Fig. 1. Identification of pexmetinib activity in Ba/F3T315I cells.
A Scheme of the screening strategy. The sensitivity of Ba/F3 and Ba/F3T315I cells to 10 µM inhibitors was assessed in 96-well plates. B IC50 ratio (parental/T315I) of 27 inhibitors that passed phase 1 (listed in Supplementary Fig. 1); the indicated three compounds were selected after phase 2 of the screening. C Ba/F3 cells, parental or expressing BCR::ABL1T315I mutant, were treated with increasing concentrations of the indicated inhibitors. Dose-response curves were obtained by non-linear fitting of normalized cell growth data. D A summary of the experimental therapeutic indexes (calculated as the [Ba/F3IL3]/[Ba/F3BCR::ABL1] IC50 ratio) is reported for WT and mutant cells (T315I, G250E, Y253F, E255K, E255V); pexmetinib and ponatinib pass the tenfold therapeutic index mark for all mutations, indicating they can safely be used against these mutants, without killing non-transformed cells. IM imatinib; NIL nilotinib; DAS dasatinib; BOS bosutinib; PON ponatinib; REB rebastinib; PEX pexmetinib. E Inhibition of recombinant WT and T315I ABL1 kinase by pexmetinib in an in vitro kinase assay.