Abstract 1567: GLR1059, next-generation nectin-4-targeted ADC with a novel mechanism-of-action payload, demonstrated significantly potent anti-tumor efficacy and reduced toxicity in preclinical evaluation

Introduction: Enfortumab Vedotin (EV), an antibody-drug conjugate (ADC) targeting Nectin-4, has emerged as a new standard-of-care for patients with metastatic urothelial cancer (UC). Promising results have also been observed in bladder cancer (BLCA) patients with ADCs targeting HER2. To identify predictive biomarkers of ADC sensitivity, we characterized a large and expanding biobank of patient-derived organoid (PDO) and xenograft (PDX) models for Nectin-4 and HER2 expression, and Nectin-4 and HER2-targeted ADC sensitivity. Methods: We generated 19 PDOs and 34 PDXs that reflect the genomic and biologic heterogeneity of human UC. A subset of these models was further characterized using a multiplatform approach, including bulk and single-cell DNA and RNA sequencing and immunoblot for Nectin-4 and HER2 expression. We leveraged these models to study the biologic determinants of sensitivity to EV and the HER2-targeted ADC trastuzumab deruxtecan (T-DXd). PDX models were treated with EV (5 mg/kg IV on day 1, 3, 6) or T-DXd (10 mg/kg IV on day 1, 21, 42) or vehicle only as control. We also studied sensitivity to T-DXd and EV, as well as to their cytotoxic payloads (exatecan and vedotin) in vitro using paired PDO models. Results: We observed high degree of variability of HER2 and Nectin-4 expression across UC PDOs and PDXs. In PDO models, sensitivity to EV correlated strongly with Nectin-4 expression, whereas HER2 expression was not strongly correlated with sensitivity to T-DXd. We also noted a poor correlation between Nectin-4 expression in PDOs and PDXs derived from the same patient. A subset of models, for example, SMBO-104 (ERBB2 wildtype with low HER2 expression), exhibited significantly greater sensitivity to EV than to T-DXd. Conversely, T-DXd was significantly more active than EV in SMBO-170, a model with ERBB2 amplification (~40 copies) and HER2 3+ expression. Sensitivity to exatecan, an analogue of the T-DXd payload deruxtecan, as measured by inhibition of cell proliferation and induction of apoptosis, was more predictive of T-DXd sensitivity than HER2 expression level. Conclusion: In this study, we generated and biologically characterized UC patient-derived models with the goal of identifying predictive biomarkers of sensitivity to Nectin-4 and HER2-targeted ADCs. We observed significant heterogeneity of HER2 and Nectin-4 expression across models. Models were identified in which T-DXd was superior to EV, and vice versa. Sensitivity to the T-DXd cytotoxic payload was more predictive of PDX response than HER2 expression levels, with significant tumor regression observed with T-DXd in BLCA models with low HER2 expression. Our data suggest that clinical trials of HER2-targeted ADCs such as T-DXd should not be restricted to patients with HER2 overexpression and that novel biomarkers will be needed to identify those UC patients most likely to benefit from FDA-approved and investigational ADCs. Citation Format: Xinran Tang, Ziyu Chen, Jasmine Thomas, Karan Nagar, John Christin, Naryan Rustgi, Sizhi Gao, Elisa de Stanchina, Jonathan Coleman, Michael Shen, Hikmat Al-Ahmadie, Gopa Iyer, Kwanghee Kim, David Solit. Modeling antibody drug conjugate sensitivity using urothelial carcinoma patient-derived models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6006.

463 Background: Enfortumab vedotin (EV) is an antibody-drug conjugate (ADC) targeting Nectin-4 (encoded by the PVRL4/NECTIN4 gene ) approved for treatment-refractory metastatic urothelial cancer. Factors that mediate sensitivity or resistance to EV are unknown. In the present study, we sought to 1) examine heterogeneity of NECTIN4 gene expression across molecular subtypes of bladder cancer and 2) determine if Nectin-4 expression mediates EV sensitivity or resistance. Methods: NECTIN4 expression data from seven muscle-invasive bladder cancer clinical cohorts (n = 1912 total patients) were used to compare relative NECTIN4 expression across molecular subtypes. The outcome of the gene expression analysis was relative NECTIN4 expression in the consensus molecular subtypes of bladder cancer. Expression of NECTIN4 was validated in multiple bladder cancer cell lines. NECTIN4 was stably over-expressed or knocked down in basal (TCCSUP and UMUC-3) and luminal (HT-1376, HT-1197 and UMUC-9) bladder cancer cell lines, respectively, and EV dose-response assays were performed, as measured by cell proliferation and clonogenic assays. Results: NECTIN4 expression is heterogenous across molecular subtypes of bladder cancer and significantly enriched in luminal subtypes (p < 0.001). NECTIN4 expression is positively correlated with the luminal markers GATA3, FOXA1, and PPARG across cohorts (Spearman’s rank correlation r = 0.57, p < 0.0001 for GATA3, r = 0.37, p < 0.0001 for FOXA1, and r = 0.56, p < 0.0001 for PPARG). NECTIN4 expression is both necessary and sufficient for EV sensitivity in luminal and basal subtypes of urothelial bladder cancer cells. Downregulation of NECTIN4 led to EV resistance, and EV-resistant cell lines expressed decreased levels of Nectin-4. Conclusions: Results of this pre-clinical study suggest that sensitivity to EV is mediated by expression of NECTIN4, which is significantly enriched in luminal subtypes of bladder cancer. Downregulation of NECTIN4 leads to resistance to EV. These findings have implications for biomarker development, patient selection and the inclusion of molecular subtyping in ongoing and future EV clinical trials. Further investigation into Nectin-4 loss as a mechanism of resistance in patients treated on EV is warranted.

Enfortumab vedotin (EV) is an antibody-drug conjugate (ADC) targeting NECTIN4 (encoded by the PVRL4/NECTIN4 gene) approved for treatment-refractory metastatic urothelial cancer. Factors that mediate sensitivity or resistance to EV are unknown. In this study, we sought to (i) examine heterogeneity of NECTIN4 gene expression across molecular subtypes of bladder cancer and (ii) determine whether NECTIN4 expression mediates EV sensitivity or resistance. Molecular subtyping and NECTIN4 expression data from seven muscle-invasive bladder cancer clinical cohorts (n = 1,915 total specimens) were used to assess NECTIN4 expression across molecular subtypes. The outcome of the transcriptomic analysis was relative NECTIN4 expression in the consensus molecular subtypes of bladder cancer. Expression of NECTIN4 was validated in bladder cancer cell lines. NECTIN4 was stably overexpressed or knocked down in basal and luminal bladder cancer cell lines and EV drug sensitivity assays were performed, as measured by cell proliferation and clonogenic assays. NECTIN4 expression is heterogenous across molecular subtypes of bladder cancer and significantly enriched in luminal subtypes. NECTIN4 expression is positively correlated with luminal markers GATA3, FOXA1, and PPARG across all cohorts. NECTIN4 expression is both necessary and sufficient for EV sensitivity in luminal and basal subtypes of urothelial bladder cancer cells. Downregulation of NECTIN4 leads to EV resistance. Sensitivity to EV is mediated by expression of NECTIN4, which is enriched in luminal subtypes of bladder cancer. These findings may have implications for biomarker development, patient selection, and the inclusion of molecular subtyping in ongoing and future EV clinical trials.See related commentary by Teo and Rosenberg, p. 4950.

Bladder urothelial carcinoma (UC) is a common malignancy and remains a significant cause of mortality; however, in recent years there have been substantial advances in the treatment of metastatic UC (mUC). This includes the approval of the antibody drug conjugate (ADC) enfortumab vedotin, which targets Nectin-4, and the fibroblast growth factor receptor (FGFR) inhibitor erdafitinib (in FGFR2/3 altered tumors). Despite the impressive efficacy of these agents, most patients will ultimately develop progressive disease, underlining the need for further therapeutic development. Previous work has demonstrated that NECTIN4 expression and FGFR3 alterations are enriched in luminal subtypes of UC and NECTIN4 expression is higher in FGFR altered tumors. We validate these findings in scRNAseq from primary tumors as well as bulk RNAseq from murine models. Given the positive correlation between NECTIN4 and FGFR3 alterations we hypothesized that FGFR3 inhibition would downregulate Nectin-4 expression. To our surprise we found in vitro treatment with erdafitinib in cell lines with FGFR3 fusion proteins (RT112, RT4, SW780) lead to an increase in Nectin-4 protein levels. Additionally, in vitro FGFR inhibition in the UMUC-14 cell line which harbors an FGFR3S249C hotspot mutation, upregulates Nectin-4 protein levels. To further investigate this phenomenon, we engineered the FGFR3 WT cell line, 5637 to overexpress FGFR3-TACC3 or FGFR3S249C. We saw that FGFR3-TACC3 and FGFR3S249C overexpression both down regulated Nectin-4 indicating that FGFR3 activity negatively regulates Nectin-4 expression. We have also investigated the association between FGFR inhibition and Nectin-4 expression in two in vivo models: (1) in a xenograft model using the RT112 line we found an overall increase in Nectin-4 expression in tumors treated with a 5-day course of erdafitinib; (2) in a UPFL1 (a cell line derived from a genetically engineered mouse with a S249C mutation) syngeneic model we also saw an increase in Nectin-4 expression after erdafitinib treatment. We have observed that the increase in Nectin-4 expression persists in vitro even after withdrawal of erdafitinib treatment, indicating that intermittent dosing of erdafitinib maybe be sufficient to prime a tumor for Nectin-4 targeted therapy. Lastly, preliminary in vitro investigation of the combination of erdafitinib and enfortumab vedotin in RT112 cells showed synergy, particularly with lower doses of both agents, providing further support of our hypothesis that FGFR3 inhibition may act to sensitize UC to Nectin-4 ADC therapy. A potential synergistic relationship is further supported by the recent results of the phase 1 trial investigating the combination of erdafitinib plus enfortumab vedotin in which the objective response rate was 100% (9/9 patients: 8 PRs & 1CR). Citation Format: Sean Clark-Garvey, Mi Zhou, Michael Sturdivant, Wolfgang Beckabir, Lucia Kim, E. Drew Toomer, Ian McCabe, Akihiro Hamada, Daniel Crona, Jeffrey S. Damrauer, William Y. Kim. FGFR inhibition upregulates Nectin-4 expression in FGFR3 altered urothelial carcinoma [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 B014.

BackgroundNectin-4 is overexpressed in multiple solid tumors with high unmet medical need, such as urothelial carcinoma (UC), esophageal cancer, non-small cell lung cancer, or triple-negative breast cancer. Enfortumab vedotin (EV),...

Background: Nectin-4 is a cell membrane adhesion protein overexpressed in several solid tumors, including urothelial, breast, lung, ovarian, and pancreatic cancers, with limited expression in normal tissues, making it an ideal target for antibody-drug conjugates (ADC). Enfortumab Vedotin (EV, PADCEV®) is an ADC targeting Nectin-4 with a monomethyl auristatin E (MMAE) payload approved for the treatment of patients with urothelial carcinoma (UC), but with limited clinical activity reported beyond UC. In addition, EV causes peripheral neuropathy and skin toxicity, leading to treatment discontinuation. To overcome these limitations and the mechanism of resistance to EV, IPH45, a novel topoisomerase I inhibitor ADC targeting Nectin-4 with an improved therapeutic index, was developed. Methods: In vitro studies were performed to investigate internalization, tumor cell killing and bystander effect, antibody-dependent cellular cytotoxicity (ADCC) and complement activation. In vivo efficacy studies were performed on cell line-derived xenografts (CDX) of triple negative breast cancer, patient-derived xenografts (PDX) of urothelial carcinoma and syngeneic tumor models expressing human Nectin-4. IPH45 efficacy was compared to EV. Toxicology studies to determine the dose range were conducted in rat and non-human primates (NHP). Results: IPH45 consists of a humanized IgG1 targeting a unique epitope in human Nectin-4, non-overlapping with EV, a cleavable linker, and a topoisomerase I inhibitor with a high drug-to-antibody ratio (DAR). In vitro, IPH45 is internalized upon binding to its target and induces direct killing of Nectin-4 expressing tumor cells as well as bystander killing of Nectin-4 non-expressing tumor cells in mixed culture. IPH45 mediates ADCC and complement-mediated killing. IPH45 demonstrates activity in CDX and PDX models with similar effective dose as EV. Moreover, IPH45 shows anti-tumor efficacy in vitro and in vivo in primary and secondary EV resistant models. In dose-range finding toxicology studies in rats and NHP, IPH45, unlike EV, does not elicit skin toxicity. IPH45 remains well tolerated up to the highest dose tested, suggesting a potentially larger therapeutic index than MMAE-based ADCs. Pharmacokinetic analyses in mice, rats, and NHP show minimal release of free toxin in the serum and half-life compatible with Q2W or less frequent dosing schedules in clinic. Conclusion: IPH45 is a topoisomerase I ADC targeting Nectin-4 with the potential for larger therapeutic index than EV, improved safety and dosing regimen, and ability to overcome primary and secondary resistance to EV or other Nectin-4 ADC in development. IPH45 is progressing to the clinic where the translatability of this unique profile into improved patient outcomes will be assessed across indications. Citation Format: Romain Remark, Cécile Bonnafous, Laura Chiossone, Caroline Soulas, Cyril Perrier, Guillaume Habif, Sivan Bokobza, Aurélie Maguer, Rachel Courtois, Julie Lopez, Grégory Fenaux, Olivier Benac, Barbara Carrette, Robin Letay-Drouet, Raja Bonifay, Séverine Augier, Léa Simon, Benjamin Rossi, Ariane Morel, Agnès Represa, Nicola Beltraminelli, Yannis Morel, Carine Paturel, Eric Vivier. Preclinical characterization of IPH45, a novel topoisomerase I inhibitor ADC targeting Nectin-4 for the treatment of Nectin-4 expressing tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6582.

Background: Antibody-drug conjugates (ADC) combine a cytotoxic agent with a monoclonal antibody for targeted delivery. Enfortumab-vedotin (EV) links a monoclonal antibody targeting NECTIN-4 with the cytotoxic agent monomethyl auristatin E (MMAE). Given the near-ubiquitous expression of NECTIN-4 in urothelial cancer (UC) tissues, EV has shown efficacy in UC and is approved for metastatic urothelial carcinoma (mUC). However, significant heterogeneity in NECTIN-4 expression within UC limits therapeutic efficacy in cases with low NECTIN-4 expression. This study evaluated cell cycle inhibitors' efficacy in UC cells with low NECTIN-4 expression. Methods: We measured NECTIN-4 and cell cycle-related molecules (Cyclin D1 and PLK1) in bladder cancer cell lines (253J, 253J-BV, 5637, RT4, T24, J82, HT1197, HT1376) and correlated these levels with sensitivity to the PLK1 inhibitor. Drug sensitivity was assessed by a CCK-8 assay over 72 hours following treatment with the PLK1 inhibitor (onvansertib). An ex vivo model using bladder tumor samples from patients validated the in vitro findings. NECTIN-4 levels in bladder cancer cell lines (HT1376 and RT4) were modulated by siNECTIN-4 transfection for 48 hours. Cell cycle analysis and the expression levels of cyclin D1 and PLK1 were examined in NECTIN-4 knockdown cell lines. Results: The therapeutic efficacy of the PLK1 inhibitor was significantly enhanced in bladder cancer cell lines with reduced NECTIN-4 expression (253J, 253J-BV, 5637, T24, and J82), as indicated by an IC50 <0.1 μM. In contrast, cell lines with high NECTIN-4 expression (RT4, HT1197, and HT1376) were resistant to onvansertib (IC50 >1 μM). NECTIN-4 expression correlated with cell cycle-related molecule levels. Consistently, bladder tumor samples showed a negative correlation between NECTIN-4 expression and PLK1 inhibitor sensitivity. PLK1 inhibitor-resistant tumors (IC50 >40 μM) had lower NECTIN-4 levels than sensitive samples (20 μM < IC50 < 40 μM). NECTIN-4 knockdown via siRNA increased G0/G1 phase cells and reduced cyclin D1 and PLK1 levels. Furthermore, siNECTIN-4-transfected cells were more sensitive to the PLK1 inhibitor than control siRNA-transfected cells. Conclusion: This study underscores the therapeutic potential of cell cycle inhibitors, notably PLK1 inhibitors, in bladder cancer cells with low NECTIN-4 expression, showing an inverse relationship between NECTIN-4 expression and sensitivity to PLK1 inhibitors. NECTIN-4 levels could predict PLK1 inhibitor treatment response. NECTIN-4 knockdown experiments confirmed that reduced NECTIN-4 expression disrupted cell cycle regulation and increased PLK1 inhibition efficacy. These findings advocate for further investigation of combination therapies involving ADCs and cell cycle inhibitors to counter resistance and improve outcomes in bladder cancer patients. Citation Format: Jee Soo Park, Ji Eun Lee, Myung Eun Lee, Jongchan Kim, Won Sik Ham. The impact of cell cycle inhibitors on bladder cancer with low NECTIN-4 expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 2050.

<div>AbstractPurpose:<p>Enfortumab vedotin (EV) is an antibody–drug conjugate (ADC) targeting NECTIN4 (encoded by the <i>PVRL4/NECTIN4</i> gene) approved for treatment-refractory metastatic urothelial cancer. Factors that mediate sensitivity or resistance to EV are unknown. In this study, we sought to (i) examine heterogeneity of <i>NECTIN4</i> gene expression across molecular subtypes of bladder cancer and (ii) determine whether NECTIN4 expression mediates EV sensitivity or resistance.</p>Experimental Design:<p>Molecular subtyping and <i>NECTIN4</i> expression data from seven muscle-invasive bladder cancer clinical cohorts (<i>n</i> = 1,915 total specimens) were used to assess <i>NECTIN4</i> expression across molecular subtypes. The outcome of the transcriptomic analysis was relative <i>NECTIN4</i> expression in the consensus molecular subtypes of bladder cancer. Expression of <i>NECTIN4</i> was validated in bladder cancer cell lines. NECTIN4 was stably overexpressed or knocked down in basal and luminal bladder cancer cell lines and EV drug sensitivity assays were performed, as measured by cell proliferation and clonogenic assays.</p>Results:<p><i>NECTIN4</i> expression is heterogenous across molecular subtypes of bladder cancer and significantly enriched in luminal subtypes. <i>NECTIN4</i> expression is positively correlated with luminal markers <i>GATA3, FOXA1</i>, and <i>PPARG</i> across all cohorts. <i>NECTIN4</i> expression is both necessary and sufficient for EV sensitivity in luminal and basal subtypes of urothelial bladder cancer cells. Downregulation of <i>NECTIN4</i> leads to EV resistance.</p>Conclusions:<p>Sensitivity to EV is mediated by expression of <i>NECTIN4</i>, which is enriched in luminal subtypes of bladder cancer. These findings may have implications for biomarker development, patient selection, and the inclusion of molecular subtyping in ongoing and future EV clinical trials.</p><p><i>See related commentary by Teo and Rosenberg, p. 4950</i></p></div>

<div>AbstractPurpose:<p>Enfortumab vedotin (EV) is an antibody–drug conjugate (ADC) targeting NECTIN4 (encoded by the <i>PVRL4/NECTIN4</i> gene) approved for treatment-refractory metastatic urothelial cancer. Factors that mediate sensitivity or resistance to EV are unknown. In this study, we sought to (i) examine heterogeneity of <i>NECTIN4</i> gene expression across molecular subtypes of bladder cancer and (ii) determine whether NECTIN4 expression mediates EV sensitivity or resistance.</p>Experimental Design:<p>Molecular subtyping and <i>NECTIN4</i> expression data from seven muscle-invasive bladder cancer clinical cohorts (<i>n</i> = 1,915 total specimens) were used to assess <i>NECTIN4</i> expression across molecular subtypes. The outcome of the transcriptomic analysis was relative <i>NECTIN4</i> expression in the consensus molecular subtypes of bladder cancer. Expression of <i>NECTIN4</i> was validated in bladder cancer cell lines. NECTIN4 was stably overexpressed or knocked down in basal and luminal bladder cancer cell lines and EV drug sensitivity assays were performed, as measured by cell proliferation and clonogenic assays.</p>Results:<p><i>NECTIN4</i> expression is heterogenous across molecular subtypes of bladder cancer and significantly enriched in luminal subtypes. <i>NECTIN4</i> expression is positively correlated with luminal markers <i>GATA3, FOXA1</i>, and <i>PPARG</i> across all cohorts. <i>NECTIN4</i> expression is both necessary and sufficient for EV sensitivity in luminal and basal subtypes of urothelial bladder cancer cells. Downregulation of <i>NECTIN4</i> leads to EV resistance.</p>Conclusions:<p>Sensitivity to EV is mediated by expression of <i>NECTIN4</i>, which is enriched in luminal subtypes of bladder cancer. These findings may have implications for biomarker development, patient selection, and the inclusion of molecular subtyping in ongoing and future EV clinical trials.</p><p><i>See related commentary by Teo and Rosenberg, p. 4950</i></p></div>

Background: Nectin-4 is a cell-adhesion molecule expressed in many solid tumors. Enfortumab vedotin (EV, PADCEV®), an antibody-drug conjugate (ADC) targeting Nectin-4 with a monomethyl auristatin E (MMAE) payload, is approved for the treatment of urothelial cancer (UC), which exhibits the highest Nectin-4 expression among all solid tumor types. To address the unmet medical need of UC patients who discontinue EV due to toxicity, lack of efficacy, or ineligibility for this approved therapy, and to expand Nectin-4 targeting in tumor indications with lower Nectin-4 expression beyond UC, we have developed IPH4502, a differentiated anti-Nectin-4 ADC conjugated to exatecan with a cleavable hydrophilic linker, and a drug-to-antibody ratio of 8. Methods: Nectin-4 immunohistochemistry (IHC) was performed on formalin-fixed, paraffin-embedded tissue-microarrays. Internalization was evaluated in vitro, and bystander effect was evaluated in vivo. In vivo studies were also conducted to evaluate anti-tumor activity using syngeneic mouse models, cell line-derived xenografts, and patient-derived xenografts (PDXs) from various indications. Results: IHC revealed that Nectin-4 is overexpressed in tumor tissues from several cancer types including but not limited to UC, esophageal cancer, triple-negative breast cancer (TNBC), non-small cell lung cancer (NSCLC), and prostate cancer. IPH4502 demonstrates strong bystander killing effect in vivo, and high internalization efficiency in vitro in comparison to other Nectin-4 ADCs. These attributes contribute to enhanced anti-tumor activity in comparison to EV, across a spectrum of Nectin-4 expression levels, ranging from low to high expression, in PDX models. Moreover, IPH4502 shows efficacy in an in vivo model with primary resistance to MMAE due to MDR1 transporter expression and demonstrates anti-tumor activity in a PDX model of UC that acquired resistance to EV. Finally, IPH4502 shows activity in PDX models from indications beyond UC. Conclusion: The strong internalization and bystander effect of IPH4502 enable an efficient anti-tumor activity in Nectin-4 positive tumor models independent of Nectin-4 expression levels. In addition, IPH4502 shows efficacy in models resistant to EV, indicating that IPH4502 has potential for UC patients relapsing or refractory to EV treatment, as well as for cancer patients treated with MMAE-based ADCs. Finally, IPH4502 shows anti-tumor activity in various preclinical cancer models, including PDX models from different indications, supporting its development beyond UC. Citation Format: Romain Remark, Cécile Bonnafous, Laura Chiossone, Caroline Soulas, Cyril Perrier, Sivan Bokobza, Rachel Courtois, Julie Lopez, Grégory Fenaux, Olivier Benac, Barbara Carrette, Robin Letay-Drouet, Raja Bonifay, Marion Gaudin, Séverine Augier, Léa Simon, Agnès Represa, Ariane Morel, Eric Vivier, Yannis Morel, Nicola Beltraminelli, Carine Paturel. IPH4502, a differentiated Nectin-4 exatecan antibody-drug conjugate [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5443.

Cutaneous reactions with enfortumab vedotin: A case series and review of the literature

TPS3159 Background: Nectin-4 is a cell adhesion molecule frequently overexpressed across multiple solid tumor types, including urothelial carcinoma (UC), esophageal cancer, non-small cell lung cancer, and triple-negative breast cancer. It plays a significant role in carcinogenesis and cancer progression and is associated with poor survival in several tumor indications. Targeting Nectin-4 with enfortumab vedotin (EV), an antibody-drug conjugate (ADC) with a monomethyl auristatin E (MMAE) payload, demonstrated clinical benefit in UC, which exhibits the highest Nectin-4 expression among all solid tumor types. EV is now approved for the treatment of UC. IPH4502 is a differentiated Nectin-4 ADC conjugated with exatecan, a topoisomerase-1 inhibitor payload with a drug-to-antibody ratio of 8 via a cleavable hydrophilic linker. IPH4502 has been developed to address the unmet medical need of UC patients who have progressed on, or are ineligible for EV, as well as to treat tumor types with lower Nectin-4 expression beyond UC. In preclinical models, internalization capability and bystander effect of IPH4502 enable an efficient antitumor activity in Nectin-4 expressing tumor models, independent of Nectin-4 expression level, as well as in models resistant to EV. Finally, IPH4502 shows antitumor activity in patient-derived xenograft models from UC and other tumor types. Methods: This is a first-in-human, open-label, multicenter, single-arm Phase 1 study to assess the safety profile (DLTs and MTD), tolerability according to NCI-CTCAE v5.0, and RP2D of IPH4502 in patients with advanced solid tumors. Secondary objectives aim to characterize the pharmacokinetic profile and evaluate the immunogenicity and preliminary efficacy of IPH4502. The study is being conducted in participants aged ≥18 years withhistologically confirmed, unresectable, locally advanced, or metastatic solid tumors known to express Nectin-4, including, but not limited to non-small cell lung, triple-negative breast, ovarian, esophageal, gastric, and colorectal cancers, as well as UC. Part 1 (Dose Escalation) will use a Bayesian Optimal Interval Design (BOIN) with backfilling of safety-cleared dose levels. This approach will guide dose escalation and help establish the MTD/MAD. Part 2 (Dose Optimization)will begin after identifying the MTD/MAD, to select the RP2D. It will enroll participants with selected tumor indications (up to 2), for whom a clinical benefit was observed in Part 1. Participants will be randomized at a 1:1 ratio to 2 dose levels, to determine the RP2D. A maximum of 105 participants will receive treatment with IPH4502 in France and the US. Clinical trial information: NCT06781983 .

4585 Background: Advanced UC is a devastating disease, however recent advances with antibody drug conjugates (ADCs), including enfortumab vedotin (EV), have improved outcomes significantly. Currently no biomarkers are clinically available to predict response to therapy. We hypothesized that benefit from EV may correlate with mRNA expression of NECTIN4, the gene encoding the relevant cell surface antigen for EV. Therefore, we performed a landscape analysis of NECTIN4 in advanced UC and correlated expression with oncologic outcomes. Methods: Bladder and upper tract UC samples were tested at Caris Life Sciences (Phoenix, AZ) with NextGen Sequencing on DNA (592 genes or whole exome) and NovaSeq on RNA (whole transcriptome). UC samples were stratified by NECTIN4 mRNA levels into four quartiles. Tumor mutational burden (TMB) totaled somatic nonsynonymous mutations per tumor (high >10 mut/Mb). Insurance claims data were used to calculate survival outcomes using Kaplan-Meier estimates. Overall survival (OS) was calculated from the date of sample collection and date of treatment initiation to date of last follow up. Time on treatment (TOT) was calculated from date of treatment initiation to date of last treatment.Survival analysis was performed between top and bottom quartiles of NECTIN4 expression. Results: A total of 6,395 patient samples were analyzed [n=4335 from primary tumor (3496 bladder/urethra, 839 upper tract), n= 2060 from metastases]. Expression of NECTIN4 was associated with higher rates of mutations in FGFR3 (18.9% vs 6.9%), ERBB2 (11.8% vs 5.9%), pTERT (77.3% vs 62.6%), CCNE1 (5.6% vs 1.7%), SDHC (8.3% vs 0.6%) and with TMB-H status (46.2% vs 35.8%) but lower rates of TP53 mutations (54.6% vs 67.7%). NECTIN4 expression positively correlated with expression of TACSTD2 (TROP2), ERBB2 (HER2) and SLITRK6. Interestingly, NECTIN4 expression inversely correlated with PDL1 expression by IHC (22c3, 26.9% vs 59.2%). Similar findings were found when analysis was performed by primary bladder versus primary upper tract, as well as primary versus metastatic site. NECTIN4 expression was associated with longer OS in the overall population, and improvement in TOT (HR 0.53) and OS (HR 0.67) for patients treated with EV (Table). NECTIN4 expression was not associated with benefit with anti-PD1/L1 therapy. Conclusions: In the largest study investigating NECTIN4 expression in UC, we demonstrate co-expression of TACSTD2 (TROP2), ERBB2 (HER2) and SLITRK6 with NECTIN4. Expression of NECTIN4 correlated with favorable prognosis and predicted benefit from EV. NECTIN4 RNA expression could be a potential biomarker for selecting patients for treatment with EV. Further validation is required. [Table: see text]

BackgroundEnfortumab vedotin (EV) is a first-in-class Nectin-4-directed antibody-drug conjugate (ADC) with demonstrated improved overall survival in patients with previously treated advanced-stage urothelial carcinoma.1 EV is comprised of a fully human...

EV is a Nectin-4 targeting antibody-drug conjugate (ADC) with an MMAE payload, recently approved for bladder cancer treatment. We established and characterized 18 bladder XPDX models representing primary and metastatic disease from naïve or clinically treated patients, some with actionable mutations. To better understand the potential additive benefit of EV in bladder cancer, we evaluated the ADC alone and in combination with agents targeting ERBB2, PIK3CA or FGFR3. In addition, we tested EV alone in ST5420B, a model established from a patient who progressed on EV after five cycles, as well as ST975B, a model which harbors a novel NECTIN4 fusion. 18 bladder XPDX models were established in immune-deficient mice, including 5 from newly diagnosed patients (2 from primary site), and 13 from recurrent disease (2 from primary site). Nectin-4, Trop2 protein and ERBB2 receptor expression was tested, and models profiled using WES and RNAseq. For in vivo studies, all models were evaluated against cisplatin, T-DXd, SG, and EV. Models with actionable mutations were tested with alpelisib, erdafitinib, and neratinib alone and in combination with EV. Endpoints in all studies included tumor volume and time from treatment initiation with %T/C values and tumor regression reported at study completion; a %T/C of ≤ 20% versus control was considered sensitive. Tumor regression (%T/C<0%) versus Day 0 tumor volume was also reported. Most models stained positive for Nectin-4 and Trop-2. FGFR3 variants were found in five models and ERBB2 mutations in two while several models reported PIK3CA variants; deletions in RB1 and CDKN2A were common. In vivo studies reported differential responses to cisplatin with the most sensitive models established from treatment-naïve patients. EV and SG tested alone reported activity in several models; EV added benefit in some combination treatments. We have characterized a panel of bladder XPDX models and benchmarked them against T-DXd, EV and SG alone and EV in combination with targeted therapies. This data is a valuable tool in further developing EV and identifying novel therapies for bladder cancer. Citation Format: Johnnie Flores, Heaven Sessions, Alyssa Simonson, Natalia Banos, Tahmineh Rouzbahani, Armando Diaz III, Jim Lund, Emiliano Calvo, Victor Moreno, Kyriakos Papadopoulos, Drew Rasco, Amita Patnaik, Scott Ulmer, Luis Rodriguez, Michael Wick. Enfortumab vedotin (EV): Efficacy comparison with trastuzumab deruxtecan (T-DXd) and sacituzumab govitecan (SG) and its potential for combination benefit in bladder cancer XPDX models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6899.