• The maximum plasma concentration (Cmax) of a single dose padsevonil (PSL) [ Time Frame: Plasma samples will be taken predose on Day 1 and 0.25, 0.5, 0.75, 1, 1.5, 3, 4, 6, 8, 12, 24, 48 and 72 hours postdose ]
  Cmax: Maximum observed plasma concentration
• The area under the curve from 0 to t (AUC0-t) of a single dose padsevonil (PSL) [ Time Frame: Plasma samples will be taken predose on Day 1 and 0.25, 0.5, 0.75, 1, 1.5, 3, 4, 6, 8, 12, 24, 48 and 72 hours postdose ]
  AUC0-t: Area under the plasma concentration-time curve from time zero to time t
• The area under the curve (AUC) of a single dose padsevonil (PSL) [ Time Frame: Plasma samples will be taken predose on Day 1 and 0.25, 0.5, 0.75, 1, 1.5, 3, 4, 6, 8, 12, 24, 48 and 72 hours postdose ]
  AUC: Area under the plasma concentration-time curve from time 0 to infinity
• The maximum plasma concentration (Cmax) of multiple doses padsevonil (PSL) [ Time Frame: Plasma samples will be taken predose and 0.25, 0.5, 0.75, 1, 1.5, 3, 4, 6, 8 and 12 hours on Day 13 ]
  Cmax: Maximum observed plasma concentration
• The area under the curve (AUCtau) over a dosing interval of multiple doses padsevonil (PSL) [ Time Frame: Plasma samples will be taken predose and 0.25, 0.5, 0.75, 1, 1.5, 3, 4, 6, 8, and 12 hours on Day 13 ]
  AUC0-tau: Area Under the Curve over a dosing interval

• The amount of padsevonil (PSL) excreted in urine [ Time Frame: Urine samples will be taken on Day 1, Day 2, Day 3, Day 4 and Day 13 ]
  Samples will be taken to assess the amount of padsevonil that is excreted in urine.
• The ratio of padsevonil (PSL) and its metabolites excreted in urine [ Time Frame: Urine samples will be taken on Day 1, Day 2, Day 3, Day 4 and Day 13 ]
  Samples will be taken to assess the metabolic ratio of padsevonil that is excreted in urine.
• Number of participants with Treatment-related Adverse events [ Time Frame: From Baseline until End-of-Treatment visit (up to Day 22) ]
  Treatment-related Adverse events is an Adverse Event for which a causal relationship between the product and the occurrence is suspected.
• Number of participants with Serious Adverse events [ Time Frame: From Baseline until End-of-Treatment visit (up to Day 22) ]
  A Serious Adverse Event (SAE) is any untoward medical occurrence that at any dose:

  • Results in death
  • Is life-threatening
  • Requires in patient hospitalization or prolongation of existing hospitalization
  • Is a congenital anomaly or birth defect
  • Is an infection that requires treatment parenteral antibiotics
  • Other important medical events which based on medical or scientific judgement may jeopardize the patients, or may require medical or surgical intervention to prevent any of the above
• Number of participants with Treatment-related Adverse events leading to discontinuation of the study [ Time Frame: From Baseline until End-of-Treatment visit (up to Day 22) ]
  An Adverse Event (AE) is any untoward medical occurrence in a patient or clinical investigation subject administered a pharmaceutical product, which does not necessarily have a causal relationship with this treatment. An AE could therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal (investigational) product, whether or not related to the medicinal (investigational) product.

• Elderly Study Participants
• Adult Study Participants

• Experimental: Adult study participants
  Participants will receive assigned single and multiple doses of padsevonil.
  Intervention: Drug: Padsevonil
• Experimental: Elderly study participants
  Participants will receive assigned single and multiple doses of padsevonil.
  Intervention: Drug: Padsevonil

Inclusion Criteria:

• Study participants in the adult cohort must be ≥18 to 64 years of age at the time of signing the informed consent form (ICF)
• Study participants in the elderly cohort must be ≥65 years of age at the time of signing the ICF
• Study participants who are overtly healthy as determined by medical evaluation, including medical history, physical examination, laboratory tests, and cardiac monitoring. In addition, elderly study participants must be considered to be in general good physical and mental health
• Study participants must have a body weight of at least 50 kg for males and 45 kg for females, and a body mass index within the range of 18 to 32 kg/m2 (inclusive)

Exclusion Criteria:

• Study participant has a current or past psychiatric condition that, in the opinion of the Investigator, could compromise the study participant's safety or ability to participate in this study, or a history of schizophrenia or other psychotic disorder, bipolar disorder, or severe unipolar depression. The presence of potential psychiatric exclusion criteria will be determined based on the psychiatric history collected at Screening
• Study participant has history or presence of cardiovascular, respiratory, hepatic, renal, gastrointestinal, endocrinological, hematological, or neurological disorders capable of significantly altering the absorption, metabolism, or elimination of drugs; constituting a risk when taking the study intervention; or interfering with the interpretation of data
• Study participant has a known hypersensitivity to any components of the study medication as stated in this protocol
• Subject has a history of unexplained syncope or a family history of sudden death due to long QT syndrome
• Study participant has abnormal blood pressure
• Study participant has had lymphoma, leukemia, or any malignancy within the past 5 years, except for basal cell or squamous epithelial carcinomas of the skin that have been resected with no evidence of metastatic disease for 3 years
• Study participant has a lifetime history of suicide attempt, or has had suicidal ideation in the past 6 months as indicated by a positive response ("Yes") to either Question 4 or Question 5 of the "Screening/Baseline" version of the Columbia-Suicide Severity Rating Scale (C-SSRS) at Screening
• Study participant has past or intended use of over-the-counter or prescription medication, including herbal medications within 2 weeks or 5 half-lives prior to dosing
• The study participant has used hepatic enzyme-inducing drugs within 2 months prior to dosing
• Study participant has previously received padsevonil (PSL) in this or another study
• Study participant has alanine aminotransferase (ALT), aspartate aminotransferase (AST), or alkaline phosphatase (ALP) >1.0x upper limit of normal (ULN)
• Study participant has bilirubin >1.0xULN (isolated bilirubin >1.0xULN is acceptable if bilirubin is fractionated and direct bilirubin <35%)
• Study participant has current or chronic history of liver disease or known hepatic or biliary abnormalities (with the exception of Gilbert's syndrome or asymptomatic gallstones)
• Study participant has any clinically relevant electrocardiogram (ECG) finding at Screening or at Baseline. Study participant has an abnormality in the 12-lead ECG that, in the opinion of the Investigator, increases the risks associated with participating in the study. In addition, any study participant with any of the following findings will be excluded: (a) QT interval corrected for heart rate using Bazett's formula (QTcB) or Fridericia's formula (QTcF) >450 ms in study participants in 2 of 3 ECG recordings; (b) other conduction abnormalities (defined as PR interval ≥220 ms); (c) irregular rhythms other than sinus arrhythmia or occasional, rare supraventricular or rare ventricular ectopic beats. In case of an out of range result, 1 repeat will be allowed. If out of range again, the study participant cannot be included