Supplementary Material for: Alternative to LRRK2-IN-1 for Pharmacological Studies of Parkinson's Disease

<br><strong><em>Background/Aims:</em></strong> LRRK2 (leucine-rich repeat protein kinase 2) is one of the most commonly accepted genes associated with Parkinson's disease (PD). The overexpression of disease-associated mutations in LRRK2 is toxic to the cells, while reduction or elimination of LRRK2 expression promotes cell health and growth. Thus, the identification of an LRRK2 inhibitor with good physiochemical and pharmacokinetic properties is of great interest for the treatment of PD. <b><i>Methods:</i></b> In this study, we have investigated LRRK2 compounds, LRRK2-IN-1 and Compound 1, in vitro and in vivo to determine how suitable they are as a selective LRRK2 tool compound. <b><i>Results:</i></b> We report that Compound 1, patented by GSK, is a potent and selective LRRK2 inhibitor with good blood-brain barrier permeability as reflected by its high brain to plasma ratio in rats. In addition, Compound 1 can significantly promote neurite outgrowth in a primary cortical culture, indicating an optimistic cellular function of this compound in a biological system. In contrast, LRRK2-IN-1 is a less selective LRRK2 inhibitor and has low brain penetration. Furthermore, LRRK2-IN-1 is cyto- and genotoxic, while Compound 1 does not exhibit any toxicity. <b><i>Conclusions:</i></b> These results suggest that Compound 1 may be a superior tool compound than LRRK2-IN-1 to advance future pharmacological research on LRRK2.