Safety and Efficacy of RHH646 for Knee Osteoarthritis

Inclusion Criteria: * Participant is ≥35 and ≤75 years old, at time of screening * Participants must weigh at least 50 kg to participate in the study and must have a body mass index (BMI) ≤35 kg/m2. BMI = Body weight (kg) / \[Height (m)\]2 * Diagnosis of tibiofemoral OA in at least one knee by standard American College of Rheumatology clinical and radiographic criteria (Altman et al 1986) at screening * K\&L grade 2 to 3 OA in the target knee evaluated with X-Ray by the Central Reader at screening * Predominantly medial tibiofemoral compartment involvement defined as medial Joint Space Narrowing (medJSN) 1-2 (Altman et al 1995; Altman, Gold 2007) and medJSN \> lateral Joint Space Narrowing (latJSN) in the target knee evaluated with X-Ray by the Central Reader at screening * Symptomatic disease, defined as having pain in the target knee at least 3 days per week during the last 3 months from screening that is relieved by analgesic therapy (e.g. acetaminophen or non-steroidal anti-inflammatory drugs), according to the investigator's evaluation and judgment of the patient's history Exclusion Criteria: * Women of child-bearing potential, defined as all women physiologically capable of becoming pregnant, unless they are using highly effective methods of contraception. In EEA countries, women of child-bearing potential will be excluded from participation in this trial, irrespective of the use of highly effective methods of contraception. * Arthroscopy of the target knee within the 6 months prior to screening or planned arthroscopy during the study * Previous surgical treatment of the target knee using mosaicplasty, microfracture, meniscectomy \>50% or osteotomy; planned surgery for either knee during the study * Unstable target knee joint (including, but not limited to, post-traumatic or congenital laxity) or insufficiently reconstructed ligaments based on medical history and/or physical examination by the investigator * Participant has severe malalignment (valgus or varus deformity) in the target knee \>7.5° based on X-ray evaluation by the Central Reader at screening. * K\&L grade 4 OA in either knee * Presence of severe hip OA that either (i) alters lower limb function to a degree that increases or abnormally changes the mechanical forces in the knee while walking, according to investigator's evaluation or (ii) currently requires or is likely to require specific medical or surgical management during the study period * Other pathologies affecting the knee, including subchondral insufficiency fractures, bone fracture (acute or subacute within the 6 months prior to screening) or bone bruise, osteonecrosis, malignant bone marrow infiltration, solid tumors, and/or patellofemoral dysplasia based on clinical assessment, or imaging * Known autoimmune disease with inflammatory arthritis (including but not limited to rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis, systemic lupus erythematosus), crystal-induced arthritides (gout or pseudogout arthritis), active acute or chronic infection of the knee joint, Lyme disease involving the knee, reactive arthritis, systemic cartilage disorders, moderate to severe fibromyalgia, a known systemic connective tissue disease or a widespread pain index \>4. * Inability to undergo MRI (e.g., claustrophobia, body size, leg not fitting in the coil) or contraindications to MRI (e.g., non MRI-compatible metallic implants, metallic foreign bodies, pacemaker, defibrillator)