Moderna Announces First Participants Dosed in Study Evaluating COVID-19 Booster Vaccine Candidates

Moderna, Inc. (Nasdaq: MRNA), a biotechnology company pioneering messenger RNA (mRNA) therapeutics and vaccines, today announced that the first participants have been dosed with the Company’s modified COVID-19 vaccines, designed to address the potential need for booster vaccine candidates, in an amendment to the ongoing Phase 2 clinical study.

mRNA-1273.351 encodes for the prefusion stabilized Spike protein of the SARS-CoV-2 variant B.1.351, first identified in the Republic of South Africa, and is being assessed as a booster vaccine to increase the breadth of response to emerging variants with key-receptor-binding domains (RBD) mutations. mRNA-1273.211 is a multivalent candidate which combines mRNA-1273, Moderna’s authorized vaccine against ancestral strains, and mRNA-1273.351 in a single vaccine, designed to elicit a broad immune response as both a primary series and when administered as a boost to those who have previously received mRNA-1273.

Previously published data has shown that vaccination with the Moderna COVID-19 Vaccine produced neutralizing titers against all key variants tested, including B.1.1.7, first identified in the UK, and B.1.351, with a 6-fold reduction in neutralizing titers against B.1.351. Out of an abundance of caution, Moderna is pursuing a clinical development strategy against these emerging variants. An amendment to the Phase 2 study will enroll 60 participants previously vaccinated with mRNA-1273 to receive a single booster dose of either:

• 20 µg of a variant-specific booster candidate, mRNA-1273.351, based on the B.1.351 variant first identified in the Republic of South Africa (N=20)
• 50 µg of mRNA-1273.351 (N=20)
• 50 µg of a multivalent booster candidate, mRNA-1273.211, which combines mRNA-1273, Moderna’s authorized vaccine against ancestral strains, and mRNA-1273.351 in a single vaccine (N=20)

In a previous protocol amendment, Phase 2 study participants vaccinated with mRNA-1273 have been offered a single 50 µg booster dose of mRNA-1273. Dosing in this protocol extension is ongoing.

In parallel, NIAID, part of the National Institutes of Health (NIH), will conduct a Phase 1 clinical trial to assess the monovalent and multivalent modified mRNA-1273 vaccines as a primary series in naïve individuals and as a booster vaccine in those previously vaccine with mRNA-1273. NIAID will initiate this study after receiving safe-to-proceed authorization from the FDA. NIAID will provide additional information when the trial begins. The clinicaltrials.gov identifier is NCT04785144.