The purpose of this study is to evaluate the antihypertensive efficacy and tolerability of 8 week treatment with Fimasartan (BR-A-657-K) 20, 60, 120, 240 mg and placebo in patients with mild to moderate essential hypertension and to determine the adequate antihypertensive dosage for later clinical study.

Fimasartan (BR-A-657-K), a selective blocker of AT1 receptor subtype, showed the rapid and potent antihypertensive effect in many hypertensive models. Phase I study, Fimasartan (BR-A-657-K) 20mg ~ 480mg single dosing with healthy subjects, demonstrated that the Fimasartan (BR-A-657-K) was very safe and well tolerated. Another phase I study, Fimasartan (BR-A-657-K) 120mg and 360mg dosing for 7 days, also showed that Fimasartan (BR-A-657-K) was safe and tolerable though one temporal adverse event was observed in high dose.

A randomized, double-blind, placebo-controlled, parallel grouped, clinical study will be conducted to evaluate the antihypertensive efficacy and tolerability and to determine adequate antihypertensive dosage of Fimasartan(BR-A-657-K) in patients with mild to moderate essential hypertension.

Approximately 182 patients will be enrolled over 12 months in 8 centers nationwide.

After 2 weeks of placebo run-in period, all subjects will be randomized into one of the following 5 groups. Subjects will take test/control drug for 8 weeks of treatment period. If subjects take any antihypertensive medications before screening, the subjects will have 1 week of wash-out period.

Group I : Placebo, Group II : Fimasartan 20 mg, Group III: Fimasartan 60 mg, Group IV : Fimasartan 120 mg, Group V : Fimasartan 240 mg,

Inclusion Criteria:

• Mild to moderate essential hypertension : sitting diastolic blood pressure measured at Screening and Baseline(Day1) are 95~114 mmHg inclusive and the difference between sitting diastolic blood pressures measured at Day -14 and Baseline(Day1) is under 7mmHg.
• Subjects who agree to participate in this sudy and give written informed consent
• Subjects considered to understand the study, be cooperative, and able to be followed-up until the end of the study

Exclusion Criteria:

• The sitting DBP is less than 94mmHg or more than 115mmHg or severe hypertensive patient with sitting systolic blood pressure over 200mmHg
• Patients with secondary hypertension
• Patients with severe renal(Creatinine more 1.5 times than upper limit of normal), gastrointestinal, hematological or hepatic(AST, ALT more 2 twice more than upper limit of normal)disease etc. which might affect absorption, disposition, metabolism or excretion of the drug
• Patients with postural hypotension
• Patients with sever insulin dependent diabetes mellitus or uncontrolled diabetes mellitus(HbA1c>9%, regimen change of oral hypoglycemic agents within 3 months, treated insulin before screening)
• Patients with a history of myocardial infarction, severe coronary artery disease or clinically significant heart failure or valvular defect in last 6 months
• Patients with consumptive disease, autoimmune disease, connective tissue disease
• Patients with a history of type B or C hepatitis
• Patients with HIV or hepatitis
• Patients with clinically significant laboratory abnormality
• Patients receiving any drugs known to affect blood pressure or medical treatments that can influence the blood pressure
• Patients with allergy or contraindication to any angiotensin II receptor antagonists
• Female of childbearing potential who does not undergo hysterectomy or is not post-menopausal
• Patients judged to have a history of alcohol or drug abuse by the investigator
• Patients with average weight > +35% or <-15% in Modified Metropolitan Life Insurance table
• Patients participated other clinical trial 3 months before Screening
• Patients judged to be inappropriate for this study by the investigator with other reasons