Juno Therapeutics Inc. JUNO shares plummeted 30.4% in pre-market trade Wednesday after the company said two patients in its cancer trial had died. Both patients experienced brain trauma earlier in the week during a phase 2 trial for a leukemia treatment, the company said. Two patients also died in early July in the same clinical trial, but the company was allowed to resume the trial without the chemotherapy drug fludarabine, which Juno believed caused the deaths in combination with the company's JCAR015 drug. This week, Juno put the trial on clinical hold, and said it is working with the Food and Drug Administration and the Data and Safety Monitoring Board, an independent expert advisory group, to "determine next steps." The company said its other product candidates targeting the B Cell Specific Antigen CD19 won't be affected. Juno shares have dropped 32.0% year-to-date, compared with a 7.8% rise in the S&P 500 SPX, -2.37% .