The novel antibody-drug conjugate enfortumab vedotin produced an impressive 44% response rate in a phase II trial of urothelial cancer patients who had been treated with standard chemotherapy and a checkpoint inhibitor.
Researchers presented results of the study of 125 patients at the American Society of Clinical Oncology annual meeting in Chicago.
Twelve percent of bladder cancer patients studied had a complete response with no detectable sign of cancer. And 38% of patients whose cancer had metastasized to the liver responded to treatment, according to lead author Daniel P. Petrylak, MD, of Yale University, New Haven, CT.
This is the highest reported response rate in metastatic urothelial cancer to liver of any single agent or combination therapy to date, according to Dr. Petrylak.
“This is an area that we know does not respond well to the checkpoint inhibitor therapy. What we’re also seeing, which is very interesting, is that there is no difference in response in those patients who have had programmed-death ligand-1 (PD-L1) progression or PD-L1 response. So [enfortumab vedotin] seems to work with responders and non-responders,” he said.
While the average overall survival was 11.7 months in the phase II trial, it’s too early to tell whether enfortumab vedotin improves survival in bladder cancer patients. The current phase III study is looking at survival, according to Dr. Petrylak.
Enfortumab vedotin could help to fill a need in the treatment of bladder cancer because outcomes from standard chemotherapy and immune checkpoint inhibitors fall short.
“About three-quarters of patients will not benefit from immune checkpoint therapy. So, there’s a need for third-line agents. In the past, we used single-agent chemotherapy for second line but really didn’t see great responses. At best, we saw 20% response rate and no improvement in survival,” Dr. Petrylak said.
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