Seattle Genetics Inc. shares dropped 12.9% in pre-market trade Tuesday after the company said the Food and Drug Administration had placed holds on several early-stage cancer clinical trials after six patients were found to have hepatotoxicity and four patients died. The clinical trials, which were testing vadastuximab talirine as a treatment for acute myeloid leukemia, were held to evaluate risk of hepatotoxicity. The trials included a phase 1/2 trial placed on full clinical hold and two phase 1 trials placed on partial clinical hold, with no new clinical trials beginning until the holds come to an end. Other clinical trials for vadastuximab talirine, including a phase 3 and phase 1/2 trial, are continuing. Seattle Genetics shares have risen 37.8% year-to-date, compared with a 10.8% rise in the S&P 500 . Seattle shares closed at $61.86 at Friday's close.
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