Fosciclopirox clinical proof of concept in patients with nonmuscle invasive and muscle-invasive bladder cancer.

Abstract

e16557 Background: Fosciclopirox (F) is being developed for the treatment of non-muscle invasive (NMIBC) and muscle invasive (MIBC) bladder cancer. F is a prodrug which is rapidly and completely metabolized in blood to its active metabolite, ciclopirox (CPX). In preclinical models of bladder cancer, CPX acts in part as a γ-secretase inhibitor by binding to γ-secretase complex proteins Presenilin 1 and Nicastrin, resulting in Notch and Wnt inhibition. The F Recommended Phase 2 Dose (RP2D), 900 mg/m2 administered IV over 20 minutes, was identified in the Phase 1 dose escalation trial (NCT03348514) in advanced solid tumor patients. Methods: The F RP2D was investigated in two early phase NMIBC and MIBC clinical proof of concept trials. In NCT04608045, neoadjuvant F was administered as monotherapy in cisplatin-ineligible (C-I) MIBC patients and in combination with gemcitabine + cisplatin in chemotherapy-eligible (C-E) MIBC patients. Clinical stage was assessed in pre-treatment (TURBT/CT) and post-treatment pathological state determined at radical cystectomy, (RC). The steady-state plasma and urine pharmacokinetics of F were also characterized. In NCT04525131, F was administered once daily for five days prior to TURBT. Pre- and post-treatment (at TURBT) bladder tumor samples underwent single cell sequencing to identify treatment effects on gene expression. Plasma, urine, and bladder tumor concentrations of F and its metabolites were determined in samples collected at TURBT. Results: Five C-E and 4 C-I MIBC patients received neoadjuvant F prior to RC. Twelve NMIBC patients received F prior to TURBT. There were no treatment-related serious adverse events observed in either study. Each patient experienced at least one treatment-emergent adverse event (TEAE), none of which resulted in study discontinuation. The most common TEAEs were nausea, fatigue, and constipation. Pathologic downstaging (< ypT2) of bladder tumors was observed in 3 C-E MIBC patients with 2 CRs (ypT0). Two of 4 C-I patients had evident clinical response by CT scan with only microscopic residual ypT2 disease. Treatment-related changes in expression of Notch 1, Notch 2, Hes 1, Hey-1, c-Myc, ß-catenin and survivin were observed in the majority of NMIBC patients. F disappeared from plasma within 2 hours of administration. The mean CPX elimination half-life of CPX, apparent systemic clearance, and volume of distribution values were 8.8 hours, 46 L/hr and 549 L, respectively. Mean plasma, tumor and urine concentrations of CPX at TURBT were approximately 27, 9 and 100 µM, respectively. Conclusions: To date, fosciclopirox is well tolerated and achieves sufficient systemic, tumor, and urine CPX exposure at the RP2D. Evidence of target inhibition was demonstrated in NMIBC tumors and preliminary signs of clinical activity observed in MIBC patients. Safety and efficacy trials are planned to confirm and expand findings in NMIBC and MIBC patients. Clinical trial information: NCT04608045; NCT04525131.