This Phase 1 long-term follow-up (LTFU) study is evaluating the extended safety profile of LX1001, an adeno-associated virus (AAV) serotype rh.10 gene therapy vector expressing human APOE2, in participants who are homozygous for the APOE4 allele and have been diagnosed with Alzheimer's disease (AD). LX1001 was previously administered in the parent study NCT03634007, and this LTFU study tracks participants for up to 260 weeks (5 years) post-administration.
The therapeutic rationale is that delivering the APOE2 gene directly to the central nervous system via intrathecal injection converts the APOE isoform profile from APOE4 (the strongest genetic risk factor for late-onset AD) toward APOE2, which is associated with significantly reduced AD risk and neuroprotective effects.
| Field | Value |
|---|---|
| NCT ID | NCT05400330 |
| Status | Active, not recruiting |
| Phase | Phase 1 |
| Study Type | Interventional |
| Allocation | Non-randomized (single group) |
| Intervention Model | Single arm (LTFU of prior treatment) |
| Masking | None (open-label follow-up) |
| Enrollment | 10 participants |
| Sponsor | Lexeo Therapeutics |
| Collaborators | Alzheimer's Drug Discovery Foundation, Weill Cornell Medicine |
| Start Date | May 2023 (actual) |
| Primary Completion | November 2028 (estimated) |
| Locations | PPD Orlando Research Unit (Florida), Duke University (North Carolina) |
Homozygous APOE4 carriers represent the highest-risk population for Alzheimer's disease[1]:
The APOE2 isoform (encoded by the APOE ε2 allele) is associated with:
LX1001 delivers a functional copy of the human APOE2 gene directly to the CNS via intrathecal AAVrh.10 administration, enabling persistent expression of APOE2 protein in the cerebrospinal fluid and brain parenchyma. This approach bypasses the blood-brain barrier delivery challenge and achieves therapeutic levels that cannot be attained with recombinant protein or small molecule approaches.
| Parameter | Value |
|---|---|
| Agent | AAVrh.10hAPOE2 (LX1001) |
| Type | Adeno-associated virus serotype rh.10 |
| Gene Delivered | Human APOE2 complementary DNA (cDNA) |
| Route of Administration | Intrathecal injection |
| Parent Study Doses | Cohort 1: 1.4×10^10 gc/mL CSF; Cohort 2: 4.4×10^10 gc/mL CSF; Cohort 3: 1.4×10^11 gc/mL CSF; Cohort 4: 1.4×10^14 gc (fixed dose) |
The AAVrh.10 serotype was selected for its favorable CNS tropism and reduced off-target distribution[2]. Compared to AAV9 (more commonly used for CNS applications), AAVrh.10 demonstrates:
| Measure | Time Frame | Description |
|---|---|---|
| Incidence of treatment-emergent adverse events | 260 weeks | All emergent adverse events collected and categorized |
| Incidence of serious adverse events | 260 weeks | All serious adverse events documented and graded |
| Measure | Time Frame | Description |
|---|---|---|
| CSF APOE isoform conversion | Up to 260 weeks | Conversion of CSF APOE isoforms from APOE4 to APOE2-APOE4 profile |
| Amyloid PET scan | Up to 260 weeks | Florbetapir PET quantification of cerebral amyloid burden |
| CSF biomarkers | Up to 260 weeks | Aβ42, Aβ42/Aβ40 ratio, total tau (T-tau), phospho-tau (P-tau) |
| Quantitative MRI | Up to 260 weeks | Volumetric MRI, white matter integrity, cortical thickness |
| Cognitive and clinical assessment | Up to 260 weeks | Standardized AD cognitive batteries (specific instruments vary) |
| Tau PET scan | Up to 260 weeks | Flortaucipir PET for tau pathology burden (LX1001-01 Cohorts 3 and 4 only) |
The parent Phase 1/2 study established LX1001 safety and dosing. Key details:
| Field | Value |
|---|---|
| NCT ID | NCT03634007 |
| Status | Completed (November 2024) |
| Phase | Phase 1/Phase 2 |
| Enrollment | 15 participants |
| Doses tested | 4 ascending dose levels (1.4×10^10 to 1.4×10^14 gene copies) |
| Design | Open-label, sequential cohort, dose-escalation |
Following intrathecal administration, LX1001 transduces cells in the central nervous system (primarily ependymal cells, meningeal cells, and possibly neurons and glia), leading to sustained APOE2 protein expression in the CSF. The therapeutic mechanism involves:
LX1001 (AAVrh.10hAPOE2) intrathecal administration
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Transduction of CNS cells (ependymal, meningeal, neurons, glia)
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Persistent APOE2 protein expression in CSF and brain parenchyma
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Isoform conversion: APOE4 → APOE2/APOE4 heterozygote profile in CSF
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Neuroprotective effects:
- Enhanced Aβ clearance and degradation
- Reduced tau phosphorylation and aggregation
- Improved synaptic function and neuronal repair
- Decreased neuroinflammation
- Preserved blood-brain barrier integrity
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Slowed/arrested disease progression in APOE4 homozygotes
APOE2 expression provides neuroprotection through multiple pathways[3]:
LX1001 represents a novel therapeutic approach targeting the fundamental genetic cause of AD in the highest-risk patient population. Unlike monoclonal antibodies that target amyloid downstream, LX1001 addresses the upstream APOE4 risk by converting the isoform profile toward a protective state.
APOE genotypes and modulate Alzheimer's disease beta-amyloid deposition. JAMA Neurology. 2011. ↩︎
AAVrh.10 serotype for CNS gene therapy. Human Gene Therapy. 2017. ↩︎
APOE2 neuroprotective mechanisms and gene therapy potential. Neurobiology of Disease. 2023. ↩︎