Vical’s Astellas-partnered CMV vaccine falls short again, this time in stem cell transplant recipients

After the cytomegalovirus (CMV) vaccine Astellas licensed from Vical failed in a phase 2 kidney transplant study, the developers' hopes for the shot rested on a phase 3 trial in hematopoietic stem cell transplant (HCT) recipients. Now, those ambitions have been shattered as well.

The vaccine, dubbed ASP0113, didn’t show a significant improvement in overall survival or reduction in CMV end-organ disease, missing the trial’s primary composite endpoint, the partners announced. The vaccine also missed secondary endpoints, which included time to first CMV presence and time to first use of antiviral therapy.

An Astellas media aide told FiercePharma that the company cannot comment on its future plans for ASP0113 as it's still assessing detailed trial data.

CMV, a type of herpes virus, infects more than half of all adults in the U.S. by age 40, according to the CDC. It usually remains latent but may become active in people with compromised immune systems. HCT and solid-organ transplant recipients, as well as infants born to mothers who first become infected during pregnancy, are at a high risk of developing severe CMV-related illness.

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Previously known as Transvax, ASP0113 is a bivalent DNA vaccine encoding CMV pp65 and gB antigens. It's designed to fight CMV infections in HCT and solid-organ transplant patients. Astellas licensed it from Vical in 2011 in a deal worth up to $130 million.

With orphan drug designations in those patient cohorts, the companies once had high hopes for the vaccine. But last September, the vaccine failed to best a placebo in fending off CMV in kidney transplant patients in a phase 2 study, wiping out its prospects in that group.

When the companies announced completion of the HCT phase 3 trial last October, Vical CEO Vijay Samant called the development “another exciting milestone,” adding that they looked forward to potentially commercializing the vaccine as a first-in-class therapy for CMV in HCT recipients. Now, in the wake of the failure, they'll either have to try another route or move on.

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While the drugmakers reported bad news for ASP0113, Vical also has a CMV vaccine intended for women before they become pregnant to reduce the chance of transmitting the virus to the fetus. The company said on its website that it has designed a phase 1 study for the shot and is evaluating whether to develop it independently or seek a partner.

New York-based Helocyte (formerly called DiaVax Biosciences) also has two CMV candidates in phase 2 development in HCT recipients—Triplex, a modified vaccinia Ankara-vectored CMV shot, and peptide vaccine PepVax. The National Cancer Institute is supporting both studies, and the Triplex test is expected to be completed this April.

Other than those candidates, VBI Vaccines’ preventative vaccine VBI-1501, developed using its enveloped virus-like particle technology, recently wrapped up a phase 1 test. Moderna also recently started human testing on its candidate dubbed mRNA-1647. VBI estimates that the prophylactic CMV vaccine market could exceed $1 billion annually.