In the present invention inventors perform studies on extracellular vesicles isolated from urine samples to assess the biomarker potential of measures of the LRRK2-Rab pathway in idiopathic and LRRK2 linked PD as well as in inhibitor dosed rodents and non-human primates. Their results show modifications in the LRRK2-Rab pathway in urinary EVs, both in disease and after LRRK2 kinase inhibitor treatment. More preciasly inventors have found in a first cohort that pS1292-LRRK2 levels were elevated in individuals carrying the LRRK2 G2019S mutation, but did not differ significantly between healthy and PD groups, whether for LRRK2 G2019S carriers or not. In a second cohort, they found that PD was statistically associated to and increase in Rab8 levels and a decrease in S910-LRRK2 and S935-LRRK2 phosphorylation rates. This study assesses LRRK2 and Rabs as a disease and pharmacodynamic marker in human urine samples and this current analysis shows LRRK2 and Rab epitopes modified in patient groups.