ATH-1105 mitigates multiple pathologies in ALS models both alone and in combination with riluzole.

Introduction: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by progressive motor neuron degeneration, muscle atrophy, and paralysis. The complexity of ALS pathology, driven by factors such as TDP-43 pathology, excitotoxicity, and neuroinflammation, has hindered therapeutic development. While riluzole (an anti-excitotoxic agent) is the current standard treatment, additional therapeutics are needed to address the broad spectrum of ALS-related pathology. ATH-1105, a small-molecule positive modulator of hepatocyte growth factor (HGF) signaling, has shown promise in preclinical models of ALS. Given the multifactorial nature of ALS and the growing recognition that combination approaches may represent the best treatment options, we investigated the therapeutic potential of ATH-1105 in a TDP-43-driven mouse model of ALS, by comparing and combining it with the known efficacious treatment of riluzole. Additionally, we characterize the mechanism by which ATH-1105 induces neuroprotective effects, emphasizing its effects on TDP-43 pathology. Methods: In vivo, the impact of daily oral treatment with ATH-1105, alone and in combination with riluzole, was evaluated in Prp-TDP43A315T hemizygous transgenic ALS mice. In vitro, the impact of ATH-1105 on TDP-43-related pathology was assessed in rat primary spinal motor neurons subjected to glutamate toxicity. To demonstrate target engagement, the neuroprotective effects of ATH-1105 were assessed via siRNA-mediated knockdown of MET (HGF receptor). Results: In vivo, ATH-1105 significantly improved neuromuscular function and reduced body weight loss, neurodegeneration, inflammation, and TDP-43 phosphorylation. The combination of ATH-1105 with riluzole led to greater therapeutic effects than either treatment alone. In vitro, the neuroprotective effects of ATH-1105 were shown to be associated with MET activation in motor neurons, which was confirmed via siRNA-mediated knockdown of MET. In motor neurons subjected to glutamate toxicity, ATH-1105 reduced extranuclear and phosphorylated TDP-43, and increased GSK3β phosphorylation (inactivation), a kinase involved in TDP-43 pathology. Additionally, ATH-1105 reduced the abnormal increase in autophagic proteins following glutamate toxicity. Discussion: Our study underscores the therapeutic potential of ATH-1105 in treating ALS, both as a standalone treatment and in combination with riluzole. ATH-1105 demonstrates neuroprotective effects that slow neuromuscular deterioration in a relevant mouse model, aligning with the need to counteract the neurodegeneration central to ALS.