Imatinib 400mg Tablet refers to the class of medicines known as tyrosine kinase inhibitors. It is used to treat blood cancer and gastrointestinal stromal tumor. Imatinib 400mg Tablet should be taken with food, but better to have it at the same time every day to get the most benefit. Imatinib mesylate would help if you continued to take it as long as your doctor advised it. The duration of therapy varies according to your need and response to treatment.