The purpose of this study is to compare the antihypertensive effect of azilsartan medoxomil versus placebo in Korean adults with essential hypertension.

The drug being tested in this study is called azilsartan medoxomil. Azilsartan medoxomil is being tested to treat Korean adults with hypertension. This study will look at changes in blood pressure in people who take azilsartan medoxomil.

The study will enroll approximately 325 patients. Participants will be randomly assigned (by chance, like flipping a coin) to one of the three treatment groups-which will remain undisclosed to the patient and study doctor during the study (unless there is an urgent medical need):

• Azilsartan medoxomil 40 mg
• Azilsartan medoxomil 80 mg
• Placebo (dummy inactive pill) - this is a tablet that looks like the study drug but has no active ingredient.

All participants will be asked to take two tablets at the same time each day throughout the study.

This multi-centre trial will be conducted in Korea. The overall time to participate in this study is 12 weeks. Participants will make 7 visits to the clinic, and will be contacted by telephone 7 days after last dose of study drug for a follow-up assessment.

Inclusion Criteria:

1. In the opinion of the investigator, the participant is capable of understanding and complying with protocol requirements.
2. The participant or, when applicable, the participant's legally acceptable representative, signs and dates a written informed consent form and any required privacy authorization prior to the initiation of any study procedures.
3. Is treated with antihypertensive therapy and has a post-washout mean sitting clinic systolic blood pressure (SBP) ≥150 and ≤180 mm Hg on Day 1; or the patient has not received antihypertensive treatment within 28 days prior to Screening and has a mean sitting clinic SBP ≥150 and ≤180 mm Hg at the Screening Visit and on Day 1.
4. Is male or female aged ≥19 years.
5. A female of childbearing potential who is sexually active with a nonsterilized male partner agrees to routinely use adequate contraception from signing of the informed consent through 30 days after last study drug dose.
6. Is willing to discontinue current antihypertensive medications on Day -21. If on amlodipine or chlorthalidone prior to Screening, the participant is willing to discontinue this medication on Day -28.

Exclusion Criteria:

1. Has received any investigational compound within 30 days prior to the first dose of study medication.
2. Has received TAK-491 in a previous clinical study or as a therapeutic agent.
3. Is an immediate family member, study site employee, or is in a dependent relationship with a study site employee who is involved in conduct of this study (eg, spouse, parent, child, sibling) or may consent under duress.
4. Has sitting trough clinic diastolic blood pressure (DBP) greater than 114 mm Hg at Day 1 (after placebo run-in).
5. Has a history of hypersensitivity to TAK-491 (azilsartan medoxomil), any of its excipients, or other angiotensin-converting enzyme (ARBs).
6. Has a history of myocardial infarction, heart failure, unstable angina, coronary artery bypass graft, percutaneous coronary intervention, hypertensive encephalopathy, cerebrovascular accident, or transient ischemic attack.
7. Has clinically significant cardiac conduction defects (e.g., 3rd degree atrioventricular block, left bundle branch block, sick sinus syndrome, atrial fibrillation, or flutter).
8. Has hemodynamically significant left ventricular outflow obstruction due to aortic valvular disease and hypertrophic obstructive cardiomyopathy (HOCM).
9. Has secondary hypertension of any etiology (e.g., renovascular disease, pheochromocytoma, Cushing syndrome).
10. Is noncompliant (less than 70% or greater than 130%) with study medication during placebo run-in period.
11. Has severe renal dysfunction or disease (confirmed by calculated creatinine clearance <30 mL/min/1.73m^2) at Screening.
12. Has known or suspected unilateral or bilateral renal artery stenosis.
13. Has a history of drug or alcohol abuse within the past 2 years.
14. Has a history of cancer that has not been in remission for at least 5 years prior to the first dose of study drug. (This criterion does not apply to those patients with basal cell or stage I squamous cell carcinoma of the skin.)
15. Has type 1 or poorly controlled type 2 diabetes mellitus (hemoglobin A1c [HbA1c]>8.0%) at Screening.
16. Has an alanine aminotransferase (ALT) level greater than 2.5 times the upper limit of normal, active liver disease, or jaundice at Screening.
17. Has hyperkalemia (defined as serum potassium greater than the upper limit of normal per the central laboratory) at Screening.
18. Has any other serious disease or condition at screening or randomization that would compromise participant safety, might affect life expectancy, or make it difficult to successfully manage and follow the participant according to the protocol.
19. Is required to take excluded medications.
20. If female, is pregnant or lactating or intending to become pregnant before, during, or within 30 days after participating in this study; or intending to donate ova during such time period.