<prompt> Imatinib used in CML acts by -Inhibiting BCRABL translocation tyrosine kinaseBlocking the action of P glycoproteinCompetitive inhibition ofATP binding site ofABL kinaseC-Kit kinase inhibition  <response>: Ans. is c i.e. Competitive inhibition of ATP binding site of ABL kinase o In CML, there is Bcr-Abl translocation which leads to unregulated activation of intracellular non-receptor tyrosine kinase, Le., Bcr-Abl tyrosine kinase. o Imatinib is a Bcr-Abl tyrosine kinase intracellular-nonreceptor tyrosine kinase inhibitor. o This drug block the activity of nonreceptor tyrosine kinase by acting as a inhibitor of the ATP binding site on the protein and prevents its phosphorylation. About option a o Imatinib does not inhibit Bcr-Abl translocation, it inhibits overactive tyrosine kinase after Bcr-Abl translocation has already occured. 