Phase 2 Study of REGN13335 in Adult Participants With Pulmonary Arterial Hypertension (PAH)

This study is researching an experimental drug called REGN13335. The study is focused on participants with Pulmonary Arterial Hypertension (PAH). The aim of the study is to see how safe and effective REGN13335 is in participants with PAH who are taking other PAH medicines. The study is looking at several other research questions, including: * What side effects may happen from taking REGN13335 * How much REGN13335 is in the blood at different times * Whether the body makes antibodies against REGN13335 (which could make REGN13335 less effective or could lead to side effects)