The primary objective of Part 1 of the study is to evaluate the safety and tolerability of S-648414 after administration of a single oral dose of S-648414 in healthy adult study participants. The primary objective of Part 2 is to evaluate the safety and tolerability of S-648414 after administration of multiple oral doses of S-648414 in healthy adult study participants. The primary objectives of Part 3 are evaluate the safety and tolerability of S-648414 after administration of multiple oral doses of S-648414 in healthy adult study participants, and to evaluate the effect of S-648414 on the pharmacokinetics (PK) of dolutegravir and the effect of dolutegravir on the PK of S-648414 in healthy adult study participants.
Amendment 2 of the study Protocol added a third part (Part 3) to the study. The revised Official Title for the Protocol is: "A Phase 1, Randomized, Double-Blind, Single-Ascending-Dose, and Food Effect Study to Assess the Safety, Tolerability, Ventricular Repolarization, and Pharmacokinetics of S-648414 in Healthy Adult Study Participants (Part 1); A Phase 1, Randomized, Double-Blind, Multiple-Ascending-Dose Study to Assess the Safety, Tolerability, and Pharmacokinetics of S-648414 and A Drug-Drug Interaction Study with the CYP3A Substrate, Midazolam, in Healthy Adult Study Participants (Part 2); and A Phase 1 Open-Label Study to Assess the Effect of S-648414 on the Pharmacokinetics of Dolutegravir and the Effect of Dolutegravir on the Pharmacokinetics of S-648414 in Healthy Adult Study Participants (Part 3)"
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
98
Tablet for oral administration
Tablet for oral administration
Solution for oral administration
Tablet for oral administration
PPD Ph 1 Clinical Research Unit
Austin, Texas, United States
P-One Clinic
Hachiōji, Toyko, Japan
Part 1: Number of Participants With Treatment-emergent Adverse Events (TEAEs)
A TEAE is any event not present before exposure to study drug or any event already present that worsens after exposure to study drug. A serious adverse event is any untoward medical occurrence that resulted in death, was life-threatening, required or prolonged inpatient hospitalization, resulted in persistent disability/incapacity, was a congenital anomaly/birth defect, or other event that may have jeopardized the participant or required intervention to prevent one of the outcomes above. The investigator assessed the intensity of each AE according to the following: Grade 1 (Mild): No or minimal interference with usual activities. Grade 2 (Moderate): More than minimal interference with usual activities, intervention indicated. Grade 3 (Severe): Inability to perform usual activities, intervention or hospitalization indicated. Grade 4 (Potentially life-threatening): Inability to perform self-care, intervention indicated to prevent permanent impairment, disability, or death.
Time frame: From dosing on Day 1 or Day 14 up to 10 days post dose
Part 2: Number of Participants With Treatment-emergent Adverse Events
A TEAE is any event not present before exposure to study drug or any event already present that worsens after exposure to study drug. A serious adverse event is any untoward medical occurrence that resulted in death, was life-threatening, required or prolonged inpatient hospitalization, resulted in persistent disability/incapacity, was a congenital anomaly/birth defect, or other event that may have jeopardized the participant or required intervention to prevent one of the outcomes above. The investigator assessed the intensity of each AE according to the following: Grade 1 (Mild): No or minimal interference with usual activities. Grade 2 (Moderate): More than minimal interference with usual activities, intervention indicated. Grade 3 (Severe): Inability to perform usual activities, intervention or hospitalization indicated. Grade 4 (Potentially life-threatening): Inability to perform self-care, intervention indicated to prevent permanent impairment, disability, or death.
Time frame: From the first dose up to 10 days after end of dosing (25 days); A TEAE was summarized to a given treatment if the event onset/worsening occurred any time after the dose of that treatment and before the dose of the next treatment.
Part 3: Number of Participants With Treatment-emergent Adverse Events
A TEAE is any event not present before exposure to study drug or any event already present that worsens after exposure to study drug. A serious adverse event is any untoward medical occurrence that resulted in death, was life-threatening, required or prolonged inpatient hospitalization, resulted in persistent disability/incapacity, was a congenital anomaly/birth defect, or other event that may have jeopardized the participant or required intervention to prevent one of the outcomes above. The investigator assessed the intensity of each AE according to the following: Grade 1 (Mild): No or minimal interference with usual activities. Grade 2 (Moderate): More than minimal interference with usual activities, intervention indicated. Grade 3 (Severe): Inability to perform usual activities, intervention or hospitalization indicated. Grade 4 (Potentially life-threatening): Inability to perform self-care, intervention indicated to prevent permanent impairment, disability, or death.
Time frame: From the first dose up to Day 36; A TEAE was summarized to a given treatment if the event onset/worsening occurred any time after the dose of that treatment and before the dose of the next treatment.
Part 3: Maximum Plasma Concentration (Cmax) of S-648414
The effect of dolutegravir on the pharmacokinetics (PK) of S-648414 was assessed after administration of multiple oral doses of S-648414 alone (Day 21) and after administration of multiple oral doses of S-648414 co-administered with dolutegravir (Day 28).
Time frame: Day 21 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8 and 12 hours postdose. Day 28 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 3: Time to Maximum Plasma Concentration (Tmax) of S-648414
The effect of dolutegravir on the pharmacokinetics (PK) of S-648414 was assessed after administration of multiple oral doses of S-648414 alone (Day 21) and after administration of multiple oral doses of S-648414 co-administered with dolutegravir (Day 28).
Time frame: Day 21 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8 and 12 hours postdose. Day 28 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 3: Plasma Concentration of S-648414 at the End of the Dosing Interval τ (Cτ)
The effect of dolutegravir on the pharmacokinetics (PK) of S-648414 was assessed after administration of multiple oral doses of S-648414 alone (Day 21) and after administration of multiple oral doses of S-648414 co-administered with dolutegravir (Day 28).
Time frame: Day 22 and Day 29 (24 hours post-dosing on Days 21 and 28)
Part 3: Area Under the Concentration-time Curve Over the Dosing Interval τ (AUC0-τ) for S-648414
The effect of dolutegravir on the pharmacokinetics (PK) of S-648414 was assessed after administration of multiple oral doses of S-648414 alone (Day 21) and after administration of multiple oral doses of S-648414 co-administered with dolutegravir (Day 28). Area under the concentration-time curve over the dosing interval τ (24 hours) was calculated by the linear up/log down trapezoidal method.
Time frame: Day 21 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8 and 12 hours postdose. Day 28 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 3: Apparent Total Clearance (CL/F) of S-648414
The effect of dolutegravir on the pharmacokinetics (PK) of S-648414 was assessed after administration of multiple oral doses of S-648414 alone (Day 21) and after administration of multiple oral doses of S-648414 co-administered with dolutegravir (Day 28). Apparent total clearance was calculated as CL/F = Dose/AUC0-τ
Time frame: Day 21 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8 and 12 hours postdose. Day 28 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 3: Maximum Plasma Concentration (Cmax) of Dolutegravir
The effect of S-648414 on the PK of dolutegravir was assessed after administration of multiple oral doses of dolutegravir alone and after administration of multiple oral doses of S-648414 co-administered with dolutegravir.
Time frame: Day 7 and Day 28 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12 and 24 hours postdose.
Part 3: Time to Maximum Plasma Concentration (Tmax) of Dolutegravir
The effect of S-648414 on the PK of dolutegravir was assessed after administration of multiple oral doses of dolutegravir alone and after administration of multiple oral doses of S-648414 co-administered with dolutegravir.
Time frame: Day 7 and Day 28 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12 and 24 hours postdose.
Part 3: Plasma Concentration of Dolutegravir at the End of the Dosing Interval τ (Cτ)
The effect of S-648414 on the PK of dolutegravir was assessed after administration of multiple oral doses of dolutegravir alone and after administration of multiple oral doses of S-648414 co-administered with dolutegravir.
Time frame: Day 8 and Day 29 (24 hours post-dosing on Day 7 and Day 28).
Part 3: Area Under the Concentration-time Curve Over the Dosing Interval τ (AUC0-τ) for Dolutegravir
The effect of S-648414 on the PK of dolutegravir was assessed after administration of multiple oral doses of dolutegravir alone and after administration of multiple oral doses of S-648414 co-administered with dolutegravir. Area under the concentration-time curve over the dosing interval τ (24 hours) was calculated by the linear up/log down trapezoidal method.
Time frame: Day 7 and Day 28 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12 and 24 hours postdose.
Part 3: Apparent Total Clearance (CL/F) of Dolutegravir
The effect of S-648414 on the PK of dolutegravir was assessed after administration of multiple oral doses of dolutegravir alone and after administration of multiple oral doses of S-648414 co-administered with dolutegravir. Apparent total clearance calculated as CL/F =Dose/AUC0-τ
Time frame: Day 7 and Day 28 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12 and 24 hours postdose.
Part 1: Maximum Plasma Concentration (Cmax) of S-648414
Time frame: Day 1 and Day 14 (for participants in the 100 mg dose group only) predose, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72 and 96 hours postdose.
Part 1: Time to Maximum Plasma Concentration (Tmax) of S-648414
Time frame: Day 1 and Day 14 (for participants in the 100 mg dose group only) predose, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72 and 96 hours postdose.
Part 1: Area Under the Concentration-time Curve From Time Zero to the Last Quantifiable Concentration After Dosing (AUC0-last) of S-648414
Area under the concentration-time curve from time zero to the time of the last quantifiable concentration after dosing, calculated by the linear trapezoidal method when concentrations are increasing and by the logarithmic trapezoidal method when concentrations are decreasing (linear up/log down trapezoidal method).
Time frame: Day 1 and Day 14 (for participants in the 100 mg dose group only) predose, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72 and 96 hours postdose.
Part 1: Area Under the Concentration-time Curve From Time Zero to Infinity (AUC0-inf) of S-648414
Area under the concentration-time curve extrapolated from time zero to infinity defined as AUC0-last + (Clast/λz), where Clast is the last measurable plasma concentration and λz is the plasma terminal elimination rate constant.
Time frame: Day 1 and Day 14 (for participants in the 100 mg dose group only) predose, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72 and 96 hours postdose.
Part 1: Terminal Elimination Half-life (t1/2,z) of S-648414
Terminal elimination half-life calculated as t1/2,z = (ln2)/λz, where λz is the terminal elimination rate constant.
Time frame: Day 1 and Day 14 (for participants in the 100 mg dose group only) predose, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72 and 96 hours postdose.
Part 1: Terminal Elimination Rate Constant (λz) of S-648414
Time frame: Day 1 and Day 14 (for participants in the 100 mg dose group only) predose, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72 and 96 hours postdose.
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Part 1: Mean Residence Time (MRT) of S-648414
Mean residence time, calculated as MRT = AUMC0-inf / AUC0-inf, where AUMC0-inf is the area under the first moment curve extrapolated to infinity.
Time frame: Day 1 and Day 14 (for participants in the 100 mg dose group only) predose, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72 and 96 hours postdose.
Part 1: Apparent Total Clearance (CL/F) of S-648414
Apparent total clearance estimated according to: CL/F = Dose / AUC0-inf.
Time frame: Day 1 and Day 14 (for participants in the 100 mg dose group only) predose, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72 and 96 hours postdose.
Part 1: Apparent Volume of Distribution in the Terminal Elimination Phase (Vz/F) of S-648414
Apparent volume of distribution in the terminal elimination phase was estimated according to: Vz /F = Dose / AUC0-inf / λz.
Time frame: Day 1 and Day 14 (for participants in the 100 mg dose group only) predose, 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72 and 96 hours postdose.
Part 1: Fraction of S-648414 Dose Excreted in Urine From 0 to 96 Hours Postdose (Feu0-96)
The fraction of S-648414 dose excreted in urine from 0 to 96 hours postdose was calculated as: Cumulative amount of S-648414 excreted in urine from time zero to 96 hours postdose (Aeu0-96) / Dose × 100
Time frame: Day 1 and Day 14 (for participants in the 100 mg dose group only) predose (-12 to 0 hours), 0 to 24 hours, 24 to 48 hours, 48 to 72 hours, and 72 to 96 hours postdose
Part 1: Renal Clearance (CLR) of S-648414
Renal clearance was estimated according to: CLR = cumulative amount of S-648414 excreted in urine from time zero to 96 hours postdose (Aeu0-96) / area under the concentration-time curve from time zero to the time of the last quantifiable concentration after dosing (AUC0-last).
Time frame: Day 1 and Day 14 (for participants in the 100 mg dose group only) predose (-12 to 0 hours), 0 to 24 hours, 24 to 48 hours, 48 to 72 hours, and 72 to 96 hours postdose
Part 2: Maximum Plasma Concentration (Cmax) of S-648414 Following Single and Multiple-dose Administration
Time frame: Day 1 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose; Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72, and 96 hours postdose.
Part 2: Time to Maximum Plasma Concentration (Tmax) of S-648414 Following Single and Multiple-dose Administration
Time frame: Day 1 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose; Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72, and 96 hours postdose.
Part 2: Area Under the Concentration-time Curve Over the Dosing Interval τ (AUC0-τ) of S-648414 Following Single and Multiple-dose Administration
Area under the concentration-time curve over the dosing interval (24 hours) on Day 1 and Day 14, calculated by the linear up/log down trapezoidal method.
Time frame: Day 1 and day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 2: Terminal Elimination Half-life (t1/2,z) of S-648414 Following Multiple-dose Administration
Terminal elimination half-life, where t1/2,z = (ln2)/λz on Day 14.
Time frame: Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72, and 96 hours postdose.
Part 2: Terminal Elimination Rate Constant (λz) of S-648414 Following Multiple-dose Administration
Terminal elimination rate constant, where λz is the magnitude of the slope of the linear regression of the log concentration versus time profile during the terminal phase on Day 14.
Time frame: Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72, and 96 hours postdose.
Part 2: Apparent Total Clearance (CL/F) of S-648414 Following Multiple-dose Administration
Apparent total clearance estimated according to: CL/F = Dose/AUC0-τ on Day 14
Time frame: Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 2: Apparent Volume of Distribution in the Terminal Elimination Phase (Vz/F) of S-648414 Following Multiple-dose Administration
Apparent volume of distribution in the terminal elimination phase on Day 14, estimated according to: Vz /F = Dose/AUC0-τ/λz
Time frame: Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, 24, 48, 72, and 96 hours postdose.
Part 2: Fraction of S-648414 Dose Excreted in Urine Over the Dosing Interval (Feu0- τ) Following Multiple-dose Administration
Fraction of dose excreted in urine over the dosing interval τ (24 hours) on Day 14 calculated as Aeu0-τ/Dose × 100, where Aeu0-τ is the amount of drug excreted in urine over the dosing interval τ (24 hours).
Time frame: Day 14 0-24 hours postdose
Part 2: Renal Clearance (CLR) of S-648414 Following Multiple-dose Administration
Renal clearance on Day 14, calculated as CLR = Aeu0-τ/AUC0-τ, where Aeu0-τ is the amount of drug excreted in urine over the dosing interval τ (24 hours)
Time frame: Day 14 0-24 hours postdose
Part 2: Maximum Plasma Concentration (Cmax) of Midazolam
The effect of S-648414 on the PK of midazolam (a cytochrome P450 3A \[CYP3A\] substrate) was assessed in Part 2 following 5 mg midazolam administration alone (Day -2) and co-administration with S-648414 30 or 50 mg (Day 14).
Time frame: Day -2 and Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 2: Time to Maximum Plasma Concentration of Midazolam
The effect of S-648414 on the PK of midazolam (a cytochrome P450 3A \[CYP3A\] substrate) was assessed in Part 2 following 5 mg midazolam administration alone (Day -2) and co-administration with S-648414 30 or 50 mg (Day 14).
Time frame: Day -2 and Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 2: Area Under the Concentration-time Curve From Time Zero to the Last Quantifiable Concentration After Dosing (AUC0-last) for Midazolam
The effect of S-648414 on the PK of midazolam (a cytochrome P450 3A \[CYP3A\] substrate) was assessed in Part 2 following 5 mg midazolam administration alone (Day -2) and co-administration with S-648414 30 or 50 mg (Day 14). Area under the concentration-time curve from time zero to the time of the last quantifiable concentration after dosing, calculated by linear up/log down trapezoidal method.
Time frame: Day -2 and Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 2: Area Under the Concentration-time Curve From Time Zero to Infinity (AUC0-inf) of Midazolam
The effect of S-648414 on the PK of midazolam (a cytochrome P450 3A \[CYP3A\] substrate) was assessed in Part 2 following 5 mg midazolam administration alone (Day -2) and co-administration with S-648414 30 or 50 mg (Day 14). Area under the concentration-time curve extrapolated from time zero to infinity defined as AUC0-last + (Clast/λz), where Clast is the last measurable plasma concentration and λz is the plasma terminal elimination rate constant.
Time frame: Day -2 and Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 2: Terminal Elimination Half-life for Midazolam
The effect of S-648414 on the PK of midazolam (a cytochrome P450 3A \[CYP3A\] substrate) was assessed in Part 2 following 5 mg midazolam administration alone (Day -2) and co-administration with S-648414 30 or 50 mg (Day 14).
Time frame: Day -2 and Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 2: Terminal Elimination Rate Constant for Midazolam
The effect of S-648414 on the PK of midazolam (a cytochrome P450 3A \[CYP3A\] substrate) was assessed in Part 2 following 5 mg midazolam administration alone (Day -2) and co-administration with S-648414 30 or 50 mg (Day 14).
Time frame: Day -2 and Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 2: Mean Residence Time for Midazolam
The effect of S-648414 on the PK of midazolam (a cytochrome P450 3A \[CYP3A\] substrate) was assessed in Part 2 following 5 mg midazolam administration alone (Day -2) and co-administration with S-648414 30 or 50 mg (Day 14). Mean residence time was calculated as MRT = AUMC0-inf/AUC0-inf where AUMC0-inf is the area under the first moment curve extrapolated to infinity.
Time frame: Day -2 and Day 14 predose (0 hours), 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 12, and 24 hours postdose.
Part 1: Change From Baseline in Fridericia's Corrected QT Interval (QTcF)
Continuous 12-lead digital electrocardiogram (ECG) recording was performed on Day 1. The QT interval is a measure between Q and T wave in heart's electrical cycle. ECGs were analyzed at a blinded, central ECG laboratory. At each specified time point, ten 14-second 12-lead ECG tracings were extracted from the continuous recordings. The median QT in each replicate was calculated; the mean of available medians was used as the participant's reportable value at that time point. QT interval was corrected for heart rate using Fridericia's correction (QTcF). Baseline was defined as the average of the measured ECG intervals from the 3 pre-dose time points (45, 30, and 15 minutes before dosing) on Day 1. Change from Baseline (ΔQTcF) was calculated based on a linear mixed-effects model with time (categorical), treatment, and time-by-treatment interaction as fixed effects and Baseline QTcF as covariate.
Time frame: Day 1: Predose at 3 time points (-45, -30 and -15 minutes), and 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, and 24 hours postdose.
Parts 1: Change From Baseline in Heart Rate (HR)
Continuous 12-lead digital electrocardiogram (ECG) recording was performed on Day 1. ECGs were analyzed at a blinded, central ECG laboratory. At each specified time point, ten 14-second 12-lead ECG tracings were extracted from the continuous recordings. The median HR in each replicate was calculated; the mean of available medians was used as the participant's reportable value at that time point. Baseline was defined as the average of the measured ECG values from the 3 pre-dose time points (45, 30, and 15 minutes before dosing) on Day 1. Change from Baseline in HR (ΔHR) was calculated based on a linear mixed-effects model with time (categorical), treatment, and time-by-treatment interaction as fixed effects and Baseline HR as covariate.
Time frame: Day 1: Predose at 3 time points (-45, -30 and -15 minutes), and 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, and 24 hours postdose.
Part 1: Change From Baseline in PR Interval
Continuous 12-lead digital electrocardiogram (ECG) recording was performed on Day 1. The PR interval is the time from the onset of the P-wave to the start of the next QRS complex. ECGs were analyzed at a blinded, central ECG laboratory. At each specified time point, ten 14-second 12-lead ECG tracings were extracted from the continuous recordings. The median PR in each replicate was calculated; the mean of available medians was used as the participant's reportable value at that time point. Baseline was defined as the average of the measured ECG intervals from the 3 pre-dose time points (45, 30, and 15 minutes before dosing) on Day 1. Change from Baseline in PR interval (ΔPR) was calculated based on a linear mixed-effects model with time (categorical), treatment, and time-by-treatment interaction as fixed effects and Baseline PR as covariate.
Time frame: Day 1: Predose at 3 time points (-45, -30 and -15 minutes), and 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, and 24 hours postdose.
Part 1: Change From Baseline in QRS Interval
Continuous 12-lead digital electrocardiogram (ECG) recording was performed on Day 1. The QRS complex is a combination of the Q wave, R wave and S wave on an ECG tracing, and represents ventricular depolarization. ECGs were analyzed at a blinded, central ECG laboratory. At each specified time point, ten 14-second 12-lead ECG tracings were extracted from the continuous recordings. The median QRS in each replicate was calculated; the mean of available medians was used as the participant's reportable value at that time point. Baseline was defined as the average of the measured ECG intervals from the 3 pre-dose time points (45, 30, and 15 minutes before dosing) on Day 1. Change from Baseline in QRS interval (ΔQRS) was calculated based on a linear mixed-effects model with time (categorical), treatment, and time-by-treatment interaction as fixed effects and Baseline QRS as covariate.
Time frame: Day 1: Predose at 3 time points (-45, -30 and -15 minutes), and 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, and 24 hours postdose.
Part 1: Placebo-corrected Change From Baseline in Fridericia's Corrected QT Interval
Continuous 12-lead digital electrocardiogram (ECG) recording was performed on Day 1. ECGs were analyzed at a blinded, central ECG laboratory. At each specified time point, ten 14-second 12-lead ECG tracings were extracted from the continuous recordings. The median QT in each replicate was calculated; the mean of available medians was used as the participant's reportable value at that time point. QT interval was corrected for heart rate using Fridericia's correction (QTcF). Baseline was defined as the average of the measured ECG intervals from the 3 pre-dose time points (45, 30, and 15 minutes before dosing) on Day 1. Change from Baseline (ΔQTcF) was calculated based on a linear mixed-effects model with time (categorical), treatment, and time-by-treatment interaction as fixed effects and Baseline QTcF as covariate. Placebo-corrected ΔQTcF (ΔΔQTcF) was calculated as the adjusted mean ΔQTcF in the S-648414 group minus adjusted mean ΔQTcF in the placebo group at each time point.
Time frame: Day 1: Predose at 3 time points (-45, -30 and -15 minutes), and 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, and 24 hours postdose.
Part 1: Placebo-corrected Change From Baseline in Heart Rate
Continuous 12-lead digital electrocardiogram (ECG) recording was performed on Day 1. ECGs were analyzed at a blinded, central ECG laboratory. At each specified time point, ten 14-second 12-lead ECG tracings were extracted from the continuous recordings. The median HR in each replicate was calculated; the mean of available medians was used as the participant's reportable value at that time point. Baseline was defined as the average of the measured values from the 3 pre-dose time points (45, 30, and 15 minutes before dosing) on Day 1. Change from Baseline (ΔHR) was calculated based on a linear mixed-effects model with time (categorical), treatment, and time-by-treatment interaction as fixed effects and Baseline HR as covariate. Placebo-corrected ΔHR (ΔΔHR) was calculated as the adjusted mean ΔHR in the S-648414 group minus adjusted mean ΔHR in the placebo group at each time point.
Time frame: Day 1: Predose at 3 time points (-45, -30 and -15 minutes), and 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, and 24 hours postdose.
Part 1: Placebo-corrected Change From Baseline in PR Interval
Continuous 12-lead digital electrocardiogram (ECG) recording was performed on Day 1. ECGs were analyzed at a blinded, central ECG laboratory. At each specified time point, ten 14-second 12-lead ECG tracings were extracted from the continuous recordings. The median PR interval in each replicate was calculated; the mean of available medians was used as the participant's reportable value at that time point. Baseline was defined as the average of the measured ECG intervals from the 3 pre-dose time points (45, 30, and 15 minutes before dosing) on Day 1. Change from Baseline (ΔPR) was calculated based on a linear mixed-effects model with time (categorical), treatment, and time-by-treatment interaction as fixed effects and Baseline PR as covariate. Placebo-corrected ΔPR (ΔΔPR) was calculated as the adjusted mean ΔPR in the S-648414 group minus adjusted mean ΔPR in the placebo group at each time point.
Time frame: Day 1: Predose at 3 time points (-45, -30 and -15 minutes), and 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, and 24 hours postdose.
Part 1: Placebo-corrected Change From Baseline in QRS Duration
Continuous 12-lead digital electrocardiogram (ECG) recording was performed on Day 1. ECGs were analyzed at a blinded, central ECG laboratory. At each specified time point, ten 14-second 12-lead ECG tracings were extracted from the continuous recordings. The median QRS duration in each replicate was calculated; the mean of available medians was used as the participant's reportable value at that time point. Baseline was defined as the average of the measured ECG intervals from the 3 pre-dose time points (45, 30, and 15 minutes before dosing) on Day 1. Change from Baseline in QRS duration (ΔQRS) was calculated based on a linear mixed-effects model with time (categorical), treatment, and time-by-treatment interaction as fixed effects and Baseline QRS as covariate. Placebo-corrected ΔQRS (ΔΔQRS) was calculated as the adjusted mean ΔQRS in the S-648414 group minus adjusted mean ΔQRS in the placebo group at each time point.
Time frame: Day 1: Predose at 3 time points (-45, -30 and -15 minutes), and 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, and 24 hours postdose.
Part 1: Number of Participants With Recorded Outlier Values for QTcF, HR, PR, and QRS
A participant was determined as an outlier if the following criteria (assessed separately) were met for the ECG intervals at any time point: QTcF: * Treatment-emergent value of \> 450 and ≤ 480 ms when not present at Baseline (new onset) * Treatment-emergent value of \> 480 and ≤ 500 ms when not present at Baseline (new onset) * Treatment-emergent value of \> 500 ms when not present at Baseline (new onset) * Increase of QTcF (ΔQTcF) from Baseline of \> 30 and ≤ 60 ms * Increase of QTcF from Baseline \> 60 ms HR: * Decrease of HR from Baseline \> 25% resulting in HR \< 50 bpm * Increase of HR from Baseline \> 25% resulting in HR \> 100 bpm PR: * Increase of PR from Baseline \> 25% resulting in PR \> 200 ms QRS: * Increase of QRS from Baseline \> 25% resulting in QRS \> 120 ms
Time frame: Day 1: Predose at 3 time points (-45, -30 and -15 minutes), and 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, and 24 hours postdose.
Part 1: Number of Participants With Treatment-emergent Changes for T-wave Morphology and U-wave Presence
T-wave abnormalities were categorized as follows: * Normal T wave: Any positive T wave not meeting any criterion below * Flat T wave: T amplitude \< 1 mm (either positive or negative) including flat isoelectric line * Notched T wave (+): Presence of notch(es) of at least 0.05 mV amplitude on ascending or descending arm of the positive T wave * Biphasic: T wave that contains a second component with an opposite phase that is at least 0.1 mV deep (both positive/negative and negative/positive and polyphasic T waves included) * Normal T wave (-): T amplitude that is negative, without biphasic T wave or notches * Notched T wave (-): Presence of notch(es) of at least 0.05 mV amplitude on descending or ascending arm of the negative T wave * U waves: Presence of abnormal U waves
Time frame: Day 1: Predose at 3 time points (-45, -30 and -15 minutes), and 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, and 24 hours postdose.