Apolo, Andrea B

TPS4642 Background: Although first-line (1L) EV + pembrolizumab has improved outcomes for patients with la/mUC, most experience disease progression, highlighting an unmet need for novel therapies. TROP2 is a glycoprotein highly expressed in several epithelial tumors, including UC. Dato-DXd is a TROP2-directed antibody–drug conjugate comprising an anti-TROP2 monoclonal antibody, a tetrapeptide-based cleavable linker, and a topoisomerase I inhibitor payload (DXd), designed to induce selective tumor-cell death and reduce systemic exposure to the payload. Dato-DXd has demonstrated durable efficacy and a manageable safety profile in patients with la/mUC both as monotherapy (TROPION-PanTumor01 [NCT03401385]) and in combination with immunotherapy (TROPION-PanTumor03 [NCT05489211]). We describe a Phase 2/3 trial comparing the efficacy and safety of Dato-DXd + platinum CT (carboplatin or cisplatin) vs gemcitabine + platinum CT in participants with la/mUC with disease progression on or after EV + pembrolizumab. Methods: TROPION-Urothelial03 (NCT07129993) is a global, multicenter, randomized, open-label, Phase 2/3 trial. In Part A (Phase 2), ~60 participants will be randomized 1:1 to receive Dato-DXd 4 or 6 mg/kg + platinum CT. In Part B (Phase 3), ~570 participants will be randomized 1:1 to receive Dato-DXd at the recommended Phase 3 dose (determined using Part A data) + platinum CT vs gemcitabine + platinum CT. Randomization in Part A is stratified by assignment of platinum CT (carboplatin vs cisplatin), and in Part B, by assignment of platinum CT, presence vs absence of liver metastasis at screening, and time to progression on 1L EV + pembrolizumab (<6 vs ≥6 months). Study treatment continues until disease progression, unacceptable toxicity, withdrawal of consent, death, loss to follow-up, or other reasons per protocol. Radiographic tumor assessments occur every 6 weeks for 54 weeks, then every 12 weeks. The primary endpoint of Part A is objective response rate (ORR) by investigator per Response Evaluation Criteria in Solid Tumours, version 1.1 (RECIST 1.1). The dual primary endpoints of Part B are progression-free survival (PFS) by blinded independent central review (BICR) per RECIST 1.1 and overall survival (OS). Secondary endpoints include duration of response by investigator per RECIST 1.1 (Part A), and PFS by investigator per RECIST 1.1 and ORR by BICR and investigator per RECIST 1.1 (Part B). In Part A, ORR will be summarized with 2-sided 95% exact confidence intervals using the Clopper–Pearson method by trial group. In Part B, PFS and OS will be compared between trial groups using a log-rank test stratified by randomization stratification factors, with hazard ratios from the stratified Cox regression model. Clinical trial information: NCT07129993 .

4514 Background: Maintenance avelumab is a standard of care in patients (pts) with la/mUC who do not progress after first-line PBC. Cabozantinib (CABO) is an oral inhibitor of MET, VEGFR and TAM, active in multiple solid tumors. We hypothesized that an avelumab (Av)-CABO combination would improve outcomes in pts with mUC with an acceptable safety profile compared to avelumab maintenance alone. Methods: MAIN-CAV (NCT05092958) is a phase III randomized, multicenter, international trial for la/mUC pts who did not progress after 4-6 cycles of any PBC (gemcitabine-cisplatin, gemcitabine-carboplatin, MVAC, ddMVAC). Pts were randomized 1:1 to Av 800 mg IV every 2 weeks alone or with CABO 40 mg daily for ≤2 years. Stratification factors were response to first-line PBC (complete response [CR] vs partial response [PR] vs stable disease [SD]) and visceral metastases. The primary endpoint was overall survival (OS); secondary endpoints included progression-free survival (PFS), safety and quality of life. The target accrual was 654 pts; the trial closed early after enrollment of 68 pts following adoption of enfortumab vedotin plus pembrolizumab as the new preferred first-line standard in the US. Results: From 3/2022 to 3/2024, 68 pts were randomized (Av n = 33; CABO-Av n = 35). Median OS was 24.8 months (mo) with Av and 23.0 mo with Avb-CABO (Hazard ratio 1.41; 95% CI 0.66–3.01; p = 0.186). Median PFS was 4.6 mo with Av vs 6.0 mo with Av-CABO (p = 0.343). Objective response rate among pts with PR or SD after first-line PBC was 20.8% with Av vs 11.5% with Av-CABO (p = 0.424). Grade ≥3 treatment-related adverse events occurred in 24.2% pts on the Av arm vs 39.4% of pts on the Av-CABO arm and CABO dose reductions occurred in 63% of pts. Conclusions: Addition of CABO to Av did not improve OS or PFS compared with Av alone in this underpowered, prematurely closed phase III trial; safety was consistent with known profiles. U10CA180821,U10CA180882; U24CA196171, U10CA180863. (CCTG);U10CA180888 (SWOG); https://acknowledgments.alliancefound.org. Clinical trial information: NCT05092958 .

4513 Background: The AMBASSADOR trial (NCT03244381) showed that in patients with high-risk muscle-invasive urothelial carcinoma after radical surgery, adjuvant pembrolizumab for one year improved disease-free survival from 14.2 to 29.6 months (Apolo et al, NEJM 2024). Here we report the HRQOL results. Methods: HRQOL was completed by 560 randomized patients and included the European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30 plus the bladder cancer supplement BLM30, and the EQ-5D-5L, which assesses overall quality of life or health state. Published minimally important difference thresholds for EQ-5D-5L is 0.06, and for EORTC instruments is 5-10 points. For all reported HRQOL data, higher score is better except BLM30 urinary symptoms, where higher score indicates more symptoms. Results: Mean changes from baseline to 12 months (corresponding to end of treatment) for each HRQOL measure are summarized in the Table. No statistically significant difference was seen between the observation vs. pembrolizumab arms. Further, numerical differences between arms for these HRQOL measures do not meet (are lower than) the published minimally clinically important difference thresholds. Conclusions: Adjuvant pembrolizumab after radical surgery for patients with high-risk muscle-invasive urothelial carcinoma improved disease-free survival without negatively affecting HRQOL. These HRQOL results add further support to adjuvant immune checkpoint blockade therapy in these patients. Support: U10CA180821, U10CA180882, UG1CA189823 (https://acknowledgments.alliancefound.org). Clinical trial information: NCT03244381 . HRQOL mean change from baseline to 12 months and between-arm comparisons. A) Observation B) Pembrolizumab Difference A vs B P-value EQ-5D-5L Index Value -.029 -.012 -.02 .45 QLQ-C30 Global Health 0.07 1.45 -1.38 .55 QLQ-C30 Physical Functioning -.089 -.069 -0.02 .99 QLQ-C30 Role Functioning 3.22 -1.23 4.45 .15 BLM30 Urinary Symptoms -3.44 -3.02 -.42 .87 BLM30 Sexual Functioning -.53 4.15 -4.68 .07

TPS890 Background: Although first-line (1L) EV + pembrolizumab has improved outcomes for patients with la/mUC, most experience disease progression, highlighting an unmet need for novel therapies. TROP2 is a glycoprotein highly expressed in several epithelial tumors, including UC. Dato-DXd is a TROP2-directed antibody–drug conjugate comprising an anti-TROP2 monoclonal antibody, a tetrapeptide-based cleavable linker, and a topoisomerase I inhibitor payload (DXd), designed to induce selective tumor-cell death and reduce systemic exposure to the payload. Dato-DXd has demonstrated durable efficacy and a manageable safety profile in patients with la/mUC both as monotherapy (TROPION-PanTumor01 [NCT03401385]) and in combination with immunotherapy (TROPION-PanTumor03 [NCT05489211]). We describe a phase 2/3 trial comparing the efficacy and safety of Dato-DXd + platinum CT (carboplatin or cisplatin) vs gemcitabine + platinum CT in participants with la/mUC with disease progression on or after EV + pembrolizumab. Methods: TROPION-Urothelial03 (NCT07129993) is a global, multicenter, randomized, open-label, phase 2/3 trial. In part A (phase 2), ~60 participants will be randomized 1:1 to receive Dato-DXd 4 or 6 mg/kg + platinum CT. In part B (phase 3), ~570 participants will be randomized 1:1 to receive Dato-DXd at the recommended phase 3 dose (determined using part A data) + platinum CT vs gemcitabine + platinum CT. Randomization in part A is stratified by assignment of platinum CT (carboplatin vs cisplatin), and in part B, by assignment of platinum CT, presence vs absence of liver metastasis at screening, and time to progression on 1L EV + pembrolizumab ( < 6 vs ≥6 months). Study treatment continues until disease progression, unacceptable toxicity, withdrawal of consent, death, loss to follow-up, or other reasons per protocol. Radiographic tumor assessments occur every 6 weeks for 54 weeks, then every 12 weeks. The primary endpoint of part A is objective response rate (ORR) by investigator per Response Evaluation Criteria in Solid Tumours, version 1.1 (RECIST 1.1). The dual primary endpoints of part B are progression-free survival (PFS) by blinded independent central review (BICR) per RECIST 1.1 and overall survival (OS). Secondary endpoints include duration of response by investigator per RECIST 1.1 (part A), and PFS by investigator per RECIST 1.1 and ORR by BICR and investigator per RECIST 1.1 (part B). In part A, ORR will be summarized with 2-sided 95% exact confidence intervals using the Clopper–Pearson method by trial group. In part B, PFS and OS will be compared between trial groups using a log-rank test stratified by randomization stratification factors, with hazard ratios from the stratified Cox regression model. Clinical trial information: NCT07129993 .

TPS714 Background: 1st-line induction platinum-based chemotherapy followed by switch maintenance Av is the current preferred standard of care in patients (pts) with aUC who do not progress after platinum-based chemotherapy. There is an significant need to further improve outcomes by combining Av with an effective, non-cross resistant therapy with non-overlapping toxicity. CABO is an oral inhibitor of MET, VEGFR and TAM family receptors involved in tumor growth, angiogenesis and immune cell regulation and has shown efficacy in UC in combination with PD-1/PD-1L1 inhibitor. We hypothesized that CABO-Av combination would improve survival vs Av alone and have an acceptable safety profile as switch maintenance therapy in mUC. Methods: MAIN-CAV is a phase III randomized, multicenter, international trial for pts with locally advanced/metastatic UC (including cN3M0 only)) who do not progress after 4-6 cycles of any platinum-based chemotherapy (gem-cis, gem-carbo, MVAC or ddMVAC). 654 adults are randomized 1:1 within 3-10 weeks (wk) after last dose of chemotherapy to receive Av 800 mg IV every 2 wk or Av and CABO 40 mg daily for up to 2 yrs. Key eligibility criteria include ECOG PS 0-1, no prior use of anti-PD(L)1, no CNS metastases, no major surgery within 4 wks, no uncontrolled hypertension or cardiovascular disorders. Pts are stratified based on 1) best response to 1L chemotherapy: complete vs partial response vs stable disease and 2) presence vs absence of visceral metastases. The primary endpoint is overall survival (OS) with assumptions of 1-sided alpha 0.025, power 80%, median OS 21 months (mo) with Av and hazard ratio 0.75, thus hypothesizing median OS 28 mo on CABO-Av. Key secondary endpoints include progression-free survival, safety, tolerability, and efficacy of CABO-Av vs Av alone based on RECIST 1.1 and iRECIST criteria (and PD-L1 status).Quality of life (QOL) are assessed using EQ-5D-5L, PROMIS-Fatigue 4a, EORTC QLQ-C30, EORTC QLQ-BLM30 between pts on CABO-Av vs Av alone. Biomarkers of response and resistance to Av will be assessed using baseline archival tissues, baseline and serial blood, ctDNA, stool and urine. Imaging studies will test the correlation of established and new radiomic signatures with survival, adverse events and QOL and incorporate both radiologic and biologic features to assess their potential association with outcomes. This trial would be the first to systematically address whether adding the multitargeted TKI, CABO, to Av improves survival vs Av alone as 1L maintenance therapy. https://acknowledgments.alliancefound.org . Support: U10CA180821, U10CA180882; U24CA196171, U10CA180863 (CCTG); Clinical trial information: NCT05092958 .

LBA531 Background: Muscle-invasive urothelial carcinoma (MIUC) is an aggressive disease with high relapse rates. Neoadjuvant platinum-based chemotherapy (NAC) is the standard of care in patients (pts) who are cisplatin (Cis)-eligible. However, many pts are Cis-ineligible or have persistent muscle-invasive disease after NAC and surgery. We evaluated pembrolizumab (Pembro) as adjuvant therapy in pts with high-risk MIUC following surgical resection. Methods: The AMBASSADOR study is an open-label, randomized, phase III trial that enrolled pts with histologically confirmed MIUC of the bladder, upper tract, or urethra who (1) had ≥ pT2 and/or pN+ or margins+ at surgery (radical cystectomy, nephrectomy, nephroureterectomy, or ureterectomy) following NAC or (2) ≥ pT3 and/or pN+ or margins+ at surgery without NAC and were either Cis-ineligible or declined adjuvant Cis-based therapy. Pts were registered ≥4 to 16 weeks after surgery and randomized 1:1 to receive Pembro 200 mg every 3 weeks for 1 year or observation (Obs). Randomization was stratified by pathologic stage, centrally tested PD-L1 status, and prior NAC. The dual primary endpoints were disease-free survival (DFS) and overall survival (OS) with a target sample size of 739 pts and required 387 DFS and 320 OS events for final analysis. Secondary objectives included evaluation of DFS and OS in PD-L1-positive and -negative pts and assessing safety. Here we present the interim DFS and OS results. Results: Between 09/2017 and 08/2021 a total of 702 pts were randomized prior to early closure due to US FDA approval of nivolumab for MIUC pts: 354 pts to Pembro and 348 pts to Obs; 13.0% vs 21.6% withdrew from study without event in the Pembro vs Obs arms, respectively. 74 pts (21%) in the Obs arm received an immune checkpoint inhibitor. Median follow-up was 22.3 months (mos) for DFS and 36.9 mos for OS. The DFS endpoint (based on 319 events needed for interim analysis) crossed the efficacy boundary. Median DFS was 29.0 months (95% confidence interval (CI) 21.8‒not evaluable (NE)) with Pembro and 14.0 months (95% CI 9.7‒20.20) with Obs (hazard ratio (HR) 0.69 [95% CI 0.55–0.87]; p=0.0013). At the interim analysis (n = 257 events), median OS was 50.9 months (95% CI 43.9‒NE) with Pembro and 55.8 months (95% CI 53.3‒NE) with Obs (HR 0.98 [95% CI 0.76–1.26]; p=0.88). Grade 3+ adverse events occurred in 48.4% and 31.8% of pts in the Pembro and Obs arms, respectively. Conclusions: Adjuvant Pembro demonstrated a statistically significant and clinically meaningful improvement in DFS vs Obs for high-risk MIUC pts after radical surgery. The OS endpoint may have been impacted by pts on the Obs arm receiving a checkpoint inhibitor. Pembro was tolerable with no new safety signals. These results support adjuvant Pembro as a new therapeutic option for pts with MIUC with high risk for recurrence. Additional follow-up is ongoing for the final DFS/OS, PD-L1 subgroups, and ctDNA analyses. Clinical trial information: NCT03244384 .

Abstract Background Treatment options for penile squamous cell carcinoma are limited. We sought to investigate clinical outcomes and safety profiles of patients with penile squamous cell carcinoma receiving immune checkpoint inhibitors. Methods This retrospective study included patients with locally advanced or metastatic penile squamous cell carcinoma receiving immune checkpoint inhibitors between 2015 and 2022 across 24 centers in the United States, Europe, and Asia. Overall survival and progression-free survival were estimated using the Kaplan-Meier method. Objective response rates were determined per Response Evaluation Criteria in Solid Tumours 1.1 criteria. Treatment-related adverse events were graded per the Common Terminology Criteria for Adverse Events, version 5.0. Two-sided statistical tests were used for comparisons. Results Among 92 patients, 8 (8.7%) were Asian, 6 (6.5%) were Black, and 24 (29%) were Hispanic and/or Latinx. Median (interquartile range) age was 62 (53-70) years. In all, 83 (90%) had metastatic penile squamous cell carcinoma, and 74 (80%) had received at least second-line treatment. Most patients received pembrolizumab monotherapy (n = 26 [28%]), combination nivolumab-ipilimumab with or without multitargeted tyrosine kinase inhibitors (n = 23 [25%]), or nivolumab (n = 16 [17%]) or cemiplimab (n = 15 [16%]) monotherapies. Median overall and progression-free survival were 9.8 months (95% confidence interval = 7.7 to 12.8 months) and 3.2 months (95% confidence interval = 2.5 to 4.2 months), respectively. The objective response rate was 13% (n = 11/85) in the overall cohort and 35% (n = 7/20) in patients with lymph node–only metastases. Visceral metastases, Eastern Cooperative Oncology Group (ECOG) performance status of 1 or higher, and a higher neutrophil/lymphocyte ratio were associated with worse overall survival. Treatment-related adverse events occurred in 27 (29%) patients, and 9.8% (n = 9) of the events were grade 3 or higher. Conclusions Immune checkpoint inhibitors are active in a subset of patients with penile squamous cell carcinoma. Future translational studies are warranted to identify patients more likely to derive clinical benefit from immune checkpoint inhibitors.

5 Background: Management options for patients (pts) with advanced (locally advanced or metastatic) PeCa are limited. The GSRGT assembled an international cohort of pts with advanced PeCa treated with ICI to evaluate toxicity and clinical outcomes. Methods: We retrospectively collected data on pts with advanced PeCa receiving ≥1 cycle of ICI between 2015-2022 at 18 medical centers in the US, Europe, and Asia. Immune-related adverse events (irAE) were graded per the Common Terminology Criteria for Adverse Events v5.0. Overall survival (OS) and progression-free survival (PFS) were estimated by the Kaplan-Meier method. Objective response rate (ORR) was determined by the clinical investigator per RECIST 1.1 criteria, whenever feasible. Results: Among 72 pts with advanced PeCa treated with ICI, 24 (33%) were Hispanic and 7 (10%) were Black. 60 (83%) pts had metastases while the remainder had locally advanced disease. The median age was 64 (inter-quartile range (IQR): 54,70) years and 48 (67%) had ECOG performance status ≥1. Most pts (n=60, 83%) were treated in the ≥2nd line setting and received pembrolizumab (n=23), nivolumab (n=15), cemiplimab (n=15), nivolumab and ipilimumab (n=7), or other anti-PD1/L1-based therapies (n=12). Among 37 pts with available data on HPV status, 24 (65%) were HPV+. 3 (4%) pts were HIV+. irAE of any grade occurred in 18 (25%) pts, 7 (10%) were grade ≥3, 7 (10%) required steroids, 6 (9%) required hospitalization, and 8 (11%) led to treatment discontinuation. The median OS and 24-month OS and median PFS and 24-month PFS were 9.4 (95%CI: 6.8, 12.8) months and 19.3% (95%CI: 9.2, 32.1) and 2.8 (95%CI: 2.1, 3.9) months and 11.2 % (95%CI: 4.9, 20.2), respectively. Among 66 pts evaluable for response, ORR was 7/66 (11%) (2 with complete response, 5 with partial response), and 16 (24%) pts had stable disease for a disease control rate of 35%. The median duration of response was 7.9 (IQR: 3, not reached) months. Conclusions: In the largest retrospective cohort of ICI-treated advanced PeCa, ICI showed no new safety signals, however, overall anti-tumor activity was limited. Future translational studies are needed to identify pts that are more likely to derive clinical benefit from ICI.