This study consists of part 1 and part 2. Part 1 is a double-blind phase, eligible patients will be randomized to Pimicotinib(ABSK021) treatment group or matching placebo group and will receive Pimicotinib(ABSK021) or matching placebo until completion of Part 1.~Part 2 is an open-label treatment phase, and all patients entering this phase will receive open-label Pimicotinib(ABSK021) until completion of 24 weeks of dosing or withdrawal from the study.
The goal of this clinical trial is to assess the efficacy and safety of Pimicotinib (ABSK021) in patients with Tenosynovial Giant Cell Tumor (TGCT). The main questions it aims to answer are:~Whether the Pimicotinib(ABSK021) works well in patients with TGCT.~Whether the Pimicotinib(ABSK021) is safe in patients with TGCT.~Participants will be asked to complete the study procedures:~Receive the administration of Pimicotinib(ABSK021) or placebo (a placebo is a look-alike substance that contains no active drug) about 24 weeks in study part 1.~Receive the administration of Pimicotinib(ABSK021) about 24 weeks in study part 2.~Complete the study procedures speficied in the protocol, which is guided by researchers.