Safety and Tolerability of CFTX-1554 in Healthy Subjects

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.