Inclusion Criteria:
* Healthy male and female subjects, ages 18 to 55 years, inclusive, at the time of signing the ICF. Healthy is defined as no clinically relevant abnormalities identified by a detailed medical history, full physical examination, including blood pressure and heart rate measurement, 12-lead ECG, and clinical laboratory tests, as evaluated by the investigator.
* Body mass index of 18.5 to 30.0 kg/m2, inclusive, and a total body weight \>50 kg (110 lbs)
* A female subject of childbearing potential who is sexually active with a nonsterilized male partner must agree to use a highly effective method of contraception from signing of informed consent and for 30 days post last dose. A male subject with a pregnant or a nonpregnant partner of childbearing potential must agree to use condom during treatment and until the end of relevant systemic exposure in the male subject for 94 days following the last dose with IMP.
* Capable of giving signed informed consent
* Ability, in the opinion of the investigator, to understand the nature of the trial and comply with protocol requirements, including the prescribed dosage regimens, scheduled visits, laboratory tests, and other trial procedures.
* Defined as sensitive to the anxiogenic effects of double-breath CO2 inhalation
Exclusion Criteria:
* Subjects with a current history of clinically significant cardiovascular pulmonary, gastrointestinal, renal, hepatic, metabolic, hematological, immunological, or neurological disease.
* Subjects with a current or past history of clinically significant respiratory conditions
* Subject with a personal or family history of sickle cell anemia
* Subject with a personal or family history of cerebral aneurysm
* Subjects with a clinically significant current or past personal or family history of any psychiatric disorder as classified by DSM-4 or DSM-5 criteria
* Subjects with epilepsy or a history of seizures except for a single seizure episode
* Subjects with a history of substance or alcohol-use disorder (DSM-5 criteria)
* Subjects who answer "Yes" on the C-SSRS Suicidal Ideation Item 4, 5 and whose most recent episode meeting criteria for this C-SSRS Item 4, 5 occurred within the last 6 months
* Subjects who, in the opinion of the investigator, present a serious risk of suicide
* Subjects with human immunodeficiency virus seropositive status or acquired immunodeficiency syndrome, chronic hepatitis B or C (defined as positive serology and aspartate aminotransferase or alanine aminotransferase elevated to \>2 × ULN)
* Subject with a positive drug screen for illicit drugs
* Subjects with a 12-lead ECG demonstrating either of the following:
* QT interval corrected for heart rate using Fridericia's formula \>450 msec (average of 3 ECGs obtained at the Screening Visit)
* QRS interval \>120 msec at the Screening Visit
* Subjects with any of the following abnormalities in clinical laboratory tests at the Screening Visit, as assessed by the local laboratory and confirmed by a single repeat measurement, if deemed necessary:
* AST or ALT ≥2 × ULN
* Total bilirubin ≥1.5 × ULN. Subjects with a history of Gilbert's syndrome may be eligible provided the direct bilirubin is \
8 units of methylxanthines per day and refuses to abstain from consumption of methylxanthine containing food and beverages while in the clinic.
* Subjects with any condition possibly affecting drug absorption
* Subjects with difficulty swallowing
* Subjects who are known to be allergic or hypersensitive to the IMP or any of its components
* Subjects with a known sensitivity or contraindication to alprazolam
* Subjects who have participated in any clinical trial within 90 days prior to signing the ICF.
* Subjects who have demonstrated a non-response to 35% CO2 double inhalation challenge in a previous trial.
* Any subject who, in the opinion of the sponsor, investigator, or medical monitor, should not participate in the trial
* Subjects with a positive SARS-CoV-2 quantitative PCR test result at Day -1, Period 1 are excluded. Results from subjects reporting a positive SARS-CoV-2 quantitative PCR test result prior to Day -1, Period need to be discussed with the sponsor/medical monitor prior to enrolment of the subject into the trial