Aduro Biotech Inc. shares plummeted as much as 22% in premarket trade Monday after the company said a patient tested positive for listeria, prompting the Food and Drug Administration to place its clinical trials on partial clinical hold. The hold is directed at Aduro's listeria-based immunotherapy construct platform and will pause new patient enrollment, though nearly all current patients will continue to receive treatment, the company said. The patient who tested positive for listeria -- which causes food poisoning that can be deadly -- was given antibiotics and subsequent blood cultures tested negative for the infection, Aduro said. The company said it is working with the FDA to get the clinical trials back on track and is "revising study protocols in accordance with feedback from the agency," it said. The hold does not affect clinical trials for Aduro's other platform technologies. Aduro shares dropped 12.5% over the last three months, compared with a 1.6% drop in the S&P 500 .
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