Part 1: For the initial evaluation of safety, pharmacokinetic exposure and pharmacodynamic response, subjects will be tapered off antihypertensive background therapy.The initial starting dose will be a sub-therapeutic dose. Dose escalation will continue with a maximum of a doubling of the previous dose until either 1) a maximum tolerated dose (MTD) is identified or 2) modeling of the pharmacokinetic (PK) data indicate that maximum exposure (Cmax) at the next planned dose level would exceed a maximum drug concentration (Cmax) which was the maximum observed drug concentration following a single subcutaneous administration in Study PB1046-PT-CL-0001.