2 September 2023
This newsletter edition features two recently published papers from a New Zealand-based group, led by Professors Nadia Mitchell and David Palmer of Lincoln University. Over the past decade, this research team have discovered and characterised naturally occurring sheep models of CLN5 and CLN6 disease that each share key clinical features of the human conditions. These models represent ideal systems for testing the clinical efficacy of gene therapies. The studies below describe some of the key natural history and IND-enabling safety and efficacy studies that contributed to the development of Neurogene’s NGN-101 therapy, currently in Phase 1/2 clinical trial for treatment of CLN5 disease. The paper Characterization of neuropathology in ovine CLN5 and CLN6 neuronal ceroid lipofuscinoses published in the journal Developmental Biology in late May, compared neurodegeneration, neuroinflammation, and lysosomal storage accumulation in CLN5-affected and CLN6-affected sheep brains from birth to end-stage disease at ?24 months of age. The disease cascade was remarkably similar for both models, and correlated with published clinical (human) data. The study identifies three potential therapeutic windows in affected sheep – presymptomatic (3 months), early symptomatic (6 months), and later disease stage (9 months of age). Beyond later-stage, the extensive loss of neurons was considered likely to diminish any chance of therapeutic benefit. Mitchell and colleagues’ subsequent paper, Long-term safety and dose escalation of intracerebroventricular CLN5 gene therapy in sheep supports clinical translation for CLN5 Batten disease, published August 8, showed that low, moderate and high doses of gene therapy delayed CLN5 disease progression in affected sheep, extended survival and slowed stereotypical brain atrophy. The benefits were observed in those treated before symptom onset (pre-symptomatically) and those treated after symptom onset – particularly in the early symptomatic stage, and the evidence suggests higher doses are likely more effective. Over the past decade, Professors Mitchell and Palmer and co-author Dr Imke Tammen have all been recipients of BDSRA Australia research grants, which have contributed vital funds toward the development of these sheep models. Prof Mitchell presented a summary of her team’s research at the US BDSRA Family Conference in July (conference registrants can view the video via the conference app). To learn more about the studies, see Gene therapy aids presymptomatic, symptomatic Batten disease sheep.
A gene-based technology that acts like a tiny ‘molecular patch’ over faulty DNA or RNA segments is a potential therapeutic solution showing promise in the treatment of Batten disease. Recent research led by Dr Jessica Centa and Prof. Michelle Hastings at the Rosalind Franklin University of Medicine and Science in Chicago showed these ‘molecular patches', known as antisense oligonucleotides or ASOs, restore production of the healthy gene product and lead to clinical improvement in a mouse model of CLN3 Batten disease. In order to validate this therapeutic approach, Centa and team have now generated a mouse model that expresses the same gene product induced by the ASO molecule, whereby faulty gene sequences (around exons 5, 7 and 8) are effectively removed or ‘skipped’, resulting in production of a correct, functional CLN3 protein. Behavioural and pathological analyses of these mice demonstrate a less severe phenotype compared with the CLN3 disease mouse model, providing evidence that ASO-induced exon skipping can have a therapeutic effect in CLN3 disease. The study entitled Protracted CLN3 Batten disease in mice that genetically model an exon-skipping therapeutic approach was published in Molecular Therapy: Nucleic Acids on June 3. Prof Hastings presented some of this research at the US BDSRA Family Conference in July. Conference registrants can view the video via the conference app (see Saturday General Session – An Overview of NCL Science).
Biological markers or ‘biomarkers’ are important tools for evaluating the presence and progression of disease, and objectively measuring the efficacy of potential therapeutics. Validated biomarkers are a significant unmet need in NCL clinical research, and is an area of focus for several research groups around the world. In this study Cerebrospinal Fluid Protein Biomarker Discovery in CLN3, a team led by Dr Forbes Porter and An Dang Do at the National Institutes of Health (NIH) in Bethesda MD, performed proteomic discovery studies using cerebrospinal fluid (CSF) samples from CLN3-affected individuals. 25 candidate biomarkers for CLN3 disease were identified, including a number of “new and intriguing candidates” warranting further investigation. Read more here. Dr Dang Do presented a summary of her team’s research at the US BDSRA Family Conference in July (conference registrants can view the video via the conference app).
Mouse models of CLN3 Batten disease have improved our understanding of the cell biology and disease mechanisms of CLN3 disease, and have been important on the path to therapeutic development. Mouse models do however have limitations in their ‘translatability’ to the human experience of the disease. For example, differences in size and anatomy of the brain, life span, and the inconsistent, subtle behavior deficits that can be difficult to evaluate in CLN3 mouse models, limits their utility in preclinical studies. This new study, A novel porcine model of CLN3 Batten disease recapitulates clinical phenotypes, characterizes a novel animal model of CLN3 disease – the miniature pig that has the most common CLN3 disease-causing mutation in humans - the 1 kb deletion or ‘exon 7-8’ deletion. In these CLN3-affected pigs, progressive neuron loss is observed in some regions the brain and the retina, particularly in later stages of the disease. Hallmarks cell pathologies are also observed in several brain regions. Additionally, affected pigs present with gait abnormalities, similar to deficits seen in human patients. Taken together, the minipig model may have utility in furthering research and development for CLN3 disease. To learn more, click here: Researchers develop minipig model to study juvenile Batten disease
A Texas-based research team has identified new cellular roles for the CLN3 protein, the loss of which contribute to lysosomal impairment and neurodegeneration in CLN3 disease. The study led by Alessia Calgani Baylor College of Medicine in Houston, showed that loss of CLN3 protein in cell cultures leads to improper targeting and trafficking of essential enzymes needed for the function of lysosomes. Lysosomes are cellular compartments that act as ‘garbage trucks’, degrading and removing proteins and other cellular waste. Calgani and colleagues showed that reduced lysosome function in CLN3-deficient cells in turn disrupts key pathways needed to create new, healthy lysosomes, therefore explaining global lysosomal dysfunction in CLN3 disease. The study, “Loss of the batten disease protein CLN3 leads to mis-trafficking of M6PR and defective autophagic-lysosomal reformation,” was published on July 3 in the highly-regarded journal Nature Communications. Dr Calgani presented a summary of her team’s research at the US BDSRA Family Conference in July (conference registrants can view the video via the conference app). A more detailed summary can be found here: Finding new CLN3 cellular roles aids juvenile Batten disease research
In 2020, Sondhi and colleagues published results from an investigative gene therapy study for the treatment of CLN2 disease. In that study, 8 children with mild to moderate CLN2 disease were treated with intraparenchymal administration (infusion of drug into the brain tissue via burr holes in the skull) of an AAV viral serotype encoding the human CLN2 gene, known as AAVrh.10hCLN2. Researchers concluded that the treatment "slowed the progression of disease in children with CLN2 disease, [however], improvements in vector design and delivery strategies will be necessary to halt disease progression using gene therapy."
In their latest study, Assessment of Safety and Biodistribution of AAVrh.10hCLN2 Following Intracisternal Administration in Nonhuman Primates for the Treatment of CLN2 Batten disease, published in August, the research team assessed whether the less invasive intracisternal delivery route (infusion into cisterna magna compartment at the base of the skull) would be safe and provide a wider distribution of the TPP-1 enzyme. The study was conducted in nonhuman primates (NHP) with intracisternal delivery to cerebral spinal fluid of AAVrh.10hCLN2. Overall, results indicate that delivery of the investigational gene therapy via the intracisternal route is safe and the doses administered led to widely distributed TPP-1 in the brain and cerebrospinal fluid (CSF) at levels that are potentially therapeutic.