Drug Development

New Listeria fears spotlighted as Aduro’s CRS-207 is slapped with partial hold


Aduro CEO Stephen Isaacs

Nagging fears that Aduro Biotech’s cancer vaccine CRS-207 could trigger serious Listeria infections mushroomed into a severe setback on Monday morning as the biotech reported that it had to halt enrollment in all of its clinical studies using that technology. The partial hold was instituted by the FDA after a patient tested positive for Listeria, which is suspected to be CRS-207, Aduro’s lead cancer vaccine.

CRS-207 is made up of reengineered Listeria monocytogenes — removing genes in order to disarm the bacteria — that express mesothelin, sparking an immune response to a protein concentrated on cancer cells. Aduro has matched it with another cancer vaccine, GVAX, hoping to provide a one-two punch against cancer, with an option to add on additional drugs to continue to build an attack on cancer cells.

Aduro’s shares $ADRO were hammered earlier this year by the failure of a combo study for pancreatic cancer. And the stock dropped 12% in pre-market trading on Monday.

This isn’t the first time that Aduro has had to deal with Listeria fears. Last fall its stock briefly tumbled when a patient taking the therapy — which is supposed to be reengineered to prevent infections — developed Listeria. That news was disclosed in a SEC filing, triggering fears that a hold could be on the way for Aduro. This second case raises fresh concerns that the drug may not have been completely disarmed, as promised.

The new setback came as a surprise to a number of analysts, who had expected that Aduro would be reporting results from a triple combo study of CRS-207, GVAX and Bristol-Myers Squibb’s Opdivo for pancreatic cancer. That trial and others which are fully enrolled will continue on schedule. Trials that have been delayed include a Phase I ovarian cancer study as well as a glioblastoma trial.

In a call with analysts, CEO Stephen Isaacs heavily emphasized that this is a partial hold after the second Listeria case seen in 350 treated patients. R&D chief Dirk Brockstedt added that the company believes that it’s “likely” that the strain discovered in the female patient is ‘207. And both emphasized that they are preparing to institute changes to the trial, including a modification of the trial protocols with a revision in antibiotic treatment and their surveillance of the patients after treatment.

“We’re optimistic this is going to be resolved and we’re doing all we can to resolve it,” Isaacs summed up.

Listeria was detected on an “indwelling port” used on devices, and some analysts are speculating that patients with such ports are likely to be barred from treatment to reduce the risk of infection.

In their statement, Aduro reported:

Aduro is working with the FDA to lift the partial hold so as to resume new patient enrollment in its LADD clinical trials. The company is revising study protocols in accordance with feedback from the agency, including the modification of antibiotic administration following treatment, extended patient surveillance, and, as a pre-emptive measure, exclusion of patients who are on or will receive certain immune-suppressive treatments or who have certain prosthetic devices. Aduro will be providing proposed revisions to the protocols, patient consent forms, and investigator brochures to the agency later this week.

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