Study Assessing Pain Relief After Replacement of the Knee

Key Inclusion Criteria:

• Primary indication of TKA is knee pain due to osteoarthritis or post-traumaticarthritis

• Scheduled to undergo primary unilateral TKA with a cemented prosthesis, without useof a surgical drain, and under bupivacaine spinal anesthesia (dextrose is permitted)

• American Society of Anesthesiology (ASA) Physical Classification System of class 1, 2, or 3

• Capable, able, and willing to comply with all trial visits and procedures.Participant must also be able to use trial required e-diary and demonstratecompletion compliance during the screening period

• English or Spanish speaking, willing, and capable of providing written informedconsent

Key Exclusion Criteria:

• Has a planned concurrent surgical procedure (e.g. bilateral TKA) at the time ofsurgery or a planned surgical procedure before the last trial visit

• Has had any previous open surgery, (e.g., ORIF for fracture, osteotomy,arthroplasty, unicompartmental knee arthroplasty, or TKA), in the trial knee at anytime in the past or arthroscopic surgery within 12 months. Has had any previoussurgery in the contralateral knee within 6 months prior to screening

• Has been administered any type of intra-articular injection within 3 months ofsurgery in the trial knee

• Unable to abstain from opioid use for knee pain (including codeine) within 2 weeks (14 days) of surgery

• Has a Body Mass Index (BMI) ≥45 kg/m²

• Is unwilling or unable to discontinue use of medications or products that can impactpain control from the Screening Visit until the last trial visit (e.g. cannabidiol (CBD) oil, Kratom)

• Has a medical condition or receiving medication such that, in the opinion of theInvestigator, participating in the trial would pose a health risk to the participantor confound the postsurgical assessments or might confound or interfere with theoutcome of the trial

• Has received/used an investigational drug, product, or device for a clinical trialwithin 30 days of screening. COVID-19 vaccines (approved or under emergency useauthorization locally) are permitted if the participant is not in a clinical trialfor the vaccine

• Has a positive drug screen at the Screening Visit or on the day of surgery

• Has participated in an ATX101 clinical trial

• Pregnant, breastfeeding, or planning to become pregnant during the trial or beforethe last trial visit

Other protocol defined Inclusion/Exclusion criteria may apply