Agilis’ Pipeline of Gene Therapies for CNS Disorders
More than 4,000 human diseases are monogenic, meaning they are caused by the functional failure of a single gene. Agilis’ programs target devastating rare monogenic diseases that affect the central nervous system (CNS). Our goal is to build a robust pipeline of product candidates to address a broad range of rare diseases of the CNS.
Targeting rare CNS diseases through gene therapy offers a number of strategic advantages compared with conventional drugs, including:
- Potential for single administration (i.e., one intervention): Non-dividing cells of the CNS are amenable to long-term expression and treatment with therapeutic DNA, presenting the potential to achieve long-term therapeutic efficacy in patients following a single administration;
- Accelerated regulatory pathway: Gene therapies for rare CNS diseases benefit from the incentives afforded to orphan drug development. This includes regulatory processing advantages, priority reviews for FDA filings and potential breakthrough designations.
Delivering gene therapy directly to the CNS provides advantages over broader systemic administration:
- Avoidance of systemic immune responses: The CNS is an immune-privileged site, with naturally low antibody levels and low immune response. Direct adminstration to the CNS allows the systemic immune responses to be by-passed. This results in a better safety profile with fewer adverse immune events (such as hypersensitivity and anaphylaxis) that can result from activation of the immune system against the gene delivery vector;
- Lower vector volumes and doses: Direct CNS administration also avoids off-target absorption of the therapeutic DNA, and enables lower volumes and doses of the gene therapy product to be used in delivering the therapeutic benefit, since the vector is not bound by antibodies, sequestered by immune cells, or taken up in non-target tissues; and
- Ability to directly access targeted cells: By exquisitely targeting key cell types, the number of cells treated becomes significantly more focused compared with indiscriminate methods of treatment, thereby focusing delivery of treatment to those cells that will most benefit.
DNA Therapeutics for AADC-Deficiency
AADC Deficiency is a rare CNS disorder arising from reductions in the enzyme aromatic L-amino acid decarboxylase (AADC) that result from mutations in the dopa decarboxylase (DDC) gene. In its severe forms, AADC Deficiency causes the inability to develop any motor strength and control (global muscular hypotonia/dystonia) resulting in breathing, feeding, and swallowing problems, frequent hospitalizations, and the need for life-long care. Many patients die in the first decade of life due to profound motor dysfunction and secondary complications such as choking, hypoxia, and pneumonia.
In an effort to address the high unmet medical need in AADC patients, Agilis has partnered with National Taiwan University to investigate a gene therapy with adeno-associated virus (AAV) delivering the human AADC gene. Status of the program:
- There have been two prospective clinical studies enrolling 18 subjects with severe AADC Deficiency by Dr. Paul Hwu and colleagues at National Taiwan University Hospital (NTUH) in Taipei, Taiwan.
- The results from the trials indicated that treated subjects were found to exhibit de novo dopamine production as visualized by F-DOPA PET imaging, the emergence of downstream dopamine metabolites, and
- The subjects demonstrated substantial gains on motor function and cognitive scales over multiple years following the single gene therapy treatment. In contrast, untreated subjects routinely show continued deterioration as the disease progresses, as observed in natural history cases.
Agilis has entered into an exclusive worldwide license agreement with National Taiwan University (NTU) for the treatment of Aromatic L-Amino Acid Decarboxylase (AADC) Deficiency using gene therapy developed by Dr. Paul Hwu, Professor of Pediatrics at NTU Hospital. Agilis will sponsor ongoing research and development of the AADC gene therapy in collaboration with Dr. Hwu, including the conduct of ongoing clinical work on AADC gene therapy and completion of nonclinical testing in advance of the pivotal clinical study, anticipated to begin in 2017. Agilis will also support ongoing manufacturing efforts for the gene therapy.
The AADC Deficiency gene therapy program is among the most advanced CNS gene therapy program in the world, with significant long-term follow-up data for over five years in some subjects. Given the devastating clinical course of disease for patients with severe AADC deficiency, their poor quality of life and refractoriness to standard therapy, any intervention to improve the most severe forms of this disorder represents a critical advance for these patients and their families.
DNA Therapeutics for Friedreich’s Ataxia
Friedreich’s ataxia (FA) is a rare and life-shortening neurodegenerative disease caused by a single defect in the FXN gene, which causes reduced production of the frataxin protein. Agilis’ program for FA is focused on engineering and delivering corrective DNA to specific CNS cells that would restore production of the frataxin protein to natural levels to improve mitochnodrial function of the cells. This program includes:
- Rigorously engineered, best-in-class DNA construct: Agilis has established an exclusive collaboration agreement with Intrexon Corporation, a leading synthetic biology company, that provides Agilis worldwide use of Intrexon’s proprietary synthetic biology technology platform for the development and commercialization of DNA therapeutics for Friedreich’s ataxia. Through Intrexon’s UltraVector® platform, Intrexon provides Agilis with industrial-scale design, high-throughput screening in biological systems, computational models, statistical methods, and advanced technologies for the combinatorial assembly of DNA constructs engineered with optimized performance characteristics for restoring lost function in the FXN gene. Through this partnership and access to the Intrexon DNA tools and technologies, Agilis has applied concepts of rational design to DNA therapeutics and developed an advanced understanding of the biology, expression, and regulation of the FXN gene and frataxin protein.
- Powerful targeting technology for safe and effective delivery of corrective DNA for the FXN gene: Agilis is optimizing a targeted vector system for precise administration of therapeutic DNA into key targets to enable safe and effective long-term expression of the frataxin protein.
Program Status: Rational Design of DNA Therapeutics
- Myriad DNA regulatory elements accessed from Intrexon’s libraries;
- Bioinformatics and data-driven algorithms applied to combinatorial design of novel DNA constructs tailored for expression in target cell types;
- Matrix of constructs engineered and screened in high-throughput, innovative cell model assays;
- Expression levels, functional responses, and protein restoration capabilities of constructs tested for optimal in vivo efficacy;
- Optimal DNA construct selected and applied to additional assays, nonclinical testing, and IND-enabling studies; and
- Vector selection based on known in vivo targeting characteristics of AAV candidates to optimize delivery of the therapeutic DNA.
DNA Therapeutics for Angelman Syndrome (AS)
Angelman syndrome is a rare genetic, neurological disorder characterized by severe developmental delays. Angelman syndrome is usually caused by deletion or mutation of the maternal UBE3a allele in the context of an anti-sense silenced paternal allele. The UBE3a gene is critical in the production of Ubiquitin Ligase E6 protein (E6-AP) in the brain which plays a role in cognitive development.
Children are often diagnosed as they begin to miss developmental milestones. The children exhibit severe learning disabilities; absence or near absence of speech; inability to coordinate voluntary movements (ataxia); jerky movements of the arms and legs; and a distinct behavioral pattern characterized by a happy disposition and unprovoked episodes of laughter and smiling. Although those with Angelman syndrome may be unable to speak, many do develop some form of alternative communication such as gesturing. In addition, children may have sufficient receptive language ability to understand simple forms of language communication.
Other symptoms of Angelman syndrome can include seizures, sleep disorders and feeding difficulties. Agilis’ program for AS is focused on engineering and delivering corrective DNA to specific CNS cells that would restore production of the protein to improve function of the cells. This program includes:
- Optimized DNA construct: Agilis has in-licensed technology developed at University of South Florida by Dr. Edwin Weeber, a world-renown expert in Angelman syndrome. Dr. Weeber continues his work and with Agilis will refine the details to establish a best-in-class DNA construct. Through this partnership, Agilis is engineering optimized DNA therapeutics and undertaking detailed study of the structure, function and regulation of the UBE3a gene.
- Precise targeting technology for delivery of DNA: Agilis is assessing innovative targeting vectors to deliver the therapeutic UBE3a DNA to key cells of the CNS, thereby supporting safe and effective long-term expression of the UBE3a gene and production the missing E6-AP protein in Angelman syndrome.
DNA Therapeutics for Cognitive Disorders
Cognitive dysfunction is a characteristic of number of neurodevelopmental and neurodegenerative disorders including rare diseases such as Angelman syndrome and Fragile X syndrome, as well as larger indications such as schizophrenia and Alzheimer’s disease. Patients with these conditions suffer from declines in cognitive function such as learning and memory. Recent research has highlighted a possible role for Reelin in each of these disorders. At present, there is no reliable treatment for these devastating disease symptoms.
Reelin is an extracellular glycoprotein that plays an important role in proper neuronal migration and maturation during development. In the adult brain, the Reelin signaling pathway has been associated with in the modulation of synaptic plasticity, dendritic spine formation, synaptic maturation, learning and memory.
Reelin interacts with the lipoprotein receptors, very-low-density lipoprotein receptor (VLDLR) and apolipoprotein receptor 2 (ApoER2), resulting in receptor dimerization, downstream signaling, and phosphorylation of the NMDA receptors allowing increases in Ca2+ influx. Enhancement in Ca2+ influx allows for stronger NMDA receptor signaling, increased membrane AMPA receptor insertion, and enhanced long-term potentiation (LTP).
Fragile X mental retardation protein (FMRP) acts as a translational repressor and Reelin mRNA has been identified as a downstream target of FMRP. Abnormal FMRP production either directly or indirectly via miRNA could be linked to Reelin abnormalities in this disorder.
In schizophrenic patients, Reelin levels are about 50% of normal. Schizophrenic patients show a reduction in Reelin signaling and decreased dendritic spine density. In Alzheimer’s disease, ApoE4 can bind with VLDLR and ApoER2 and compete with Reelin for these receptors, thereby interfering with normal Reelin signaling. Such activities may promote the pathogenesis associated with Alzheimer’s through increased phosphorylation of the microtubule-associated protein tau and a reduction in the clearance of amyloid beta (Aβ), a key component of amyloid plaques. Aβ interacts with the signalling pathways that also regulate tau phosphorylation. Hyperphosphorylated tau is known to disrupt its normal function in regulating axonal transport and leads to the accumulation of neurofibrillary tangles and toxic species of soluble tau. Reelin has been shown have potentially beneficial effects in reducing tau phosphorylation and amyloid production, while a reduction of Reelin signaling in the adult brain, as occurs in aging and in the presence of ApoE4, leaves neurons susceptible to toxic damage caused by Aβ. Using novel technologies leading to Reelin supplementation, Agilis is working to identify potential therapeutics for these devastating diseases.