LX1001 Phase 1/2 Trial (NCT03634007)

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Overview

flowchart TD LX1001_Phase_1_2_Trial__NCT036["LX1001 Phase 1/2 Trial (NCT03634007) - Gene Ther"] -->|"references"| LDLR["LDLR"] LX1001_Phase_1_2_Trial__NCT036["LX1001 Phase 1/2 Trial (NCT03634007) - Gene Ther"] -->|"references"| LRP1["LRP1"] LX1001_Phase_1_2_Trial__NCT036["LX1001 Phase 1/2 Trial (NCT03634007) - Gene Ther"] -->|"references"| APOE["APOE"] style LX1001_Phase_1_2_Trial__NCT036 fill:#4fc3f7,stroke:#333,color:#000

This Phase 1/2 open-label, dose-escalation clinical trial evaluated the safety, tolerability, and preliminary efficacy of LX1001, an adeno-associated virus (AAV) serotype rh.10 gene therapy vector expressing human [APOE2](/entities/apoe2), in participants who are homozygous for the [APOE4](/proteins/apoe) allele and have been diagnosed with [Alzheimer's disease](/diseases/alzheimers-disease) (AD). The study established the maximum tolerable dose across four ascending dose cohorts and generated initial evidence regarding APOE isoform conversion in the cerebrospinal fluid.

The trial ran from November 2019 to November 2024 and enrolled 15 participants across four dose levels. Participants completing the parent study were enrolled in the long-term follow-up study [NCT05400330](/clinical-trials/nct05400330-lx1001-ltfu), which tracks safety and biomarker outcomes for up to 260 weeks post-administration.

Trial Details

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LX1001 Phase 1/2 Trial (NCT03634007)

Overview

Mermaid diagram (expand to render)

Trial Details

| Field | Value |
|-------|-------|
| NCT ID | NCT03634007 |
| Status | Completed (November 2024) |
| Phase | Phase 1 / Phase 2 |
| Study Type | Interventional |
| Allocation | Non-randomized |
| Intervention Model | Sequential (dose escalation) |
| Masking | None (open-label) |
| Enrollment | 15 participants (actual) |
| Sponsor | Lexeo Therapeutics |
| Collaborators | Alzheimer's Drug Discovery Foundation, Weill Cornell Medicine |
| Start Date | November 2019 (actual) |
| Completion Date | November 2024 (actual) |
| Locations | K2 Medical Research (Maitland, FL), PPD Orlando (FL), Weill Cornell Medicine (NY), Duke University (NC) |

Scientific Rationale

APOE4 Homozygosity as Highest Genetic Risk Factor

Homozygous [APOE4](/proteins/apoe) carriers represent the highest-risk population for Alzheimer's disease[@sullivan2011]:

APOE4/4 homozygotes have a 10-12× increased risk of AD compared to APOE3/3 carriers
APOE4 homozygous prevalence: ~1-2% of the general population, but ~10-15% of all AD cases
Earlier disease onset: APOE4/4 carriers develop AD symptoms approximately 5-10 years earlier than APOE3/3 carriers
Mechanistic burden: APOE4 drives amyloid accumulation, tau pathology, neuroinflammation, BBB dysfunction, and impaired lipid transport

APOE2 Neuroprotection

The [APOE2](/entities/apoe2) isoform is associated with significantly reduced AD risk and multiple neuroprotective properties:

Reduced AD risk: APOE2 carriers have ~40-50% lower risk of AD compared to APOE3/3
Enhanced amyloid clearance: APOE2 efficiently promotes Aβ degradation and perivascular transport
Improved synaptic integrity: Better support of dendritic spine maintenance and neuronal repair
Anti-inflammatory: Reduced microglial activation and pro-inflammatory cytokine production

Gene Therapy Strategy

LX1001 delivers the [APOE2](/entities/apoe2) gene directly to the CNS via intrathecal AAVrh.10 administration, enabling persistent expression of APOE2 protein in the CSF and brain parenchyma. This approach:

Bypasses the blood-brain barrier delivery challenge

Achieves sustained therapeutic APOE2 levels not attainable with recombinant protein

Converts the APOE isoform profile from APOE4 toward APOE2-APOE4 (heterozygote)

Provides potential disease-modifying effects by addressing the upstream genetic risk

Intervention

LX1001 Gene Therapy Vector

| 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 |
| Vector Production | 293T cell-based producer system |
| Quantification | Droplet digital PCR (ddPCR) |

Dose Cohorts

| Cohort | Dose | Participants | Description |
|--------|------|-------------|-------------|
| Cohort 1 | 1.4×10^10 gc/mL CSF | ~3-5 | Low-dose initial safety |
| Cohort 2 | 4.4×10^10 gc/mL CSF | ~3-5 | Mid-dose escalation |
| Cohort 3 | 1.4×10^11 gc/mL CSF | ~3-5 | High-dose escalation |
| Cohort 4 | 1.4×10^14 gc (fixed dose) | ~3-5 | Fixed dose (~3.4×10^11 gc/mL CSF based on 409 mL average CSF volume) |

AAVrh.10 Serotype

The AAVrh.10 serotype was selected for[@tai2017]:

High neuronal and glial transduction efficiency
Lower prevalence of pre-existing neutralizing antibodies in human populations
Efficient CNS penetration when delivered directly to CSF
Established safety profile in prior gene therapy applications

Eligibility Criteria

Inclusion Criteria

Genetic status: APOE4 homozygotes (confirmed by genotyping)

Age: 50 years or older

Cognitive diagnosis: Mild cognitive impairment due to AD or mild-to-moderate dementia due to AD

CSF biomarkers: Evidence of AD-consistent CSF biomarkers (Aβ42, tau, p-tau)

AAV serology: Serum neutralizing anti-AAVrh10 titer <1:100

Infectious disease screen: No active hepatitis (A, B, or C) or HIV infection

Contraception: Fertile individuals must use barrier birth control for study duration

Washout: No experimental medications or protocols for at least 4 weeks prior to enrollment

Data privacy: Participants agree not to post study data on social media

Exclusion Criteria

Anti-amyloid therapies: Currently receiving or unable to wash out from monoclonal anti-amyloid therapy (aducanumab, lecanemab)

Anticoagulation: Unable to wash out from anti-coagulant medications

Spinal procedure contraindication: Does not fit American Journal of Neuroradiology recommendations for image-guided spinal procedures

Significant comorbidities: Malignancy, heart failure, liver or renal failure, HIV positive

Active infection: Elevated WBC, fever >38.5°C, infiltrate on chest X-ray

Prior gene/cell therapy: Prior or concurrent participation in any gene or cell therapy study

Imaging exclusions: >4 cerebral microhemorrhages, superficial siderosis, macrohemorrhage on screening MRI

MRI/PET/CSF inability: Cannot participate in required imaging or CSF collection procedures

Anesthesia contraindication: Cannot undergo procedures without general anesthesia (other than for gene therapy administration itself)

Hypersensitivity: Clinically significant hypersensitivity to study drug components (corticosteroids, proton-pump inhibitors)

Pregnancy/nursing: Pregnant or nursing

Outcome Measures

Primary Endpoints

| Measure | Time Frame | Description |
|---------|------------|-------------|
| Proportion of participants with treatment-emergent adverse events and serious adverse events | 1 year | Adverse events categorized and graded per CTCAE |
| Proportion of participants with treatment-emergent adverse events and serious adverse events at each dosage level | 1 year | Dose-stratified safety analysis |

Secondary Endpoints

The trial assessed multiple secondary endpoints including:

APOE isoform conversion: CSF APOE isoform shift from APOE4 toward APOE2-APOE4 profile
Amyloid PET: Florbetapir PET quantification of cerebral amyloid burden
CSF biomarkers: Aβ42, Aβ42/Aβ40 ratio, total tau, phospho-tau
Quantitative MRI: Volumetric analysis, white matter integrity
Cognitive outcomes: ADAS-Cog, CDR-SB, and other standardized batteries
Tau PET: Flortaucipir PET for tau pathology (primarily Cohorts 3 and 4)

Study Design

Screening Period (up to 42 days)
↓
Intrathecal LX1001 Administration (Day 0)
↓
Post-administration Follow-up (52 weeks per cohort)
↓
Safety monitoring: weeks 4, 8, 12, 26, 39, 52
CSF/blood biomarkers: weeks 4, 12, 26, 52
Amyloid PET: baseline and week 52
MRI: baseline and week 52
Cognitive assessments: baseline, weeks 26 and 52
↓
Completion → Enrollment in NCT05400330 (LTFU)

Dose Escalation Safety Review

Independent Safety Review Committee evaluated data after each cohort:

Review all adverse events and serious adverse events

Assess dose-limiting toxicities (DLTs)

Determine if escalation to next cohort is safe

Establish maximum tolerated dose (MTD) or recommended Phase 2 dose (RP2D)

Results and Findings

The trial was completed in November 2024. Top-line results have been reported:

Safety profile: LX1001 demonstrated an acceptable safety profile across all dose cohorts
APOE conversion: Evidence of APOE isoform conversion from APOE4 to APOE2-APOE4 in CSF
Biomarker trends: Changes in CSF and imaging biomarkers consistent with biological activity
Dosing: Fixed dose (Cohort 4) established as the recommended dose for further development

Detailed results will be published in peer-reviewed journals and presented at scientific conferences.

Mechanism of Action

APOE2 Expression Cascade

Following intrathecal administration, LX1001 transduces cells in the CNS, leading to sustained APOE2 protein expression:

Intrathecal AAVrh.10hAPOE2 administration
↓
Transduction of CNS cells (ependymal cells, meningeal cells, choroid plexus)
↓
Persistent APOE2 protein expression in CSF
↓
Isoform competition: APOE2 competes with endogenous APOE4 for lipid binding
↓
CSF APOE profile shifts from APOE4/APOE4 → APOE2/APOE4 heterozygote
↓
Neuroprotective effects across multiple pathways:
• Enhanced amyloid clearance (microglial degradation + perivascular transport)
• Reduced tau phosphorylation and aggregation
• Improved synaptic function and neuronal repair
• Decreased neuroinflammation
• Preserved blood-brain barrier integrity
↓
Disease modification in APOE4 homozygotes

Key Molecular Mechanisms

APOE2 provides neuroprotection through[@kelleher2023]:

Amyloid clearance: APOE2-Aβ complex is more efficiently cleared by microglial receptors (LDLR, LRP1)

Lipid transport: APOE2 supports neuronal lipid homeostasis, maintaining membrane integrity

Anti-inflammatory: Reduced NF-κB activation and microglial pro-inflammatory cytokine production

BBB protection: Preserved blood-brain barrier through pericyte and endothelial support

Tau modulation: Reduced kinase activity and enhanced phosphatase function

Clinical Significance

First Gene Therapy Targeting APOE4

LX1001 represents a groundbreaking approach as the first gene therapy to directly address the APOE4 genetic risk factor in AD:

Upstream targeting: Addresses the fundamental genetic cause rather than downstream amyloid
Persistent expression: Multi-year APOE2 expression vs. periodic antibody administration
APOE4-specific: Direct mechanism targeting highest-risk patient population
Disease-modifying potential: Could provide sustained disease modification

Comparison to Anti-Amyloid Antibodies

| Aspect | LX1001 Gene Therapy | Anti-Amyloid Antibodies (Aduhelm, Leqembi) |
|--------|---------------------|-------------------------------------------|
| Target | APOE4 isoform conversion | Amyloid-beta plaques |
| Mechanism | Genetic (upstream) | Immunological (downstream) |
| Duration | Persistent (multi-year) | Periodic (monthly infusions) |
| Population | APOE4 homozygotes only | Broad AD population |
| Route | Single intrathecal injection | Monthly IV infusion |
| Side effects | Intrathecal procedure risks | ARIA (amyloid-related imaging abnormalities) |

Future Development

The success of NCT03634007 supports continued development of LX1001:

Phase 2/3 efficacy trials in APOE4 homozygotes with early AD

Combination approaches with anti-amyloid or anti-tau therapeutics

Expansion to other APOE4-associated neurodegenerative conditions

Optimization of delivery and dosing regimens

Long-Term Follow-up

Participants completing this study are enrolled in [NCT05400330](/clinical-trials/nct05400330-lx1001-ltfu), tracking:

5-year (260-week) safety profile
Long-term biomarker trends (CSF APOE, amyloid PET, tau PET, MRI)
Cognitive and clinical outcomes over extended follow-up
Delayed adverse event monitoring

Cross-References

[APOE Gene and Alzheimer's Risk](/proteins/apoe)
[APOE2 Neuroprotection](/entities/apoe2)
[APOE4 Homozygosity and Alzheimer's](/mechanisms/apoe4-alzheimers)
[Gene Therapy for Alzheimer's Disease](/mechanisms/gene-therapy-alzheimers)
[AAV Vector CNS Delivery](/mechanisms/aav-gene-therapy-vectors-neurodegeneration)
[Intrathecal Drug Delivery](/mechanisms/intrathecal-delivery)
[APOE and Lipid Metabolism](/mechanisms/apoe-lipid-metabolism-alzheimers)
[LTFU Study: NCT05400330](/clinical-trials/nct05400330-lx1001-ltfu)
[Alzheimer's Disease Therapeutics](/therapeutics/alzheimers-disease-therapeutics)

External Links

[ClinicalTrials.gov - NCT03634007](https://clinicaltrials.gov/study/NCT03634007)
[ClinicalTrials.gov - NCT05400330 (LTFU)](https://clinicaltrials.gov/study/NCT05400330)
[Lexeo Therapeutics Pipeline](https://www.lexeotx.com/pipeline)
[Alzheimer's Drug Discovery Foundation](https://www.alzdiscovery.org/)
[Weill Cornell Medicine - Alzheimer's Disease Research Unit](https://weillcornell.org/)

References

[NCT03634007 - Gene Therapy for APOE4 Homozygote of Alzheimer's Disease](https://clinicaltrials.gov/study/NCT03634007)

[Rosenberg et al., AAV gene therapy for APOE4 homozygote Alzheimer's disease (2022)](https://alz-journals.onlinelibrary.wiley.com/doi/10.1002/trpi.20220004)

[Kelleher et al., APOE2 neuroprotective mechanisms and gene therapy potential (2023)](https://pubmed.ncbi.nlm.nih.gov/36965941/)

[Sullivan et al., APOE genotypes modulate AD beta-amyloid deposition (2011)](https://pubmed.ncbi.nlm.nih.gov/21911610/)

[Tai et al., AAVrh.10 serotype for CNS gene therapy (2017)](https://pubmed.ncbi.nlm.nih.gov/27852111/)

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