Therapeutic approaches to slow or block the progression of
Parkinson disease (PD) do not exist. Genetic and biochemical studies implicate α-
synuclein and
leucine-rich repeat
kinase 2 (LRRK2) in late-onset PD. LRRK2
kinase activity has been linked to neurodegenerative pathways. However, the therapeutic potential of LRRK2
kinase inhibitors is not clear because significant toxicities have been associated with one class of LRRK2
kinase inhibitors. Furthermore, LRRK2
kinase inhibitors have not been tested previously for efficacy in models of α-
synuclein-induced neurodegeneration. To better understand the therapeutic potential of LRRK2
kinase inhibition in PD, we evaluated the tolerability and efficacy of a LRRK2
kinase inhibitor,
PF-06447475, in preventing α-
synuclein-induced neurodegeneration in rats. Both wild-type rats as well as transgenic G2019S-LRRK2 rats were injected intracranially with adeno-associated viral vectors expressing human α-
synuclein in the substantia nigra. Rats were treated with
PF-06447475 or a control compound for 4 weeks post-viral transduction. We found that rats expressing G2019S-LRRK2 have exacerbated dopaminergic neurodegeneration and
inflammation in response to the overexpression of α-
synuclein. Both neurodegeneration and
neuroinflammation associated with G2019S-LRRK2 expression were mitigated by LRRK2
kinase inhibition. Furthermore,
PF-06447475 provided neuroprotection in wild-type rats. We could not detect adverse pathological indications in the lung, kidney, or liver of rats treated with
PF-06447475. These results demonstrate that pharmacological inhibition of LRRK2 is well tolerated for a 4-week period of time in rats and can counteract dopaminergic neurodegeneration caused by acute α-
synuclein overexpression.