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Meissa Vaccines Begins Study of RSV Vaccine Candidate in Seronegative Children

· No vaccine is currently approved to protect against respiratory syncytial virus (RSV)

· RSV is the leading cause of infant hospitalization in the United States and is considered the “missing” pediatric vaccine

· Previous clinical data in seropositive adult and pediatric participants showed MV-012-968 was well-tolerated, appropriately attenuated, and stimulated RSV-specific mucosal IgA, despite pre-existing immunity to RSV

REDWOOD CITY, Calif., June 30, 2021 – Meissa Vaccines (“Meissa”), a biotechnology company developing vaccines to prevent serious viral respiratory infections, announced today the first seronegative participants have received MV-012-968, Meissa’s intranasal live attenuated RSV vaccine candidate, in a Phase 1c study in infants and young children. The study is enrolling up to 45 participants between the ages of six and 24 months at three sites in the U.S. to evaluate the safety and immunogenicity of MV-012-968 ( Identifier: NCT04909021). Meissa is developing MV-012-968 as a needle-free, adjuvant-free vaccine to protect infants and at-risk, older adults from respiratory syncytial virus (RSV).

RSV is a leading cause of respiratory infections such as bronchiolitis and viral pneumonia in infants. In the United States, approximately 1% of infants are hospitalized because of RSV each year. Globally in children under 5 years of age, RSV causes more than 66,000 deaths per year and approximately three million hospitalizations (Anderson 2013). Since the discovery of RSV in 1956, no vaccine has been approved for prevention.

“We believe that our intranasal live attenuated RSV vaccine candidate, developed on Meissa’s AttenuBlockTM vaccine platform, offers the potential to finally immunize against RSV, which has evaded other vaccine technologies for more than 60 years,” said Martin Moore, Ph.D., CEO and cofounder of Meissa Vaccines. “We have initiated this study in seronegative infants and young children based on supportive data from studies in seropositive adults and children showing MV-012-968 is well-tolerated and induces mucosal (IgA) antibodies, which protect against RSV infection. The development of a safe and effective RSV vaccine is a significant global health priority that could save thousands of lives and protect the health of millions of people around the world.”

Preliminary data from a Phase 1b study in RSV-seropositive participants between the ages of 15 and 59 months showed that a single intranasal dose of either 10^4 or 10^5 PFU of MV-012-968 was well-tolerated, did not result in detectable shed vaccine virus, indicating appropriate attenuation, and stimulated RSV-specific mucosal IgA in a dose-dependent manner ( Identifier NCT04444284). Data from a completed Phase 1a study showed a 10^6 PFU dose of MV-012-968 was safe and well-tolerated among healthy RSV sero-low adults and resulted in no detectable nasal shedding of infectious vaccine virus, while inducing RSV-specific mucosal IgA in the majority of vaccine recipients, despite pre-existing immunity to RSV ( Identifier NCT04227210).

About MV-012-968

MV-012-968 was generated using the company’s proprietary AttenuBlockTM synthetic biology platform with the goal of creating safe, potent, stable, and cost-effective intranasal vaccines. Intranasal vaccines generate both serum (IgG) antibodies that circulate in the blood and mucosal (IgA) antibodies in the nasal cavity. Mucosal antibodies are important for blocking infection and transmission of respiratory viruses.

About AttenuBlockTM Platform

Meissa’s AttenuBlock platform incorporates 10 years of research and development at Emory University, where researchers employed rational and precise codon deoptimization and other genetic strategies to modernize live attenuated vaccines (Nature Communications, 2016). AttenuBlock is a live attenuated vaccine platform designed to solve prior vaccinology obstacles, such as suboptimal immune responses, over- and under-attenuation, and vaccine genetic instability.

About Meissa Vaccines

Meissa Vaccines was founded with a mission to protect people everywhere from life threatening respiratory viruses and a commitment to develop innovative technologies capable of delivering effective vaccines at a global scale. Meissa is advancing live attenuated vaccine candidates against respiratory syncytial virus (RSV), SARS-CoV-2 (COVID-19), and human metapneumovirus (hMPV). These vaccine candidates have been developed using the company’s proprietary AttenuBlockTM synthetic biology platform, which includes codon deoptimization and technologies exclusively licensed from Emory University and Children’s Healthcare of Atlanta. Meissa’s vaccine candidates are formulated to be delivered as a single, intranasal, adjuvant-free, needle-free dose and are designed to prevent infection and disease and generate a strong, durable immune response. Meissa is headquartered in Redwood City, Calif.

Meissa Contacts:

For Clinical Trials:

Corporate Contact: Bill Daly, Chief Business Officer, Meissa Vaccines,

For Media Only: Jessica Yingling, Ph.D., Little Dog Communications, +1.858.344.8091,


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