To Assess Allisartan Isoproxil/Amlodipine in Patients With Essential Hypertension Uncontrolled With Amlodipine or Allisartan Isoproxil

Inclusion Criteria: * Patients 18-70 years old with mild to moderate essential hypertension; * Untreated patients (either newly diagnosed essential hypertension or those patients with a history of hypertension but have not been taking any antihypertensive drugs for at least 2 weeks before the first visit) must have an office msSBP ≥ 150 mmHg and \< 180 mmHg and DBP\<110 mmHg; * Patients who had not received regular treatment with Amlodipine Besylate (5 mg/day) (less than 4 weeks of medication intake or a history of missing doses for 5 or more days within the 4 weeks before screening) with the mean sitting blood pressure of 140 mmHg≤ SBP \<180 mmHg and DBP\<110 mmHg; * Patients currently receiving other antihypertensive agents (non-study medications for at least 2 weeks prior to screening) with the mean sitting blood pressure of 140 mmHg≤ SBP \<180 mmHg and DBP\<110 mmHg, and the clinician determined that it was appropriate to switch to Amlodipine Besylate (5 mg/day); * Patients who have been stably treated with Amlodipine Besylate (5 mg/day) for at least 4 weeks with the mean sitting blood pressure of 140 mmHg≤ SBP \<180 mmHg and DBP\<110 mmHg. During randomization for the double-blind treatment period, mean sitting blood pressure should be 140 mmHg≤ SBP \<180 mmHg and DBP\<110 mmHg; * Participants enrolled in the ambulatory blood pressure monitoring (ABPM) study should have 24-hour mean ambulatory blood pressure ≥130/80 mmHg after 4 weeks of monotherapy treatment; Exclusio…