A Study to Investigate the Safety and Efficacy of KER-012 in Combination With Background Therapy in Adult Participants With Pulmonary Arterial Hypertension (PAH) (TROPOS Study).

This is a randomized, phase 2, double-blind, placebo-controlled study of KER-012 in combination with background therapy in participants with PAH of World Health Organization (WHO) Group 1, functional class II-III. Participants will be randomly assigned in a 2:2:2:3 ratio to receive KER-012 (Dose A), KER-012 (Dose B), KER-012 (Dose C), or placebo by subcutaneous injection (SC) every 4 weeks for a period of 24 weeks in the placebo-controlled treatment period of the study while on background therapy. Evaluations will include changes in pulmonary vascular resistance (PVR), 6-minute walk distance (6MWD), and safety parameters. Participants who have not discontinued early from the placebo-controlled treatment period and have had their post-treatment period PVR assessment will be able to continue into the 72-week extension period in which KER-012 treated participants will continue to receive their same assigned dose level from the treatment period every 4 weeks and placebo treated participants will receive KER-012 (Dose B) every 4 weeks while on background therapy.