Neoadjuvant enfortumab vedotin (Padcev) showed promising antitumor activity in patients with muscle-invasive bladder cancer (MIBC) who were ineligible for cisplatin therapy, according to preliminary findings from cohort H of the phase 1b/2 EV-103 clinical trial.
Analysis of data from 22 patients in this cohort, which enrolled individuals who were eligible for surgical treatment but ineligible for cisplatin-based chemotherapy, revealed a pathologic complete response (pCR) rate of 36.4%, said Daniel P. Petrylak, MD, Professor, Medical Oncology and Urology, and Co-Leader, Cancer Signaling Networks, Yale Cancer Center, Smilow Cancer Hospital at Yale New Haven, CT, at the 2022 American Society of Clinical Oncology Genitourinary Cancers Symposium.
“All patients were able to undergo surgery and there was no delay in surgery due to neoadjuvant enfortumab vedotin,” said Dr Petrylak.
The standard of care for patients with MIBC is cisplatin-based chemotherapy with radical cystectomy and pelvic lymph node dissection (PLND). “Cisplatin-ineligible patients do not have established neoadjuvant treatment options known to prolong survival prior to undergoing radical cystectomy and PLND,” he said, creating an unmet need in this patient population.
Enfortumab vedotin is an antibody–drug conjugate delivering monomethyl auristatin E to targeted tumor cells expressing Nectin-4. It has been shown to improve overall survival compared with chemotherapy in patients with previously treated locally advanced/metastatic urothelial carcinoma. Preclinical studies suggest that antibody–drug conjugates using monomethyl auristatin E can induce immunogenic cell death and may enhance antitumor immunity.
Based on previous results from EV-103, the FDA granted a breakthrough therapy designation to enfortumab vedotin plus pembrolizumab (Keytruda) as a first-line treatment for patients with unresectable locally advanced or metastatic urothelial cancer who are unable to receive cisplatin-based chemotherapy.
Cohort H of the single-arm phase 1b/2 EV-103 trial enrolled 22 patients with clinical stage T2-T4aN0M0 MIBC who were eligible for surgical treatment but ineligible for cisplatin-based chemotherapy. Patients were administered 3 cycles of neoadjuvant enfortumab vedotin monotherapy on days 1 and 8 of every 3-week cycle followed by radical cystectomy and PLND within 4 weeks and follow-up imaging every 12 weeks for the first 2 years, and then every 24 weeks.
Median patient age was 74.5 years. The median enrollment time from diagnosis was 1.6 months. Approximately two-thirds (68.2%) of patients had cT2N0 disease. Histologic type was transitional-cell carcinoma only in 68.2% of patients, transitional-cell carcinoma with squamous differentiation in 13.6%, and transitional-cell carcinoma with other histologic variants in 18.2%.
The most common reasons for cisplatin ineligibility were creatinine clearance <60 mL/min and ≥30 mL/min (11 patients; 50.0%), and grade ≥2 hearing loss (9 patients; 40.9%).
Some 19 of the 22 patients completed all 3 cycles of neoadjuvant enfortumab vedotin and all enrolled patients underwent surgery without delay. The median duration of neoadjuvant treatment was 2.1 months, with the time from the end of neoadjuvant treatment to surgery being 1.8 months. All 3 patients off-study died during the perioperative period—1 due to acute kidney injury, 1 to cardiac arrest, and 1 to pulmonary embolism.
In addition to the pCR rate of 36.4%, 11 (50.0%) patients were downstaged by central pathology review following neoadjuvant treatment.
The observed safety profile of neoadjuvant enfortumab vedotin monotherapy in EV-103 was consistent with the known adverse event profile in other settings “of enfortumab vedotin,” Dr Petrylak said. The most common treatment-emergent adverse events were fatigue (45.5%), alopecia (36.4%), and dysgeusia (36.4%). Four patients had grade 3 treatment-emergent adverse events.
Addressing the seemingly high rate of perioperative deaths, he noted that “these are an older group of patients, and 2 of those 3 patients had residual disease, and previous research has shown that bladder cancer treatments may cause thrombogenic events, pointing to the 2 events that were cardiovascular in nature. It is a concern, and this is going to be monitored in phase 3 studies, and, of course, if there is a safety signal that is concerning, the studies will be appropriately evaluated,” he said.
Discussant Guru P. Sonpavde, MD, Director, Bladder Cancer Program, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA, said that antibody–drug conjugate development in earlier disease settings such as MIBC is rational. While the pCR rate in EV-103 is impressive, “will pCR here translate into improved long-term outcomes [and cure more patients]?” he asked. “Is this good quality pCR or just a shallow pCR? I think this remains to be seen.” The stakes are higher in the perioperative setting, he added, where a better therapeutic index is needed.
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