Charcot-Marie-Tooth (CMT) disease type 2D is caused by dominant mutations in GARS, encoding glycyl-tRNA synthetase (GlyRS). CMT is a clinically and genetically heterogeneous collection of disorders in which peripheral motor and sensory axons degenerate. The diseases specifically affect the peripheral nervous system and are characterized by progressive motor neuron degeneration, muscle atrophy, and sensory loss. None of the CMT disease subtypes have a targeted treatment, thus CMT remains an unmet medical need. The genetic heterogeneity makes it unlikely that a single therapy will be effective for all forms of CMT. Although gene therapies have emerged strongly for monogenic diseases such as CMT, the large number of different mutations involved, and the small number of patients affected by each mutation render classic gene therapy onerous for CMT2D. Identifying a causal treatment strategy applicable to different mutations in GARS would therefore be the most attractive therapeutic approach for CMT2D. Also, being able to directly engage with the GlyRS protein itself is key to CMT2D remediation. Our previous work has established that a major source of the toxicity of the CMT-causing mutant GlyRS is originated from the extracellular space, where mutant proteins aberrantly interact with Neuropilin 1 (Nrp1) receptor and antagonize a signaling pathway important for motor neuron maintenance. We designed a novel strategy based on our structural insight of the GlyRS mutants. We found that different CMT2D mutations caused a shared conformational change in GlyRS that exposes new protein surfaces at the dimer interface to solution. By using two different peptides from the dimer interface of GlyRS as antigens for immunization, we have successfully obtained two monoclonal antibodies (mAbs) (one for each peptide) from mouse hybridomas that can block the pathological Nrp1 interaction and exhibit promising pan-mutant selectivity. These two mAb candidates will be characterized for their biophysical properties, and used for conducting pharmacodynamic, pharmacokinetic, and in vivo efficacy studies in a mouse model of the human disease to evaluate whether they have sufficient biological activity to warrant further development to treat CMT2D.
This application is in response to FOA PAR-18-761 to conduct pharmacodynamic, pharmacokinetic, and in vivo efficacy studies to evaluate two novel monoclonal antibodies that have been designed to recognize a specific region of glycyl-tRNA synthetase (GlyRS) and to demonstrate that these antibodies have sufficient biological activity to warrant further development to treat Charcot-Marie-Tooth disease type 2D (CMT2D).
