Study to Evaluate the Safety and Efficacy of CNTX-4975 in Subjects With Chronic, Moderate to Severe Osteoarthritis Knee Pain

Inclusion criteria

• Radiography of both knees with a posterior-anterior, fixed flexion view taken during the Screening period. The index knee must show evidence of chronic OA.
• Moderate to severe pain in the index knee associated with OA must be stable for a minimum of 2 months prior to Screening, as assessed by the Investigator.
• A specified mean pain score in the index knee over the 7 days prior to dosing, based on question A1 of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC A1).
• Specified baseline and screening scores on the WOMAC A1
• Body Mass Index ≤ 45 kg/m2.
• Subjects must have had a therapeutic failure (no relief, or inadequate relief), and/or AEs resulting in stopping treatment, and/or contraindication to the standard of care appropriate to the severity of the index knee OA pain they are experiencing.

Exclusion criteria

• Joint replacement surgery of the index knee at any time, or open surgery of the index knee in the past 12 months.
• Prior arthroscopic surgery of the index knee within 3 months of Screening.
• Any painful conditions of the index knee due to joint disease other than OA.
• Mild pain in the non-index knee when walking.
• Other chronic pain anywhere in the body that requires the use of analgesic medications.
• Secondary OA of the index knee due to acute traumatic injury.
• Significant current or past instability (e.g., cruciate ligament tear or rupture or previous repair) or misalignment (> 10 degrees varus or valgus) of the index knee
• Has used topical capsaicin on the index knee within 90 days of Screening.
• Corticosteroid injection in the index knee within 90 days of Screening.
• Received IA viscosupplementation (e.g., Synvisc®, Hyalgan®) within 90 days of Screening.
• Prior participation in an ALGRX 4975 or CNTX-4975 study.
• Has any of the following characteristics:

• active or historic substance use disorder within the previous year as defined by the Diagnostic and Statistical Manual for Mental Health Disorders, fifth edition, or
• tests positive upon urine drug screen for a substance of abuse.
• Has moderate to severe depression or anxiety.