SUMMARY: The FDA on April 3, 2023, granted accelerated approval to Enfortumab vedotin-ejfv (PADCEV®) with Pembrolizumab (KEYTRUDA®) for patients with locally advanced or metastatic urothelial carcinoma who are ineligible for Cisplatin-containing chemotherapy. The American Cancer Society estimates that in the United States for 2023, about 82,290 new cases of bladder cancer will be diagnosed and approximately 16,710 patients will die of the disease. Bladder cancer is the fourth most common cancer in men, but it is less common in women. Urothelial cancer accounts for 90% of all bladder cancers and can also be found in the renal pelvis, ureter and urethra. Approximately 12% of urothelial cancer cases at diagnosis are locally advanced or metastatic.
Patients with urothelial carcinoma are currently treated in the first line setting with a Platinum based chemotherapy regimen, and a checkpoint Inhibitor (PD-1 or PD-L1 inhibitor) in the second line setting. However, approximately 50% of patients with advanced urothelial carcinoma are ineligible for Cisplatin-based chemotherapy due to toxicities, and responses are rarely durable. There is therefore a critical need for effective and tolerable first line treatment options in locally advanced or metastatic urothelial carcinoma.
Enfortumab vedotin-ejfv (PADCEV®) is a first-in-class Antibody-Drug Conjugate (ADC) that targets Nectin-4, a cell adhesion molecule highly expressed in urothelial cancers and other solid tumors. Nectin-4 has been implicated in tumor cell growth and proliferation. Following binding to Nectin-4 on the cell surface, Enfortumab vedotin becomes internalized and is processed by lysosomes, with the liberation of its cytotoxic payload, MonoMethyl Auristatin E (MMAE), which in turn disrupts microtubule assembly, leading to cell cycle arrest and apoptosis. Enfortumab vedotin resulted in significantly longer Overall Survival, Progression Free Survival, and a higher Overall Response Rate, than standard chemotherapy, in patients with locally advanced or metastatic urothelial carcinoma, who had previously received Platinum-based treatment and a PD-1 or PD-L1 inhibitor. Preclinical studies with Enfortumab vedotin have shown hallmarks of immune cell death potentially augmented by PD-1/PD-L1 inhibitors, and the rationale for this clinical trial was based on results from a previous cohort study.
Pembrolizumab (KEYTRUDA®) is a fully humanized, Immunoglobulin G4, anti-PD-1, monoclonal antibody, that binds to the PD-1 receptor and blocks its interaction with ligands PD-L1 and PD-L2. By doing so, it unleashes the tumor-specific effector T cells, and is thereby able to undo PD-1 pathway-mediated inhibition of the immune response. Pembrolizumab is the first agent to improve Overall Survival over chemotherapy, in the second line setting, for patients with recurrent, advanced urothelial carcinoma, and a significant proportion of patients who respond, have very durable responses.
EV-103 is an ongoing multi-cohort, open-label, global, multicenter Phase Ib/II study, investigating Enfortumab vedotin alone or in combination with Pembrolizumab and/or chemotherapy in first or second line settings, in patients with locally advanced or metastatic urothelial cancer, and in patients with muscle-invasive bladder cancer. The present FDA approval was based on Objective Response Rates (ORR) and median Duration of Response (DOR) in combined Dose Escalation/Cohort A and Cohort K of this study, also known as KEYNOTE-869 trial. The Dose Escalation Cohort and Cohort A were single-arm cohorts treating patients with Enfortumab vedotin plus Pembrolizumab, whereas patients in Cohort K were randomized to either Enfortumab vedotin monotherapy or Enfortumab vedotin in combination with Pembrolizumab. Patients had not received prior systemic therapy for locally advanced or metastatic urothelial cancer and were ineligible for Cisplatin-containing chemotherapy. Ineligibility for Cisplatin-based chemotherapy could be due to at least one of the following: Glomerular filtration rate (GFR) less than 60 mL/min, ECOG Performance Status of 2, Grade 2 or more hearing loss, or New York Heart Association Class III heart failure. In this analysis, a total of 121 patients (N=121) received Enfortumab vedotin plus Pembrolizumab. Patients received Enfortumab vedotin 1.25 mg/kg IV (up to a maximum of 125 mg for patients 100 kg or more) on days 1 and 8 and Pembrolizumab 200 mg IV on day 1, every 3 weeks. Treatment was continued until disease progression or unacceptable toxicity. The major efficacy outcome measures were Objective Response Rate (ORR) and Duration of Response (DOR) determined by Blinded Independent Central Review.
Patients treated with a combination of Enfortumab vedotin and Pembrolizumab had an Objective Response Rate of 68%, with 12% of patients experiencing a Complete Response. The median Duration of Response for the Dose Escalation cohort plus Cohort A was 22 months and for Cohort K was Not Reached. The most common Treatment Related Adverse Events (TRAE) were peripheral sensory neuropathy (55.6%), fatigue (51.1%), and alopecia (48.9%). Two thirds of patients had Grade 3 TRAEs, and the most common toxicities were increased lipase, maculopapular rash, and fatigue.
It was concluded that in Cisplatin-ineligible patients with unresectable locally advanced or metastatic urothelial cancer, treatment with Enfortumab vedotin and Pembrolizumab combination in chemo naïve patients, resulted in high Overall Response Rate, along with a safety profile that was tolerable. The authors added that Antibody-Drug Conjugates have the potential to make a greater impact in treating bladder cancer, especially in combination with checkpoint inhibitors, as shown in this trial and these data support ongoing investigations of first line Enfortumab vedotin and Pembrolizumab in patients with locally advanced or metastatic urothelial cancer.
Enfortumab Vedotin Plus Pembrolizumab in Previously Untreated Advanced Urothelial Cancer. Hoimes CJ, Flaig TW, Milowsky M, et al. DOI: 10.1200/JCO.22.01643 Journal of Clinical Oncology 41, no. 1 (January 01, 2023) 22-31.
