This study will have a main 24-week treatment period and a 28-week extension period of treatment. The China extension to MK-7264-030 (NCT03449147) will enroll a total of approximately 160 Chinese participants. The initial China Extension protocol (amendment 3) will include the Gefapixant 15 mg BID treatment arm; this treatment arm will not be included in subsequent protocol amendments (eg amendment 5).
The primary objective of this study will be to evaluate the efficacy of gefapixant (MK-7264) in reducing cough frequency as measured over a 24-hour period. It is hypothesized that at least one dose of gefapixant is superior to placebo in reducing coughs per hour (over 24 hours) at Week 24.