Abstract PR005: Final results from a Phase I trial of intravesical chemoimmunotherapy with gemcitabine and Bacillus Calmette-Guérin (BCG) for patients with BCG-exposed high-grade non-muscle invasive bladder cancer

Abstract Background: Although retreatment with BCG is considered standard of care for patients with BCG-exposed high-grade (HG) non-muscle invasive bladder cancer (NMIBC), less than 50% of patients are expected to respond. As such, the ability to augment the efficacy of BCG in this population remains a critical unmet need. Preclinical studies suggest that intravesical gemcitabine (Gem) may demonstrate synergistic efficacy with BCG by favorably altering the tumor microenvironment. We therefore sought to evaluate the safety, tolerability, and preliminary clinical efficacy of GemBCG in patients with BCG-exposed HG NMIBC through an IRB-approved Phase I/II clinical trial. Methods: Patients with BCG-exposed papillary HG NMIBC (Ta/T1) with or without carcinoma in situ (CIS) that recurred within 24 months of BCG therapy were eligible for this trial. Exclusion criteria included BCG-unresponsive disease, contraindication to BCG therapy, or ureteral/urethral urothelial disease. Consenting patients underwent complete transurethral resection of bladder tumors followed by intravesical Gem twice weekly (weeks 1, 4, 7, 10) for a total of 8 doses. Dose escalation of Gem was performed from 50-2000 mg using a Bayesian modified continual reassessment method. Intravesical Gem instillations alternated with weekly intravesical TICE BCG therapy (weeks 2, 3, 5, 6, 8, 9) for a total of 6 doses fixed at 50 mg followed by maintenance BCG in responders. Complete response (CR) rates and progression to muscle-invasive bladder cancer (MIBC) or cystectomy were evaluated at 12 months of follow up in the Phase I cohort. Results: A total of 25 patients was enrolled (median age 70 years [IQR 64-75]), all of which have at least 12 months of follow up. Of these, 88% (22/25) were male. Median duration of bladder cancer treatment prior to enrollment was 385 days (IQR 173-634), and 28% (7/25) previously received either maintenance therapy (3/25) or >1 induction courses of BCG (4/25). Based on centralized pathology review, a total of 68% had CIS ± papillary disease (8 HGTa, 5 HGT1, and 4 Tis), while 32% had papillary-only disease (4 HGTa and 4 HGT1). No dose limiting toxicities were observed, and 14/25 patients were treated at the maximum tolerated dose. The treatment was well tolerated with no patient experiencing treatment-related Grade 3-5 toxicity. CR rates at 6 months and 12 months were 96% (24/25) and 92% (23/25), respectively. No progression to MIBC or radical cystectomy was observed. Conclusion: Combination GemBCG in BCG-exposed HG NMIBC is well tolerated and appears to provide excellent cancer control. Based on these encouraging findings and the ongoing phase II portion (NCT04179162), a prospective randomized controlled trial comparing GemBCG to BCG alone for BCG-exposed NMIBC is planned through the National Clinical Trial Network (Alliance A032303). Citation Format: Syed M. Alam, Christopher D. Gaffney, Jessica Lavery, Merve Basar, Neeta D'Souza, Christian Hernandez, Melissa McCarter, Patricia Moran, Kristen Stasi, Kara Worth, Daniel Sjoberg, Guido Dalbagni, Timothy Donahue, Sherri Donat, Dean Bajorin, Bernard H. Bochner, Alvin Goh, Judy Sarungbam, Hikmat Al-Ahmadie, Eugene J. Pietzak. Final results from a Phase I trial of intravesical chemoimmunotherapy with gemcitabine and Bacillus Calmette-Guérin (BCG) for patients with BCG-exposed high-grade non-muscle invasive bladder cancer [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr PR005.