T allele carriers in the medical therapy (MT) treatment arm exhibited significantly higher (worse) ON total UPDRS at 18 and 24 months compared to C/C MT subjects (A, *, p = 0.017 and p = 0.019, respectively). T allele carriers also displayed higher (worse) PDQ-39 scores at 12 and 24 months compared to C/C subjects on MT (B, *, p = 0.033 and p = 0.018, respectively). No significant differences were observed between T allele carriers and C/C subjects receiving deep brain stimulation (DBS, ON medication and ON stimulation) at any time point (C, D, p > 0.05). Values represent the mean ± SEM.