Latest progress and challenges in drug development for degenerative motor neuron diseases

Motor neuron diseases are sporadic or inherited fatal neurodegenerative conditions. They selectively affect the upper and/or lower motor neurons in the brain and spinal cord and feature a slow onset and a subacute course contingent upon the site of damage. The main types include amyotrophic lateral sclerosis, progressive muscular atrophy, primary lateral sclerosis, and progressive bulbar palsy, the pathological processes of which are largely identical, with the main disparity lying in the location of the lesions. Amyotrophic lateral sclerosis is the representative condition in this group of diseases, while other types are its variants. Hence, this article mainly focuses on the advancements and challenges in drug research for amyotrophic lateral sclerosis but also briefly addresses several other important degenerative motor neuron diseases. Although the precise pathogenesis remains elusive, recent advancements have shed light on various theories, including gene mutation, excitatory amino acid toxicity, autoimmunology, and neurotrophic factors. The US Food and Drug Administration has approved four drugs for use in delaying the progression of amyotrophic lateral sclerosis: riluzole, edaravone, AMX0035, and tofersen, with the latter being the most recent to receive approval. However, following several phase III trials that failed to yield favorable outcomes, AMX0035 has been voluntarily withdrawn from both the US and Canadian markets. This article presents a comprehensive summary of drug trials primarily completed between January 1, 2023, and June 30, 2024, based on data sourced from clinicaltrials.gov. Among these trials, five are currently in phase I, seventeen are in phase II, and eleven are undergoing phase III evaluation. Notably, 24 clinical trials are now investigating potential disease-modifying therapy drugs, accounting for the majority of the drugs included in this review. Some promising drugs being investigated in preclinical studies, such as ATH-1105, are included in our analysis, and another review in frontiers in gene therapy and immunotherapy has demonstrated their therapeutic potential for motor neuron diseases. This article was written to be an overview of research trends and treatment prospects related to motor neuron disease drugs, with the aim of highlighting the latest potentialities for clinical therapy.