4-Chlorophenylhydrazine hydrochloride (p-Chlorophenylhydrazine HCl) is used as a pharmaceutical intermediate.

ERK Inhibition Assay: Compounds are assayed for the inhibition of ERK2 by a spectophotometric coupled-enzyme assay. In this assay, a fixed concentration of activated ERK2 (10 nM) is incubated with various concentrations of the compounds in DMSO (2.5%) for 10 min. at 30 °C in 0.1 M HEPES buffer, pH = 7.5, containing 10 mM MgCl2, 2.5 mM phosphoenolpyruvate, 200 μM NADH, 150 μg/mL pyruvate kinase, 50 μg/mL lactate dehydrogenase and 200 μM erktide peptide. The reaction is initiated by the addition of 65 μM ATP. The rate of decrease of absorbance at 340 nM is monitored. The IC50 is evaluated from the data as a function of inhibitor concentr