INtraVESical immunoTherapy (INVEST) prior to radical cystectomy for bladder cancer: trial protocol

High-risk non-muscle-invasive bladder cancer (HRNMIBC) has a variable prognosis, managed predominantly by local surgical resection and intravesical Bacillus Calmette-Guérin (BCG), or radical cystectomy (RC). Current treatments are poorly tolerated, have supply limitations and often fail to control the disease. Treatments overcoming these limitations are needed to improve HRNMIBC outcomes. Many novel agents have been approved in recent years (including systemic pembrolizumab, nogapendekin alfa inbakicept-pmln, N-803), but long-term efficacy is unknown. Given advanced bladder cancer findings, we believe direct intravesical administration of atezolizumab may aid with managing HRNMIBC or muscle-invasive bladder cancer in patients who are ineligible for cisplatin-based neoadjuvant chemotherapy.

The INtraVESical immunoTherapy (INVEST) trial is a UK-based, open-label, non-randomised, single-centre, Phase Ib dose escalation, window of opportunity study exploring atezolizumab administration via intravesical routes (passive instillation and direct injection [sub-urothelial]) in patients with bladder cancer with all stages undergoing RC. For both routes, an initial dose confirmation stage will determine toxicity and recommended atezolizumab dosage, followed by a dose expansion stage to further evaluate safety and toxicity at the recommended dose.

We aim to investigate safety (primary) and preliminary activity (secondary) of intravesical atezolizumab delivered by passive instillation and direct injection into the tumour/bladder wall in patients with bladder urothelial cell carcinoma prior to RC. Primary endpoints include dose limiting toxicities and adverse events. Secondary endpoints include progression-free survival, pathological complete response rate and treatment compliance. Exploratory endpoints include pharmacokinetic profile (assessed by serum and urine concentrations at prespecified timepoints), spatial analysis of atezolizumab distribution within RC tissue by imaging mass spectrometry and overall survival.

Atezolizumab will be administered intravesically by either passive instillation or direct injection into the tumour/bladder wall. Cohorts will receive either 600 mg or 1200 mg doses administered as a single dose or as multiple doses (weekly for 3-6 weeks).

International Standard Randomised Controlled Trial Number: ISRCTN15842444, registered 2 December 2022.