Targeting Amyotrophic Lateral Sclerosis with Gene Therapy: From Silencing Genes to Enhancing Neuroprotection

Abstract

Gene therapy is emerging as a transformative approach for treating amyotrophic lateral sclerosis (ALS), a progressive and fatal neurodegenerative disease. While gene replacement has shown a groundbreaking success in spinal muscular atrophy, the complexity of ALS-due to frequent gain-of-function mutations and a heterogeneous etiology-presents significant challenges. Importantly, approximately 90% of ALS cases are sporadic, with unknown genetic mutation, further complicating patient stratification and therapeutic targeting. As a result, gene therapy strategies must often address multiple pathological mechanisms simultaneously. So far, current gene therapy strategies aim to either suppress toxic gene expression or promote neuroprotection, predominantly via viral-mediated delivery systems. This review will provide an overview of emerging preclinical and clinical gene therapy approaches for ALS, focusing on two main strategies: gene silencing and neuroprotection. Gene silencing techniques, including antisense oligonucleotides (ASOs), viral-mediated RNA interference, and gene editing, have demonstrated efficacy in reducing mutant gene expression, particularly in SOD1 and C9orf72 models, although clinical translation has so far yielded limited success. The recent Food and Drug Administration's approval of the ASO therapy Qalsody for SOD1-ALS underscores the clinical potential of these approaches. Neuroprotective strategies aim to enhance motor neuron survival through delivery of trophic factors, often targeting both central and peripheral tissues to harness retrograde transport mechanisms. We will discuss the advantages and limitations of various delivery vectors, targeting specificity, timing of intervention, and translational challenges, alongside current clinical trial data. This review aims to synthesize how these approaches may converge to address the multifaceted nature of ALS and guide the development of next-generation therapeutics.