved motor function baseline; too severe = poor outcomes | REGENERATE-PD |
| Positive levodopa response (≥30%) | Confirms intact dopaminergic terminals that can receive neurotrophic support | All trials |
| DAT scan positive | Confirms presynaptic dopaminergic deficit | REGENERATE-PD secondary endpoint |
| No cognitive impairment (MMSE ≥26) | Protects informed consent and reduces placebo effect | REGENERATE-PD |
| No atypical parkinsonism | PSP/MSA/CBS have different pathology — not targetable by GDNF/CDNF | All trials exclusion |
| Biomarker | Source | What It Measures | Status in Trials |
|---|---|---|---|
| Dopamine transporter (DaT) | SPECT imaging | Presynaptic terminal integrity | Primary imaging endpoint |
| FDG-PET | PET | Regional brain metabolism | Secondary endpoint |
| Alpha-synuclein (total, p-S129) | CSF, blood | Disease burden/progression | Exploratory |
| Neurofilament light (NfL) | CSF, blood | Neurodegeneration rate | Exploratory, trending down with treatment |
| GDNF levels | CSF | Vector expression (gene therapy only) | Safety monitoring |
| Anti-AAV2 antibodies | Blood | Pre-existing immunity | Safety screen |
| Inflammatory cytokines | CSF | Immune response to vector | Safety monitoring |
Key insight: NfL trends may serve as early surrogate endpoints — if neurotrophic factors slow neurodegeneration, NfL should decrease relative to natural history. This is being tracked in the 5-year follow-up study (NCT07081841).
A critical and underappreciated barrier:
| Program | Expected Milestone | Timeframe |
|---|---|---|
| AB-1005 REGENERATE-PD | Phase 2 interim analysis | 2026 H1 |
| AB-1005 REGENERATE-PD | Phase 2 primary completion | 2026 H2 |
| HER-096 (CDNF mimetic) | Phase 2 initiation | 2026 H1-H2 |
| AAV9-GDNF BBB-crossing | IND filing / Phase 1 start | 2027 |
| AAV-BDNF | First-in-human study | 2028+ |