Background: Fosciclopirox (Ciclopirox Prodrug, CPX-POM) is being developed for the treatment of non-muscle invasive and muscle invasive (MIBC) bladder cancer. CPX-POM selectively delivers its active metabolite, ciclopirox (CPX), to the entire urinary tract following systemic administration. In a validated, chemical carcinogen mouse model of bladder cancer, CPX-POM treatment results in significant decreases in bladder weight, a clear migration to lower stage tumors, dose-dependent reductions in Ki67 and PCNA staining, and inhibition of Notch 1 and Wnt signaling. The safety, dose tolerance, pharmacokinetics and pharmacodynamics of IV CPX-POM have recently been characterized in 19 patients with advanced solid tumors (CPX-POM-001, NCT03348514). The safety and dose tolerance of IV CPX-POM was characterized across a dose range of 30 to 1200 mg/m². The CPX-POM Recommended Phase 2 Dose (PR2D) of 900 mg/m² administered IV over 20 minutes on Days 1-5 every 21 days was selected. Methods: Twelve cisplatin ineligible MIBC patients (Stage >T2, NO-N1, M0), scheduled for radical cystectomy (RC) will be enrolled in this window of opportunity study. Patients will receive two 21-day treatment cycles followed by RC within 14 days of completion of the second cycle. Safety and tolerability assessments will be made based on observed adverse and serious adverse events, physical examination, vital signs, electrocardiogram, clinical laboratory tests, and concomitant medications. Assessment of complete and partial pathologic response will be determined at RC. Ki67, Notch and Wnt signaling, and CD8+ lymphocyte tumor infiltration will be determined by immunohistochemistry. An unbiased approach to characterizing CPX-POM mechanisms of action will also be employed using RNAseq and ChIPseq. Serial blood (plasma) and complete urine specimens will be collected on Days 5-6 of Cycle 1 for determination of drug and metabolite concentrations by LC-MS/MS. Plasma and urine steady-state pharmacokinetics of CPX-POM, CPX and ciclopirox glucuronide will be characterized. Urine ß-glucuronidase activity is also being determined by ELISA. Clinical trial information: NCT03348514