Major

• Stable New York Heart Association (NYHA) Class II or III HF diagnosis, evident at least 6 months prior to enrolment as confirmed by medical history.
• Documented prior objective evidence of heart failure
• Screening ejection fraction ≥50%.
• Adequate bone marrow reserve and organ function at the Screening
• Receiving standard of care heart failure therapy at stable doses for at least 30 days prior to Screening.

Major

• Participant in any other study and has received any other investigational drug within 30 days prior to screening or 5-half-lives, whichever is longer, or any other investigational implanted device within 30 days prior to screening, or are taking part in a nonmedication study which, in the opinion of the Investigator, would interfere with study compliance or outcome assessments.
• Prior diagnosis of hypertrophic cardiomyopathy or a known infiltrative or storage disorder causing HFpEF and/or cardiac hypertrophy, such as amyloidosis, Fabry disease, or Noonan syndrome with LV hypertrophy.
• Persistent or permanent atrial fibrillation and is not therapeutically anticoagulated for at least the 4 weeks prior to the initial screening visit or is not adequately rate controlled within 6 months prior to informed consent according to investigator discretion.
• Other medical or psychiatric conditions that, in the opinion of the Investigator, would preclude obtaining voluntary consent/assent or would confound the objectives of the study.