Compound 6 was also tested for cytotoxicity in the SH-SY5Y and HepG2 cell lines, with IC 50 values of 5.8 µM and 7.1 µM, respectively (Figure ). The substantial cytotoxicity of these compounds (observed at 1000-fold higher concentrations than the IC 50 ) might be the result of unspecific binding due to the high lipophilicity of the scaffold. However, this work was only meant to explore the N-dialkyl O-arylcarbamate warhead, not to produce developable lead compounds. Thus, a chosen O-arylcarbamate warhead can still be installed on a less cytotoxic scaffold to reap the benefits of pseudo-irreversible inhibition.