Alnylam reported early clinical data for brezosiran, its investigational RNAi therapy for Huntington’s disease, with patients receiving the highest dose showing about 60% to 64% average reductions in mutant huntingtin levels in cerebrospinal fluid across assay types. The company characterized the safety and tolerability profile as encouraging. Alnylam said it plans to start a placebo-controlled study next year to test whether brezosiran can slow disease progression, moving beyond biomarker readouts. The update was presented at the European Huntington’s Disease Network Clinical Research Congress. For the field, the key near-term question is whether deeper or more durable knockdown translates into measurable clinical slowing, not just target engagement. brezosiran joins a growing set of neurogenetic and RNA-based strategies competing on measurable biomarker endpoints in early studies.