On Monday, Aduro Biotech (ADRO) fell as much as 22% after the company announced that a patient tested positive for listeria. Due to this development the FDA had to place the clinical trials on a partial hold. The clinical trials placed on clinical hold are those with the LADD program. LADD means the Listeria-based immunotherapy construct programs. 

What does this partial trial hold mean? The partial trial hold means that no new patients can be recruited into the LADD trials, but those who are already taking the drug can still do so. These patients have been taking the drug for six months or more, and they are allowed to continue to receive treatment. The partial hold will give time for the FDA to evaluate further the recent development with respect to the single patient in the study with listeria. 

The listeria was found in a blood culture sample of a patient being treated with pancreatic cancer. The patient was immediately given antibiotics, and has since been tested again for any listeria. After subsequent tests there has been no listeria in the patient. While it seems that this issue may be resolved quickly, it all depends how fast the FDA moves. Also, if the FDA has reason to believe that patients are at risk they could place a full clinical hold at any moment. 

Aduro is quickly working with the FDA to resolve the issue, and hopefully will be able to start recruitment again. They will even have to take into account new study modification protocols such as administering antibiotics to all those patients that have completed the LADD trials. Even if things were to sour with the LADD programs, Aduro has backup drugs. Two other types of drugs it has are the STING drug program, and B Select Monoclonal antibodies program.