Seattle Genetics said three of its clinical trials have been put on full or partial hold after four patients died from liver damage.

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Three of Seattle Genetics’ early-stage clinical trials have been placed on hold after four patients died from liver damage.

One trial was placed on a full hold by the Food and Drug Administration, and the other two on partial holds. All trials use the drug vadastuximab talirine to treat acute myeloid leukemia.

The company is investigating whether the drug being tested is related to the deaths.

“Seattle Genetics is working diligently with the FDA to determine whether there is any association between hepatotoxicity and treatment with SGN-CD33A, to promptly identify appropriate protocol amendments for patient safety and to enable continuation of these trials,” the company said in a news release.

The affected patients had received stem-cell transplants either before or since starting treatment. Six patients have been diagnosed with liver damage, known as hepatotoxicity, including four who died.

More than 300 patients have been treated with the drug.

Seattle Genetics specializes in developing antibody-drug conjugates, or ADCs.

The drugs target specific cells and dump toxins into certain cells to fight cancer.

The company’s stock plummeted Tuesday after the clinical holds were announced, closing down $9.50, or 15.4 percent, at $52.36.