Inclusion Criteria: (For Dose Escalation and Dose Expansion) - Subjects must have a tumor positive for Nectin-4 expression (as measured by central laboratory using primary or metastatic tumor tissue - Histologically confirmed malignant solid tumors (excluding sarcoma) that have failed at least one cytotoxic therapy for metastatic disease or for which no life prolonging treatment exists - Measurable disease according to RECIST criteria (version 1.1) (Eisenhauer, et. al.) defined as tumor lesions that are accurately measured in at least one dimension (longest diameter in the plane of measurement is to be recorded) with a minimum size of: - 10mm by CT scan (CT scan slice thickness no greater than 5mm - 10 mm caliper measurement by clinical exam (lesions which cannot be accurately measured with calipers should be recorded as nonmeasurable - 20 mm by chest X-ray - ≥ 15 mm in short axis for lymph nodes when assessed by CT scan (CT scan slice thickness recommended to be no greater than 5 mm) Note: bone lesions, ascites, and pleural effusions are not considered measurable lesions - Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 - Negative pregnancy test (women of childbearing potential) - Hematologic function, as follows: - a. Absolute neutrophil count (ANC) ≥ 1.0 x109 /L - b. Platelet count ≥ 100 x 109/L - c. Hemoglobin ≥ 8.5 g/dL - Renal function, as follows: serum creatinine ≤ 2.0 mg/dL, or measured 24 hour creatinine clearance of ≥ 45 mL/min - Total bilirubin ≤3.0 x upper limit of normal (ULN) - Serum albumin > 2.5 g/dL - Aspartate aminotransferase (AST) ≤ 1.5 x ULN or ≤5 x ULN if known liver metastases - Alanine aminotransferase (ALT) ≤ 1.5 x ULN or ≤ 5 x ULN if known liver metastases - International normalized ratio (INR) < 1.5 (or ≤ 3 if on warfarin or other medications for therapeutic anticoagulation) - Women and men of childbearing potential must be advised and agree to practice effective methods of contraception during the course of the study Inclusion Criteria for Dose Expansion Only: In addition to the inclusion criteria listed above, the following criteria will also be required for each expansion cohort: Expansion Cohort 1: Breast Cancer - Subjects with Histologically or cytologically diagnosed metastatic breast cancer Expansion Cohort 2: Bladder Cancer - Histologically or cytologically confirmed metastatic visceral bladder cancer - Subjects receiving growth factors for ≥ 3 months prior to study entry are eligible Expansion Cohort 3: Lung plus other solid tumor cancer - Histologically or cytologically confirmed metastatic non-small cell lung cancer (NSCLC) or any other solid tumor cancer Exclusion Criteria: - Preexisting neuropathy Grade ≥ 3 - Uncontrolled brain or epidural spinal metastases - Use of any investigational drug within 14 days or 5 half-lives prior to first dose of study drug - Any anticancer therapy including: small molecules, immunotherapy, chemotherapy, monoclonal antibody therapy, radiotherapy or any other agents to treat cancer within 28 days prior to first dose of study drug - Active angina or Class III or IV Congestive Heart Failure (New York Heart Association CHF Functional Classification System) or clinically significant cardiac disease within 12 months of the first dose of study drug, including myocardial infarction, unstable angina, grade 2 or greater peripheral vascular disease, congestive heart failure, uncontrolled hypertension, or arrhythmias not controlled by medication - Known HIV, AIDS, hepatitis C, or hepatitis B surface antigen - Decompensated liver disease as evidenced by clinically significant ascites refractory to diuretic therapy, hepatic encephalopathy, or coagulopathy - History of thromboembolic events and bleeding disorders ≤ 3 months (e.g.,deep vein thrombosis ( DVT) or pulmonary embolism ( PE)) prior to first dose of study drug - Major surgery within 28 days prior to first dose of study drug - Active infection requiring treatment ≤7 days prior to first dose of study drug - Anti-androgen therapy initiated within 28 days of enrollment (for prostate cancer patients only)