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opportunistic infections like PML. He cited a May 14, 2009 article in Blood, the hematology journal, which says that between 0.07% and 0.5% of patients with blood cancers are thought to have PML.
What made the Tysabri case different is that the drug is designed to treat multiple sclerosis, a disease which isn’t normally associated with PML. Researchers now say that about 1 in 1,000 patients on Tysabri can expect to get PML. Even with that risk, the FDA has allowed the drug to stay on the market, because of the benefit it provides in reducing MS flare-ups.
Since the Seattle Genetics drug is still relatively new, it’s too early to say what kind of PML incidence rate it may have over time. What is known so far is that there are two reported cases out of more than 2,000 patients who have gotten the drug in clinical trials and in the marketplace, Siegall says. He said the Favus report was incorrect, because it said there were two PML cases of out just 410 patients.
Siegall declined to say what an acceptable PML incidence rate might be. “We have been watching this from Day 1, and we will continue to watch it,” Siegall says.
For what it’s worth, I listened to the entire FDA advisory panel proceedings over the summer during which experts reviewed the drug’s safety and effectiveness, and I don’t recall PML being raised as a point of discussion. Siegall sounded a bit irritated about the PML case coming up in the marketplace the way it did today.
“Adcetris has been used in a lot of patients, and provided an amazing opportunity for patients to get strong anti-tumor activity against fatal diseases. The testimonials I hear from families, and doctors have been overwhelming and incredibly heartwarming. I’m thrilled with the impact Adcetris has had on patients,” he says.
“As a public company CEO, I have to realize that there are some people who say things that are over-the-top positive, and some people who say things that are over-the-top negative, and incorrect. It happens,” Siegall says. “People will throw mud. I have to live with this and keep my focus on treating patients with cancer.”