The 6 MWT was an assessment where the distance that a participant could walk on a flat and hard surface in 6 minutes was measured. Participants were asked to perform the test at a pace that was comfortable to them, with as many breaks as they needed, and under supervision of a qualified professional. Study discontinuation & death were incorporated into endpoint definition through ranking in hypothesis testing of treatment difference. Missing data resulting from study discontinuation were imputed using control-based multiple imputation method to estimate treatment effect.

Efficacy analysis set (EAS): NYHA functional Class II / III randomized participants. 'Number of Participants Analyzed' = participants evaluable for the outcome measure. Five participants (ARRY-371797 [n=3], placebo [n=2]) discontinued the study before week 24 due to the sponsor's decision to terminate and were excluded from the primary analysis. All participants reported under 'Number of Participants Analyzed' contributed data to table but may not have evaluable data for every row.

The 6 MWT was an assessment where the distance that a participant could walk on a flat and hard surface in 6 minutes was measured. Participants were asked to perform the test at a pace that was comfortable to them, with as many breaks as they needed, and under supervision of a qualified professional.

EAS included all NYHA functional Class II or III randomized participants. All participants reported under 'Overall Number of Participants Analyzed' contributed data to the table but may not have evaluable data for every row. "Number Analyzed" signifies number of participants evaluable for specified rows of respective arms.

The KCCQ measured the effects of symptoms, functional (physical) limitations, and psychological distress on an individual's health-related quality of life. It contains 23 items, which assessed the ability to perform activities of daily living, frequency and severity of symptoms, the impact of these symptoms, and health-related quality of life. PL was a single questionnaire with score range of 0 to 100, where higher scores reflected better physical functioning status. TSS included frequency and severity of symptoms, and the impact of these symptoms. TSS scores were transformed to a range of 0 to 100, where higher scores reflected better health status.

EAS included all NYHA functional Class II or III randomized participants. All participants reported under 'Overall Number of Participants Analyzed' contributed data to the table but may not have evaluable data for every row. Here, "Number Analyzed" signifies participants evaluable for specified rows.

PGI-S is a global index that rate the severity of the disease using a 5-point scale. In this outcome the number of participants with improvements in PGI-S the severity of their heart failure symptoms and in the severity of their PL were reported. Measured by the scale of: none, mild, moderate, severe or very severe (listed from better to worse).

EAS included all NYHA functional Class II or III randomized participants. All participants reported under 'Overall Number of Participants Analyzed' contributed data to the table but may not have evaluable data for every row. "Number Analyzed" signifies number of participants evaluable for specified rows of respective arms.

PGI-C is a global index that rate the severity of the disease using a 7-point scale. In this outcome the number participants with improvements in their heart failure symptoms and "in their physical activity limitations?", were reported. Measured by the scale of: very much better, moderately better, a little better, no change, a little worse, moderately worse, very much worse (listed from better to worse).

EAS included all NYHA functional Class II or III randomized participants. All participants reported under 'Overall Number of Participants Analyzed' contributed data to the table but may not have evaluable data for every row. "Number Analyzed" signifies number of participants evaluable for specified rows of respective arms.

NT pro-BNP is a cardiac biomarker that is released in the blood in response to changes in the pressure inside of the heart. Levels go up when heart failure develops or gets worse, and levels go down when heart failure is stable or improves. This biomarker helps to measure the changes in the severity of heart failure over time in response to therapy.

EAS included all NYHA functional Class II or III randomized participants. All participants reported under 'Overall Number of Participants Analyzed' contributed data to the table but may not have evaluable data for every row. "Number Analyzed" signifies number of participants evaluable for specified rows of respective arms.

Defined as the time from randomization to the first occurrence of any event of death due to any cause, or worsening heart failure (HF-related hospitalization or HF-related urgent care visit). Kaplan-Meier method and cox regression model were used for analysis.

The safety analysis set (SAS) included all participants who received at least 1 dose of study intervention regardless of NYHA functional class.

OS was defined as time from randomization to death due to any cause. Participants who did not have a death date were censored for OS at their last contact date. Kaplan-Meier method and cox regression model were used for analysis.

The SAS included all participants who received at least 1 dose of study intervention regardless of NYHA functional class.

An AE was any untoward medical occurrence in a participant who received investigational product without regard to possibility of causal relationship. Treatment-emergent AEs were events that occurred between first dose of study drug and up to 30 days after last dose. Serious adverse event (SAE) was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly. AEs included both SAEs and all Non-SAEs. Grade >=3 AEs meant severe AEs.

The SAS included all participants who received at least 1 dose of study intervention regardless of NYHA functional class.

Following parameters were analyzed for laboratory examination: hematology (eosinophils, erythrocytes, hemoglobin, hematocrit, granulocytes, leukocytes, lymphocytes, monocytes, platelets, neutrophils, nucleated erythrocytes); blood chemistry (alanine aminotransferase, albumin, alkaline phosphatase, aspartate aminotransferase, bicarbonate, bilirubin, blood urea nitrogen, C-reactive protein, calcium, chloride, creatinine, creatine kinase, epidermal growth factor receptor, follicle stimulating hormone, gamma glutamyl transferase, glucose, magnesium, N-Terminal ProB-type natriuretic peptide, phosphate, potassium, protein, sodium, potassium, thyrotropin, troponin I, troponin T, urate).

The SAS included all participants who received at least 1 dose of study intervention regardless of NYHA functional class.

Following vital sign parameters were assessed: diastolic blood pressure, systolic blood pressure, heart rate, and body weight. Vital sign abnormalities criteria included: a) systolic blood pressure (mmHg): decrease (change <= -20, or value <90) and increase (change >=20, or value >140); b) diastolic blood pressure (mmHg): decrease (change <= -15, or value <60) and increase (change >=15, or value >90); c) heart Rate (bpm) decrease: (change <= -15, or value <50) and increase (change >=15, or value >100); d) weight: (kg) decrease (Change <= -7%) and increase (Change > =7%).

The SAS included all participants who received at least 1 dose of study intervention regardless of NYHA functional class. Here, "Number Analyzed" signifies number of participants evaluable for specified rows of respective arms.

Following parameters were analyzed: heart rate, QT interval, corrected QT (QTc) interval, Bazett's correction QT (QTcB) interval, and Fridericia's correction (QTcF) interval. Criteria for notable ECG values were as follows: QT interval (in millisecond [msec]) new (newly occurring post-baseline value) greater than (>) 450, 480, 500, increase from baseline >30, increase from baseline >60; corrected QT interval by Fredericia formula (QTcF) in msec new (newly occurring post-baseline value) > 450, 480, 500, increase from baseline >30, increase from baseline >60; corrected QT interval by Bazett's formula (QTcB) in msec new (newly occurring post-baseline value) > 450, 480, 500, increase from baseline >30, increase from baseline >60; heart rate in bpm new (newly occurring post-baseline value) <60 and >100.

The SAS included all participants who received at least 1 dose of study intervention regardless of NYHA functional class. Here, "Number of Participants Analyzed" signifies number of participants evaluable for this outcome measure and "Number Analyzed" signifies number of participants evaluable for specified rows of respective arms.

Arrhythmia assessment: incidence of new and clinically significant ventricular or atrial arrhythmias was assessed by an implantable cardioverter defibrillator (ICD) or CRT defibrillator (CRT-D) applicable device interrogations.

The SAS included all participants who received at least 1 dose of study intervention regardless of NYHA functional class. Here, "Number Analyzed" signifies number of participants evaluable for specified rows of respective arms.