A Dose Escalation Study in Solid Tumors and a Dose Expansion Study of PRN1371 in Adult Patients With Metastatic Urothelial Carcinoma

Inclusion Criteria: * Age ≥ 18 years * Histological or cytological documentation of an advanced solid tumor * Subject must have metastatic or recurrent disease and have failed first-line systemic treatment, and if indicated, failed approved second-line therapy, and for whom no standard therapy options are anticipated to result in a durable remission * Subject must have evaluable, progressive, and measurable disease per the Response Evaluation Criteria in Solid Tumors (RECIST) guidelines, Version 1.1 * Adequate bone marrow, liver, and renal function * Patient has an Eastern Cooperative Oncology Group (ECOG) performance status ≤ 1 For Part B (expansion) in subjects metastatic urothelial carcinoma: * The patient's tumor has been evaluated and prospectively identified as having FGFR 1, 2, 3, or 4 genetic alterations. Exclusion Criteria: * Patients who have received adequate prior treatment with a highly selective FGFR inhibitor * Patients with other major uncontrolled medical conditions, e.g., recent myocardial infarction, stroke, diabetes, active hepatitis * Patients who have received prior systemic anticancer therapy ≤ 3 weeks prior to study start (6 weeks for nitrosourea, antibodies, or mitomycin-C) * Patients diagnosed with another primary malignancy within 3 years prior to study start, with the exception of adequately treated basal cell carcinoma, squamous cell carcinoma, or other non-melanomatous skin cancer, or carcinoma in situ of the uterine cervix * Patients with glioblastoma multiforme * Patient has a primary neoplasm of the brain or known uncontrolled metastases to the central nervous system (CNS).