Abstract

TPS4624 Background: MIBC is a systemic disease as >40% of patients (pts) ultimately develop recurrence after radical cystectomy (RC). For pts who cannot receive or refuse cisplatin-based chemotherapy there is no standard-of-care neoadjuvant therapy. Single-agent pembrolizumab, given neoadjuvantly in patients with T2-4N0M0 MIBC, was effective in PURE-01 trial. A proportion of these pts refused RC and were cured with pembro and redo transurethral resection of the bladder tumor (reTURBT; Bandini et al. PMID: 32979511). There are increasing concerns by the pts related to the need to undergo RC whenever they achieve a clinical complete response (cCR) with TURBT and systemic therapy. INCB099280 is a potent, orally bioavailable, selective, small molecule that targets PD-L1 that is being developed for the treatment of advanced malignant diseases. A phase 1, dose-escalation and expansion study is ongoing in pts with select advanced solid tumors (NCT04242199); safety and preliminary efficacy results have been reported (Prenen et al. ESMO-IO 2023). Our hypothesis is that INCB099280 can be offered in biomarker-selected pts as a maintenance therapy instead of any additional treatment, provided that a cCR after the induction phase is obtained. Methods: Pts should have a predominant urothelial carcinoma (UC) histology, have a clinical stage T2-T4N0M0 MIBC, be ineligible for or refuse to receive cisplatin-based chemotherapy. The study will also select pts with a circulating tumor DNA (ctDNA)-positive test (Signatera ctDNA assay) and will be staged with pelvic MRI. Pts will receive 12 weeks of INCB099280 at the dose of 400 mg twice daily (BID), continuously. Restaging will be planned with ctDNA, imaging and reTURBT. Pts who will achieve a cCR (i.e., no evidence of residual disease at the histological examination, clearance of ctDNA and the evidence of no residual detectable disease at cross-sectional imaging, evaluated locally) will receive additional INCB099280 400 mg BID for a maintenance period of 12 months. Pts with evidence of high grade or infiltrating residual disease will be discontinued from the study. Those with a Ta/T1-low grade disease will be managed according to physician’s preference: they may be eligible to continue within the study protocol and receive maintenance INCB099280 400 mg BID for a total period of 12 months. The primary endpoint is the proportion of cCR and the study is planned according to A'Hern one-stage binomial design, with H0 ≤5% and H1 ≥20%, 5% one-sided Alpha, 80% power and 10% drop-out rate. The overall sample size Will be of 30 pts. Secondary endpoints will include safety (CTCAE v.5.0), event-free survival, bladder-intact overall survival (OS) and OS (EUCT number: 2024-511029-73-00). Clinical trial information: 2024-511029-73-00.