The objective of this study is to compare the efficacy and safety of combined administration of TAK-536CCB (Fix-dose combination of Azilsartan and Amlodipine) and Hydrochlorothiazide (HCTZ) with those of TAK-536CCB in patients with Grade I or II essential hypertension.

This study is a randomized, double-blind, multicenter, phase 2/3 study to evaluate the efficacy and safety of combined administration of TAK-536CCB and Hydrochlorothiazide (HCTZ) with those of TAK-536CCB or Hydrochlorothiazide in patients with grade I or II essential hypertension.

This study consists of a 4-week single-blind placebo run-in period and a 10-week double-blind treatment period.

Inclusion Criteria:

1. Grade I or II essential hypertension.
2. An office sitting systolic blood pressure of ≥ 150 and < 180 mmHg, and an office sitting diastolic blood pressure of ≥ 95 and < 110 mmHg during the placebo run-in period at Week -2 and Week 0.
3. Male or female aged 20 years or older at the time of providing informed consent.
4. Outpatient.

Exclusion Criteria:

1. Secondary hypertension, grade III hypertension or malignant hypertension.
2. An office sitting systolic blood pressure of ≥160 mmHg or sitting diastolic blood pressure of ≥100 mmHg recorded while on combined therapy with 3 or more antihypertensives within 4 weeks prior to the initiation of the placebo run-in period and at Week -4.

3 Evident white coat hypertension or white coat phenomenon. 4. Day-night reversed lifestyle, such as night-time workers. 5. Sleep apnea syndrome requiring treatment. 6. Have any of the cardiovascular disease or symptoms listed below:

• Heart disease: myocardial infarction (within 24 weeks before the placebo run-in period), coronary arterial revascularization (within 24 weeks before the placebo run-in period), severe valvular disease, atrial fibrillation, or following diseases which require medication: angina pectoris, congested heart failure, or arrhythmia.

• Cerebrovascular disease: cerebral infarction, cerebral hemorrhage (within 24 weeks before the placebo run-in period), or transient ischemic attack (within 24 weeks before the placebo run-in period).

• Vascular diseases: peripheral arterial disease with intermittent claudication, artery dissection, aneurysm

• Advanced hypertensive retinopathy: bleeding, exudation, or papilledema (within 24 weeks before the placebo run-in period).

  7. Clinically significant hepatic disorder. 8. Clinically significant renal impairment. 9. Significantly low or high Potassium or Sodium levels. 10. Complicated by gout, or had a past history of gout within 24 weeks prior to the initiation of the placebo run-in period, or complicated by hyperuricemia requiring medication.

  11. Diabetic subject on insulin treatment or poorly controlled type 2 diabetes mellitus.

  12. Have a malignant tumor.