Moderna has dosed the first participant in the Phase 2 study of the company's Omicron-specific booster candidate (mRNA-1273.529).
Moderna’s announcement follows a similar move by Pfizer and BioNTech, which have also begun a clinical trial of an Omicron vaccine candidate in healthy adults 18-55 years of age.
In the case of Moderna, the company said the Omicron trial will be an extension of an earlier study that will evaluate the immunogenicity, safety, and reactogenicity of mRNA-1273.529 as a single booster dose in adults aged 18 years and older. The company plans two cohorts: individuals who previously received the two-dose primary series of mRNA-1273 with the second dose being at least six months ago (cohort 1), or who have received the two-dose primary series and a 50-µg booster dose of mRNA-1273 with the booster dose being at least three months ago (cohort 2). Participants in both cohorts will receive a single booster dose of mRNA-1273.529.
Moderna said it expects to enroll approximately 300 participants into each cohort of this study, which will be conducted at up to 24 sites in the U.S. Additionally, Moderna is evaluating the inclusion of mRNA-1273.529 in its multivalent booster program.
Neutralizing antibody study
Moderna also said it published study results on neutralizing antibody data against the Omicron variant six months following a booster dose in The New England Journal of Medicine. “While Omicron neutralization had declined 6.3-fold from peak titers at day 29 post-boost, levels remained detectable in all participants. Neutralizing titers against Omicron declined more rapidly than titers against the ancestral strain of the virus (D614G), which declined 2.3-fold over the same time period,” the company said.
The data on neutralizing antibodies came from 20 booster recipients each of mRNA-1273 at the 50-µg and 100-µg dose levels, multivalent candidate mRNA-1273.211 at the 50-µg and 100-µg dose levels, and multivalent candidate mRNA-1273.213 at the 100-µg dose level. Neutralizing antibodies against Omicron were assessed in a pseudovirus neutralization titer (ID50) assay (PsVNA) conducted at laboratories established by the National Institute of Allergy and Infectious Diseases' (NIAID) Vaccine Research Center and Duke University Medical Center.