Effects of Iron Therapy in Heart Failure With Preserved Ejection Fraction and Iron Deficiency (PREFER-HF)

Inclusion Criteria: * Subjects with stable chronic HF (NYHA II/IV functional class) on optimal background therapy (as determined by the investigator) for at least 4 weeks with no dose changes of heart failure drugs during the last 2 weeks (with the exception of diuretics). In general, optimal pharmacological treatment should include an angiotensin-converting enzyme inhibitor or angiotensin II receptor blocker and a beta blocker unless contraindicated or not tolerated and diuretic if indicated. * Left ventricular ejection fraction \>45% (value within 3 months of planned date of randomization). * BNP \>100 pg/mL and/or N-terminal-pro-BNP \>400 pg/mL at the screening visit. * Subject must be capable of completing the 6 minute walking test * Screening serum ferritin \<100 ng/mL or 100-300 ng/mL with transferrin saturation \<20%. * At least 18 years of age. * Before any study-specific procedure, the appropriate written informed consent must be obtained. Exclusion Criteria: * Subject has known sensitivity to any of the products to be administered during dosing. * History of acquired iron overload. * History of erythropoietin-stimulating agent, i.v. iron therapy, and/or blood transfusion in previous 6 weeks prior torandomization. * Oral iron therapy at doses \>100 mg/day in previous 1 week prior to randomization. Note: ongoing use of multivitamins containing iron \<75 mg/day is permitted. * Exercise training programme(s) in the 3 months prior to screening or planned in the next 6 months. * Known active bacterial infection. * Chronic liver disease (including active hepatitis) and/or screening alanine transaminase or aspartate transaminase above three times the upper limit of the normal range. * Subjects with known hepatitis B surface antigen positivity and/or hepatitis C virus ribonucleic acid positivity. * Vitamin B12 and/or serum folate deficiency. If deficiency-corrected subject may be rescreened for inclusion. * Subjects with known seropositivity to human immunodeficiency virus. * Clinical evidence of current malignancy with exception of basal cell or squamous cell carcinoma of the skin, and cervical intraepithelial neoplasia. * Currently receiving systemic chemotherapy and/or radiotherapy. * Renal dialysis (previous, current, or planned within the next 6 months). * Unstable angina pectoris as judged by the investigator; severe valvular or left ventricular outflow obstruction disease needing intervention; atrial fibrillation/flutter with a mean ventricular response rate at rest \>100 beats per minute. * Acute myocardial infarction or acute coronary syndrome, transient ischemic attack, or stroke within the last 3 months prior to randomization. * Coronary artery bypass graft, percutaneous intervention (e.g. cardiac, cerebrovascular, and aortic; diagnostic catheters are allowed), or major surgery, including thoracic and cardiac surgery, within the last 3 months prior to randomization. * Subject currently is enrolled in or has not yet completed at least 30 days since ending other investigational device or drug study(ies), or subject is receiving other investigational agent(s). * Subject of childbearing potential who is pregnant (e.g. positive human chorionic gonadotropin test) or is breastfeeding. * Subject will not be available for all protocol-specified assessments. * Subject has any kind of disorder that compromises the ability of the subject to give written informed consent and/or to comply with study procedures.