Zarka, Jabra

Abstract Enfortumab vedotin (EV), pembrolizumab, and EV plus pembrolizumab (EV/P) have rapidly reshaped the treatment landscape of advanced urothelial carcinoma, but toxicity increasingly determines treatment delivery, treatment continuity, and real-world benefit. As EV/P moves into broader clinical use, clinicians must distinguish adverse events related to antibody-drug conjugate exposure from immune-mediated toxicities and recognize syndromes in which both mechanisms may contribute. In this practical, mechanism-informed review, we synthesize pivotal trials, mature follow-up reports, and representative real-world cohorts describing the safety of EV monotherapy, pembrolizumab monotherapy, and EV/P in urothelial carcinoma. Because adverse-event reporting and ascertainment are heterogeneous across studies, including differences in preferred terms, composite categories, grading frameworks, and treatment-related versus all-cause reporting, we emphasize clinically interpretable patterns rather than pooled estimates. EV monotherapy is characterized by cutaneous toxicity, peripheral neuropathy, hyperglycemia, dysgeusia, and ocular events, including early epithelial/metabolic events and cumulative neuropathy. Pembrolizumab monotherapy has a lower overall high-grade toxicity burden but is defined by immune-mediated endocrinopathies, pneumonitis, hepatitis, colitis, and nephritis. Combination therapy produces a predictable overlap of these toxicity domains, creating diagnostic and management challenges for syndromes such as skin toxicity, diarrhea, fatigue, and pulmonary symptoms. We provide comparative visual toxicity signatures, regimen-specific summary tables, temporal toxicity mapping, and a pragmatic attribution framework that classifies events as EV-predominant, immune-predominant, overlap/indeterminate, or high-risk requiring initial interruption of both agents. This review aims to support bedside recognition, provisional attribution, early management, and safer implementation of EV/P in contemporary urothelial carcinoma practice.

Abstract Background and Objective Management of von Hippel–Lindau (VHL) disease is challenging due to multisystem involvement and limited systemic treatment options. Belzutifan has shown promising efficacy in clinical trials; however, real-world data remain limited. We aimed to evaluate its effectiveness and safety in a real-world cohort. Methods We conducted a retrospective study of 59 patients with VHL disease treated with belzutifan between August 2021 and January 2026. Objective response rates (ORR) for renal cell carcinoma (RCC), central nervous system hemangioblastomas (CNS HB), and pancreatic neuroendocrine tumors (pNET) were assessed by an independent radiologist. Retinal hemangioblastoma outcomes were evaluated through ophthalmology records by chart review. Results Median follow-up was 29 months. ORR was 27.6%, 39.6%, and 85.7% for RCC, CNS HB, and pNET, respectively. Among 13 patients with retinal hemangioblastomas (20 eyes), 17 eyes (85%) showed improvement. At data cutoff, 47 patients (79.6%) remained on treatment, while 12 (20.3%) discontinued (7 due to adverse events, 3 to disease progression, and 2 to other reasons). The most common adverse event was anemia (86.4%). Grade ≥3 events occurred in 10 patients (16.9%). The procedure rate per patient-year decreased from 0.35 in the 3 years prior to treatment to 0.08 during follow-up (Incidence Rate Ratio, 0.23; 95% CI, 0.12–0.47; P < 0.001) Conclusions Belzutifan demonstrated efficacy across VHL-associated lesions, with favorable safety profile. Most adverse events were grade 1–2. A reduction in procedure rate was observed after treatment initiation.

e21521 Background: Outcomes following tumor-infiltrating lymphocyte (TIL) therapy vary in real-world practice, and accessible predictors are needed to inform patient selection and timing of referral. We evaluated whether baseline disease burden, metastatic distribution, and treatment delivery factors are associated with outcomes following TIL therapy. Methods: We retrospectively analyzed patients with metastatic melanoma treated with TIL therapy across Mayo Clinic sites (N = 27 infused). Baseline disease burden was characterized using AJCC metastatic stage and organ-specific involvement. A composite high visceral burden variable was defined as the presence of M1d disease and/or liver metastases. Bridging therapy use prior to infusion was recorded. Post-infusion IL-2 exposure was categorized as low (0-2 doses) vs. high (3-6 doses). Best overall response (BOR) was summarized using RECIST-based standard criteria. Overall survival (OS) and progression-free survival (PFS) were measured from TIL infusion and estimated using Kaplan–Meier methods with univariable Cox regression. Results: Median age at infusion was 62.0 years; 59.3% were male. Melanoma subtypes included cutaneous (81.5%) and mucosal (18.5%). Bridging therapy was used in 48.1%. Baseline metastatic stage was M1a/M1b in 18.5%, M1c in 63.0%, and M1d in 18.5%. Median follow up was 8.3 months. BOR included complete response (18.5%), partial response (37.0%), stable disease (22.2%), and progressive disease (22.2%), yielding an objective response rate of 55.6% and disease control rate of 77.8%. Patients with high visceral disease burden experienced inferior OS vs. those without high visceral burden (median 5.2 vs 13.4 months; HR 4.77, 95% CI 1.22–18.63; p = 0.014). Bridging therapy was not associated with OS or PFS. Higher post-infusion IL-2 exposure (seen in 77.8% of patients) was associated with improved OS (median 9.0 vs 3.7 months; HR 0.16, 95% CI 0.04–0.67, p = 0.005), likely reflecting early post-infusion clinical tolerance rather than a causal treatment effect. Median PFS for the cohort was 3.6 months and did not differ by IL-2 exposure ( p = 0.3), metastatic stage ( p = 0.8), bridging therapy ( p = 0.7), liver metastases ( p = 0.2), or LDH above upper limit of normal ( p = 0.1). Conclusions: The above findings are hypothesis generating and will support evaluation in larger cohort. In this real-world cohort of patients treated with TIL therapy, baseline visceral disease burden was strongly associated with survival outcomes, while bridging therapy did not compromise post-infusion efficacy among patients proceeding to infusion. Post-infusion IL-2 exposure correlated with OS and likely reflects early treatment tolerance. These readily available clinical features may inform patient counseling, referral timing, and sequencing decisions as TIL therapy enters broader clinical use.

9557 Background: High-dose interleukin-2 (IL-2) is administered following tumor-infiltrating lymphocyte (TIL) therapy, yet cardiotoxicity frequently limits dose delivery. The clinical significance of peri-dose troponin elevations during IL-2 remains poorly defined. We evaluated troponin kinetics during IL-2 dosing and their association with significant cardiac events and IL-2 interruption. Methods: We retrospectively analyzed patients with metastatic melanoma treated with TIL therapy followed by inpatient high-dose IL-2 at Mayo Clinic Rochester (N = 24; 87 IL-2 doses). High-sensitivity troponin and ECGs were obtained before and after each IL-2 dose. Clinically significant cardiac events were defined as QTc prolongation > 480 ms, arrhythmias (excluding isolated sinus tachycardia), new ECG abnormalities, vasopressor requirement, or cardiology consultation. Dose-level outcomes included cardiac events and subsequent IL-2 dose interruption. Paired troponin changes were assessed using Wilcoxon signed-rank testing. Dose-level associations were evaluated using clustered logistic regression to account for repeated IL-2 doses within patients. Results: 24 patients received 87 IL-2 doses (median 3 [IQR 2 - 5]). Median age was 63 years (IQR 54 - 70), and 58% were male. Baseline troponin median was 11 ng/L (IQR 6 - 21); 38% had baseline troponin > 14 ng/L. Post-dose troponin exceeded 14 ng/L in 16/24 patients (67%) and 48/87 doses (52%). Median delta troponin was 0 ng/L (IQR −1 to 6; range −24 to 133), with post-dose levels higher than pre-dose values ( p = 0.02). Clinically significant cardiac events occurred in 33% of patients; no post-IL-2 reductions in left ventricular ejection fraction were observed. At the dose level, cardiac events occurred only when post-dose troponin exceeded 14 ng/L (15/48 [31%] vs 0/39 doses; p < 0.001). In clustered logistic regression, post-dose troponin ≥15 ng/L was independently associated with cardiac events (OR 9.6, 95% CI 1.5 - 60.6; p = 0.02) and subsequent IL-2 dose interruption (OR 3.4, 95% CI 1.1 - 10.7; p = 0.04). When modeled continuously, each 1-unit increase in log-transformed post-dose troponin was associated with higher odds of cardiac events (OR 3.3, 95% CI 1.6 - 6.7; p = 0.001) and IL-2 interruption (OR 2.8, 95% CI 1.6 - 4.9; p < 0.001). Baseline troponin correlated with peak post-dose troponin (ρ = 0.44, p = 0.04). Conclusions: Peri-dose troponin elevations are common during post-TIL high-dose IL-2; however, higher post-dose troponin independently identifies clinically significant cardiac toxicity and predicts IL-2 interruption after accounting for repeated dosing within patients. Baseline troponin modestly predicts peak elevations, supporting standardized, risk-stratified troponin monitoring and prospective evaluation of toxicity-adaptive IL-2 delivery strategies in TIL therapy.

9551 Background: Lymphodepleting (LD) chemotherapy is required prior to tumor-infiltrating lymphocyte (TIL) therapy, yet the depth, kinetics, and completeness of peripheral T-cell recovery in practice remain poorly defined. Using a pooled, multi-institution cohort, we characterized longitudinal CD4 and CD8 T-cell reconstitution and the prevalence of CD4 lymphopenia following TIL therapy. Methods: We conducted a retrospective multicenter study across Mayo Clinic, Moffitt Cancer Center, and Massachusetts General Hospital of patients with metastatic melanoma treated with TIL (N = 41, median follow-up 7.6 months). Absolute CD4 and CD8 T-cell counts and CD4:CD8 ratios were assessed at baseline (pre-LD), week 4, month 3, and month 6 post-TIL. Clinically significant CD4 lymphopenia was defined as CD4 < 200 cells/µL. All patients received Pneumocystis jirovecii and antiviral prophylaxis, with antibacterial and antifungal prophylaxis administered per institutional protocols. Post-TIL infections were recorded. Paired changes from baseline were evaluated using Wilcoxon signed-rank testing. Results: Median age was 65 years (range 35-79), and 68% were male. At baseline, 16 patients (39%) had CD4 counts below the institutional lower limit of normal prior to LD. Eighteen patients (44%) received bridging therapy prior to TIL and had lower baseline CD4 and CD8 counts compared with those who did not ( p < 0.05 for both); however, post-TIL CD4 and CD8 recovery trajectories did not differ between groups. CD4 counts declined sharply following LD and demonstrated incomplete and heterogeneous recovery. Median CD4 decreased from 490 cells/µL at baseline to 250 at week 4, 290 at month 3, and 220 at month 6, remaining significantly below baseline at all post-TIL timepoints ( p < 0.05). Clinically significant CD4 lymphopenia was observed in 45% (10/22) of evaluable patients at month 3 and in 50% (44%, 7/16) at month 6. In contrast, CD8 counts increased early after TIL (median 240 to 590 cells/µL at week 4; p = 0.004) and remained higher than baseline at month 6. The CD4:CD8 ratio inverted from a median of 2.02 at baseline to 0.46 at week 4 and remained below 1.0 through month 6, reflecting sustained CD4 suppression despite CD8 recovery. Post-TIL infections occurred despite widespread prophylaxis, including bacterial (13%), viral (10%), and fungal (4.9%) infections. Conclusions: In a multi-institution cohort, LD chemotherapy preceding TIL is associated with profound and prolonged CD4 T-cell suppression, persistent CD4:CD8 inversion, and a high prevalence of CD4 < 200 cells/µL through 6 months. These findings identify delayed immune reconstitution as a common and clinically relevant consequence of TIL therapy and support prospective optimization of antimicrobial prophylaxis duration, vaccination timing, and immune monitoring strategies.

5068 Background: 177 Lu-PSMA-617 (LuPSMA) is a groundbreaking therapy for mPC, but biomarkers are urgently needed to improve patient selection. Plasma-derived EVs are emerging blood-based markers of tumor burden. Here, we analyzed levels of EVs of 123 patients (pts) from 4 cohorts: a pre- and during LuPSMA treatment for a contemporary prospective Mayo Clinic cohort, pre-treatment plasma levels of EVs for a historical Tulane cohort, localized prostate cancer (LPC) after radical prostatectomy (RP), and male healthy donors (HD). Methods: Blood samples were collected from 51 pts pre-cycles (pre-C) 1-3 of LuPSMA at Mayo Clinic from 12/2024-12/2025 and 26 pts pre-C1 at Tulane Cancer Center between 12/2018-1/2025. Small and large EVs were incubated with fluorescently conjugated antibodies (PSMA, STEAP1, CEACAM5, and TROP2) and enumerated using nanoscale flow cytometry. EVs from blood samples of 10 HD and 36 LPC post-RP from 6/2020-8/2024 at Mayo Clinic as controls. AUC-ROC and logistic regression analyses were performed to identify marker signatures associated with PSA50 response. Results: Baseline demographics are shown in the table. Median levels of PSMA, STEAP1, CEACAM5, and TROP2 EV/milliliter (mL) were all significantly higher for pts with mPC (pooled Tulane and Mayo cohorts) compared to LPC post-RP (p<0.001) and HD (p<0.001). In the Mayo cohort, 10 of 51 pts (20%) had undetectable PSA pre-C1. There were no significant differences in median pre-C1 plasma EV levels for these 4 different types of EVs comparing pts with undetectable vs detectable PSA. For 41 Mayo pts with detectable PSA pre-C1, 20 achieved PSA50 response at time of data cutoff (49%), while 7 pts (17%) had persistent PSA rise on LuPSMA. For pts who achieved PSA50, there was a significant decline in both CEACAM5 and TROP2 EVs/mL pre-C1 compared to pre-C3 (19 x 10 6 vs 5.8 x 10 6 , p=0.003 and 16 x 10 6 vs 5.5 x 10 6 , p<0.001, respectively), while no significant changes occurred for the 7 pts with no PSA response. A composite score of pre-C1 CEACAM5 and TROP2 EVs (large- and small-sized EVs) demonstrated the strongest association with PSA50 response (OR=2.96, 95% CI: 1.27-6.44, p=0.038), achieving AUC of 0.73. PSMA and STEAP1 EVs did not show any significant changes from pre-C1 to pre-C3. Conclusions: Plasma-derived EVs are a promising biomarker to identify patients who will benefit from LuPSMA. Longer follow-up and enrolling a larger cohort are underway. Clinical trial information: NCT06200103 . Median values for pre-LuPSMA (Mayo and Tulane), post-RP for LPC, and HD. Mayo mPC (n=51) Tulane mPC (n=26) LPC (n=36) HD (n=10) Age (range) 73 (57-87) 71 (54-83) 66 (56-77) 55 (50-57) Prior lines (range) 1 (1-3) 4 (1-11) - - Gleason score 9 8 7 - PSA (range) 1.0 (0-182) 75 (0.8-503) - - PSMA EV/mL 3.7 x 10 6 14 x 10 6 2.0 x 10 6 1.4 x 10 6 STEAP1 EV/mL 30 x 10 6 45 x 10 6 12 x 10 6 12 x 10 6 CEACAM5 EV/mL 17 x 10 6 5.1 x 10 6 3.7 x 10 6 3.9 x 10 6 TROP2 EV/mL 13 x 10 6 5.2 x 10 6 4.5 x 10 6 3.6 x 10 6