AAV gene therapy for Tay-Sachs disease

Abstract

Tay-Sachs disease (TSD) is an inherited neurological disorder caused by deficiency of hexosaminidase A (HexA). Here, we describe an adeno-associated virus (AAV) gene therapy expanded-access trial in two patients with infantile TSD (IND 18225) with safety as the primary endpoint and no secondary endpoints. Patient TSD-001 was treated at 30 months with an equimolar mix of AAVrh8-HEXA and AAVrh8-HEXB administered intrathecally (i.t.), with 75% of the total dose (1 × 10¹⁴ vector genomes (vg)) in the cisterna magna and 25% at the thoracolumbar junction. Patient TSD-002 was treated at 7 months by combined bilateral thalamic (1.5 × 10¹² vg per thalamus) and i.t. infusion (3.9 × 10¹³ vg). Both patients were immunosuppressed. Injection procedures were well tolerated, with no vector-related adverse events (AEs) to date. Cerebrospinal fluid (CSF) HexA activity increased from baseline and remained stable in both patients. TSD-002 showed disease stabilization by 3 months after injection with ongoing myelination, a temporary deviation from the natural history of infantile TSD, but disease progression was evident at 6 months after treatment. TSD-001 remains seizure-free at 5 years of age on the same anticonvulsant therapy as before therapy. TSD-002 developed anticonvulsant-responsive seizures at 2 years of age. This study provides early safety and proof-of-concept data in humans for treatment of patients with TSD by AAV gene therapy.

Extended Data Fig. 1 |. Structural brain MRI in healthy children during development and an infantile TSD patient.

T2 brain MRIs at 7 and 12 months of age in healthy children are from the MRI Atlas of Normal Myelination (www.myelinationmriatlas.com) with permission from Dr. Achint Singh. The T2 brain MRI of an 11-month-old infantile Tay-Sachs disease child was kindly provided by a family of a deceased child through the National Tay-Sachs and Allied Disease Association with permission to publish it here.

Extended Data Fig. 2 |. Volumetric calculations of lateral ventricular size and size of the lentiform nucleus.

TSD-001 has larger ventricles consistent with cortical atrophy whereas the relevance of TSD-002 ventricular size remains unclear and could be associated with normal brain development.

Extended Data Fig. 3 |. DTI of normal brain development.

Tractography of the normal developing brain from Hermoye et al, 2006. The color scheme of the tractography pathways is based on a standard red-green-blue (RGB) color code that shows the spatial locations of terminal regions of each pathway (right-left: red; dorsal-ventral: blue; and, anterior-posterior: green.

Extended Data Fig. 4 |. DTI results.

a, Mean diffusivity (MD) maps of TSD-002 brain indicating regions of interest (ROI) for calculation of DTI parameters. MD quantifications over time are displayed below the images for various ROIs in the brain for both TSD-001 and TSD-002. b, Axial diffusivity (AD) and c, radial diffusivity (RD) measurements are also shown for the same brain ROIs over time for both patients. Data is represented as mean±SD of pixel intensity in the ROI. In TSD-002 both optic radiations show stable FA values and increased average diffusivity values. AD values remain stable even when FA decreases, as shown in the anterior corpus callosum for TSD-001.

Fig. 1 |. Longitudinal safety and immunological studies.

a,b, Serum levels of liver enzymes alanine aminotransferase (a; ALT) and aspartate aminotransferase (b; AST) enzymes in TSD-001 and TSD-002 patients before treatment (Pre-TX); weeks 1, 2 and 3 (W1, W2 and W3) and months 1, 2, 3 and 6 (M1, M2, M3 and M6). Shaded bars (a,b) represent the normal interval for both assays. Dashed line (b) indicates the maximum value reported in patients with TSD c, Total anti-AAVrh8 IgG in serum quantified by enzyme-linked immunosorbent assay. Vertical gray arrow indicates that both patients received i.v. immunoglobulin 1 month after treatment. d, Neutralizing antibody titers to AAVrh8 capsid quantified by a transduction assay. e–h, Peripheral blood mononuclear cells were isolated from patients TSD-001 and TSD-002 before treatment and at various time points thereafter to assess T cell responses by interferon-γ ELISpot assays using stimulation with pools of overlapping peptides spanning AAVrh8 VP1 (e,f) or human HEXA and HEXB proteins (g,h). Unstimulated or CD3/CD28-stimulated peripheral blood mononuclear cells were included in all assays as negative and positive controls. Data are presented as mean ± s.d. and were calculated from triplicate technical replicates for each sample. Statistical analysis was performed using two-way analysis of variance or mixed effects analysis (due to missing samples), followed by a Dunnett post hoc test to determine statistical significance of peptide pool stimulation versus the unstimulated sample (*P < 0.05). TSD-001 data in a–d are represented by blue circles and connecting lines, whereas TSD-002 data are represented by red triangles and connecting lines. D, day; NAb, neutralizing antibody; SFU, spot forming units.

Fig. 2 |. Longitudinal biochemical and neurological function outcome measures.

a,b, HexA activity was measured in CSF (a) and serum (b) of TSD-001 (blue bars) and TSD-002 (red bars) patients and non-TSD individuals (gray bars; data are presented as mean and s.d. calculated from enzyme activity in samples from three different individuals). CSF was collected on the treatment day before infusion (D0) and months 3 and 6 (M3 and M6). Serum was collected at weeks 1-3 (W1-W3) and months 2, 3 and 6 (M2, M3 and M6). c, Mass spectrometry quantification of GM2 ganglioside species in CSF at day 0 and months 3 and 6. TSD-001 data are represented by blue circles and connecting lines. TSD-002 data are represented by red triangles and connecting lines. d, Western blot analysis of HEXA protein expression in CSF of TSD-001 and TSD-002 patients at day 0 (D0) and months 3 and 6 (M3 and M6). Transthyretin (TTR), which is the most abundant protein in CSF, was used as a loading control. Arrowheads indicate the location of the bands corresponding to the HEXA protein. Western blots were performed once. e, CHOP-INTEND (Children’s Hospital of Philadelphia Infant Test of Neuromuscular Disorders) scores for TSD-001 and TSD-002 measured 2 days before treatment and up to 6 or 12 months after treatment. 4MU, 4-methyllumbelliferone.

Fig. 3 |. Anatomical MRi findings in patients with TSD who were treated with rAAVrh8.HEX/HEXB vectors.

a, Thalamic targeting in TSD-002. T1-weighted coronal (left panel) and T2-weighted coronal and axial (middle and right panels) MRI immediately after bilateral thalamic injection. Injection locations and injectate distribution are denoted by yellow arrows. b, T2-weighted MRI of TSD-001 (top) and TSD-002 (bottom) at 0, 3 and 6 months after treatment (patients age in months is shown in each MRI). The pretreatment MRI for TSD-002 shows incomplete myelination in the posterior internal capsule, as well as the parietal and occipital tracts. After treatment, the degree of myelination, as shown by the darkening of white matter, suggests stabilization over time and potential improvement in the anterior and posterior corpus callosum (yellow arrowheads). c, Quantification of whole-brain and various structure volumes in TSD-001 and TSD-002. M, month; Pre-TX, before treatment.

Fig. 4 |. DTI in TSD patients treated with rAAVrh8.HEX/HEXB vectors.

a, Color tractography maps before and after treatment from TSD-002. Before treatment, TSD-002 shows incomplete myelination. At 6 months after treatment (13 months of age), myelination was increased in the external capsule (white arrowhead) and the optical radiations (yellow arrowhead). Visual comparison of tract development in these areas suggests a myelination stage comparable to a 6- to 9-month-old healthy infant (Extended Data Fig. 1). The color scheme of the tractography pathways is based on a standard red-green-blue color code that shows the spatial locations of terminal regions of each pathway (red, right to left; blue, dorsal to ventral; green, anterior to posterior). b, Quantification of fractional anisotropy (FA) in various brain structures of TSD-001 (blue line) and TSD-002 (red line) at 0, 3 and 6 months after treatment. Data are presented as mean±s.d. of pixel intensity in the regions of interest in the structures analyzed. M, month; Pre-Tx, before treatment.