A Multiple-Dose Pharmacokinetics Study of Two Gefapixant (AF-219/MK-7264) Formulations

Inclusion Criteria:

- Must be informed of the nature of the study and have provided written informed
voluntary consent;

- Able to speak, read, and understand English;

- Healthy males or females, of any race, between 18 and 55 years of age, inclusive;

- Body mass index (BMI) >18.5 and <32.0 kg/m2 and weigh 50 - 100 kg;

- In good general health;

- Non-smokers or intermittent (social) smokers for at least 5 years, and able to
refrain from smoking (or using nicotine) while in confinement;

- If a female of child-bearing potential (i.e., have not undergone a hysterectomy or
bilateral oophorectomy) or not post-menopausal (defined as no menses for at least 12
months), agree to use 2 forms of acceptable birth control; or if a male, they and/or
their partner of child-bearing potential agree to use 2 forms of acceptable birth
control; when in line with the preferred life style of the subject, true and complete
abstinence (not periodic abstinence) is acceptable;

Exclusion Criteria:

- Any disease or condition that might affect drug absorption, metabolism, or excretion
or clinically significant cardiovascular, hematological, renal, hepatic, pulmonary,
endocrine, gastrointestinal, immunological, dermatological, neurological, or
psychiatric disease;

- Clinically significant illness or clinically significant surgery within 4 weeks
before the administration of study medication;

- Any past sinus surgery, upper respiratory tract infection within 2 weeks before
dosing, or history of hay fever during the time of the year that dosing will be
taking place;

- History of GERD, heartburn, or nausea more than once a month, or any similar symptoms
requiring the regular use of antacids, or any use of H2 histamine blockers or proton
pump inhibitors within 12 months of Screening;

- Have a positive screening test for Helicobacter pylori;

- QTcB >450 msec in males or >470 msec in females;

- Known or suspected hypersensitivity or allergic reaction to any of the components of
gefapixant or omeprazole capsules;

- If female, is pregnant or breast feeding, or has a positive pregnancy test pre dose;

- Blood loss or blood donation of >550 mL within 90 days or plasma donation >500 mL
within 14 days before administration of the first dose of study drug;

- Chronic use of any systemic medications (other than allowable oral and implanted
contraceptives and with the exception of vitamins taken at standard supplement
doses); use of a drug therapy (including herbal preparations, e.g., St. John's wort)
known to induce or inhibit hepatic drug metabolism within 30 days before the first
dose of study medication; or use of any medications [prescription or over the counter
(OTC)], including antacids, high dose multivitamins, nutritional supplements, and
herbal preparations, within 14 days before the first dose of study drug;

- Past or current history or evidence of drug or alcohol abuse, regular use of more
than 2 units of alcohol per day (1 unit of alcohol = 150 mL of wine, 360 mL of beer,
or 45 mL of alcohol 40%), use of any recreational soft drugs (e.g., marijuana) within
3 months of screening, use of any hard drugs (such as cocaine, phencyclidine (PCP),
and crack) within 1 year of screening, and/or a positive screen for substances of
abuse or alcohol at screening or pre dose;

- Ingestion of grapefruit or grapefruit juice within 48 hours before dose
administration;

- Positive screen for hepatitis B surface antigen (HBsAg), hepatitis C antibody, or
human immunodeficiency virus (HIV) antibody;

- Receipt of an investigational product or device, or participation in a drug research
study within a period of 30 days (or 5 half lives of the drug, whichever is longer)
before the first dose of study medication;

- Receipt of an investigational immunomodulator or monoclonal antibody within 180 days
(or 5 half lives, whichever is longer) before the first dose of study medication.