Study of Cabiralizumab in Patients With Pigmented Villonodular Synovitis / Diffuse Type Tenosynovial Giant Cell Tumor

Inclusion Criteria:

* Histologically confirmed diagnosis of inoperable PVNS/ dt-TGCT or potentially resectable tumor that would result in unacceptable functional loss or morbidity as determined by a qualified surgeon or multi-disciplinary tumor board (must be documented in the CRF during screening)
* Measurable PVNS/dt-TGCT by RECIST 1.1 on MRI
* ECOG performance status \<1

Exclusion Criteria:

* Prior therapy with an anti-CSF1R antibody
* Prior therapy with PLX3397 unless discontinued for intolerance (i.e., non-progression on prior kinase inhibitor)
* Liver function tests (including ALT, AST, and total bilirubin), outside of the range of local laboratory normal at Screening
* Inadequate organ or bone marrow function
* History of congestive heart failure or myocardial infarction \<1 year prior to first study dose administration
* Significant abnormalities on ECG at Screening
* Contraindications to MRI and use of intravenous gadolinium-based contrast agents
* Creatine Kinase ≥ 1.5x the upper limit of normal
* Positive test for latent TB at Screening (Quantiferon test)
* Active known or suspected autoimmune disease