The purpose of the study is to evaluate the safety and how well the medication sotatercept works versus placebo in treating Heart Failure with a Preserved Ejection Fraction. The study will also look at information obtained from the tests performed as part of the study to see if subjects have improvement in symptoms of heart failure. Participation in this study will last approximately 26 months. During the study period subjects will be asked to attend regular study visits with the research coordinator. These visits will include such activities as blood tests, questionnaires, physical evaluation by a study doctor, a right heart catheterization with exercise, echocardiogram, and 6 minute hall walks. There will be 35 visits as part of participation in this clinical trial.

Participants will be randomized to either the treatment group (and receive the medication) or the control group (and not receive the medication). Subjects will have a 66:33 chance of receiving the study medication during their participation in the trial. The treatment assignment is determined by randomization, where a computer selects at random which treatment group you will be in (like drawing straws). Neither the subject, nor the blinded personnel will know which group subjects are in. Neither the subject nor the study doctor will decide what group subjects are assigned.