Longitudinal personalized urinary tumor DNA analysis in muscle-invasive bladder cancer from the neoadjuvant immunotherapy trial RJBLC-I2N003.

552 Background: RJBLC-I2N003 is an investigator-initiated study to evaluate the clinical activity and predictive biomarkers for neoadjuvant immunotherapy with toripalimab (anti-PD-1) in muscle invasive bladder cancer (MIBC). Methods: Twenty patients with pathologically confirmed MIBC were enrolled and received toripalimab (3 mg/kg Q2W, 4 cycles) before radical cystectomy. The safety and efficacy of neoadjuvant toripalimab were assessed. Serial urinary cell-free DNA (ucfDNA) and blood cell-free DNA (bcfDNA) were obtained at baseline and after each cycle of toripalimab treatment. Personalized minimal residual disease (MRD) assays and low-pass whole genome sequencing (LP-WGS) were applied to analyze liquid biopsy samples. Results: Eighteen patients (90%) completed all 4 cycles of neoadjuvant treatment. Grade 3-4 immune-related adverse events occurred in two patients (10%). Eight patients (40%) achieved a pathological complete response (pCR). Thirteen patients (65%) had no remaining invasive disease (pCR or pTisN0/pTaN0). Pre-treatment somatic variants and copy number abnormalities were prevalently detected in ucfDNA as compared to bcfDNA. On-treatment urinary tumor DNA (utDNA) clearance was associated with objective responses. Preliminary concordance was observed between molecular and pathological MRD status. Conclusions: These findings suggest that neoadjuvant administration of PD-1 blockade followed by surgical resection represents a feasible and efficacious approach to treat MIBC. The exploratory biomarker assessment demonstrates the potential utility of longitudinal personalized utDNA analysis to complement existing trial endpoints.