mRNA Vaccine Shows Positive Interim Phase I Results

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Participants in two dosing cohorts in Moderna’s mRNA-1273 study reached or exceeded neutralizing antibody titers generally seen in convalescent sera.

Moderna announced positive interim clinical data from a Phase I study of mRNA-1273, its vaccine candidate against the SARS-CoV-2 virus. The results showed that all eight participants in the 25-µg and 100-µg dose cohorts reached or exceeded the levels of neutralizing antibody titers generally seen in blood samples from people who have recovered from COVID-19 after two doses of the vaccine.

In a May 18, 2020 press statement, the company reported dose-dependent increases in immunogenicity for the 25-µg, 100-µg, and 250-µg dose levels, and between prime and boost within the 25 µg and 100 µg dose levels. All participants ages 18–55 (n=15 per cohort) across all three dose levels seroconverted by day 15 after a single dose, the company reported.

At day 43-two weeks following the second dose-the 25-µg dose level showed binding antibodies at the levels seen in convalescent sera from people who have recovered from COVID-19. For those at the 100-µg dose level (n=10), levels of binding antibodies significantly exceeded the levels seen in convalescent sera. Samples are not yet available for remaining participants, the company said.

The available neutralizing antibody data for the first four participants the 25-µg and 100-µg dose level cohorts showed the vaccination elicited neutralizing antibodies in all eight participants at or above levels generally seen in convalescent sera at day 43, as measured by plaque reduction neutralization assays against live SARS-CoV-2.

The company reported in the press statement that mRNA-1273 was “generally safe and well tolerated, with a safety profile consistent with that seen in prior Moderna infectious disease vaccine clinical studies.”

Moderna reported it plans to change its Phase II study to 50-µg and 100-µg dose levels, with the goal of selecting a dose for pivotal studies. The Phase I study-led by the National Institute of Allergy and Infectious Diseases, part of the National Institutes of Health-will be amended to include a 50-µg dose level cohort across each of the three age groups. The company said it anticipates the dose for the Phase III study-expected to start in July 2020-to be between 25–100 µg.


The company also reported preclinical results from a viral challenge study in mice, which showed vaccination with mRNA-1273 prevented viral replication in the lungs of animals challenged with SARS-CoV-2.

Funding from the Biomedical Advanced Research and Development Authority within the Department of Health and Human Services, which supported the planning for the Phase II and Phase III studies of mRNA-1273, will support the execution of these studies, as well as the scale-up of manufacturing at Moderna and Lonza Ltd.

FDA granted fast-track designation to mRNA-1273 on May 12, 2020.

Source: Moderna