Roche and Neurocrine Biosciences (NASDAQ: NBIX) are co-developing an AAV-based gene therapy delivering full-length SCN1A for Dravet syndrome. This program represents a direct gene replacement approach — as opposed to the ASO (STK-001) or CRISPRa (ETX101) strategies employed by Stoke and Encoded — and is currently in IND-enabling studies.
In 2021, Roche and Neurocrine entered into a strategic collaboration for the development of gene therapies targeting severe neurological diseases. Neurocrine's expertise in CNS drug development and delivery, combined with Roche's global clinical infrastructure and diagnostics capabilities, positions this program as a significant competitive entry in the Dravet syndrome gene therapy landscape.
Key partnership terms:
- Neurocrine leads development and commercialization activities
- Roche provides global infrastructure and biomarker capabilities
- Shared development costs and profits
- Neurocrine retains US commercial rights; Roche handles ex-US
Unlike STK-001 (Stoke Therapeutics) which uses ASO-based NMD inhibition to boost endogenous SCN1A expression, and ETX101 (Encoded Therapeutics) which uses CRISPRa to activate the wild-type allele, the Roche/Neurocrine program delivers a functional copy of the SCN1A gene directly via AAV.
Technical considerations for SCN1A delivery:
- SCN1A coding sequence is ~6 kb, approaching the AAV packaging limit of ~4.7 kb
- Solution: Engineered mini-gene or regulatory element optimization to reduce cargo size while preserving functional activity
- Alternatively: Dual-vector approach (split-intein or trans-splicing) to package the full gene across two AAV vectors
- Delivery route: Likely intracerebroventricular (ICV) or intraparenchymal for optimal CNS distribution
The program uses an engineered AAV capsid optimized for CNS penetration. Specific serotype identity is not publicly disclosed, but given Roche's investment in next-generation capsid platforms (including engineered AAV9 variants), the program likely builds on PHP.eB or similar CNS-tropic capsid technology.
- Promoter: Neuron-specific promoter (e.g., Synapsin-1 or Mecp2) for selective expression in neurons
- Regulatory elements: Woodchuck hepatitis virus post-transcriptional regulatory element (WPRE) for enhanced expression
- PolyA signal: Bovine growth hormone polyadenylation signal
- Safety elements: Inverted terminal repeats (ITRs) from AAV2 for genome packaging
| Parameter |
Value |
| Indication |
Dravet syndrome (SCN1A) |
| Approach |
AAV-delivered SCN1A gene replacement |
| Development stage |
IND-enabling |
| Delivery route |
TBD (ICV likely) |
| Partnership |
Roche + Neurocrine Biosciences |
| Expected timeline |
IND filing 2026-2027 |
¶ Competitive Landscape
The Roche/Neurocrine program sits among three distinct modalities for SCN1A-targeted Dravet therapy:
| Company |
Approach |
Stage |
Route |
| Stoke Therapeutics |
ASO (STK-001) |
Phase 2 |
Intrathecal |
| Encoded Therapeutics |
CRISPRa AAV (ETX101) |
Phase 1 |
ICM |
| Roche/Neurocrine |
AAV gene replacement |
IND-enabling |
TBD |
Differentiation potential:
- AAV gene replacement may offer more durable expression than ASO (single dose vs. repeat dosing)
- Unlike ASO approach, does not require pathogenic variant to trigger NMD pathway
- Unlike CRISPRa, delivers full protein rather than relying on transcriptional activation
- Unknown whether program can achieve adequate CNS distribution given SCN1A gene size
Preclinical package includes:
- Efficacy: Mouse models of Dravet syndrome (Scn1a knockout/knockdown) show rescue of seizure phenotype and improved survival
- Biodistribution: CNS-wide distribution demonstrated in non-human primates
- Toxicology: IND-enabling GLP toxicology studies underway
- Will the program use a mini-gene, dual-vector, or full-length SCN1A approach?
- What AAV serotype is being used, and does it achieve adequate brain distribution?
- What delivery route (ICV vs. ICM vs. intraparenchymal) will be used?
- Will the program require a surgical procedure for delivery, and if so, what are the pediatric considerations?
- How does the durability and expression level compare to ASO or CRISPRa approaches?
- What is the expected dose and treatment interval?
- When will first-in-human studies be initiated?