Alnylam's brezosiran lowers mutant huntingtin 60-64% in highest-dose group in phase 1b trial
ALNY•Alnylam Pharmaceuticals reported that brezosiran reduced cerebrospinal fluid mutant huntingtin by 60-64% on average at three months in the highest-dose group, with a maximum individual reduction of 83%. A pivotal placebo-controlled study is planned for 2027, pending regulatory alignment.
1. Phase 1b results
Alnylam Pharmaceuticals reported positive initial Phase 1b results for brezosiran, an investigational Huntington's disease treatment. At the highest dose, mean cerebrospinal fluid mutant huntingtin levels fell 60-64% at three months; the largest individual reduction was 83%.
2. Follow-up and next steps
Follow-up of up to 12 months showed no dose-dependent increases in cerebrospinal fluid inflammatory markers, neurofilament light chain or brain ventricular volume. The durability of huntingtin lowering supports potential twice-yearly dosing, and an open-label extension will evaluate treatment every six months for up to 36 months. A placebo-controlled pivotal study is planned for 2027, pending regulatory alignment, to assess whether brezosiran slows disease progression in adults.
