Targeting TDP-43 in ALS: Regulatory hurdles, trial design deficiencies, and the causal evidence gap for CTx1000.

The therapeutic landscape for amyotrophic lateral sclerosis (ALS) has been characterized by decades of clinical trial failures, often attributed to biological heterogeneity, end-point insensitivity, and a profound evidence gap regarding target engagement. With TAR DNA-binding protein 43 (TDP-43) aggregation emerging as a hallmark feature in the vast majority of ALS cases, new precision-medicine modalities - most notably the proteolysis-targeting chimera (PROTAC) CTx1000 - aim to address the underlying causal pathology through selective degradation of mislocalized TDP-43. This review critically evaluates the regulatory hurdles and trial design deficiencies that have historically undermined ALS clinical development, and incorporates the dual sequestration hypothesis as a framework to interpret the convergence of TDP-43 pathology across neurodegenerative diseases. It concludes that it is imperative that the field adopts more rigorous biomarker-led methodologies, and that although target-specific degraders offer a sophisticated technological leap, their success depends on addressing fundamental knowledge gaps in target engagement, age-dependent vector tropism, and trial design architecture.