Shares of Juno Therapeutics closed down nearly 11 percent Thursday, after the company halted the development of an experimental leukemia treatment, following the deaths of five patients in its trials.
The drug, known as JCAR015, was being tested in adults with relapsed acute lymphoblastic leukemia, or ALL, a rare and deadly blood cancer, the company said in a statement.
The company said it and its partner Celgene opted to end the trial after the "unfortunate and unexpected toxicity" of the drug.
"We experienced a setback in 2016," the drug developer said. "We have made a strategic decision to cease Juno development of JCAR015" and to redirect resources to the advancement of other potential drug candidates.
Along with this news, the biotechnology company announced its fourth-quarter results Wednesday.
Juno reported a quarterly net loss of 51 cents per share, compared to a Thomson Reuters consensus estimate of a 61-cent loss. The Seattle-based company reported quarterly sales of $21.2 million, topping a Reuters forecast of $14.6 million.
The stock closed in the green Wednesday, after Juno beat Wall Street expectations on both the top and bottom lines, but it pared back those gains Thursday morning as investors learned of the discontinuation of JCAR015. Management spent much of the time on its earnings call Wednesday afternoon discussing this development.
As of Thursday's close, shares of Juno have lost more than 47 percent over the past twelve months.