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Chimerix Stock Plunges After Anti-Infection Drug Fails Phase 3 Trial

Xconomy Raleigh-Durham — 

A drug meant to fight a broad spectrum of viruses has failed a key study in the prevention of a potentially fatal infection in transplant patients, crushing the stock price of the drug’s developer, Chimerix.

Durham, NC-based Chimerix (NASDAQ: CMRX) said Monday that its drug brincidofovir did not meet a Phase 3 study goal of preventing cytomegalovirus infection in stem cell transplant patients through 24 weeks following the transplant. Of those who received the Chimerix drug, fewer developed CMV infections while on the drug. Those findings were consistent with Phase 2 study results.

But that wasn’t enough for a successful trial, because the patient group receiving brincidofovir, in a 10-week period off of the drug, showed an increase in CMV infections compared against the placebo group. Also, more patients in the group receiving the drug died, but Chimerix said that the increase in patient deaths was not statistically significant.

Chimerix’s stock plunged on the news, dropping more than 81 percent to $6.55 as of 2:30 p.m.

In a conference call, Chimerix executives said the company is still evaluating the data and plans to present full results at the tandem meetings for the Center for International Blood & Marrow Transplant Research and the American Society for Blood and Marrow Transplantation, scheduled for February in Honolulu, HI.

“Given that we have only top-line results to date, we have much work to do to understand why this trial was not successful,” Garrett Nichols, Chimerix’s chief medical officer said.

The company said its preliminary analysis suggests that the increase in CMV infections and patient deaths stem from confirmed cases of graft-versus-host-disease (GVHD), a sometimes fatal complication in which newly transplanted donor cells attack the body of the transplant recipient. Chimerix says that both GVHD and the use of corticosteroids are risk factors for late CMV infection that occurs after transplant recipients stop receiving the antiviral drug.

Chimerix does not yet have any products on the market. Brincidofovir is the most advanced compound in the company’s pipeline. Chimerix developed the drug as an antiviral that the company hoped would target a wide range of viruses, comparable to the Gilead Sciences (NASDAQ: GILD) drug cidofovir, but without the risk of kidney damage associated with the Gilead drug. Developed as a pill, the Chimerix drug is also easier to give to patients than the intravenously administered Gilead drug.

Brincidofovir entered the spotlight last year when the drug was pressed into emergency use treating Ebola patients. Chimerix dropped plans for an Ebola clinical trial not because of problems with the drug, but because it could not enroll enough patients for the trial.

The failure in CMV could complicate Chimerix’s study of brincidofovir in other applications. Brincidofovir is currently in a separate Phase 3 trial as a treatment for adenovirus, which is usually held in check in healthy people but can become deadly in patients with weakened immune systems, such as those undergoing transplant procedures. Asked about plans to treat adenovirus, Chimerix CEO Michelle Berrey said on the conference call that the company would continue with trials but the company needs to meet with the FDA before proceeding with a new drug application. There are currently no FDA-approved treatments for adenovirus.

Berrey said Chimerix would also continue an animal study evaluating the drug as a potential smallpox countermeasure. The Biomedical Advanced Research and Development Authority is funding Chimerix’s smallpox research through a $435 million contract. In October, Chimerix announced that all of the rabbits in the company’s smallpox animal study survived. On Monday, Berrey told analysts that the company hopes to enter negotiations with the government on a stockpiling agreement for the drug.

Chimerix is halting further enrollment in two separate late-stage studies evaluating brincidofovir’s ability to prevent CMV in kidney transplant patients until it gets complete data from the failed clinical trial. Patients who are already enrolled will continue in the studies.

Berrey said that Chimerix has enough funds to continue its brincidofovir research. Through the third quarter, the company reported $378.4 million in capital.