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Moderna Shares Positive Early Coronavirus Vaccine Data

Moderna has announced positive interim clinical data for SARS-CoV-2 messenger RNA vaccine mRNA-1273. In all trial participants to date, the vaccine candidate led to seroconversion with binding antibody levels either at or above levels seen in convalescent sera. 

The vaccine was previously granted fast track designation by the US Food and Drug Administration and the potential scale-up of manufacturing for the vaccine has been funded by the US Biomedical Advanced Research and Development Authority (BARDA).

Data were from the phase 1 study led by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH). mRNA-1273 is an mRNA vaccine against SARS-CoV-2 encoding for a prefusion stabilized form of the Spike protein.

After 2 doses, across the 25 µg and 100 µg dose cohorts, mRNA-1273 triggered dose-dependent increases in immunogenicity.

Specific immunogenicity data are available for the 25 µg and 100 µg dose level after 2 doses, and at the 250 µg level after 1 dose. All participants across the 3 dose levels seroconverted by day 15 after the first vaccination.

For the first 4 participants in both the 25 µg and 100 µg dose level cohorts, neutralizing antibody data are also available. Vaccination elicited neutralizing antibodies in these 8 participants, as measured by plaque reduction neutralization assays.

The vaccine was found safe and well tolerated, and the firm reported a similar safety profile to past infectious disease vaccine studies. The only grade 3 adverse event in the 25 and 100 µg cohorts was a single incidence of erythema (redness) at the injection site.

In the 250 µg dose group, 3 participants experienced transient and self resolving adverse events. There were no grade 4 or serious adverse events reported.

In mouse models, mRNA-1273 stopped viral replication in the lungs of animals challenged with SARS-CoV-2. Neutralizing titers in human participants were consistent with those in mouse models.

The firm has adjusted its phase 2 study dosages in order to study 50 µg and 100 µg administration. Previously, Moderna was planning for the 600 participants to be assigned to receive placebo, 50 μg, or 250 μg of the vaccine in both vaccinations.

“These interim phase 1 data, while early, demonstrate that vaccination with mRNA-1273 elicits an immune response of the magnitude caused by natural infection starting with a dose as low as 25 µg,” said Tal Zaks, MD, PhD, Chief Medical Officer at Moderna, in a statement. “When combined with the success in preventing viral replication in the lungs of a pre-clinical challenge model at a dose that elicited similar levels of neutralizing antibodies, these data substantiate our belief that mRNA-1273 has the potential to prevent COVID-19 disease and advance our ability to select a dose for pivotal trials.”
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