Gene Therapy in Sheep CLN5 CLN6

1. CLN5
CLN6
GENE THERAPY IN SHEEP
- current and planned New Zealand research
Introduction
We have been exploring viral-mediated gene
therapy in sheep with naturally occurring
CLN5 and CLN6 Batten disease. Sheep have
large human-like brains and disease
development in affected sheep closely
follows that in patients, so they are ideal
models for studies on possible treatments.
Gene therapy uses disabled viruses to carry
a normal copy of a mutated gene into cells.
Adeno-associated viral (AAV) vectors were
used to deliver the CLN5 or CLN6 gene into
the brain. Treated sheep are monitored by
similar outcome measures to those used in
humans, including an ovine-specific Batten
disease rating scale (oBDRS), maze testing,
and CT and MRI scans.
Conclusion: Ongoing studies in sheep suggest that brain-directed and ocular gene therapy
are promising therapeutic options for Batten disease patients, especially those with CLN5
disease. We thank CureKids NZ, Canterbury Medical Research Foundation and the BDSRA for their financial support.
Nadia Mitchell1,2, Samantha Murray2, Martin Wellby1, Graham Barrell1, Steven Gray3 and David Palmer1
1Agriculture and Life Sciences, Lincoln University, New Zealand; 2Department of Radiology, University of Otago, Christchurch, New Zealand;
3Gene Therapy Center, University of North Carolina, Chapel Hill, NC, USA
Methods
AAV vectors are injected into the
cerebrospinal fluid (CSF) of affected sheep
brains at either:
1. 3 months of age (pre-symptomatic)
2. 6-7 months of age (early symptomatic)
3. 9 months of age (late symptomatic)
CLN-/-
scAAV9.CLN5 or
scAAV9.CLN6
• •
•
• •
•
Vitreous
Retina
CLN5 gene therapy – promising results for translation
• Treatment at 3 months of age prevents intracranial volume loss (brain atrophy) and stereotypical disease development (except for loss of vision).
• Clinical disease is stabilised in sheep treated at 6 months of age, and intracranial volumes are retained.
• Disease progression was slowed in sheep treated at 9 months of age, and intracranial volume loss is slowed.
• 3-D reconstructions demonstrate the structural integrity of treated brains compared to the marked atrophy in the untreated brain.
Sheep received LD (low dose, 2 x 1012 vg) or HD (high dose, 5 x 1012 vg) scAAV9.CLN5 at 3, 6 or 9 months of age.
CLN6 gene therapy – increased doses
One out of six CLN6 affected sheep responded well to intraventricular scAAV9.CLN6 gene therapy and this led to
a Phase I/II clinical trial. Further attempts in sheep have not been as successful. As the CLN6 protein is not
secreted from the cell, we need to correct as many brain cells as we can to correct the disease. Our next step is to
trial even higher doses (5 x 1013 vg) of scAAV9.CLN6 delivery to the CLN6 affected sheep brain in October 2018.
Even when we do have a positive effect on the brain, treated
sheep still loss their vision. We are testing intravitreal gene
therapy into one eye. Early electroretinography findings
suggest that retinal function may be preserved in the treated
eye. Next we will try combined brain and eye injections.
Ocular gene therapy – attempting to fix vision loss
Control
20m
Untreated
19m
Treated at:
3m 6m 9m
19m 19m 19m
Vol: 103.5 mL 77.9 mL 101.1 mL 90.3 mL 88.1 mL
Untreated eye Treated eyescAAV9.CLN5 or
scAAV9.CLN6