Inclusion Criteria:  Subject ≥ 18 years A confirmed diagnosis of TGCT Measurable disease based on RECIST v1.1 Symptomatic disease Stable prescription of analgesic regimen Agrees to follow contraception guidelines Adequate hematologic, hepatic, and renal function, at Screening Willing and able to complete self-assessment instruments throughout the study  Exclusion Criteria:  Prior investigational drug use within 4 weeks or 5 half-lives of Baseline Current or prior radiotherapy within 3 months before Baseline Current or prior active cancer within 3 years before Baseline that requires/required therapy (eg, surgery, chemotherapy, or radiation therapy) Known metastatic TGCT or malignant transformation of diffuse-type TGCT Hepatitis C virus (HCV) or hepatitis B virus (HBV) or known active or chronic infection with human immuno deficiency virus (HIV) Known active tuberculosis (TB) Significant concomitant arthropathy in the affected joint, serious illness, uncontrolled infection, or a medical or psychiatric history Women who are pregnant or breastfeeding Screening Fridericia-corrected QT interval(QTcF) ≥450ms (men) or ≥470ms (women) MRI contraindications (eg, pacemaker, loose metallic implants) History of hypersensitivity to any ingredient in the study drug History of drug or alcohol abuse within 3 months before Baseline Has any other severe acute or chronic medical or psychiatric condition or clinically significant laboratory abnormality that may increase the risk associated with study participation/treatment, interfere with interpretation of study results, or, in the Investigator's opinion, make the subject inappropriate for this study A person who is held in detention as the result of a judicial or official decision or who is in a subordinate relationship to the Sponsor or Investigator A subject who, in the opinion of the Investigator, should not participate in the study for any reason, including if there is a question about the subject's ability to comply with study requirements