This study is researching an experimental drug called REGN7544 (called study drug). The study is focused on adult patients (18 to 85 years) hospitalized due to a serious infection (called sepsis) and receiving standard-of-care medications for low blood pressure (called vasopressors) due to sepsis. The aim of the study is to see how safe, tolerable, and effective the study drug is by observing the effects on blood pressure and the total amount of vasopressor dose received during the stay in the hospital. The study is looking at several other research questions, including: * How the study drug changes the blood pressure and the amount of intravenous (IV) fluids given to participants with low blood pressure due to sepsis * 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 drug less effective or could lead to side effects)