Moderna, Inc. announced positive interim Phase I clinical data of mRNA-1273, its vaccine candidate against SARS-CoV-2, led by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH).

Immunogenicity data are currently available for the 25 µg and 100 µg dose level after two doses (day 43) and at the 250 µg level after one dose (day 29). Dose dependent increases in immunogenicity were seen across the three dose levels, and between prime and boost within the 25 µg and 100 µg dose levels. All participants ages 18-55 across all three dose levels seroconverted by day 15 after a single dose. At day 43 at the 25 µg dose, levels of binding antibodies were at the levels seen in convalescent sera (blood samples from people who have recovered from COVID-19) tested in the same assay. At day 43, at the 100 µg dose, levels of binding antibodies significantly exceeded the levels seen in convalescent sera.  

At this time, neutralizing antibody data are available only for the first four participants in each of the dose level cohorts. Consistent with the binding antibody data, mRNA-1273 vaccination elicited neutralizing antibodies in all eight of these participants, as measured by plaque reduction neutralization (PRNT) assays against live SARS-CoV-2. The levels of neutralizing antibodies at day 43 were at or above levels generally seen in convalescent sera. mRNA-1273 was generally safe and well tolerated.

Preclinical results from a viral challenge study in mice conducted in collaboration with NIAID showed mRNA-1273 prevented viral replication in the lungs of animals challenged with SARS-CoV-2.

Based on the interim Phase I data, the Moderna-led Phase II study will be amended to study two dose levels, 50 µg and 100 µg, with the aim of selecting a dose for pivotal studies. The NIAID-led Phase I study is being amended to include a 50 µg dose level cohort across each of the three age groups. Moderna anticipates the dose for the Phase 3 study to be between 25 µg and 100 µg and expects Phase III trial initiation in July, subject to finalization of the clinical trial protocol.

Funding from BARDA within the U.S. Department of Health and Human Services, supported the planning for the Phase II and Phase III studies of mRNA-1273 and will also support the execution of these studies, as well as the scale-up of mRNA-1273 manufacturing both at the company’s facilities and that of its strategic collaborator, Lonza Ltd.