A polytherapy approach demonstrates therapeutic efficacy for the treatment of SOD1 associated amyotrophic lateral sclerosis.

BACKGROUND: SOD1 mutations are a significant contributor of familial amyotrophic lateral sclerosis (ALS) cases. SOD1 mutations increase the propensity for the protein to misfold and aggregate into insoluble proteinaceous deposits within motor neurons and neighbouring cells. The small molecule, CuATSM, has repeatedly shown in mouse models to be a promising therapeutic treatment for SOD1-associated ALS and is currently in Phase II/III clinical trials for the treatment of ALS. We have previously shown CuATSM stabilises various ALS-associated variants of the SOD1 protein, reducing misfolding and toxicity. Two additional FDA-approved small molecules, ebselen and telbivudine, have also been identified to reduce mutant SOD1 toxicity, providing additional potential therapeutic candidates that could be used in combination with CuATSM. Here, we aimed to investigate if CuATSM, ebselen and telbivudine (CET) polytherapy could improve on the therapeutic efficacy of CuATSM monotherapy for the treatment of SOD1-associated ALS. METHODS: We utilised a 3D checkerboard approach to investigate whether a matrix of different concentrations CuATSM, ebselen and telbivudine could provide therapeutic improvements on cell survival, SOD1 folding and aggregation in SOD1(G93A)-transfected NSC-34 cells, compared to CuATSM alone. To progress the preclinical development of CET polytherapy, we evaluated the bioavailability and safety of in vivo polytherapy administration. Furthermore, we assessed and compared the effects of CET- and CuATSM-treatment on disease onset, motor function, survival and neuropathological features in SOD1(G93A) mice. FINDINGS: CET polytherapy reduced inclusion formation and increased cell survival of NSC-34 cells overexpressing SOD1(G93A) compared to higher concentrations of CuATSM monotherapy. In addition, CET administration was bioavailable and tolerable in mice. CET treatment in SOD1(G93A) mice delayed disease onset, reduced motor impairments, and increased survival compared to vehicle- and CuATSM-treated mice. In line with these findings, biochemical analysis of lumbar spinal cords showed CET administration improved SOD1 folding, decreased misfolded SOD1 accumulation, and reduced motor neuron loss. INTERPRETATION: These findings support CET polytherapy as an advantageous alternative compared to CuATSM monotherapy and highlight the potential of utilising small molecules targeting SOD1 as a polytherapy avenue for the treatment of SOD1-associated ALS. FUNDING: This work was supported by a FightMND Drug Development Grant, an Australian National Health and Medical Research Council (NHMRC) Investigator Grant (No. 1194872) and a Motor Neuron Disease Research Institute of Australia Bill Gole Postdoctoral Fellowship.