ARQ 069, an analog of ARQ 523, inhibits FGFR in an enantiospecific manner. ARQ 069 targets the unphosphorylated, inactive forms of FGFR1/FGFR2 kinases ( IC 50 s of 0.84 μM and 1.23 μM, respectively). ARQ 069 inhibits FGFR1/FGFR2 autophosphorylation ( IC 50 s of 2.8 and 1.9 μM, respectively) through a mechanism in anon-ATP competitive dependent manner.