Alnylam says brezosiran, its experimental RNAi therapy for Huntington’s disease, showed gene-silencing signals in an early study presented at the European Huntington’s Disease Network Clinical Research Congress. The company reported that patients receiving the highest dose saw mutant huntingtin levels in spinal fluid fall by about 60% to 64% on average. Alnylam described the safety profile as “encouraging” and said it plans to start a placebo-controlled study next year to determine whether the therapy can slow disease progression. The readout underscores continued investment in RNA drugs for neurodegeneration, where biomarker success has not always translated to clinical benefit. The update comes as Huntington’s drug development remains a high-bar category, with recent disappointments in the field. Alnylam’s next step is specifically focused on clinical efficacy, not just biomarker knockdown.