Tangent- emactuzumab vs placebo in Tenosynovial Giant Cell Tumor

If you agree to take part in this study, you will get a random assignment to a study drug group, which means that the study drug group you will be in is selected by chance (like rolling dice). In this study, for every 2 people who will receive emactuzumab, 1 person will receive placebo (2:1 ratio). A placebo is an inactive substance that has no drug in it. Study participants will get the study drug every 2 weeks for approximately 10 weeks. A needle will be inserted into a blood vessel and connected to an intravenous infusion containing the study drug or placebo. The infusion will last for about 1.5 hours. A scan called magnetic resonance imaging (MRI) will be arranged every 6 weeks after Day 1 for the first 6 months, then every 8 weeks for the next 6 months, and then every 12 weeks for the remainder of the study to assess your tumor(s) size. The "range of movement" (how far your joint moves) of your affected joint will be assessed by a qualified physiotherapist or other qualified healthcare professional. The total number of visits in the study may be more than 15 if you take part in the open-label part, but your participation in the study will not last longer than 2 years.