To characterize pharmacokinetic profile of test product compared to that of the corresponding reference product in adult patients, who are diagnosed to have Chronic Myeloid Leukemia & Gastrointestinal Stromal Tumor under Fed Conditions.

To characterize pharmacokinetic profile of Imatinib Mesylate tablets EQ 400 mg base of Amneal Pharmaceuticals LLC, compared to that of the reference product - GLEEVEC® (imatinib mesylate) tablets 400 mg in adult patients, who are diagnosed to have CML or GIST and are presently receiving stable dose of imatinib mesylate tablets 400 mg, and assess their bioequivalence.

Inclusion Criteria:

• Age 18 to 55 years (both inclusive) and either sex
• Diagnosed case of Philadelphia chromosome positive (Ph+) CML patients in chronic phase or GIST and presently being treated with imatinib 400 mg tablets.
• Willing to give written informed consent for participation in the study as well as willing and able to comply with study visit schedule and other protocol requirements.
• Female patients of child bearing potential (except for those who have completed one year since menopause or have gone through hysterectomy or bilateral tubal ligation) must have negative serum pregnancy test at the screening, negative urine pregnancy test on check in to housing, must be non-lactating at screening and must agree to use effective contraception (barrier or hormonal) for the study period.

Exclusion Criteria:

• History of hypersensitivity to imatinib mesylate or to any of the excipients as judged by investigator.
• Patient of CML receiving treatment in Myeloid Blast Crisis or Accelerated Phase
• Abnormal laboratory results as below:
• History of a heart failure, renal insufficiency, hypereosinophilic syndrome (HES), myelodysplastic syndrome (MDS)/ myeloproliferative disease (MPD) or acute systemic mastocytosis (ASM).
• History of therapy with any of the following as per timelines before randomization: inducers of CYP3A4 activity and inhibitors of CYP3A4 activity, within 14 days, investigational product/device within last one month
• Alcohol or any drug dependence within past one year.
• Blood donation/loss exceeding 200 ml within last 60 days.