AAV9-Mediated Gene Therapy for Infantile-Onset Pompe's Disease

Authors, Journal, Affiliations, Type, DOI

• Authors: Xiuwei Ma, Lu Zhuang, Wenhao Ma, Jun Li, et al.
• Journal: New England Journal of Medicine, 2025;392:2438–2446
• Affiliations: Chinese People's Liberation Army General Hospital, Beijing; Genecradle Therapeutics, Beijing; Beijing Children's Hospital, Capital Medical University
• Type: Brief report / first-in-human pilot trial
• DOI: https://doi.org/10.1056/NEJMoa2407766
• Funding: National Natural Science Foundation of China; National High Level Hospital Clinical Research Funding
• Trial Registry: ChiCTR2200063229

Overview

GC301, a recombinant AAV9 vector carrying codon-optimized human acid α-glucosidase (rAAV9-coGAA), was administered as a single intravenous infusion (1.2 × 10¹⁴ vg/kg) to four infants with infantile-onset Pompe disease. Three of four patients survived the 52-week observation period with improvement in cardiac outcomes (LVM index, LVEF) and psychomotor milestones; one patient died after parents declined invasive ventilation for respiratory failure. No anti-GAA antibodies were detected in any patient throughout the observation period — a key advantage over enzyme-replacement therapy. This is the first published human clinical data for systemic AAV9-GAA gene therapy in infantile-onset Pompe disease.

Keywords

Pompe disease, acid α-glucosidase (GAA), adeno-associated virus serotype 9 (AAV9), enzyme-replacement therapy, infantile-onset, lysosomal storage disorder, GC301, gene therapy, CRIM status, Hammersmith Infant Neurological Examination (HINE)

Key Takeaways

Study Design and Methods

• Eligible patients: infants <6 months with infantile-onset Pompe disease, cardiomegaly, hypotonia, and biallelic pathogenic GAA variants; modified Ross class IV (severe HF) excluded
• Sentinel design: Patient 1 enrolled first, monitored ≥4 weeks for ≥grade 3 drug-related AE before additional enrollment
• Dose: 1.2 × 10¹⁴ vector genomes/kg IV over 55–77 minutes, with prophylactic prednisolone
• All patients had received 1–5 prior rhGAA infusions; none received immune-tolerance induction
• Primary outcome: safety (adverse events, labs); secondary: efficacy (psychomotor and cardiac outcomes)
• Observation period: 52 weeks; long-term 5-year follow-up ongoing at 6-month intervals

Patient Characteristics

• 4 patients enrolled (Sept 2022 – March 2023)
• CRIM status: 3 patients predicted CRIM-positive by genotype; CRIM status uncertain for Patient 1
• Patient 2 was preterm (35+6 weeks), with septal hypertrophy noted at birth — disease onset likely in utero

Safety

• Most common AEs: Mild/moderate respiratory tract infections, hyperlipidemia, BNP elevation, diarrhea — all 4 patients
• Hyperlipidemia and BNP elevation: transient, asymptomatic, no treatment required
• Severe AEs (across 3 patients): Pneumonia (Patients 1, 2, 4); left ventricular dysfunction (Patient 1); bronchitis (Patient 2) — none attributed to GC301 by investigators
• Elevated AST/ALT in Patients 1, 2, 3 — no bilirubin or ALP abnormalities
• Patient 2 withdrew at week 21 due to respiratory failure; parents declined invasive ventilation; died 8 hours after cessation of care

Psychomotor Outcomes

• HINE scores increased to ≥62 in 3 patients within 4 weeks of injection
• Patients 3 and 4: HINE scores 74 and 75 respectively at 12 months of age — within normal range (reference >72 at 12 months for full-term infants)
• Patient 2: HINE improved from 45.5 at baseline to 53 at week 20 (6 months of age)
• Patients 1, 3, 4 attained the ability to sit without assistance, stand with assistance, and walk with assistance by week 52
• By February 2025 (22–29 months post-infusion), Patients 3 and 4 could stand and walk without assistance
• Mechanism: AAV9 crosses the blood–brain barrier (unlike rhGAA), potentially clearing CNS glycogen accumulation

Cardiac Outcomes

• LVM index (normal <64 g/m²):
  • Patient 1: decreased from 157.15 → 67.83 at week 24 (LVM z-score 13.05 → 2.29); transiently worsened during pneumonia (week 30) but remained below baseline
  • Patient 4: LVM index decreased over observation period despite 3 intercurrent infections
  • Patient 3: decreased initially, then increased with recurrent respiratory infections
  • Patient 2: no notable improvement
• LVEF: Improved in Patients 1, 3, 4; remained above lower normal limit in all 4 (except transient decrease in Patient 1 with pneumonia)
• Wall thickness (LV posterior wall and IVS during diastole) remained constant in Patients 1, 2, 4

GAA Enzyme Activity and Vector Genome

• GAA enzyme activity (dried blood spots) increased after GC301 injection in all 4 patients
• After week 2: remained above baseline in Patients 1, 3, 4 throughout observation
• Patient 1: GAA activity decreased to near baseline during frequent respiratory infections — infection can impair gene therapy efficacy
• Vector DNA (whole blood): decreased progressively after injection; undetectable at end of study in 3 surviving patients (likely due to anti-AAV9 antibody clearance)

Host Immune Response (Critical Finding)

• Anti-GAA binding antibodies: NOT detected in any patient at any time point (all 4 patients; unlike ERT recipients who develop anti-rhGAA IgG regardless of CRIM status)
• GAA-specific cellular immune responses (IFN-γ ELISpot): not detected in any patient
• Pre-existing anti-AAV9 neutralising antibody titers: <1:20 to 1:262 (range consistent with prior IV AAV studies)
• Post-injection: AAV-binding IgG developed and persisted throughout observation in all 4 patients (expected)
• Clinical implication: Gene therapy-induced immune tolerance to the transgenic GAA product may avoid the major limitation of ERT (persistent anti-rhGAA antibodies reduce efficacy, especially in CRIM-negative patients)

Respiratory Infection as a Confounding Factor

• All 4 patients experienced pneumonia during follow-up
• Respiratory infections associated with increased LVM index/z-score in Patients 1, 2, 3 — suggesting infections worsen cardiac function
• GAA activity dropped during infections in Patient 1 — infections may reduce gene therapy efficacy
• Proposed mechanisms: airway involvement in Pompe disease; AAV9 does not transduce alveolar cells; hypothetical "immunity gap" after COVID-19 social-isolation measures

Limitations of the Document

• Very small sample size (n=4): No control arm; preliminary safety and efficacy data only
• GAA activity measured in dried blood spots only: Plasma/leukocyte assays would provide better insight into cross-correction of affected tissues
• CRIM status undetermined for Patient 1: CRIM status is an important prognostic factor; uncertainty limits interpretation of immune tolerance findings
• One patient death: Confounded by parental refusal of invasive ventilation; not a drug-related AE per investigator assessment, but outcome reflects real-world disease severity
• Respiratory infection confounding: Infections affected both cardiac function and GAA activity — difficult to disentangle treatment effect from infection effect
• No CNS imaging or cognitive testing: AAV9 CNS penetration is inferred from HINE improvement; direct evidence of CNS glycogen clearance not demonstrated
• 52-week follow-up insufficient: Long-term durability of effect, vector dilution in growing infants, and re-dosing limitations are unaddressed

Key Concepts Mentioned

• concepts/AAV-Gene-Delivery — AAV9 systemic delivery platform; IV route; immune responses; paediatric dilution challenge
• concepts/Pompe-Disease — clinical features, natural history, ERT limitations, CNS involvement
• CRIM status — cross-reactive immunologic material; CRIM-negative predicts worse outcomes with ERT

Key Entities Mentioned

• entities/Genecradle-Therapeutics — manufacturer and study collaborator for GC301

Wiki Pages Updated

• wiki/sources/aav9-pompe-nejm-2025.md — created (this file)
• wiki/concepts/AAV-Gene-Delivery.md — updated with Pompe clinical data and IV immune tolerance finding
• wiki/concepts/Pompe-Disease.md — created (new concept page)
• wiki/sourceindex.md — new entry added
• wiki/wikiindex.md — Pompe-Disease concept entry added; AAV-Gene-Delivery description updated