The purpose of this study is to learn which doses of PS433540 should be given to patients with high blood pressure to lower their blood pressure. This study will also examine how safe PS433540 is when taken by patients with high blood pressure. Approximately 720 patients will be evaluated so that about 375 patients will be entered into the treatment phase of the study and be given PS433540.

Inclusion Criteria:

• Males or females 18 - 70 years
• Mean seated Systolic Blood Pressure (SBP) ≥ 140 mmHg and < 180 mmHg and mean seated Diastolic Blood Pressure (DBP) > 90 and < 109 mmHg at two consecutive qualifying visits (Visits 3/3.5 and Visit 4). The mean difference in DBP between the two consecutive qualifying visits must be ≤ 10 mmHg.
• Women of child-bearing potential (WOCBP) must use two reliable forms of contraception if sexually active. Alternatively, female subjects must be postmenopausal (for at least 1 year).

Exclusion Criteria:

• Subjects with serious disorders which may limit the ability to evaluate the efficacy or safety of PS433540, including cardiovascular (includes subjects who are known to have coronary artery disease), renal (including the absence of one kidney), pulmonary, hepatic, gastrointestinal (including clinically significant malabsorption), endocrine/metabolic, hematologic, neurologic and psychiatric diseases.
• History of malignancy other than adequately treated basal cell or squamous cell skin cancer.
• Subjects with a history of myocardial infarction or New York Heart Association (NYHA) class II-IV heart failure.
• Subjects with a history of cerebrovascular accident or transient ischemic attack.
• Subjects with clinically significant cardiac conduction defects, including second or third degree Atrioventricular Block (AV block), left bundle branch block, sick sinus syndrome, atrial fibrillation, atrial flutter, an accessory bypass tract, or any arrhythmia requiring medication.
• Subjects with hemodynamically significant valvular disease.
• Subjects with history of type 1 diabetes mellitus and subjects with a history of type 2 diabetes mellitus using antihyperglycemic medication (oral medication, insulin, or exenatide) are excluded.