Safety and Efficacy Study of GRT6005 in Patients With Osteoarthritis (OA) Knee Pain

Inclusion Criteria: * Diagnosis of osteoarthritis (OA) of the knee * OA knee pain present for at least 3 months * OA knee pain is the predominant (ie, most painful) pain condition * Patients require medication on at least 4 of 7 days per week to treat OA knee pain for at least 1 month. * Dissatisfaction with current OA knee pain treatment and willingness to stop taking all pain medications except for the study drug and allowed rescue medication * Average daily pain rating of at least 5 on a 0 to 10 point numerical rating scale during the 1 week prior to randomization * Female patients either postmenopausal, surgically sterile or practicing a medically acceptable method of contraception * Male patients either status post-bilateral vasectomy or using barrier contraception Exclusion Criteria: * Knee pain due to a disorder other than OA * Other pain that can confound the assessment of, or contribute to, pain at the reference knee * Surgery at the reference knee within 6 months of Screening or a history of joint replacement surgery at the reference knee * Trauma to the reference knee within 6 months of Screening with active symptoms * Steroid injections in the reference knee within 3 months of Screening * Hyaluronic acid injections in the reference knee within 6 months of Screening * Body Mass Index \> 40 kg/m2 * Patient with any protocol-excluded or clinically significant medical, surgical, or medication history that would limit the patient's ability to complete or participate in this clinical trial or could confound the study assessments