A Study Evaluating Pain Relief and Safety of Orally Administered CR845 in Patients With Osteoarthritis of Hip or Knee

This is a multicenter, randomized, double-blind, placebo-controlled, titration-to-effect study of orally administered CR845 in patients with osteoarthritis of the hip or knee. The study schedule consists of a Screening Period (up to 14 days), a blinded 4- week Titration-to-Effect Period with weekly visits, a blinded 4-week Maintenance Treatment Period at the optimal dose level determined for each patient, and a 1-week Follow-up Period. Eligible patients will be randomized to receive either CR845 or placebo in a 2:1 ratio. Randomization will be stratified based on a patient's primary OA joint (knee vs. hip). Every patient will be started on a 1-mg dose of CR845 or matching placebo. During the post-randomization Titration-to-Effect period, the dose of study drug may be increased to 2.5 mg or 5 mg in a double-blind fashion. Patients may know their dose is being changed but will not know whether they were randomized to active study drug or placebo. Approximately 330 patients will be enrolled in this study. During the Screening, Titration-to-Effect and Follow-up Period, pain intensity scores will be obtained at specified time points. Blood sampling and safety assessments will be conducted during this period as well. The use of rescue medication for the treatment of any pain (including but not limited to headache, menstrual cramps, or non-target joint pain) during the study will be discussed with the patients at the Screening Visit. Acetaminophen is the only allowable rescue medication for pain beginning from Day -5 until the end of the Maintenance Treatment Period. Starting at the Screening Visit Acetaminophen will be provided as 325-mg tablets and its use (number of tablets taken in the previous 24 hours) will be reported each evening in the patient diary.