Disclosed herein are phenyl-urea and phenyl-carbamate derivatives of formula I where the substituents are as defined herein. Also disclosed are pharmaceutical compositions containing the compounds, and methods of their use for preventing, reversing, slowing, or inhibiting protein aggregation and therefore treating diseases that are associated with protein aggregation, including neurodegenerative diseases such as Parkinson&rsquo；s disease, Alzheimer&rsquo；s disease, Lewy body disease, and multiple system atrophy. Examples of the compounds of formula I include 3-((1H-indol-3-yl)methoxy)-5-butylphenyl-(2-(4-methylpiperazin-1-yl)ethyl)carbamate and 1-(3-(2-(1H-indol-3-yl)ethyl)-5-isopropylphenyl)-3-(2-(4-methylpiperazin-1-yl)ethyl)thiourea.
