Cough monitoring was conducted for 24 hours while awake, at pre-dose on Day 0 (baseline), and after administration of the study drug on Day 7 and Day 14 in Periods 1 and 2. The cough frequency is the coughs/hour over each 24-hour period. Awake objective cough frequency was analyzed using Mixed Effect Model for Repeated Measures (MMRM) to evaluate the results of the 2-period cross-over study. Baseline cough frequency was derived from the cough monitoring performed at the beginning of each treatment period while the post-treatment cough frequency was derived from the cough monitoring performed at the end of the dosing period. A negative change indicates a decrease in cough frequency, while a positive change indicates an increase in cough frequency.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

Cough monitoring was conducted for 24 hours while awake, at pre-dose on Day 0 (baseline), and after administration of the study drug on Day 7 and Day 14 in Periods 1 and 2. The cough frequency is the coughs/hour over each 24-hour period. Awake objective cough frequency was defined as the total number of cough events during the monitoring period the participant was awake divided by the total duration for the monitoring period the participant was awake. Baseline cough frequency was derived from the cough monitoring performed at the beginning of each treatment period while the post-treatment cough frequency was derived from the cough monitoring performed at the end of the dosing period.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

Cough monitoring was conducted for 24 hours while awake, at pre-dose on Day 0 (baseline), and after administration of the study drug on Day 7 and Day 14 in Periods 1 and 2. The cough frequency is the coughs/hour over each 24-hour period. Awake objective cough frequency was defined as the total number of cough events during the monitoring period the participant was awake divided by the total duration for the monitoring period the participant was awake. Baseline cough frequency was derived from the cough monitoring performed at the beginning of each treatment period while the post-treatment cough frequency was derived from the cough monitoring performed at the end of the dosing period. A negative value indicates a decrease in cough frequency.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

Awake objective cough frequency was defined as the total number of cough events during the monitoring period the participant was awake divided by the total duration for the monitoring period the participant was awake. Percent change from baseline in awake objective cough frequency (0-6 hours after the morning dose) was reported at each dosing interval. Percent change in awake cough frequency = 100 X (post treatment cough frequency - baseline cough frequency) divided by the baseline cough frequency. A negative value indicates a decrease in cough frequency.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

Awake objective cough frequency was defined as the total number of cough events during the monitoring period the participant was awake divided by the total duration for the monitoring period the participant was awake. Change from Baseline in awake cough frequency = post-treatment awake cough frequency - Baseline awake cough frequency. A negative value indicates a decrease in cough frequency. A positive value indicates an increase in cough frequency. Baseline cough frequency was derived from the cough monitoring performed at the beginning of each treatment period while the post-treatment cough frequency was derived from the cough monitoring performed at the end of the dosing period. Awake objective cough frequency for Period 1 was analyzed for using MMRM to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

Awake objective cough frequency was defined as the total number of cough events during the monitoring period the participant was awake divided by the total duration for the monitoring period the participant was awake. Change from baseline in awake cough frequency = post-treatment awake cough frequency - Baseline awake cough frequency. A negative value indicates a decrease in cough frequency. A positive value indicates an increase in cough frequency. Baseline cough frequency was derived from the cough monitoring performed at the beginning of each treatment period while the post-treatment cough frequency was derived from the cough monitoring performed at the at the end of the dosing period. Awake objective cough frequency for Period 2 was analyzed using MMRM to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

Awake objective cough frequency was defined as the total number of cough events during the monitoring period the participant was awake divided by the total duration for the monitoring period the participant was awake. The number of participants that met responder criteria for ≥70%, ≥50%, ≥30%, and ≥20% change (reduction) from baseline levels in 24-hour awake cough frequency was reported (Period 1 and Period 2 combined) at Day 7.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

Awake objective cough frequency was defined as the total number of cough events during the monitoring period the participant was awake divided by the total duration for the monitoring period the participant was awake. The number of participants that met responder criteria for ≥70%, ≥50%, ≥30%, and ≥20% change (reduction) from baseline levels in 24-hour awake cough frequency was reported (Period 1 and Period 2 combined) at Day 14.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

24-hour objective cough frequency = total number of coughs during the monitoring period divided by the total duration for the monitoring period. A negative value indicates a decrease in cough frequency. A positive value indicates an increase in cough frequency. 24-hour objective cough frequency was analyzed using MMRM to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

24-hour objective cough frequency = total number of coughs during the monitoring period divided by the total duration for the monitoring period. A negative value indicates a decrease in cough frequency. A positive value indicates an increase in cough frequency. 24-hour objective cough frequency for Period 1 was analyzed using MMRM to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

24-hour objective cough frequency = total number of coughs during the monitoring period divided by the total duration for the monitoring period. A negative value indicates a decrease in cough frequency. A positive value indicates an increase in cough frequency. 24-hour objective cough frequency for Period 2 was analyzed using MMRM to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

24-hour objective cough frequency = total number of coughs during the monitoring period divided by the total duration for the monitoring period.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

24-hour objective cough frequency = total number of coughs during the monitoring period divided by the total duration for the monitoring period. A negative value indicates a decrease in cough frequency. A positive value indicates an increase in cough frequency. 24-hour objective cough frequency was analyzed using MMRM to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

24-hour objective cough frequency = total number of coughs during the monitoring period divided by the total duration for the monitoring period. Percent change in cough frequency = 100 X (post treatment cough frequency - baseline cough frequency) divided by the baseline cough frequency. A negative value indicates a decrease in cough frequency. A positive value indicates an increase in cough frequency.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

Sleep Objective Cough Frequency = Total number of cough events during the monitoring period the participant is asleep divided by the total duration (in hours) for the monitoring period the participant is asleep. 24-hour sound recordings were collected with a digital recording device. A negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency. Sleep cough frequency was analyzed using MMRM to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

Cough VAS is scored from 0 to 100 using a 10 mm visual analogue scale with 0 at 0mm and 100 at 10mm with 0 (no cough) and 100 (most severe cough). Baseline cough VAS is defined as average of screening and baseline cough VAS. A negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency. Cough VAS was analyzed using MMRM to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

CQLQ is a 28-item scale that has 4 possible responses: 1 = strongly disagree; 2 = disagree; 3 = agree; 4 = strongly agree. Subjects were instructed to circle only 1 response. The total CQLQ score is the sum of the individual item scores; the lowest possible score is 28 and the highest 112. Low CQLQ scores for both total and the 6 domains indicate less impact of cough on health-related quality of life. A negative result indicates a decrease in cough impact on quality of life. CQLQ was analyzed using MMRM to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

The daily CSD Score is calculated using the daily CSD instrument, a 7-item, disease specific, patient-reported outcome measure with a recall period of "today" (the current day). The measure evaluates frequency of cough (3 items); intensity of cough (2 items); and sleep disruption due to cough (2 items). Each of these 7 items is rated on an 11-point scale, ranging from 0 (best) to 10 (worst), with higher scores indicating greater severity. The total daily CSD score is the sum of these 7 item scores (Min=0, Max=70). Baseline CSD score = average of CSD scores at screening and baseline. A negative result indicates a decrease in cough severity, while a positive result indicates an increase in cough severity. CSD was analyzed using MMRM to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

UCSD SOBQ is a 24-point item scale to assess shortness of breath questionnaire that has a 6-point scale ranging from 0 to 5 (0 = "not at all", to 5 = "maximal or unable to do because of breathlessness". Lowest possible score is 0 and the highest possible score is 120. The higher the score the more out of breath the participant is reporting. A negative value indicates less breathlessness. UCSD SOBQ was analyzed using MMRM to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

The Borg 10 scale assesses post-treatment breathlessness during perceived exertion while exercising. The scale ranges from 0 to 10 where 0 = nothing at all, 1 = very weak, 3 = moderate, 5 = strong, 7 = very strong, 10 = extremely strong. The lowest possible score is 0 and the highest possible score is 10. A negative value indicates less breathlessness. Cough Borg CR10 was analyzed using MMRM to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

The Borg 10 scale assesses post-treatment breathlessness during perceived exertion while exercising. The scale ranges from 0 to 10 where 0 = nothing at all, 1 = very weak, 3 = moderate, 5 = strong, 7 = very strong, 10 = extremely strong. The lowest possible score is 0 and the highest possible score is 10. The percentage of participants with Borg CR10 perception of breathless value ≥5 was assessed.

The analysis population includes all randomized participants who received at least 1 dose of study drug. Two participants that had missing values for Day 14 were excluded.

PGIC is the participant self-reported overall improvement of cough following administration of study drug. The PGIC has a 7-point rating scale of "very much improved", "much improved", 'minimally improved", "no change", "minimally worse", "much worse" and "very much worse".

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

PGIC is the participant self-reported overall improvement of cough following administration of study drug. The PGIC has a 7-point rating scale of "very much improved", "much improved", 'minimally improved", "no change", "minimally worse", "much worse" and "very much worse".

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

CGIC is the clinician's-reported overall improvement of participant's cough following administration of study drug. The CGIC has a 7-point rating scale of "very much improved", "much improved", 'minimally improved", "no change", "minimally worse", "much worse" and "very much worse".

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

At the end of the treatment period, participants were asked "How likely would you be to take this medication for at least 6 months?" The degree of taste acceptability was measured on a scale of "extremely unlikely", "unlikely", "neither", "likely" and "extremely likely."

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

At the end of the treatment period, the participant was asked "How likely would you be to take this medication for at least one year?" The degree of taste acceptability was measured on a scale of "extremely unlikely", "unlikely", "neither", "likely" and "extremely likely."

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

Awake objective cough frequency was defined as the total number of cough events during the monitoring period the participant was awake divided by the total duration for the monitoring period the participant was awake. Baseline cough frequency was derived from the cough monitoring performed at the beginning of each treatment period.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

24-hour objective cough frequency = total number of coughs during the monitoring period divided by the total duration for the monitoring period. Baseline 24-hour cough frequency in Periods 1 and 2 was evaluated based on the participant's randomized group (gefapixant or placebo).

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

24-hour objective cough frequency = total number of coughs during the monitoring period divided by the total duration for the monitoring period. Baseline 24-hour cough frequency for Period 1 was evaluated based on the participant's randomized group (gefapixant or placebo).

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

24-hour objective cough frequency = total number of coughs during the monitoring period divided by the total duration for the monitoring period. Baseline 24-hour objective cough frequency for Period 2 was evaluated based on the participant's randomized group (gefapixant or placebo).

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

Sleep Objective Cough Frequency = Total number of cough events during the monitoring period the participant is asleep divided by the total duration (in hours) for the monitoring period the participant is asleep. 24-hour sound recordings were collected with a digital recording device. Baseline sleep cough frequency was evaluated based on the participant's randomized group (gefapixant or placebo).

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

Cough VAS is scored from 0 to 100 using a 10 mm visual analogue scale with 0 at 0mm and 100 at 10mm with 0 (no cough) and 100 (most severe cough). Baseline cough VAS was defined as average of screening and baseline cough VAS.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

CQLQ is a 28-item scale that has 4 possible responses: 1 = strongly disagree; 2 = disagree; 3 = agree; 4 = strongly agree. Subjects were instructed to circle only 1 response. The total CQLQ score is the sum of the individual item scores; the lowest possible score is 28 and the highest 112. Low CQLQ scores for both total and the 6 domains indicate less impact of cough on health-related quality of life. Baseline cough CQLQ was evaluated based on the participant's randomized group (gefapixant or placebo).

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

The daily CSD Score is calculated using the daily CSD instrument, a 7-item, disease specific, patient-reported outcome measure with a recall period of "today" (the current day). The measure evaluates frequency of cough (3 items); intensity of cough (2 items); and sleep disruption due to cough (2 items). Each of these 7 items is rated on an 11-point scale, ranging from 0 (best) to 10 (worst), with higher scores indicating greater severity. The total daily CSD score is the sum of these 7 item scores (Min=0, Max=70). Baseline CSD score = average of CSD scores at screening and baseline.

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

UCSD SOBQ is a 24-point item scale to assess shortness of breath questionnaire that has a 6-point scale ranging from 0 to 5 (0 = "not at all", to 5 = "maximal or unable to do because of breathlessness". Lowest possible score is 0 and the highest possible score is 120. The higher the score the more out of breath the participant is reporting. Baseline of UCSD SOBQ was evaluated based on the participant's randomized group (gefapixant or placebo).

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.

The Borg 10 scale assesses post-treatment breathlessness during perceived exertion while exercising. The scale ranges from 0 to 10 where 0 = nothing at all, 1 = very weak, 3 = moderate, 5 = strong, 7 = very strong, 10 = extremely strong. The lowest possible score is 0 and the highest possible score is 10. The baseline of cough Borg CR10 was evaluated based on the participant's randomized group (gefapixant or placebo).

The analysis population includes all randomized participants who had a baseline and at least 1 post-baseline frequency values, were enrolled into the study under protocol amendment 3, and had otherwise complied with the protocol without any major protocol deviations. Participants enrolled prior to protocol amendment 3 were not included in the efficacy analysis.