BIIB094 is an antisense oligonucleotide (ASO) targeting the LRRK2 protein that was tested in a randomized controlled phase 1 trial called REASON in patients with Parkinson's disease[1]. The study consisted of two parts: the first part included 40 participants who received a single dose of BIIB094 in the range of 10-150 mg or placebo, and the second part included 42 participants who received four doses of BIIB094 in the range of 40-120 mg or placebo every four weeks[1]. Researchers have developed a new methodology to measure biomarkers in cerebrospinal fluid, including total LRRK2 and phosphorylated Rab10 (pRab10), to monitor treatment efficacy[1]. The study demonstrates the first evidence of LRRK2-ASO modulatory effects on cerebrospinal fluid biomarkers in patients with Parkinson's disease[1]. The treatment was well tolerated and showed a dose-dependent reduction in cerebrospinal fluid biomarker levels[1]. The results suggest the successful engagement of the LRRK2 target and the potential of this treatment to slow the progression of Parkinson's disease[1].