The present invention relates to isolated polypeptides which comprise an
amino acid sequence consisting of a mutated functional Abl kinase domain,
said mutated functional kinase domain being resistant to inhibition of
its tyrosine kinase activity by
N-[4-methyl-3-(4-pyridin-3-yl-pyrimidin-2-ylamino)-phenyl]-4-(4-methyl-pi-
perazin-1-ylmethyl)-benzamide or a salt thereof, to the use of such
polypeptides to screen for compounds which inhibit the tyrosine kinase
activity of such polypeptides, to nucleic acid molecules encoding such
polypeptides, to recombinant vectors and host cells comprising such
nucleic acid molecules and to the use of such nucleic acid molecules in
the production of such polypeptides for use in screening for compounds
which inhibit the tyrosine kinase activity of such polypeptides.