This study is researching an experimental drug called REGN7544 (called "study drug"). The study is focused on participants with POTS. The aim of the study is to see how safe, tolerable, and effective the study drug is. The study is looking at several other research questions, including: * How the study drug changes heart rate and blood pressure in participants with POTS * What side effects may happen from taking the study drug * How much study drug is in the blood at different times * Whether the body makes antibodies against the study drug (which could make the study drug less effective or could lead to side effects)