Placebo to gefapixant 7.5 and 50mg tablets administered orally

Participants were classified as responders based on the magnitude of the percent change from baseline in Awake Objective cough frequency: 1. ≥70% Reduction=1 if Percent Change from Baseline in cough frequency at the end of the dosing interval ≤-70.0%; 0 Otherwise; 2. ≥50% Reduction=1 if Percent Change from Baseline in cough frequency at the end of the dosing interval ≤ -50.0%; 0 Otherwise; 3. ≥30% Reduction=1 if Percent Change from Baseline in cough frequency at the end of the dosing interval ≤ -30.0%; 0 Otherwise. These responder definitions were not mutually exclusive. A participant who achieved a 1 for ≥70% Reduction for a particular period and dosing interval, were by definition, classified as ≥50% Reduction and ≥ 30% Reduction.

Participants were classified as responders based on the magnitude of the percent change from baseline in Awake Objective cough frequency: 1. ≥70% Reduction=1 if Percent Change from Baseline in cough frequency at the end of the dosing interval ≤-70.0%; 0 Otherwise; 2. ≥50% Reduction=1 if Percent Change from Baseline in cough frequency at the end of the dosing interval ≤ -50.0%; 0 Otherwise; 3. ≥30% Reduction=1 if Percent Change from Baseline in cough frequency at the end of the dosing interval ≤ -30.0%; 0 Otherwise. These responder definitions were not mutually exclusive. A participant who achieved a 1 for ≥70% Reduction for a particular period and dosing interval, were by definition, classified as ≥50% Reduction and ≥ 30% Reduction.

Awake (0-8 hours) Objective Cough Frequency is the total number of cough events during the monitoring period the participant was awake for the first 8 hours after the participant took their study medication divided by 8 or the total duration (in hours) for the monitoring period the participant was awake whichever is less. 24-hour sound recordings were collected using a digital recording device. Results are change from baseline: a negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

Cough frequency was analyzed using a mixed model repeated measures (MMRM) to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

Total (0-24 hours) Objective Cough Frequency is the total number of cough events during the monitoring period divided by the total duration (in hours, i.e., 24 hours mostly) for the monitoring period. 24-hour sound recordings were collected using a digital recording device. Results are change from baseline: a negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

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.

Total (0-24 hours) Objective Cough Frequency is the total number of cough events during the monitoring period divided by the total duration (in hours, i.e., 24 hours mostly) for the monitoring period. 24-hour sound recordings were collected using a digital recording device. Results are change from baseline: a negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

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.

Sleep Objective Cough Frequency is the 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 recording were collected with a digital recording device. Results are change from baseline: a negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

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.

Sleep Objective Cough Frequency is the 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 recording were collected with a digital recording device. Results are change from baseline: a negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

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 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. Results are change from 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 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. Results are change from 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 LCQ-Acute is a 19-item health-related quality-of-life (HRQoL) questionnaire specific for acute cough which contains three domains (i.e., physical, psychological, and social). It is calculated as a mean score for each domain ranging from 1 (worst) to 7 (best), and total score ranging from 3 (worst) to 21 (best). Each item on the LCQ-acute assesses symptoms or the impact of symptoms on HRQoL in the last 24 hours using a 7-point Likert scale ranging from 1 to 7. Higher scores indicate better HRQoL. Participants' perception of their cough severity was assessed, based on the LCQ-Acute score, at Baseline and last day of dose.

LCQ 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.

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. Results are change from baseline: a negative result indicates a decrease in cough severity, while a positive result indicates an increase in cough severity.

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.

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. Results are change from baseline: a negative result indicates a decrease in cough severity, while a positive result indicates an increase in cough severity.

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.

Awake (0 - 8 hours) Objective Cough Frequency is the total number of cough events during the monitoring period the participant was awake for the first 8 hours after the participant took their study medication divided by 8 or the total duration (in hours) for the monitoring period the participant was awake whichever is less. 24 hour sound recordings were collected with a digital recording device. Baseline measurements were not available by individual arm because baseline cough frequencies were measured before participants received the first dose of study drug. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

Total (0 - 24 hours) Objective Cough Frequency is the total number of cough events during the monitoring period divided by the total duration (in hours) for the monitoring period. 24 hour sound recordings were collected using a digital recording device. Baseline measurements were not available by individual arm because baseline cough frequencies were measured before participants received the first dose of study drug. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

Sleep Objective Cough Frequency is the 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 recording were collected with a digital recording device. Baseline measurements were not available by individual arm because baseline cough frequencies were measured before participants received the first dose of study drug. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

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 frequency, while a positive result indicates an increase in cough frequency. Baseline measurements were not available by individual arm because baseline cough frequencies were measured before participants received the first dose of study drug. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

The LCQ-Acute is a 19-item health-related quality-of-life (HRQoL) questionnaire specific for acute cough which contains three domains (i.e., physical, psychological, and social). It is calculated as a mean score for each domain ranging from 1 (worst) to 7 (best), and total score ranging from 3 (worst) to 21 (best). Each item on the LCQ-acute assesses symptoms or the impact of symptoms on HRQoL in the last 24 hours using a 7-point Likert scale ranging from 1 to 7. Higher scores indicate better HRQoL. As per the Statistical Analysis Plan, each domain and total LCQ score change from baseline were analyzed without the treatment by dose interaction. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

Cough VAS: scored from 0 to 100 using a 10 mm visual analogue scale with 0 (no cough) and 100 (most severe cough) mm. Baseline cough VAS is defined as average of screening and baseline cough VAS. Baseline measurements were not available by individual arm because baseline cough frequencies were measured before participants received the first dose of study drug. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

Gefapixant 7.5, 15, 30 and 50 mg, tablet(s) administered by mouth, twice daily, for 4 days each in Period 1 and placebo to gefapixant 7.5, 15, 30 and 50 mg, tablet(s) administered by mouth, twice daily, for 4 days each in Period 2. For Cohort 2, there was a 14 to 21-day washout period between treatment periods.

Placebo to gefapixant 7.5, 15, 30 and 50 mg, tablet(s) administered by mouth, twice daily, for 4 days each in Period 1 and gefapixant 7.5, 15, 30 and 50 mg, tablet(s) administered by mouth, twice daily, for 4 days each in Period 2. For Cohort 2, there was a 14 to 21-day washout period between treatment periods.

Total of all reporting groups

Placebo tablet administered by mouth BID for 4 days.

Gefapixant 100 mg tablet administered by mouth BID for 4 days.

Placebo tablet administered by mouth BID for 4 days.

Gefapixant 150 mg tablet administered by mouth BID for 4 days.

Placebo tablet administered by mouth BID for 4 days.

Gefapixant 200 mg tablet administered by mouth BID for 4 days.

Placebo tablet administered by mouth BID for 4 days.

Awake Objective Frequency (per hour) is the total number of cough events during the monitoring period (in general, 24-hr interval) the participant is awake divided by the total duration (in hours) for the monitoring period the participant is awake. 24-hour sound recordings were collected using a digital recording device.

Analysis population consisted of all participants in Cohort 2 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

Awake Objective Cough Frequency (per hour) is the total number of cough events during the monitoring period (in general, 24-hr interval) the participant is awake divided by the total duration (in hours) for the monitoring period the participant is awake. 24-hour sound recordings were collected using a digital recording device. Percent Change in Awake Cough Frequency is the change from baseline in awake cough frequency x 100, divided by baseline awake cough frequency. A negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

Analysis population consisted of all participants in Cohort 1 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

Awake Objective Cough Frequency (per hour) is the total number of cough events during the monitoring period (in general, 24-hr interval) the participant is awake divided by the total duration (in hours) for the monitoring period the participant is awake. 24-hour sound recordings were collected using a digital recording device. Percent Change in Awake Cough Frequency is the change from baseline in awake cough frequency x 100, divided by baseline awake cough frequency. A negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

Analysis population consisted of all participants in Cohort 2 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

Participants were classified as responders based on the magnitude of the percent change from baseline in Awake Objective cough frequency: 1. ≥70% Reduction=1 if Percent Change from Baseline in cough frequency at the end of the dosing interval ≤-70.0%; 0 Otherwise; 2. ≥50% Reduction=1 if Percent Change from Baseline in cough frequency at the end of the dosing interval ≤ -50.0%; 0 Otherwise; 3. ≥30% Reduction=1 if Percent Change from Baseline in cough frequency at the end of the dosing interval ≤ -30.0%; 0 Otherwise. These responder definitions were not mutually exclusive. A participant who achieved a 1 for ≥70% Reduction for a particular period and dosing interval, were by definition, classified as ≥50% Reduction and ≥ 30% Reduction.

Analysis population consisted of all participants in Cohort 1 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

Participants were classified as responders based on the magnitude of the percent change from baseline in Awake Objective cough frequency: 1. ≥70% Reduction=1 if Percent Change from Baseline in cough frequency at the end of the dosing interval ≤-70.0%; 0 Otherwise; 2. ≥50% Reduction=1 if Percent Change from Baseline in cough frequency at the end of the dosing interval ≤ -50.0%; 0 Otherwise; 3. ≥30% Reduction=1 if Percent Change from Baseline in cough frequency at the end of the dosing interval ≤ -30.0%; 0 Otherwise. These responder definitions were not mutually exclusive. A participant who achieved a 1 for ≥70% Reduction for a particular period and dosing interval, were by definition, classified as ≥50% Reduction and ≥ 30% Reduction.

Analysis population consisted of all participants in Cohort 2 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

Awake (0-8 hours) Objective Cough Frequency is the total number of cough events during the monitoring period the participant was awake for the first 8 hours after the participant took their study medication divided by 8 or the total duration (in hours) for the monitoring period the participant was awake whichever is less. 24-hour sound recordings were collected using a digital recording device. Results are change from baseline: a negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

Cough frequency was analyzed using a mixed model repeated measures (MMRM) to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

Analysis population consisted of all participants in Cohort 1 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

Awake (0-8 hours) Objective Cough Frequency is the total number of cough events during the monitoring period the participant was awake for the first 8 hours after the participant took their study medication divided by 8 or the total duration (in hours) for the monitoring period the participant was awake whichever is less. 24-hour sound recordings were collected using a digital recording device. Results are change from baseline: a negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

Cough frequency was analyzed using a mixed model repeated measures (MMRM) to evaluate the results of the 2-period cross-over study. The derived change measured at each dose were the repeated measures.

Analysis population consisted of all participants in Cohort 2 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

Total (0-24 hours) Objective Cough Frequency is the total number of cough events during the monitoring period divided by the total duration (in hours, i.e., 24 hours mostly) for the monitoring period. 24-hour sound recordings were collected using a digital recording device. Results are change from baseline: a negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

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.

Analysis population consisted of all participants in Cohort 1 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

Total (0-24 hours) Objective Cough Frequency is the total number of cough events during the monitoring period divided by the total duration (in hours, i.e., 24 hours mostly) for the monitoring period. 24-hour sound recordings were collected using a digital recording device. Results are change from baseline: a negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

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.

Analysis population consisted of all participants in Cohort 2 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

Sleep Objective Cough Frequency is the 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 recording were collected with a digital recording device. Results are change from baseline: a negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

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.

Analysis population consisted of all participants in Cohort 1 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

Sleep Objective Cough Frequency is the 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 recording were collected with a digital recording device. Results are change from baseline: a negative result indicates a decrease in cough frequency, while a positive result indicates an increase in cough frequency.

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.

Analysis population consisted of all participants in Cohort 2 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

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. Results are change from 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.

Analysis population consisted of all participants in Cohort 1 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

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. Results are change from 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.

Analysis population consisted of all participants in Cohort 2 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

The LCQ-Acute is a 19-item health-related quality-of-life (HRQoL) questionnaire specific for acute cough which contains three domains (i.e., physical, psychological, and social). It is calculated as a mean score for each domain ranging from 1 (worst) to 7 (best), and total score ranging from 3 (worst) to 21 (best). Each item on the LCQ-acute assesses symptoms or the impact of symptoms on HRQoL in the last 24 hours using a 7-point Likert scale ranging from 1 to 7. Higher scores indicate better HRQoL. Participants' perception of their cough severity was assessed, based on the LCQ-Acute score, at Baseline and last day of dose.

LCQ 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.

Analysis population consisted of all randomized participants in Periods 1 and 2 who received at least 1 dose of study drug, were compliant with the study procedure and had available data.

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. Results are change from baseline: a negative result indicates a decrease in cough severity, while a positive result indicates an increase in cough severity.

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.

Analysis population consisted of all participants in Cohort 1 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

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. Results are change from baseline: a negative result indicates a decrease in cough severity, while a positive result indicates an increase in cough severity.

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.

Analysis population consisted of all participants in Cohort 2 for Periods 1 and 2 who were randomized, received at least 1 dose of study drug, were compliant with the study procedure and had available data for this outcome measure.

Awake Objective Cough Frequency (per hour) is the total number of cough events during the monitoring period (in general, 24-hr interval) the participant is awake divided by the total duration (in hours) for the monitoring period the participant is awake. 24 hour sound recordings were collected using a digital recording device. Baseline measurements were not available by individual arm because baseline cough frequencies were measured before participants received the first dose of study drug. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

Analysis population consisted of all randomized participants in Periods 1 and 2 who received at least 1 dose of study drug, were compliant with the study procedure and had available data.

Awake (0 - 8 hours) Objective Cough Frequency is the total number of cough events during the monitoring period the participant was awake for the first 8 hours after the participant took their study medication divided by 8 or the total duration (in hours) for the monitoring period the participant was awake whichever is less. 24 hour sound recordings were collected with a digital recording device. Baseline measurements were not available by individual arm because baseline cough frequencies were measured before participants received the first dose of study drug. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

Analysis population consisted of all randomized participants in Periods 1 and 2 who received at least 1 dose of study drug, were compliant with the study procedure and had available data.

Total (0 - 24 hours) Objective Cough Frequency is the total number of cough events during the monitoring period divided by the total duration (in hours) for the monitoring period. 24 hour sound recordings were collected using a digital recording device. Baseline measurements were not available by individual arm because baseline cough frequencies were measured before participants received the first dose of study drug. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

Analysis population consisted of all randomized participants in Periods 1 and 2 who received at least 1 dose of study drug, were compliant with the study procedure and had available data.

Sleep Objective Cough Frequency is the 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 recording were collected with a digital recording device. Baseline measurements were not available by individual arm because baseline cough frequencies were measured before participants received the first dose of study drug. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

Analysis population consisted of all randomized participants in Periods 1 and 2 who received at least 1 dose of study drug, were compliant with the study procedure and had available data.

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 frequency, while a positive result indicates an increase in cough frequency. Baseline measurements were not available by individual arm because baseline cough frequencies were measured before participants received the first dose of study drug. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

Analysis population consisted of all randomized participants in Periods 1 and 2 who received at least 1 dose of study drug, were compliant with the study procedure and had available data.

The LCQ-Acute is a 19-item health-related quality-of-life (HRQoL) questionnaire specific for acute cough which contains three domains (i.e., physical, psychological, and social). It is calculated as a mean score for each domain ranging from 1 (worst) to 7 (best), and total score ranging from 3 (worst) to 21 (best). Each item on the LCQ-acute assesses symptoms or the impact of symptoms on HRQoL in the last 24 hours using a 7-point Likert scale ranging from 1 to 7. Higher scores indicate better HRQoL. As per the Statistical Analysis Plan, each domain and total LCQ score change from baseline were analyzed without the treatment by dose interaction. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

Analysis population consisted of all randomized participants in Periods 1 and 2 who received at least 1 dose of study drug, were compliant with the study procedure and had available data.

Cough VAS: scored from 0 to 100 using a 10 mm visual analogue scale with 0 (no cough) and 100 (most severe cough) mm. Baseline cough VAS is defined as average of screening and baseline cough VAS. Baseline measurements were not available by individual arm because baseline cough frequencies were measured before participants received the first dose of study drug. Baseline summaries were evaluated based on the participant's randomized group (gefapixant or placebo).

Analysis population consisted of all randomized participants in Periods 1 and 2 who received at least 1 dose of study drug, were compliant with the study procedure and had available data.

Gefapixant 100 mg tablet administered by mouth BID or 4 days.

Gefapixant 150 mg tablet administered by mouth BID for 4 days.

Gefapixant 200 mg tablet administered by mouth BID for 4 days.

Placebo tablet administered by mouth BID for 4 days each.

Gefapixant 7.5 mg tablet administered by mouth BID for 4 days.

Gefapixant 15 mg tablet administered by mouth BID for 4 days.

Gefapixant 30 mg tablet administered by mouth BID for 4 days.

Gefapixant 50 mg tablet administered by mouth BID for 4 days.

Placebo tablet administered by mouth BID for 4 days each.