Leucin-rich repeat kinase 2 (LRRK2) plays an important role in the onset of sporadic as well as familial Parkinson’s disease. Pathogenic gain-of-function mutations of LRRK2 are associated with aberrant LRRK2 hyperactivity which results in neurotoxicity and protein aggregation caused by dysfunctional autophagy and vesicle trafficking. Thus, the development of LRRK2 inhibitors represents a promising strategy for the treatment of Parkinson’s disease. Interestingly LRRK2 mutations have also been reported to increase the risk for the onset of different types of cancer (e.g. breast, thyroid, lung). Several studies suggest that LRRK2 is involved in the regulation of different cancer-related pathways (e.g. ATM-p53-p21-pathway, JNK pathway). Deregulation of LRRK2 activity caused by mutations has been shown to interfere with these pathways thereby increasing the risk to develop certain types of cancer. Since anti-cancer treatments mostly target the same pathways, we hypothesized that LRRK2 inhibitors may affect anti-cancer treatments in specific cancer cell types. In this study we report on the analyses of various inhibitors (e.g. MLi-2 and PF-06447475) on LRRK2 autophosphorylation at S935 in a cellular phosphorylation assay using the non-small cell lung cancer cell line A549 in comparison to biochemical LRRK2 activity assays. Furthermore, we compare the direct LRRK2 inhibitor effect on the proliferation of 140 cell lines, as well as their potential combinatorial impact on the potency of chemotherapeutic agents (e.g. Adriamycin). The observed effects can help to understand the implications of pharmaceutical LRRK2 inhibition in the treatment of both Parkinson’s disease and cancer. Citation Format: Franziska Fimm-Todt, Joachim Lauterwasser, Eva-Maria Egenter, Christian Weber, Daniel Feger, Katharina Schaich, Sarah Ulrich, Oliver Siedentopf, Frank Totzke, Michael Kubbutat, Jan Erik Ehlert. Cytotoxic effects of LRRK2 inhibitors in combined treatment with chemotherapeutic agents on a large panel of cancer cell lines [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4072.