Imatinib primarily acts on?

ANSWER: (B) Tyrosine kinaseREF: Harrison 17th edition chapter-104, Goodman &GiIlman 2008 edition page 895Imatinib is the drug of choice for chronic phase of CMLMOA:Imatinib inhibits protein tyrosine kinase activities of ABL and its activated derivatives v-ABL, BCR-ABL, and EVT6-ABL, the platelet-derived growth factor receptor (PDGFR), and KIT receptor tyrosine kinases.Adverse effects:Imatinib is administered orally. The main side effects are fluid retention, nausea, muscle cramps, diarrhea, and skin rashes. The management of these side effects is usually supportive. Myelosuppression is the most common hematologic side effect. Myelosuppression, while rare, may require holding drug and/or growth factor support. Doses <300 mg/d seem ineffective and may lead to development of resistance.