Inclusion Criteria:

1. Age ≥20 years
2. A diagnosis of TGCT (i) that has been histologically confirmed by a pathologist1 and (ii) associated with severe morbidity or functional limitations and not amenable to improvement with surgery determined consensually by qualified personnel (eg, 2 surgeons or a multi-disciplinary tumor board).
3. Measurable disease as defined by RECIST version 1.1 (except that a minimal size of 2 cm is required), assessed from MRI scan by a central radiologist.

Exclusion Criteria:

1. Known metastatic TGCT.
2. Pre-existing increased serum transaminases; total bilirubin or direct bilirubin (>upper limit of normal); or active liver or biliary tract disease, including increased alkaline phosphatase.
3. Significant concomitant arthropathy in the affected joint, serious illness, uncontrolled infection, or a medical or psychiatric history that, in the Investigator's opinion, would likely interfere with a participant's study participation or the interpretation of his or her results.
4. Use of strong cytochrome P450 3A inducers, including St John's wort, proton pump inhibitors and potassium-competitive acid blockers, or other products known to cause hepatotoxicity.