Meeks, Joshua J.

TPS913 Background: A subset of patients with MIBC who receive neoadjuvant therapy (NAT) prior to radical cystectomy (RC) have a pathologic complete response (pCR) at the time of RC. With pCR rates of 22-42% in patients with MIBC following NAT (+/- ICI), whether a subset of patients with good clinical response to NAT can avoid RC is an important unanswered question, especially with the development of more active systemic therapies. HCRN 16-257 evaluated maintenance nivolumab in lieu of cystectomy in patients with MIBC who experienced clinical complete response (cCR) following neoadjuvant GC and nivolumab. The cCR rate was 48%, but 8/33 (24%) patients who elected bladder preservation subsequently underwent cystectomy for local disease recurrence. The RETAIN trial also evaluated omission of local therapy following neoadjuvant therapy with a 2-year bladder preservation rate in patients with ≤T1 disease following NAC of 54% (22/41). Of the 9/25 (36%) patients on that trial developed metastatic disease, 8/9 developed localized disease before metastasizing. These data illustrate the critical role that local therapy plays in patients with MIBC. For this reason, we believe that radiotherapy to the bladder combined with ICI will improve bladder intact event-free survival (BI-EFS). This trial also allows for patients to opt for bladder preservation based on a good clinical response to NAT. Methods: This is a single arm, phase 2 trial (NCT07061964) evaluating risk-adapted bladder preservation therapy for patients with MIBC following NAT. NAT consists of any NCCN guideline concordant therapy for MIBC. Patients with cT2-T4aN0M0 MIBC who complete NAT will be eligible if they have ≤T1 disease on post-NAT TURBT, confirmed by biopsies of prior tumor sites and systematic sampling (left/right lateral walls, dome, posterior wall, trigone). Patients will receive 55 Gray (Gy) in 20 fractions of radiotherapy (RT) to the bladder with 1 year of pembrolizumab. The primary objective is to evaluate whether 3-year BI-EFS is at least 70% in participants with < = T1 (without multifocal CIS) following NAT and RT with 1 year of pembrolizumab. Secondary objectives include local muscle invasive recurrence-free survival, metastasis-free survival (MFS), overall survival (OS), the rate of salvage cystectomy, and evaluation of the frequency and severity of toxicities in participants who receive RT and pembrolizumab. Plasma and urine will be banked for future correlative studies. S2427 was activated in September 2025 with an accrual goal of 111 patients. Clinical trial information: NCT07061964 .

LBA629 Background: Whether BCG strain influences clinical efficacy is unclear. BCG shortages and a reliance on a single strain may impact disease outcomes. Evidence also suggests that priming with intradermal (ID) BCG vaccination prior to intravesical (IVe) BCG enhances anti-tumor immunity and cancer clearance. Co-primary objectives address these issues. Methods: The trial design calls for 924 eligible patients with BCG naïve non-muscle invasive bladder cancer (NMIBC) (HG Ta/T1 +/- CIS or CIS alone) with negative purified protein derivative (PPD) to be randomized in a 1:1:1 ratio, to IVe TICE (Arm 1), IVe Tokyo-172 (Arm 2), or ID + IVe Tokyo-172 (Arm 3) BCG, stratifying on age group and clinical stage. IVe BCG included 6 weekly instillations (induction) and three weekly instillations (maintenance) at 3 and 6 months (mo), then every 6 mo for 3 years. Objective 1 tests whether Tokyo-172 BCG is non-inferior (NI) to TICE BCG, specifying a NI hazard ratio=1.34 (84% power). Objective 2 tests whether priming with ID prior to IVe Tokyo-172 is superior to IVe Tokyo-172 (HR=0.71, 83% power). The primary endpoint is high-grade recurrence-free survival (HG-RFS) censored at last cystoscopy, using a one-sided α=0.021 for each test. A Cox model adjusting for the stratification factors is used. Secondary endpoints include adverse events, 6-mo biopsy-proven complete response (CR) in patients with CIS +/- Ta, T1, duration of CR, PPD conversion and HG-RFS, progression-free survival (PFS) and quality of life. Max follow-up is 5 years. Results: 1000 (984 eligible) patients were enrolled from 2/17-12/20. Median (IQR) follow up is 4.6 (3.6, 5.0) yrs. Median age (range) is 70 yrs (26, 99), 17% are female, 9% are non-white, and 34% had CIS at entry. HG-RFS, CR, duration of CR at 4 yrs, and PFS were similar among arms (Table). PPD conversion occurred in 29% and was not correlated with HG-RFS. Gr 1-2 AE rate was similar (67%, 71%, and 67%) and Gr 3-4 (no Gr 5s) rate was 6%, 11%, and 14% for Arms 1,2, and 3, respectively. Conclusions: Tokyo-172 is non-inferior to TICE BCG in terms of HG RFS and CIS CR and is similar for PFS. Gr 3-4 AE rate is higher with Tokyo-172. Priming with Tokyo-172 BCG does not improve HG RFS. PPD conversion is not prognostic. Clinical trial information: NCT #03091660 . CIS Component N (eligible) 5-yr HG RFS HG RFSHR (95.8% CI) @ 5-yrPFS PFS HR(95% CI) @ CR %(95% CI) 4 yr CR duration Tice Ive 333 (330) 58% 79% 62%; 71/114(53%, 71%) 80% Tokyo Ive 332 (327) 64% *0.82(0.63, 1.08) 79% *0.99(0.70, 1.39) 60%; 66/110(50%, 69%) 83% Tokyo ID + Ive 335 (327) 63% **1.00(0.76, 1.33) 77% **1.07(0.76, 1.51) 63%; 69/109(54%, 72%) 80% 3 mo. PPD + conversionY vs. N 782 evaluable225 (29%)557 (71%) 69%67% ^HR=0.91(0.68, 1.22) * Tokyo-172 vs. Tice, ** Tokyo Priming vs. Tokyo no priming. ^conversion to PPD + vs. – @ adjusted for 2 strat factors (and arms for PPD model). PFS event = MIBC, metastasis, or death.

TPS4630 Background: Bacillus Calmette-Guérin (BCG) is the standard first-line therapy for patients with high-risk non–muscle-invasive bladder cancer (NMIBC) with carcinoma in situ (CIS) ± papillary tumors; however, patients whose disease is unresponsive to BCG therapy are unlikely to benefit from further courses of BCG. Bladder-preserving treatment options for patients with BCG-unresponsive NMIBC with CIS ± Ta/T1 include intravesical gene therapy (nadofaragene firadenovec-vncg), intravesical chemotherapy (gemcitabine and docetaxel), and immunotherapy (intravenous pembrolizumab and intravesical nogapendekin alfa inbakicept-pmln). In a pivotal phase 3 study, 53.4% of participants (55/103) with BCG-unresponsive NMIBC with CIS ± Ta/T1 achieved a complete response (CR) within 3 months of a single instillation of nadofaragene firadenovec, and of them, 45.5% (25/55) maintained a CR at 12 months. Nadofaragene firadenovec in combination with chemotherapy or immunotherapy may further improve clinical efficacy. ABLE-22 (NCT06545955) is an interventional study evaluating the safety and efficacy of nadofaragene firadenovec alone or in combination with chemotherapy (gemcitabine and docetaxel) or immunotherapy (pembrolizumab) in participants with high-risk BCG-unresponsive NMIBC. Participants not responding at month 3 will be offered reinduction. Methods: ABLE-22 will include approximately 40 to 75 sites across the United States and Canada; sites in Asia, Australia, and Europe may be included. Participants (anticipated N = 150) will be randomly assigned 1:1:1 to receive nadofaragene firadenovec (n = 50), nadofaragene firadenovec plus gemcitabine and docetaxel (n = 50), or nadofaragene firadenovec plus pembrolizumab (n = 50). Adults aged ≥18 years with documented NMIBC with CIS ± Ta/T1 that is unresponsive to ≥2 courses of BCG therapy within the last 12 months are eligible to enroll. The primary endpoint is CR (defined as absence of low- and high-grade NMIBC) at months 3 or 6, as participants with persistent NMIBC (any CIS, low-grade Ta, and > 3 cm or multifocal high-grade Ta) will be offered reinduction once, at month 3. Secondary endpoints include durability of CR, incidence of muscle-invasive progression, cystectomy-free survival, pathologic staging, overall survival, and safety. Durability of CR will be followed up to month 36 (assessed quarterly for the first 24 months); all other secondary endpoints will be assessed up to and including month 36. Exploratory endpoints include changes in expression of potential biomarkers in blood and urine. Results from this investigational, randomized, multicenter, open-label study evaluating the safety and efficacy of nadofaragene firadenovec alone or in combination with chemotherapy or immunotherapy are expected July 2028. Clinical trial information: NCT06545955 .

TPS891 Background: Bacillus Calmette-Guérin (BCG) is the standard first-line therapy for patients with high-risk non–muscle-invasive bladder cancer (NMIBC) with carcinoma in situ (CIS) ± papillary tumors; however, patients whose disease is unresponsive to BCG therapy are unlikely to benefit from further courses of BCG. Bladder-preserving treatment options for patients with BCG-unresponsive NMIBC with CIS ± Ta/T1 include intravesical gene therapy (nadofaragene firadenovec-vncg), intravesical chemotherapy (gemcitabine and docetaxel), and immunotherapy (intravenous pembrolizumab and intravesical nogapendekin alfa inbakicept-pmln). In a pivotal phase 3 study, 53.4% of participants (55/103) with BCG-unresponsive NMIBC with CIS ± Ta/T1 achieved a complete response (CR) within 3 months of a single instillation of nadofaragene firadenovec, and of them, 45.5% (25/55) maintained a CR at 12 months. Nadofaragene firadenovec in combination with chemotherapy or immunotherapy may further improve clinical efficacy. ABLE-22 (NCT06545955) is an interventional study evaluating the safety and efficacy of nadofaragene firadenovec alone or in combination with chemotherapy (gemcitabine and docetaxel) or immunotherapy (pembrolizumab) in participants with high-risk BCG-unresponsive NMIBC. Reinduction for nonresponders once at month 3 will also be evaluated. Methods: ABLE-22 will include approximately 40 to 75 sites across the United States and Canada; however, sites in Asia, Australia, and Europe may be included. Participants (anticipated N=150) will be randomly assigned 1:1:1 to receive nadofaragene firadenovec (n=50), nadofaragene firadenovec plus gemcitabine and docetaxel (n=50), or nadofaragene firadenovec plus pembrolizumab (n=50). Adults aged ≥18 years with documented NMIBC with CIS ± Ta/T1 that is unresponsive to ≥2 courses of BCG therapy within the last 12 months are eligible to enroll. The primary endpoint is CR (defined as absence of low- and high-grade NMIBC) at months 3 or 6, as participants with persistent NMIBC (any CIS, low-grade Ta, and >3 cm or multifocal high-grade Ta) will be offered reinduction once, at month 3. Secondary endpoints include durability of CR, incidence of muscle-invasive progression, cystectomy-free survival, pathologic staging, overall survival, and safety. Durability of CR will be assessed quarterly up to and including month 24; all other secondary endpoints will be assessed up to and including month 36. Exploratory endpoints include changes in expression of potential biomarkers in blood and urine. Results from this investigational, randomized, multicenter, open-label study evaluating the safety and efficacy of nadofaragene firadenovec alone or in combination with chemotherapy or immunotherapy are expected July 2028. Clinical trial information: NCT06545955 .

4574 Background: Mutations of COMPASS-related proteins KMT2D, KMT2C, and KDM6A are observed in 66% of advanced urothelial carcinomas (UC). In vivo, the administration of tazemetostat, an enzymatic EZH2 inhibitor (EZH2i), reduced tumor burden and enhanced the immune response in animal models of UC. We hypothesized that tazemetostat might improve response to immunotherapy in advanced UC. Methods: ETCTN 10183 (NCT03854474) is a multicenter pilot study evaluating the safety and efficacy of tazemetostat 800 mg BID+ pembrolizumab 200 mg given every three weeks for up to two years in patients (pts) with platinum-refractory (Arm A) or cisplatin/chemo-ineligible advanced UC (Arm B). The primary objective was to identify the recommended phase two dose (RP2D) of tazemetostat in combination with pembrolizumab. Secondary objectives included safety, response rate, and progression-free survival. Translational objectives included determining tumor mutational burden in COMPASS-related genes, tumor subtyping, TCR clonality, T cell infiltration, and PDL-1 expression. Results: There were no dose-limiting toxicities in the safety lead-in phase (n=6 pts), and the RP2D for tazemetostat was established at 800 mg BID. Baseline characteristics for Arm A N=12, Arm B N=13: 72% males; 96% white, 4% Black; 88% ECOG PS 0-1; 88% had bladder primary, 20% Stage III, 72% stage IV; 80% had visceral or bone metastases. The median number of cycles was 5 in Arm A (range 1-35) and 4 in Arm B (range 2-12). Treatment related G3/4 adverse events (AEs) were observed in 8 patients, most common were anemia and lymphopenia (n=2 each). Treatment related G1/2 AEs included nausea (n=6); skin and subcutaneous tissue disorders (n=3); anemia, lymphopenia, and thrombocytopenia (n=2 each). Among evaluable patients (n=10 in each arm), partial response rate was: Arm A 30%, Arm B 20%; stable disease: Arm A 30%, Arm B 30%; and progressive disease: Arm A 30%, Arm B 20%. 8 pts were on study treatment for ≥ 9 cycles (5 in Arm A, 3 in Arm B). All pts are off protocol treatment. Median progression-free survival was 3.06 (95% CI: 1.38-7.75) months for Arm A and 3.02 (95%CI: 2.4-5.65) for Arm B. Conclusions: Tazemetostat 800 mg BID and pembrolizumab combination is feasible and well-tolerated in patients with advanced UC. In this pilot study, improvement in efficacy relative to historical controls of pembrolizumab alone appears to be modest. Response in tumors with COMPASS-related mutations and EZH2 activity will be evaluated. Clinical trial information: NCT03854474 .

4601 Background: Cretostimogene grenadenorepvec is a type-5 oncolytic adenovirus designed to selectively replicate in bladder cancer cells with alterations in the retinoblastoma pathway. Additionally, the virus is engineered to express the GM-CSF transgene, resulting in a potent oncolytic immunotherapy mode of action. Cretostimogene monotherapy recently received Food and Drug Administration (FDA) Fast Track and Breakthrough Therapy Designations (BTD) in the BCG-Unresponsive, High-Risk, non-Muscle Invasive Bladder Cancer with Carcinoma in Situ (BCG-UR HR NMIBC with CIS) indication with a Complete Response (CR) at any time rate of 76%. This phase-2 study assessed the potential synergy between intravesical cretostimogene and pembrolizumab in patients with BCG-UR, HR NMIBC, with CIS, with or without Ta/T1 tumors. This combination has also received BTD from the FDA. Methods: 35 pts were treated with cretostimogene (1x1012 viral particles) in combination with pembrolizumab at a dose of 400 mg IV q6 weeks. Cretostimogene induction was given as 6 weekly intravesical instillations followed by 3 weekly maintenance doses at months 3, 6, 9, 12, and 18. Pts with persistent CIS or high-grade Ta tumors at the 3mo assessment were eligible for re-induction. Pembrolizumab was administered for up to 24mo. Response assessments included cystoscopy, urine cytology, cross-sectional imaging, and mandatory bladder mapping biopsies at 12mo. The primary endpoint was CR at 12mo. Secondary endpoints included CR at any time, duration of response (DOR), CR at 24mo, cystectomy-free survival, and safety. Exploratory endpoints included analyses of baseline viral receptor expression, free E2F levels, PD-L1 status, urinary cytokine panels and measures of viral replication. Results: 30/35 pts are evaluable per protocol for the primary endpoint. Five pts discontinued prior to the 12mo time point. The CR rate in the Intention to Treat (ITT) population at 12mo and any time, was 57% (20/35) (95% CI 40-73%) and 83% (29/35) (95% CI 66-93%), respectively. Median DOR has not been reached but exceeds 21mo. The current CR rate in the ITT population at 24mo is 46% (16/35) (95% CI 29-63%). Three pts have yet to reach the 24mo time point. Cystectomy-free survival at 21mo is 80%. Complete data on the ITT and evaluable patient cohorts will be presented. Analyses of treatment-related adverse events (AE) are consistent with the individual agents and demonstrate no synergistic toxicity. Conclusions: The efficacy and safety of cretostimogene plus pembrolizumab for treatment of BCG-UR, HR NMIBC with CIS demonstrates best-in-class CR and DOR compared to current FDA-approved therapies, with an acceptable AE profile. Further investigation of this promising combination therapy is warranted and may serve to address a considerable unmet need. Clinical trial information: NCT04387461 .

529 Background: Radical cystectomy is recommended for patients with BCG-unresponsive (BU) non-muscle invasive bladder cancer (NMIBC) due to high risk of progression. Improved methods for assessing these risks would greatly facilitate the potential for bladder preservation. Here, we tested the capacity of the urinary comprehensive genomic profile (uCGP) to predict event-free survival (EFS) in patients with BU-NMIBC treated with atezolizumab in the single arm phase 2 trial SWOG S1605. Methods: Urine was collected from patients with BU NMIBC (CIS, Ta, T1) treated with at least one dose of intravenous atezolizumab at baseline and before the 5th cycle of therapy (3 months). The uCGP was assessed using UroAmp (Convergent Genomics). Risk scores for recurrence at baseline and at 3 months were calculated by a prespecified machine learning algorithm incorporating alterations in 60 genes and low pass whole genome sequencing, and categorized as high versus low. Molecular response was classified based on change in uCGP between the two time points. Risk scores and molecular response were submitted to SWOG for clinical correlation with EFS using a Cox model, adjusting for CIS status. Time to event was calculated from date of study entry (baseline risk) or from the 2nd collection time (3-month risk) to first high grade (HG) recurrence or persistent CIS at 3 months. Death unrelated to bladder cancer and patients last known to be alive without HG recurrence were censored at date of last visit. Results: Samples were provided at baseline in 89 patients and before the 5th cycle in 77; 68 had both samples available for paired analysis. The risk score at baseline was classified as high in 69% of samples (73% for CIS ±Ta/T1 and 62% for Ta/T1). At 12 and 18 months the EFS probabilities were 26% and 23% for high-risk and 67% and 51% for low-risk patients, respectively, with a HR of 2.82 (95% CI: 1.58, 5.03; p<0.001). The risk score at the 3-month timepoint was classified as high in 81% of samples, and the EFS probabilities at 12 and 18 months after urine collection were 26% and 22% for high-risk and 80% and 72% for low-risk patients, respectively, with a HR of 3.39 (95% CI: 1.41, 8.13; p<0.006). Molecular response to treatment was classified as complete (CR) in 8%, partial (PR) in 14%, stable (SD) in 25% and progression (PD) in 46%, with 7% having no detectable genomic abnormalities at both time points. Clinical recurrence was observed by 18 months in 0/6 patients with CR, 7/9 (78%) with PR, 11/14 (79%) with SD and 25/33 (76%) with PD by genomic profile. Conclusions: This study suggests that uCGP at baseline and after 4 cycles of treatment can identify genomic patterns associated with an increased risk of HG persistence, recurrence or progression in BU NMIBC treated with immune checkpoint inhibition. Future studies will determine if this can be used to guide early treatment intensification.

506 Background: Despite response to systemic therapy, few metastatic urothelial carcinoma (mUC) patients (pts) achieve durable responses. Mutations in the COMPASS-related proteins KMT2D, KMT2C, and KDM6A are found in 66% of UC patients suggesting histone regulation may be an acquired mechanism of tumor viability. We previously found regression of UC in mice when treated with EZH2 inhibitor, tazemetostat. In vivo administration of tazemtostat enhanced the immune response with direct regulation of cytokines and antigen recognition machinery (MHCI and MHCII). We hypothesized that restoration of epigenetic imbalance, combined with immunotherapy, may improve outcomes in mUC pts. Methods: ETCTN 10183 (NCT03854474) is a pilot study evaluating the efficacy of tazemetostat 800 mg BID + pembrolizumab 200 mg every 3 weeks for cisplatin-refractory (Cohort A) or cisplatin/chemo-ineligible advanced UC (Cohort B) pts, with N=12 pts in each cohort. The primary objective is to identify the recommended phase two dose (RP2D) of tazemetostat in combination with pembrolizumab. Secondary objectives include RECIST-based response rate, safety, and progression-free survival. The maximum planned treatment duration is 2 years. Translational objectives include defining total and COMPASS-related genes tumor mutational burden, tumor subtyping, TCR clonality, T cell infiltration, and PDL-1 expression. Results: In the safety lead-in phase, 6 mUC pts were treated. There were no dose-limiting toxicities (DLTs). The RP2D for tazemetostat was established at 800 mg BID. Here we report results of fully accrued cohort A (N=12); 67% males, 33% females, 83% white, 8.3% Black, and 25% Hispanic/Latino ethnicity. The primary sites of UC were: bladder (n=9, 75%), renal pelvis (n=2, 17%), and ureter (n=1, 8.3%). The median (interquartile range, IQR) time since primary diagnosis was 1.1 years (0.7, 1.9); 11/12 patients had non-nodal metastatic disease; 10/12 had 1 or more visceral/bone metastasis. Median number of treatment cycles was 5 (IQR: 3-11; range 1-35). Median duration on protocol treatment was 12 weeks (IQR: 7-30; range 3-107 weeks). Three pts had treatment related grade 3/4 AEs: grade 4 sepsis (n=1), grade 3 lymphopenia (n=2); anemia, increased alkaline-phosphatase, and HSV oral infection (n=1 each). Best response was partial response (PR) in 3 pts (25%) and 3 (25%) had stable disease. Median PFS was 3.1 months (95%CI: 2.3-NA), and median overall survival was 8.0 months (95% CI: 4.7 – NA). Conclusions: The RP2D dose for tazemetostat is 800 mg + 200 mg Pembrolizumab q 3 weeks. The combination was feasible, well tolerated, and resulted in durable responses in poor-risk chemo-refractory UC patients. Clinical trial information: 03854474 .

TPS586 Background: Chemoradiotherapy(CRT) is a SOC for patients with muscle invasive bladder cancer (MIBC) who refuse or are not fit for radical cystectomy. Radiotherapy and chemotherapy are known to increases the PD-L1 expression in bladder cancer. Based on these observations, we hypothesized that addition of atezolizumab to CRT will increase its efficacy. Methods: This is a randomized phase III trial testing CRT with and without atezolizumab for 6 months in 475 patients with MIBC. Pts will be stratified on performance status (0-1 vs. 2); clinical stage (T2 vs T3/T4a, chemotherapy(cisplatin vs 5FU+mitomycin vs gemcitabine); and radiation field (bladder only vs small pelvis). Patients will undergo biopsy 18 week from registration. If they have residual disease they will be taken off protocol treatment and can proceed with alternative SOC option including radical cystectomy. Patients will be followed for 5 years. The primary end point of the study is bladder intact event –free survival (BIEFS). The event is comprised of: recurrence or residual muscle-invasive bladder cancer at 18 weeks or later, clinical evidence of nodal or metastatic disease, radical cystectomy, or death due to any cause. This composite endpoint is reflective of the intent of bladder preservation strategy with radical cystectomy included as one of the outcomes. Secondary end points include overall survival, modified event free survival, pathologic response at 18 weeks, metastasis free survival, cancer specific survival, rate of salvage cystectomy, rate of adverse event and QOL & PRO end points. The expected 3 year BIEFS for the control arm is 52%. The study leadership concluded that a 12% improvement in this endpoint is meaningful for this patient population. With a sample size of 475 patients the study has 85% power to detect the improvement from 52% to 64% in the BIEFS at 3 years (hazard ratio=0.68). The study team will perform translational studies evaluating tumor tissue, whole blood and urine for molecular and immunologic markers of immune response and response to RT. Successful completion of this trial could lead to a new treatment paradigm for patients with muscle invasive bladder cancer. Clinical trial information: NCT03775265.