Assess and compare the efficacy and safety of 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 in 12 weeks of therapy

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.

Inclusion Criteria:

1. Subjects of both sex aged 18-75 inclusively.

2. Subjects who signed their written Informed Consent for participation in the study and willing to adhere to all Protocol procedures.

3. Subjects with documented diagnosis of grade I-II primary arterial hypertension within at least 3 months before screening.

4. Systolic blood pressure (SBP) (when seated) at Screening (Day -14)

   • For subjects administered with anti-hypertensive therapy: SBP ≤ 179 Hg
   • For subjects receiving no anti-hypertensive therapy (so called 'naïve' patients): 140≥SBP ≤179.

5. As per investigator's judgment, subjects with controlled arterial hypertension must benefit from the therapy switch to 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, .

6. For subjects administered with anti-hypertensive drugs: the anti-hypertensive drug may be safely cancelled during the "wash-out" period according to the investigator's judgment.

7. For women of child-bearing potential: negative urine pregnancy test at screening (Day -14). 8. Systolic blood pressure (SBP) (when seated) at Randomization (Day 0) ≥140 mmHg and ≤179 mmHg.

9. For women of child-bearing potential: negative urine pregnancy test at Randomization (Day 0)

Exclusion Criteria:

1. Grade III Arterial Hypertension.
2. Arterial hypotension (SPB ≤100 mm Hg) at Screening (Day -14) and/or Randomization (Day 0).
3. Subjects needing treatment with more than one anti-hypertensive drug (more than one active substance, including complex drugs).
4. Secondary (symptomatic) arterial hypertension.
5. Known bilateral renal arterial stenosis or unilateral renal arterial stenosis.
6. Hyperpotassemia >5,0 mmol/l (as per blood biochemistry results at Screening).
7. Primary hyperaldosteronism.
8. Known hypersensitivity to angiotensin-II receptors antagonists or any other study drug or comparator component.
9. Contraindications for use of angiotensin-II receptors antagonists.
10. Myocardial infarction and or unstable angina, and/or acute cerebrovascular accident/transient ischemic attack, and/or percutaneous coronary intervention, and/or coronary arterial bypass graft, acute coronary arteries involvement, and/or obliterative vascular atherosclerosis of low extremities, and/or grade III and IV retinopathy in anamnesis.
11. Clinically significant cardiac valves damage.
12. Cardiomyopathies
13. Chronic Heart failure (CHF) (except for CHF FC I NYHA).
14. Creatinine clearance less than 60 ml/min/1.73m2 calculated by Cockroft-Gault formula.
15. Known moderate to severe hepatic insufficiency and/or transaminase increase: AST and/or ALT ≥2*ULN.
16. History of infections (HIV, hepatitis B or C, syphilis).
17. Uncontrolled Diabetes mellitus, Glycosylated hemoglobin level (HbA1c) >7%.
18. Severe systemic diseases, such as gastro-intestinal tract diseases, autoimmune disorders, blood disorders and other conditions which may affect on the study drugs' absorption, distribution and and excretion.
19. Clinically significant abnormalities of laboratory parameters.
20. Drug or alcohol addiction, psychiatric disorders.
21. Medical history of oncological disease within 5 years before screening.
22. Subjects with biliary tracts obstruction.
23. Subjects with genetic disorders, such as galactose intolerance, congenital lactase insufficiency and glucose-galaclose malabsorption syndrome.
24. Any other acute disease or progression and/or decompensation at the moment of enrollment
25. Necessity to administer or administration of prohibited concomitant drugs from the "List of Prohibited Drugs" within 14 days before enrollment
26. Pregnancy or breast-feeding period; fertile women not using adequate contraception methods
27. Participation in another clinical trial within 3 months before Screening.
28. Other medical or psychiatric conditions or lab abnormalities that may increase potential risk associated with study participation and IP administration, or that may affect study results interpretation and as per investigator's judgment, make the subject ineligible.
29. Study site personnel or Sponsor's representatives immediately involved in the study.
30. Subjects, excluded from the study may not be included in it again.