CMV Vaccine Trials: Moderna’s CMV mRNA Vaccine Enters Phase III

CMV Vaccine Trials: Moderna’s CMV mRNA Vaccine Enters Phase III

Moderna’s CMV vaccine has progressed to the Phase III clinical trial stage.

Moderna has been testing an experimental mRNA vaccine aimed at combating the human cytomegalovirus (CMV), which poses significant health risks to newborns and immunocompromised patients.

In a recent study published by Weill Cornell Medicine in the Journal of Infectious Diseases, researchers have reported the potential of Moderna’s experimental mRNA vaccine in protecting adults against CMV, which could potentially also stop the transmission of the virus from mothers to their infants during pregnancy.

The study compared the immune responses evoked by Moderna’s mRNA vaccine to those generated by a previous vaccine candidate, namely, the MF59-adjuvanted glycoprotein B (gB) proten subunit vaccine (gB/MF59) developed by Sanofi. The team used the data and patient samples from a gB/MF59 Phase II trial in adolescent girls as a benchmark to assess the new mRNA-based vaccine. The comparison is particularly important as gB/MF59 demonstrated promise in Phase II clinical trials but did not advance to Phase III. Moderna’s vaccine not only targets gB but also incorporates a second target, a five-unit protein complex vital for the virus’ ability to infect epithelial cells in the mouth and nose.

Moderna’s CMV vaccine demonstrated superior capability in preventing the virus from infecting cells in the mouth and nose — key entry points for the virus — and in triggering the immune system to eliminate CMV-infected cells.

“We learned that the newer vaccine has the potential to be more effective than a previous CMV vaccine candidate because some of the functional immune responses it elicits are higher in magnitude,” said senior author Dr. Sallie Permar, the chair of the Department of Pediatrics and Nancy C. Paduano Professor in Pediatrics at Weill Cornell Medicine, in a news release.

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CMV infection is the leading cause of congenital infections affecting approximately one in every 200 newborns. During pregnancy, CMV infection is responsible for causing severe birth defects and brain damage in newborns.

However, the development of an effective vaccine that can target CMV infection has been extremely challenging. The progress of Moderna’s vaccine to Phase III clinical trials is a historic milestone as it is the first CMV vaccine candidate to reach this advanced stage of testing.

“After more than 50 years of research, we are closer than ever to having a licensed CMV vaccine,” Permar said.

History of Vaccine Development for CMV Infections

1960s to 1970s: This period marked the beginning of the effort toward understanding the CMV virus as it was recognized to be a significant cause of congenital infection and disease.

1980s: With developments in virology and immunology, the structure, genetics and the human body’s response to the infection were studied more closely, which provided the foundation for vaccine development in future.

1990s: The earliest vaccine development efforts were on live attenuated vaccines and the targeting of specific CMV proteins such as gB.

2000s: Many vaccine candidates were tested in this decade, some of which include:

  • The gB/MF59 vaccine targeted CMV gB along with the MF59 adjuvant and demonstrated promise in early clinical trials; it was one of the first vaccines to advance to Phase II trials.
  • The Towne vaccine was a live attenuated vaccine that was considered owing to its safety and immunogenicity in healthy adults and CMV-seronegative recipients of kidney transplants from seropositive donors.

2010s to 2020s: CMV vaccine research made considerable progress because of novel vaccine technologies such as mRNA vaccine platforms, which subsequently helped in the rapid development of COVID-19 vaccines and has been responsible for Moderna’s CMV vaccine too.

Related: Pneumococcal Vaccination for Adults: Conversation with Vaccine Scientists Dr. Heather Platt and Dr. Ulrike Buchwald from Merck – Xtalks Life Science Podcast Ep. 140

Challenges and Future Directions for CMV Vaccine Research

The development of an effective CMV vaccine, including the requirement for a vaccine that is safe and effective across many populations such as pregnant women, newborns and immunocompromised individuals, is still a challenge. CMV vaccine development has been a difficult endeavor owing to the virus’ complex immunobiology as well as its ability to establish latent infection and evade the immune system. Moreover, the durability of protection and vaccine’s ability to prevent congenital CMV infection continues to be an important topic of research.

There are ongoing studies that are not only focused on vaccine development but also on the improvement of diagnostic methods for the early detection of CMV infection, particularly in newborns. Furthermore, although antiviral treatments are available for managing CMV infection in immunocompromised patients, there is a need for new therapeutic options with fewer side effects.

As is evident from the history of CMV vaccine research, it has been a journey of incremental progress, evolving techniques and improving our understanding of viral immunology. We can only hope that Moderna’s Phase III trial is successful and helps reduce the burden of congenital CMV infections in the future. As we await further results from this trial, the healthcare and life sciences communities should be encouraged by the possibility of a CMV vaccine that could protect millions of newborns from this silent threat.

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