Inclusion Criteria :

• Male or female patient not at childbearing potential ≥18 year-old or legal age of majority.
• Female patient if she has undergone sterilization at least 3 months earlier or is postmenopausal.
• Post-menopausal status is defined by having no menses for 12 months without an alternative medical cause.
• In females not treated with hormonal replacement therapy (HRT), menopausal status is confirmed by a high follicle stimulating hormone (FSH) level greater than 40 IU/L.
• In females on HRT and whose menopausal status is in doubt (ie, in women aged less than 45 years), a highly effective contraception methods will be required. Contraception should be used during the whole study and for at least seven days corresponding to time needed to eliminate study treatment.
• Symptomatic stable angina pectoris (typical or atypical symptoms with an average of at least once weekly episodes over the past month).
• Patients with non-obstructive (<50% stenosis) coronary arteries or intermediate stenosis (between 50 and 70%) should have fractional flow reserve (FFR) >0.80 or instantaneous wave-free ratio (iFR) >0.89 on angiogram, documented within the previous 24 months*. In patients with stenting, a minimum diameter stenosis of <10% is required; OR Coronary computed tomography angiography (CCTA) with finding of non-obstructive coronary arteries within the past 24 months* in patients without previous elective percutaneous coronary intervention (PCI). *Note: in cases of clinically suspected progression of atherosclerosis as per the Investigator, a more contemporary (i.e., 6 months) evidence should be provided.
• Baseline global coronary flow reserve (CFR) (measured during the study) assessed by 13N-ammonia or 82Rubidium positron emission tomography (PET) scan <2.0.

Exclusion Criteria:

• Any use of nitrates (except short-acting nitrates) and/or dipyridamole and/or phosphodiesterase type 5 (PDE 5) inhibitors within one week prior to baseline PET scan or anticipated to be used during the study.
• Esophageal dysmotility or esophagitis.
• Patients with acute coronary syndrome (ACS) (myocardial infarction [MI] and/or unstable angina) in previous 3 months.
• Unsuccessful or incomplete coronary revascularization with residual obstructive stenosis or coronary artery disease (CAD) progression in native vessels as documented on invasive coronary angiography (≥50% stenosis) within 24 months of enrollment.
• Percutaneous coronary intervention performed at the time of an ACS (MI or unstable angina).
• Recent elective PCI within the past 3 months.
• Patients with history of coronary artery bypass grafting (CABG).
• Recent (≤3 months) major surgery (i.e., valvular surgery, surgery for congenital heart disease), stroke, transient ischemic attack [TIA], sustained ventricular arrhythmia, clinically significant structural heart disease (moderate-severe valvular disease, hypertrophic cardiomyopathy, congenital heart disease, pulmonary hypertension).
• Regional local flow abnormal perfusion defects at baseline PET scan*. *Note: if contemporary evidence with invasive coronary angiography or coronary computed tomography angiography (CCTA) demonstrates non-obstructive coronary arteries or if the regional local flow abnormal perfusion defect on PET scan is consistent with previous studies then patient qualifies for the study.
• Patients with cardiac conduction abnormalities (second or third degree atrioventricular [AV] block, sick sinus syndrome, symptomatic bradycardia, sinus node disease).
• History of known carotid stenosis.
• Contraindication or known hypersensitivity to adenosine or regadenoson.
• Contraindication to aminophylline.
• Contraindication to vasodilator stress PET scan.
• Inability to discontinue treatment with methylxanthines treatment within 24 hours prior to PET scan.
• Patient unable to read, understand and fill a questionnaire without any help (e.g., partially visually impaired or blind).
• Systolic blood pressure (SBP) <110 mmHg at baseline.
• Presence at baseline of symptomatic orthostatic hypotension (SBP decrease of 20 mmHg or more at Minute 3 or Minute 5 between seated and standing position), or asymptomatic orthostatic hypotension with a decrease in SBP equal or greater than 30 mmHg at Minute 3 or Minute 5 when changing from the seated to the standing position.
• Renal impairment with estimated glomerular filtration rate (eGFR) <50 mL/min/1.73 m2 at screening and baseline.
• Drug-induced liver injury related criteria:
• Underlying hepatobiliary disease.
• ALT >3 times the upper limit of normal (ULN).