Efficacy and Safety Evaluating Study to Compare Kanarb (Fimasartan) and Cozaar® (Losartan) in Adult Patients With Grade I-II Arterial Hypertension

1. To evaluate efficacy of 12-week Kanarb (Fimasartan), manufactured by Boryung Pharmaceutical Co., Ltd, Republic of Korea, tablets 60/120 mg and Cozaar® (Losartan), manufactured by MERCK SHARP \& DOHME B.V., Netherlands, tablet 50/100 mg in adult patients with Grade I-II arterial hypertension. 2. To evaluate safety of 12-week Kanarb (Fimasartan), manufactured by Boryung Pharmaceutical Co., Ltd, Republic of Korea, tablets 60/120 mg and Cozaar® (Losartan), manufactured by MERCK SHARP \& DOHME B.V., Netherlands, tablet 50/100 mg in adult patients with Grade I-II arterial hypertension. 3. Assess the pharmacokinetics parameters of Kanarb (Fimasartan), manufactured by Boryung Pharmaceutical Co., Ltd, Republic of Korea in adult patients with arterial hypertension I-II stage after a single dose. Starting dose of Kanarb (Fimasartan), manufactured by Boryung Pharmaceutical Co., Ltd, Republic of Korea is 60 mg, orally, once a day in the morning. The planned study duration for each subject is 18 weeks maximum: The screening period could takes up to 2 weeks (including the 1-week "wash-out" period ) - the screening period duration depends on the prior anti-hypertensive therapy: * "naive" subjects who never received therapy (which must be reflected in the source documents), may be randomized after completion of all screening procedures; * Subjects receiving anti-hypertensive therapy which may be discontinued without prior dose reduction must undergo a 7 days "wash-out" period, so the screening period will take at least 7 days; * Subjects, receiving anti-hypertensive therapy which requires dose reduction before discontinuation must undergo the 7 days "wash-out" period after the last dose administration, so the screening period will consist of dose reduction period and a "wash-out" period. Treatment period - 12 weeks. Follow-up period - 4 weeks. The subjects will visit the clinical site every 4 weeks to measure ABP. The dose will be doubled in case if SBP ≥140 mmHg or DBP ≥90 mmHg at Visit 3 (Day 28) or at Visit 4 (Day 56). If necessary, the dose of the study drug may be increased based on the assessment of patient's condition performed at the phone contact (Day14±3). Patient may be called for an unscheduled visit for treatment adjustment (decided individually, with possibility of dose titration as per investigator's judgment, indicated in source documents). When possibilities are, the patient should be administrated by the study medication at the same time in the morning. Governing conditions for defining the time of the drug administration is the subject comfort and the time of its visits the research center. If laboratory tests are scheduled, a patient should come to the research center fasting (food is prohibited for 8 hours before the visit). All of the clinical evaluations are conducted on the next morning after taking the medication. On the visit day a patient comes to the research center not taking the drug, and after all the planned procedures are conducted the patient is administrated by the drug.