A Double-blind, Randomized, Placebo-controlled Phase 3 Study of Orally Administered PLX3397 in Subjects With Pigmented Villonodular Synovitis or Giant Cell Tumor of the Tendon Sheath

This is a Phase 3 clinical study, which aims to evaluate the effectiveness of an
investigational drug called pexidartinib for the treatment of certain tumors for which
surgical removal could cause more harm than good.

The main purpose of this study is to gather information about the investigational drug
pexidartinib, which may help to treat tumors of pigmented villonodular synovitis (PVNS) or
giant cell tumor of the tendon sheath (GCT-TS).

The study consists of two parts with a follow-up period. In Part 1, eligible study
participants will be assigned to receive either pexidartinib or matching placebo for 24
weeks. A number of assessments will be carried out during the course of the study, including
physical examinations, blood tests, imaging studies, electrocardiograms, and questionnaires.
MRI scans will be used to evaluate the response of the tumors to the treatment. Some
subjects, assigned to placebo in Part 1 transitioned to pexidartinib for Part 2.

Then a protocol amendment was written to allow only pexidartinib patients to continue into
Part 2. Part 2 is a long-term treatment phase in which all participants receive open-label
pexidartinib. There was also a follow-up period added to Part 2.