A Four-Week Multicenter Study Evaluating the Safety and Efficacy of Gefapixant (AF-219/MK-7264) in Subjects With Osteoarthritis of the Knee

Study Overview
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Brief Summary
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The purpose of this study is to assess the efficacy of a single dose level of gefapixant (AF-219/MK-7264) in subjects with moderate to severe pain associated with osteoarthritis (OA) of the knee compared with placebo after 4 weeks of treatment. The study will also assess the safety and tolerability, changes in physical function, stiffness, treatment response and health outcomes.

Detailed Description
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Subjects who satisfy entry criteria at Screening will enter the Washout Phase, discontinuing their current nonsteroidal anti-inflammatory drug (NSAID) therapy. Up to 220 subjects who fulfill flare (and other entry) criteria will be randomized to gefapixant or placebo. Subjects will complete Treatment Visits 1, 2, 3, and 4 weeks after starting study drug. At each Treatment Visit, subjects will undergo efficacy assessments and safety procedures. During the Washout and Treatment Phases subjects will complete the 'average pain' Numeric Pain Rating Scale (NPRS) and count of rescue medication used for the preceding 24 hours. Subjects will return 2 weeks after their last Treatment Visit (for a Follow-Up Visit).

Conditions
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Osteoarthritis of the Knee

Intervention / Treatment
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* Drug: Gefapixant
* Drug: Sugar Pill


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Men or women Women of child bearing potential must not be pregnant during the study and must use two forms of birth control Men and their female partners must use two forms of birth control Clinical and radiographic evidence of chronic knee osteoarthritis An average NPRS score of >=5 and <=9 over a 4-7 day washout period of their previous osteoarthritis medications Ambulatory Have provided written informed consent

Ages Eligible for Study
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Minimum Age: 40 Years
Maximum Age: 80 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Placebo Comparator: Sugar pill<br> | Drug: Sugar Pill<br>* Placebo<br>|
| Experimental: Gefapixant<br> | Drug: Gefapixant<br>* BID<br>* Other names: MK-7264;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| The Primary Efficacy Endpoint of This Study is the Weekly Average Daily NPRS (Average Pain) | Subjects were instructed to select a number on a scale that best described their knee arthritis pain during the past 24 hours. The scale was between 0 and 10 where 0 was no pain and 10 was the worst possible pain. The scale was completed by telephone (an interactive voice response system [IVRS]) every evening before bedtime. | 2 Weeks | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| WOMAC Scores | This is the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). This is a questionnaire that asks subjects to evaluate their pain, stiffness, and physical activities affecting their knee over the past 48 hours. Subjects evaluate their pain, stiffness and physical activities by selecting a number between 0 and 10 where 0 is no pain/no stiffness/no difficulty doing physical activities and 10 is extreme pain/extreme stiffness/extreme difficulty doing physical activities. The questionnaire was administered at Screening, Baseline and at the end of Week 4 by telephone (an interactive voice response system [IVRS]) before bedtime. The scores for each category are totaled (range is 0-100). A lower total score means less pain and a higher total score means greater pain. | 4 Weeks | 
| SF-36 | The SF-36 (acute version 2) was a 36 question survey administered at Baseline and at the end of study or early termination (Week 4). The questionnaire contained numerous domain scores to evaluate physical function, mental function, general health, bodily pain, social functioning and vitality. The question of interest for the analysis was question #1 regarding walking pain. Scores range from 0 - 100. A lower score means decreased pain while walking and a higher score means increased pain while walking. | 4 Weeks |