The Moderna RSV vaccine was 83.7% effective against RSV-associated lower respiratory tract disease (RSV-LRTD) in adults age 60 and older, according to phase 3 trial data, the company reports.

mRNA-1345 is an investigational RSV vaccine that consists of a single mRNA sequence encoding for a stabilized prefusion F glycoprotein. The vaccine uses the same lipid nanoparticles (LNPs) as in the Moderna COVID-19 vaccines. The F glycoprotein is on the surface of the virus and is required for infection by helping the virus to enter host cells. It exists in two states, prefusion and postfusion. The prefusion conformation is a significant target of potent neutralizing antibodies and is highly conserved across both RSV-A and RSV-B subtypes.

According to positive topline data from Moderna’s ConquerRSV Phase 3 pivotal efficacy trial, mRNA-1345 met primary efficacy endpoints, including vaccine efficacy (VE) of 83.7% against RSV-LRTD) as defined by two or more symptoms, and 82.4% VE against RSV-LRTD defined by three or more symptoms.

The ConquerRSV trial studied approximately 37,000 adults 60 years or older in 22 countries, including the US (NCT05127434). The primary efficacy endpoints were based on two definitions of RSV-LRTD defined as either two or more symptoms, or three or more symptoms of disease. The interim analysis was based on 64 cases of RSV-LRTD with two or more symptoms, of which 55 occurred in the placebo group and 9 occurred in the mRNA-1345 group, and 20 cases of RSV-LRTD with three or more symptoms, of which 17 cases were observed in the placebo group compared with three cases observed in the mRNA-1345 group.

mRNA-1345 was well tolerated with no safety concerns identified, according to the company. Based on these results, Moderna intends to submit for regulatory approval in the first half of 2023.

“Today’s results represent an important step forward in preventing lower respiratory disease due to RSV in adults 60 years of age and older. These data are encouraging, and represent the second demonstration of positive phase 3 trial results from our mRNA infectious disease vaccine platform after, Spikevax, our COVID-19 vaccine. We look forward to publishing the full data set and sharing the results at an upcoming infectious disease medical conference,” said Stéphane Bancel, Moderna’s Chief Executive Officer.

Moderna RSV Vaccine Receives FDA Breakthrough Therapy Label

Based on the above data, mRNA-1345 was granted Breakthrough Therapy Designation by the US FDA in January 2023.

The FDA’s Breakthrough Therapy Designation is granted to expedite the development and review of drugs that are intended to treat a serious condition, and when preliminary clinical evidence indicates the drug or vaccine may demonstrate substantial improvement over available therapy on a clinically significant endpoint(s).1

“The FDA’s Breakthrough Designation for mRNA-1345 further emphasizes the significant health impact of RSV in older adults and the high unmet need,” said Stéphane Bancel, Chief Executive Officer of Moderna. “With this designation, we look forward to productive conversations with the FDA in the hopes of bringing our RSV vaccine candidate for older adults to the market safely and quickly. Moderna’s mRNA platform has now demonstrated two positive Phase 3 infectious disease trial results and we continue to advance a portfolio of respiratory mRNA vaccines targeting the most serious diseases. We are grateful to the FDA for this designation.”

mRNA-1345 was previously granted Fast Track designation by the FDA in August 2021. Moderna intends to submit a license application for regulatory approval in the first half of 2023.