Dose Escalation, Expansion Study of Vofatamab (B-701) in Treatment of Locally Advanced or Metastatic Urothelial Cell Carcinoma

Key Disease Specific Inclusion Criteria: 1. Stage IV, locally advanced or metastatic (T4b, any N; or any T, N2-3) urothelial bladder cancer or TCC arising in another location of the urinary tract, including urethra, ureter, and renal pelvis 2. Histological or cytological diagnosis of UCC. 3. Relapsed after or are refractory to at least one prior line of chemotherapy which has not included a taxane (with the exception of Cohort 3 of Phase 2 and Phase 2b Monotherapy Expansion of Phase 2b which will allow the enrollment of patients with prior treatment with a taxane) 4. Subjects must have received at least one prior chemotherapeutic regimen (at least one cycle each) for advanced or metastatic/recurrent disease, of which at least one regimen included a platinum agent (unless contraindicated). 5. Prior neoadjuvant or adjuvant chemotherapy (without a taxane, except Cohort 3 of Phase 2 and Phase 2b Monotherapy Expansion, which will allow the enrollment of subjects with prior treatment with a taxane) is permitted and will not be counted as first-line chemotherapy, as long as the subject has not progressed within 12 months of the last dose. 6. Measurable disease according to Response Evaluation Criteria in Solid Tumors Version 1.1 (RECIST v1.1) Phase 2 and Phase 2b Specific Inclusion Criteria: 1. Patient must be confirmed to have a FGFR3 genomic alteration at the time of documentation of advanced disease. 2. Relapsed after or are refractory to an immune checkpoint inhibitor. This inclusion criterion does not apply if the checkpoint inhibitor is contraindicated. Main Exclusion Criteria: * Prior anti-cancer therapy within 2 weeks prior to Cycle 1, Day 1 * Prior treatment with an inhibitor that is targeted primarily to FGFRs * Clinically significant comorbid medical conditions or lab abnormalities * History of major bleeding (requiring a blood transfusion ≥ 2 units) not related to a tumor within the past 12 months * History of clinically significant coagulation or platelet disorder in the past 12 months * Currently receiving anticoagulation treatment * Incomplete healing from wounds from prior surgery * Known active bacterial, viral, fungal, mycobacterial, parasitic, or other infection at screening * Presence of positive test results for Hepatitis B or Hepatitis C * Known history of human immunodeficiency virus (HIV) seropositive status