Moderna is halting development of an mRNA vaccine for congenital cytomegalovirus after its candidate failed to protect women from the virus in a large phase 3 trial, the biotech announced in a post-market Oct. 22 release.
While the mRNA-1647 vaccine was well-tolerated, the shot’s ability to prevent infection was well below the company’s target, ranging from 6% to 23% depending on how CMV cases are defined.
The phase 3 trial enrolled 7,454 women between the ages of 16 to 40 years from 13 countries. Congenital CMV occurs when an infant catches the virus from its mother during childbirth. The virus sits idle in many infected people, but can reactivate later in life. In babies, the virus can cause growth problems and hearing loss, among other potential complications.
The CDC estimates that more than 50% of adults have been infected by CMV by age 40.
“We are clearly disappointed by the failure to prevent primary infection because it means there is still no vaccine for the prevention of congenital CMV despite the many decades of work by the field,” Moderna President Stephen Hoge, M.D., said in the release.
The study “was particularly challenging,” Hoge said in a separate blog post, writing that the objective was “to prevent primary infection from a latent virus, rather than preventing symptomatic disease.”
“This makes this trial unique in our pipeline; it was the only clinical trial in which the prevention of primary infection was a primary endpoint,” the leader wrote.
Related
The company will continue to test if the vaccine protects against reactivated CMV in the context of a bone marrow transplant, Hoge added. That phase 2 trial is set to enroll around 224 patients and wrap up in August 2026.
Moderna said that it does not expect the discontinuation to impact its financial guidance for 2025 or its plans to breakeven in 2028.
The scrapped congenital CMV program and the targeting of mRNA vaccines by the federal government puts all the more pressure on Moderna’s oncology efforts to deliver. The biotech’s oncology head Kyle Holen, M.D., recently told Fierce at the European Society of Medical Oncology (ESMO) meeting that most of Moderna’s upcoming investigational new drug applications will be in cancer indications, not infectious disease.
At ESMO, the Big Biotech shared phase 1/2 data from 29 patients who received two doses of cancer vax mRNA-4359 in combination with Merck & Co.’s Keytruda, showing an objective response rate of 24% in evaluable patients. Based on the results, Moderna plans to expand mRNA-4359 into lung cancer, Holen told Fierce.
