The study will consist of 2 parts, i.e. a single ascending dose part with integrated food effect assessment and assessment of relative bioavailability (Part A), and a multiple ascending dose part (Part B).

Part A will have a randomized, double-blind, placebo-controlled design. Subjects will receive single ascending doses of CFTX-1554 or placebo (as liquid formulation under fasted condition) in 7 subsequent cohorts. Drug intake under fed conditions, and as capsule under fasted conditions and under fed conditions (Periods 2 to 4), compared to liquid formulation under fasted conditions (Period 1) (1 single dose level only) will be assessed.

Part B will have a randomized, double-blind, placebo-controlled design, assessing multiple ascending oral doses of CFTX-1554 or placebo in 4 subsequent cohorts.

INCLUSION CRITERIA:

• Body mass index 18.0 to 30.0 kg/m2
• Females may be of childbearing potential but not pregnant or lactating, or of nonchildbearing potential; all females will be required to have a negative serum pregnancy test conducted at screening, (each) admission, and follow-up.
• Female subjects of childbearing potential who have a fertile male sexual partner must agree to use adequate contraception from at least 4 weeks prior to first administration of study drug until 90 days after the follow up visit.
• Male subjects, if not surgically sterilized, must agree to use adequate contraception and not donate sperm from first admission to the clinical research center until 90 days after the follow-up visit.
• All prescribed medication must have been stopped at least 30 days prior to first admission to the clinical research center.
• All over-the-counter medication, vitamin preparations and other food supplements, or herbal medications must have been stopped at least 14 days prior to first admission to the clinical research center.
• Ability and willingness to abstain from alcohol from 48 hours before screening and first admission to the clinical research center.
• Ability and willingness to abstain from methylxanthine-containing beverages or food (coffee, tea, cola, chocolate, energy drinks) and grapefruit (juice) from 48 hours before first admission to the clinical research center.
• Good physical and mental health on the basis of medical history, physical examination, clinical laboratory, ECG, and vital signs, as judged by the Investigator.
• Willing and able to sign the Informed Consent Form.

EXCLUSION CRITERIA:

• Previous participation in the current study
• History of relevant drug and/or food allergies
• Allergy or hypersensitivity to active ingredient or excipients of the study drug
• Using nicotine-containing products within 60 days prior to the first study drug administration
• History of alcohol abuse or drug addiction (including soft drugs like cannabis products) within 1 year before screening
• Positive drug and alcohol screen in urine (opiates, methadone, cocaine, amphetamines [including ecstasy], cannabinoids, barbiturates, benzodiazepines, tricyclic antidepressants, nicotine metabolites [cotinine], and alcohol) at screening or at one of the admissions to the clinical research center
• Average intake of >24 units of alcohol/week
• Positive screen for hepatitis B surface antigen, hepatitis C virus antibodies, or human immunodeficiency virus 1 and 2 antibodies
• Participation in a drug study within 30 days prior to the first study drug administration in the current study (counting from the follow-up visit to the screening visit). Participation in ≥4 other drug studies in the 12 months before the first study drug administration in the current study
• Donation or loss of >450 mL of blood within 60 days pribefore the first study drug administration. Donation or loss of >1.5 L of blood in male subjects) or >1.0 L of blood in female subjects in the 10 months before the first study drug administration in the current study.
• Significant and/or acute illness within 5 days before the first study drug administration that may impact safety assessments, in the opinion of the Investigator.
• Unwillingness to consume the Food and Drug Administration (FDA) breakfast or intolerance to any of the ingredients of the FDA breakfast (Cohort A5 only)
• Vaccination against SARS-CoV-2 planned between 2 weeks before first admission and follow-up.
• Positive nasopharyngeal PCR test for SARS-CoV-2 on Day -1, or any known contact with a person who tested positive for SARS-CoV-2 or with a COVID 19 patient within 2 weeks before admission.