Based on strong pre-clinical evidence of the effects of Nilotinib on neurodegenerative pathologies, including autophagic clearance of neurotoxic proteins, neurotransmitters (dopamine and glutamate), immunity and behavior, the investigators conducted an open label pilot clinical trial in advanced PD with dementia (PDD) and Dementia with Lewy Body (DLB) (stage 3-4) patients. Participants (N=12) were randomized 1:1 to once daily oral dose of 150mg and 300mg Nilotinib for 6 months. The investigators' data suggest that Nilotinib penetrates the brain and inhibits CSF Abelson (Abl) activity via reduction of phosphorylated Abl in agreement with pre-clinical data. Several studies show that CSF alpha-Synuclein and Abeta42 are decreased and CSF total Tau and p-Tau are increased in PD and DLB. The investigators' data show attenuation of loss of CSF alpha-Synuclein and Abeta40/42 with 300mg (50% of the CML dose) compared to 150mg Nilotinib after 6 months treatment. CSF homovanillic acid (HVA), which is an end by-product of dopamine, is significantly increased; and CSF total Tau and p-Tau are significantly reduced (N=5, P<0.05) with 300mg Nilotinib between baseline and 6 months treatment. Despite the reduction of L-Dopa replacement therapies in our study, UDPRS I-IV scores improved with 150mg (3.5 points) and 300mg (11 points) from baseline to 6 months and worsened (13.7 points and 11.4 points) after 3 months withdrawal of 150mg and 300mg, respectively. Other non-motor functions e.g. constipation was resolved in all patients and cognition was also improved (3.5 points) using both the Mini-Mental Status Exam (MMSE) or the Scales for Outcomes in Parkinson's Disease-Cognition (SCOPA-Cog) between baseline and 6 months. MMSE scores returned to baseline after 3 months of Nilotinib withdrawal. These data are very compelling to evaluate the effects of Nilotinib in a phase II, randomized, double-blind, placebo-controlled trial in patients with PD.