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Seattle Genetics stays step ahead of rivals with bladder cancer data

Seattle Genetics and Astellas on Friday said their bladder cancer drug Padcev kept patients with advanced-stage bladder cancer alive and in remission longer than did chemotherapy in a late-stage trial. The announcement came after an early data analysis, which found the drug improved survival.The companies plan to ask the Food and Drug Administration confirm Padcev’s approval for use in this group of patients. In December 2019, the FDA granted an accelerated approval to Padcev based on the drug’s ability to shrink tumors in a study that didn’t compare it to chemotherapy.

The earlier-than-expected results keep Seattle Genetics one step ahead of Immunomedics, which has a similarly acting drug called Trodelvy. Immunomedics, which on Sunday agreed to a $21 billion buyout by Gilead, is scheduled to release data from a mid-stage bladder cancer trial of Trodelvy in combination with Merck & Co.’s Keytruda at a European medical meeting this weekend.

The Padcev data marks another step in the progress of a class of cancer drugs known as antibody-drug conjugates, or ADCs, which combine a tumor-targeting antibody with a toxic chemical. Seattle Genetics is one of the field’s pioneers and won of the field’s first approvals when it brought its blood-cancer drug Adcetris to market in 2011. Its second ADC OK came eight years later with the FDA’s conditional clearance for Padcev.

The accelerated approval, granted last December, was for bladder cancer patients who have been previously treated with chemotherapy and an immunotherapy like Merck & Co.’s Keytruda. Padcev won that clearance based on its ability to shrink tumors in 44% of these patients, whose cancers had spread. The study from which Seattle Genetics announced results Friday was designed to confirm the drug’s benefit.

Results show the company succeeded. The trial found Padcev reduced these patients’ risk of death by 30% when compared to chemotherapy, and reduced their risk of progression by 39%. The companies said the trial didn’t reveal any side effects that haven’t already been identified. Treatment with Padcev can cause elevated blood sugar, suppressed white blood cell counts and anemia.

Winning full approval, should the FDA agree, would help Seattle Genetics and Astellas shore up Padcev’s competitive position against Trodelvy, an ADC used in breast cancer that Immunomedics has also been developing for bladder cancer. Data this weekend at the European Society of Medical Oncology’s virtual meeting should give Padcev’s developers a better idea of how competition could shape up.

Immunomedics’ trial is testing Trodelvy and Merck’s Keytruda in up to 62 patients who have progressed on chemotherapy and measures how many go into remission. Merck, which just put $1.7 billion into Seattle Genetics, also has a Phase 3 study underway comparing Keytruda and Padcev to chemotherapy.

Seattle Genetics and Astellas have to be more concerned about the competitive threat, however, now that Gilead has offered to buy Immunomedics. The large biotech, which has significantly expanded its cancer business under CEO Dan O’Day, can draw on greater commercial muscle than Immunomedics could alone.