- Tumors either got smaller or stopped growing in more than two-fifths of certain advanced urothelial cancer patients put on an experimental drug from Seattle Genetics, according to clinical trial data presented Monday at the American Society of Clinical Oncology's annual meeting.
- The Phase 2 trial looked at patients previously treated with platinum-based chemotherapy and a PD-1 or PD-L1 checkpoint inhibitor. Among patients who had not responded to these inhibitors, 41% responded to Seattle Genetics' drug, enfortumab vedotin. So did 38% of patients with cancer that spread to the liver.
- The trial also enrolled patients who previously received a checkpoint inhibitor and no platinum-based chemotherapy — but data from that group, which is still enrolling, wasn't reported at ASCO. Still, Seattle Genetics has said it is confident in the results seen thus far and plans to file its drug for approval later this year.
Seattle Genetics built its now two-decades-old business around ADCs, or antibody drug conjugates. The strategy has resulted in one product, Adcetris (brentuximab vedotin), but that number could soon rise.
Executives said in February that enfortumab vedotin, also an ADC, is "on the path to becoming" the company's next marketed drug. A positive readout in an ongoing Phase 2 trial, they argued, would set it up for a regulatory filing in 2019 under the Food and Drug Administration's accelerated approval program.
The company didn’t have to wait long to get that readout; topline results announced in March showed an objective response rate of 44% in the study’s first cohort — the one where patients had already been treated with platinum-based chemotherapy and a PD-1 or PD-L1 checkpoint inhibitor.
More complete data presented at ASCO found 12% of those patients had no detectable signs of cancer after receiving enfortumab vedotin. Median overall survival was a little less than a year.
On safety, a release from ASCO said the drug was well-tolerated, with 40% to 50% of patients experiencing fatigue, hair loss and decreased appetite.
ASCO noted too how patients had a median of three prior systemic treatments in the locally advanced or metastatic setting before getting Seattle Genetics’ drug.
The clinical activity seen in the Phase 2 study closely resemble what investigators saw in earlier testing. That’s reassuring, according to Arlene Siefker-Radtke, a professor at the University of Texas MD Anderson Cancer Center.
Siefker-Radtke foresees enfortumab vedotin, should it gain approval, being a welcome addition to clinicians’ list of advanced urothelial cancer treatments.
Currently, most patients are put on chemotherapy or checkpoint inhibitors, though Johnson & Johnson did in April receive FDA approval for Balversa (erdafitinib) in patients who have two types of mutation in a gene called FGFR.
“We clearly need more options,” she said in an interview with BioPharma Dive. “Having platinums, having immunotherapy and having an FGFR-targeted agent isn't enough. And it really is thrilling seeing enfortumab vedotin come into play.”
Enfortumab vedotin is now being investigated in a Phase 3 trial as well as another study enrolling newly diagnosed patients with advanced urothelial cancer. Astellas is jointly developing the drug with Seattle Genetics.