Astellas, Seattle Genetics' Padcev bladder cancer trial stops early with 30% death risk reduction

Seattle Genetics and Astellas’ hot-shot newcomer Padcev now has what every cancer drugmaker is looking for: Randomized trial data showing it can help patients live longer.

Friday, the partners unveiled data showing that the antibody-drug conjugate had nailed its primary endpoint in a study of bladder cancer patients who had already received platinum-based chemo and a PD-1/PD-L1 inhibitor. In that group, Padcev slashed the risk of death by 30% compared with chemo.

The drug also significantly pared down patients’ combined risk of disease progression or death, slashing it by 39% to hit a key secondary endpoint.

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With the interim results, the trial will stop early, and the companies will submit the data to the FDA in hopes of converting Padcev’s initial accelerated approval, granted late last year on the back of single-arm phase 2 results, into a full one.

The trial, called EV-301, “is the first randomized trial to show overall survival results compared to chemotherapy” in this population, “and we are encouraged by the potential this may have in helping patients who have otherwise limited alternatives,” Astellas oncology chief Andrew Krivoshik, M.D., Ph.D., said in a statement.

About 522,000 patients globally will be diagnosed with urothelial cancer—the most common type of bladder cancer, and the type tested in EV-301—in 2020, the companies said, noting that about 80% of those patients don’t respond to PD-1/PD-L1 drugs after chemo has failed in the front-line setting.

The performance has analysts at SVB Leerink “encouraged,” analyst Andrew Berens wrote in a Friday note to clients, particularly considering that Padcev demonstrated survival benefits that drugs such as Merck & Co.'s Keytruda and AstraZeneca’s Imfinzi “have failed to provide.”

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Berens also expects to see Padcev’s survival benefit “raise the bar for its competitor Trodelvy,” a rival antibody drug conjugate from Immunomedics, soon to be part of Gilead after this week’s $21 billion buyout agreement. Immunomedics is set to present data in third-line bladder cancer at this weekend’s European Society for Medical Oncology virtual congress—results it hopes will help it net an accelerated approval in the first half of next year.

Those advantages will only fuel what’s so far been an impressive launch for Padcev. In its first quarter on the market after a mid-December FDA green light, the drug “blew out expectations … exceeding consensus estimates" four- to fivefold by tallying $34.5 million in sales, J.P. Morgan analyst Cory Kasimov wrote in a note to clients at the time.

More recently, in Q2, Padcev generated $57.2 million, marking a 66% increase over its Q1 haul.

Berens and his Leerink colleagues expect the drug to ultimately rack up peak sales of about $7.8 billion in metastatic bladder cancer, with non-muscle invasive bladder cancer chipping in another $1.8 billion or so.