In short
MRNA encoding human cytomegalovirus UL131A is an investigational mRNA vaccine component studied for the prevention of cytomegalovirus (CMV) infection. It is part of the mRNA-1647 vaccine, which was tested in a Phase 3 trial involving 7,484 healthy participants aged 16 to 40 years. The trial has been completed, and the vaccine is not yet authorised as a medicine.
Key points
- Phase 3 trial completed in healthy participants aged 16 to 40 years.
- The trial enrolled 7,484 participants to evaluate efficacy, safety, and immunogenicity.
- The vaccine is given as a three-dose intramuscular injection schedule.
- The primary goal was to prevent primary CMV infection in CMV-seronegative female participants.
- There is currently no approved vaccine to prevent CMV infection.
- The trial was a randomised, observer-blind, placebo-controlled study.
What is MRNA encoding human cytomegalovirus UL131A?
MRNA encoding human cytomegalovirus UL131A is a messenger RNA (mRNA) molecule that carries the genetic instructions for making the UL131A protein of human cytomegalovirus (CMV). It is an investigational substance, meaning it is not yet authorised as a medicine. The substance is one of six mRNA components of the mRNA-1647 vaccine, alongside mRNA encoding CMV glycoprotein B, glycoprotein H, glycoprotein L, UL128, and UL130. The vaccine is being developed by Moderna Biotech Spain S.L.
How does MRNA encoding human cytomegalovirus UL131A work?
The substance is an mRNA molecule that instructs cells in the body to produce the UL131A protein found on the surface of cytomegalovirus. UL131A is part of a protein complex that the virus uses to enter human cells. By presenting this protein to the immune system, the vaccine aims to train the body to recognise and respond to CMV before a natural infection occurs. The mRNA-1647 vaccine combines six different CMV proteins to generate a broad immune response.
Which conditions is it used or studied for?
- Cytomegalovirus infection (CMV) — a common viral infection that spreads through saliva and other body fluids. Most infected people have no symptoms, but infection during pregnancy can pass to the unborn child and cause congenital CMV infection, which may lead to hearing loss, learning problems, or vision abnormalities.
How is MRNA encoding human cytomegalovirus UL131A given?
In the clinical trial, the mRNA-1647 vaccine containing this substance was given as an intramuscular injection. The vaccination schedule consisted of three doses, with the third injection followed by assessments starting 28 days later. The trial also included a placebo arm using sodium chloride 0.9% solution for injection.
What do the clinical trials show?
One Phase 3 trial (NCT05085366) has been completed. It was a randomised, observer-blind, placebo-controlled study that enrolled 7,484 healthy participants aged 16 to 40 years. The main goals were to demonstrate whether the vaccine can prevent primary CMV infection in CMV-seronegative female participants and to evaluate safety and reactogenicity on a three-dose schedule.
The trial measured primary CMV infection, defined as seroconversion from a negative to a positive result for serum IgG against at least one of four CMV antigens not encoded by the vaccine (pp150, pp28, pp52, pp38). Safety assessments included solicited adverse reactions through 7 days after each injection, unsolicited adverse events through 28 days after each injection, medically attended adverse events through 6 months after the last injection, and serious adverse events from consent through end of study.
What side effects are known?
The trial collected data on solicited adverse reactions through 7 days after each injection, including local reactions at the injection site and systemic reactions such as fever, muscle aches, and tiredness. The study also monitored unsolicited adverse events, medically attended adverse events, and serious adverse events throughout the follow-up period. Detailed side effect results from the completed trial have not been published in the provided sources.