TRC105 in Adults With Advanced/Metastatic Urothelial Carcinoma

Background: \- Urothelial cancer (tumors of the bladder, urethra, ureter, or renal pelvis) often responds initially to standard chemotherapy treatments, but frequently recurs and can often spread to other parts of the body. TRC105, an experimental drug that blocks the development of the new blood vessels needed for tumor growth, may be able to shrink or stabilize urothelial cancer tumors. TRC105 has been given previously to individuals with other types of cancer, and researchers are interested in determining its safety and effectiveness in treating urothelial cancer. Objectives: \- To determine the safety and effectiveness of TRC105 as a treatment for metastatic urothelial cancer that has not responded to standard treatments. Eligibility: \- Individuals at least 18 years of age who have been diagnosed with urothelial cancer that has spread to other parts of the body and has not responded to standard chemotherapy. Design: * Participants will be screened with a physical examination, medical history, blood tests, and tumor imaging studies. * Participants will receive TRC105 intravenously once every 2 weeks on days 1 and 15 of a 28-day treatment cycle. The first dose of TRC105 will be given over a 4-hour period; participants who do not have side effects may receive the next dose over 2 hours. If the second dose is tolerated, subsequent doses can be given over at least 1 hour. * To help prevent known side effects of TRC105, participants will take two doses (one in the morning and one in the evening) of the steroid dexamethasone on the day before each infusion is scheduled. Participants may have additional dexamethasone 30 minutes before infusion, and may have the infusion slowed or stopped to adjust for side effects. * Participants will be monitored with blood samples, physical examinations, and tumor imaging studies through the cycles of treatment. * Participants will continue to take TRC105 for as long as the treatment is effective against the cancer and as long