Aduro slips after trial patient comes down with a dangerous infection

Aduro CEO Stephen Isaacs

Aduro BioTech ($ADRO), developing an immunotherapy combination treatment for cancer, watched its share price dip on Tuesday after quietly disclosing that a trial patient developed a serious infection tied to the company's re-engineered bacterial treatment.

The biotech's top program is a combination of GVAX and CRS-207, the latter of which is a cancer therapy created by rewiring the bacterium Listeria to safely seek out malignant cells and spur an immune attack. But in the company's ongoing Phase IIb trial in pancreatic cancer, one patient came down with listeriosis, a Listeria-caused infection that can be deadly for people with compromised immune systems.

Aduro buried the disclosure on page 31 of its standard quarterly SEC filing, writing a one-paragraph explanation that was eventually ferreted out by investors, who sent the company's share price down about 14% on Tuesday morning. The company explained that the infection has since cleared up, but the issue qualified as a serious adverse event, reaching Grade 3 on a one-to-5 scale with 5 meaning death.

"With respect to this event, our understanding is that, in violation of the protocol, the patient's central line port had been accessed during infusion of CRS-207 being given through a separate line," the company said. Weeks later, that patient developed symptoms consistent with listeriosis and tested positive for Listeria monocytogenes at the site of infusion, according to Aduro. All other blood samples turned up negative, and the company treated the patient with antibiotics and resumed dosing thereafter, Aduro said.

The worry, for investors, is that the FDA might clamp a clinical hold on the program to ensure Aduro's Listeria-based therapy is working as promised. The company says CRS-207 is safe for administration thanks to a proprietary process by which scientists delete two genes responsible for Listeria's virulence, but if patients start turning up with listeriosis, the treatment could be in trouble.

A similar issue cropped up for Advaxis ($ADXS) and its vaccine for HPV-related cancer. Last month, the company revealed that one patient in its clinical program had trace amounts of Listeria monocytogenes two years after dosing, leading the FDA to put its four ongoing trials on hold.

- read the filing