P-1485. Safety and Immunogenicity of mRNA-1982 and mRNA-1975, mRNA Vaccine Candidates for Prevention of Lyme Disease in Healthy Adults: Interim Results of a Phase 1/2, Randomized, Observer-Blind, Placebo-Controlled, Dose-Ranging Trial

Abstract Background The incidence of Lyme disease, caused by infection with Borrelia bacteria, continues to rise globally. Previously developed Lyme disease vaccines based on Borrelia OspA antigens elicited antibody responses that correlated with protection; however, no Lyme disease vaccine is currently available for use in humans. Two investigational mRNA vaccines encoding OspA antigens and formulated in a lipid nanoparticle are in development: a monovalent vaccine (mRNA-1982) that covers serotype 1, and a heptavalent vaccine (mRNA-1975) that covers serotypes 1-7. Methods This ongoing Phase 1/2, randomized, observer-blind, placebo-controlled dose-ranging trial in healthy adults 18-70 years of age evaluated the safety and immunogenicity of mRNA-1982 and mRNA-1975 at up to 4 dose levels administered as a 3-injection series at 0, 2, and 6 months (NCT05975099). An interim analysis was conducted with follow-up through 28 days after the 3rd injection for safety and reactogenicity evaluation. Immunogenicity was evaluated by serotype-specific anti-OspA IgG binding antibody responses and by levels of LA-2 equivalent antibody (serotype 1 only). Results At the interim analysis, 745 of 806 enrolled participants completed the 3-injection study vaccine series. Approximately 1% of enrolled participants were seropositive at baseline for prior Borrelia infection. Both mRNA-1982 and mRNA-1975 elicited predominantly mild to moderate reactogenicity that was dose-dependent and increased with each successive injection, with no safety concerns identified. Serotype-specific anti-OspA IgG binding antibody geometric mean-fold rise from baseline and proportions of participants with high levels of LA-2 equivalent antibody responses (≥75% and ≥90% LA-2 inhibition) increased in a dose-dependent manner and with each successive injection across the vaccine groups, compared with no increase in the placebo group. Conclusion Interim data from this ongoing Phase 1/2 trial show that both mRNA-1982 and mRNA-1975 are generally safe and elicit dose-dependent reactogenicity and immunogenicity that increased with each of 3 successive injections. These data will inform the product(s), regimen(s) and dose range(s) to be evaluated in future clinical trials. Disclosures Nina H. Lin, MD, Moderna, Inc: Stocks/Bonds (Public Company) Christina Dold, PhD, Moderna: Stocks/Bonds (Public Company) Meredith Finn, PhD, Moderna: Stocks/Bonds (Public Company) Jacqueline Dooley, BA, Moderna: Stocks/Bonds (Public Company) Rujun Teng, MS, Moderna Inc.: Advisor/Consultant Emma Viscidi, PhD, MHS, ModernaTX: Employee|ModernaTX: Stocks/Bonds (Public Company) Anthony Rizk, PharmD, MBA, Moderna, Inc.: Employee of Moderna, Inc.|Moderna, Inc.: Stocks/Bonds (Public Company) Haixing Wang, PhD, Moderna, Inc.: Stocks/Bonds (Public Company) Doran Fink, MD, PhD, ModernaTX, Inc.: Employee|ModernaTX, Inc.: Stocks/Bonds (Public Company)