Enfortumab Vedotin Demonstrates Additional Mechanisms of Action in UC Models

In urothelial carcinoma (UC) models, enfortumab vedotin-ejfv (Padcev) appeared to promote multiple mechanisms of action such as bystander cell killing, supporting the use of the agent either alone or in combination with pembrolizumab (Keytruda), according to findings from a poster presentation presented during the 2020 AACR Virtual Annual Meeting II.

The study evaluated enfortumab vedotin’s mechanism of action in 2 UC models, T-24 and UM-UC-3, which were sensitive to the antibody-drug conjugate (ADC) in vitro and in vivo and had been engineered to express Nectin-4. Lead author, Bernard A. Liu, and fellow investigators sought to not only define the processes by which enfortumab vedotin induces immunogenic cell death but also describe the agent’s additional mechanisms of action. Enfortumab vedotin is an ADC that includes a Nectin-4–targeting human monoclonal antibody conjugated to monomethyl auristatin E (MMAE), a microtubule disrupting agent, via a protease-cleavable linker. Nectin-4 is a cell adhesion protein that is highly expressed in several solid tumors, including urothelial, breast, gastric, and lung carcinomas.¹

In Nectin-4 expressing cell lines, enfortumab vedotin internalized with Nectin-4, trafficked to lysosomal vesicles, and released intracellular MMAE as shown by intracellular MMAE accumulation. Liu said results indicated that enfortumab vedotin’s anticancer mechanisms extended beyond targeted auristatin delivery, cell cycle arrest, and apoptosis to include bystander cell killing and hallmarks of immunogenic cell death (ICD), such as endoplasmic reticulum (ER) stress, immune cell recruitment, and activation. Additional hallmarks of ICD observed with enfortumab vedotin included the extracellular release of adenosine triphosphate and HMGB1 in both Nectin-4 expressing cell lines.¹

Specifically, enfortumab vedotin demonstrated its bystander effect by release of the cell permeable MMAE from Nectin-4-positive cells to kill Nectin-4-negative cancer cells in an admixed cellular assay. Enfortumab vedotin’s bystander effect supports future clinical studies in heterogeneous Nectin-4 expressing tumors, according to Liu, a senior scientist specializing in Cancer Biology at Seattle Genetics in Bothell, Washington, who noted that the ADC also demonstrated increased expression of HLA/MHC-Class I and Class II, thereby activating the adaptive immune response as a potential mechanism for neoantigens display.¹

Immune Profiling Assessments

In the T-24 Nectin-4 xenograft model, immune cell recruitment and activation induced potent anti-tumor activity. Investigators used immunohistochemistry (IHC), RNA-Seq, flow cytometry, and immune cytokine paneling to measure recruitment and activation. An additional immune profiling assessment underscored an enhancement of the immune cell markers seen in 6 of 7 tumors compared with animals who were not treated or non-binding ADC control-treated animals.¹

Investigators said their RNA-Seq supported analysis of gene signatures validated their qualitative IHC analysis of immune cell recruitment and added that additional gene signature analyses identified gene transcripts associated with microtubule disruption, mitotic arrest, and ER stress. Additionally, a Luminex assessment of mouse cytokines showed coincident changes in RNA expression of genes associated with macrophage activation such as MIP1α and MIPβ, suggesting that enfortumab vedotin can activate antigen-presenting cells.¹

Expanding The Enfortumab Vedotin Knowledge Base

Findings from Liu et al’s study expand the pool of available data on enfortumab vedotin in UC. Enfortumab vedotin received an accelerated approval in December 2019 for adults with locally advanced or metastatic UC who previously received a PD-1/L1 inhibitor and a platinum-containing chemotherapy in the neoadjuvant, adjuvant, locally advanced, or metastatic setting.² Notably, enfortumab vedotin is the first FDA-approved Nectin-4–directed ADC.³

Enfortumab vedotin’s accelerated approval was based on findings from the phase 2 single-arm EV-201 study (NCT03219333). The confirmed objective response rate was 44% (95% CI, 35.1-53.2), with a 12% complete response rate and a 32% partial response rate. EV-201 enrolled 125 patients with locally advanced or metastatic UC who either received prior treatment with a PD-1 or PD-L1 inhibitor and platinum-based chemotherapy; or never received platinum-containing chemotherapy and were not eligible for cisplatin.^2,3

The confirmatory phase 3 EV-301 study (NCT03474107) has been initiated to verify enfortumab vedotin’s efficacy in this setting. Enfortumab vedotin is also being evaluated in other solid tumors in the phase 2 EV-202 trial (NCT04225117), including hormone receptor-positive/HER-negative breast cancer, triple-negative breast cancer, non-squamous non–small cell lung cancer, head and neck cancer, and gastric and esophageal cancer.

Future directions for clinical investigations involving enfortumab vedotin should also include demonstrating the anti-tumor activity of the ADC and an anti–PD-1 inhibitor and confirming immunogenic cell death and immune cell memory in vivo using a vaccine-based approach, according to Liu. Results from Liu et al’s analysis, coupled with what is currently known about enfortumab vedotin’s safety and efficacy in UC, provide the rationale for subsequent studies of enfortumab vedotin in combination with PD-1/L1 inhibitors. The viability of this combination modality was previously established in the phase 1/2 EV-103 study (NCT03288545), which tested several regimens including enfortumab vedotin and pembrolizumab, in patients with locally advanced or metastatic UC.

References

1. Liu BA. Enfortumab vedotin, an anti-Nectin-4 ADC demonstrates bystander cell killing and immunogenic cell death anti-tumor activity mechanisms of action in urothelial cancers. Poster presented at: the 2020 American Association of Cancer Research Virtual Meeting II; June 22-24. Abstract 5581.
2. Padcev. Prescribing information. Astellas Pharma US; 2019. Accessed June 22, 2020. https://www.accessdata.fda.gov/drugsatfda_docs/label/2019/761137s000lbl.pdf
3. FDA grants accelerated approval to Astellas’ and Seattle Genetics’ Padcev (enfortumab vedotin-ejfv) for people with locally advanced or metastatic urothelial cancer, the most common type of bladder cancer. News release. Seattle Genetics. December 18, 2019. Accessed June 22, 2020. https://investor.seattlegenetics.com/press-releases/news-details/2019/FDA-Grants-Accelerated-Approval-to-Astellas-and-Seattle-Genetics-PADCEV-enfortumab-vedotin-ejfv-for-People-with-Locally-Advanced-or-Metastatic-Urothelial-Cancer-the-Most-Common-Type-of-Bladder-Cancer/default.aspx