Seattle Genetics Sees Updated Side Effect Warning in Drug Label

Xconomy Seattle — 

Seattle Genetics is getting some new warnings, including one new language about a potentially deadly brain infection, put into the FDA-approved prescribing information of its lone marketed product.

The company (NASDAQ: SGEN) said today it is working on an update to the label for brentuximab vedotin (Adcetris), which will include a boxed warning about the risk of patients on the lymphoma drug getting a potentially fatal brain infection called progressive multifocal leukoencephalopathy (PML). Seattle Genetics’ original drug label, cleared by the FDA in August, said there had been a case of PML in clinical trials, but now that the drug has been used more widely on the market, Seattle Genetics discovered a second case last fall, and said today it has learned of a suspected third case of PML. That information is prompting new warning language that’s supposed to help doctors spot signs of PML.

Several new biotech drugs have been linked to cases of PML, including Roche and Biogen Idec’s hit lymphoma drug rituximab (Rituxan). The Seattle Genetics drug is designed to hit a different target on cancer cells, and it is approved for use in a couple of rare malignancies—Hodgkin’s disease and anaplastic large cell lymphoma. The new treatment has shown strong ability to shrink tumors in clinical trials in the majority of patients who have essentially run out of options, and it has beaten Wall Street’s initial sales expectations. Now Seattle Genetics is looking to expand use of the drug to larger groups of patients. One of those label-expansion studies showed that the new drug shouldn’t be used in combination with a chemotherapy agent known as bleomycin, because of an elevated rate of lung toxicity, so a warning about that is also being incorporated into the Adcetris label.

The bleomycin warning isn’t much of a concern, because even though it’s part of a typical chemo regimen, Adcetris was never approved to be used in combination with that drug, and researchers are hopeful that Adcetris might be able to replace bleomycin for use in some patients, because the new drug has a milder side effect profile when used on its own.

“Our first priority is patient safety. By developing these agreed upon label updates with the FDA regarding PML and the contraindication with bleomycin, we aim to heighten awareness among healthcare professionals in order to most safely treat their patients with Adcetris. Although PML in lymphoma patients can be caused by factors such as underlying disease and prior therapies that affect the immune system, a contributory role of Adcetris cannot be excluded,” said Tom Reynolds, the chief medical officer of Seattle Genetics, in a statement.

Previous studies have said patients with blood cancers have about a 0.07 percent chance (1 in 1,400) of getting PML. Seattle Genetics didn’t say what the ratio is for patients getting Adcetris, but it has had two confirmed cases, and one suspected case, out of more than 2,000 patients worldwide who have gotten the new drug.

Shares of Seattle Genetics fell about 6.3 percent to $17.28 at 10:14 am Eastern time.

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