Seattle Genetics Plunges After Drug Studies Halted on Deaths

Updated on
  • Shares drop 14 percent after several cancer trials halted
  • Four patients with liver damage died on drugmaker’s therapy

Seattle Genetics Inc. plunged the most in five years after U.S. regulators halted several early-stage blood cancer studies following the deaths of four patients who suffered from liver damage.

The Food and Drug Administration halted the trials testing Seattle Genetics’s acute myeloid leukemia, or AML, therapy, called SGN-CD33A. Two studies, including a final-stage trial, are still enrolling patients, the drugmaker said in a statement Tuesday. The shares fell 14 percent to $53.11 at 9:42 a.m. in New York, after earlier falling as much as 16 percent, the biggest intraday drop since November 2011.

Six patients taking SGN-CD33A developed liver damage, including the four who died, according to the company. There were several cases of a potentially dangerous condition called veno-occlusive disease, in which blood vessels into the liver are blocked. Veno-occlusive disease is an occasional side effect of the stem cell transplantation that AML patients often receive, as was the case for those who got the Seattle Genetics drug.

More than 300 patients have been treated with SGN-CD33A in clinical trials, and the company is working with the FDA to figure out whether the liver damage is related to the drug. SGN-CD33A, one of Seattle Genetics’s lead experimental therapies, is designed to find cancer cells with a particular marker called CD33 and deliver a powerful chemotherapy to kill them.

About 20,000 patients will be diagnosed with AML this year in the U.S., according to the National Institutes of Health, and about 10,000 will die.

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