Proof-Of-Concept Of A Low-Dose Unmodified Mrna-Based Rabies Vaccine Formulated With Lipid Nanoparticles In Human Volunteers: A Phase 1 Trial

Introduction: In a first-in-human study immune responses to rabies virus glycoprotein (RABV-G)-mRNA vaccine were dependent on the route of administration, necessitating specialized devices. Following successful preclinical studies with mRNA encapsulated in lipid nanoparticles (LNP), we tested an mRNA-LNP formulation (CV7202).Methods: In this phase 1, multi-center, controlled study in Belgium and Germany we enrolled 55 healthy 18-40-year-olds to receive intramuscular injections of 5 mu g (n = 10), 1 mu g (n = 16), or 2 mu g (n = 16) CV7202 on Day 1; subsets (n = 8) of 1 mu g and 2 mu g groups received second doses on Day 29. Controls (n = 10) received rabies vaccine, Rabipur, on Days 1, 8 and 29. Safety and reactogenicity were assessed up to 28 days post-vaccination using diary cards; immunogenicity was measured as RABV-G-specific neutralizing titers (VNT) by RFFIT and IgG by ELISA.Results: As initially tested doses of 5 mu g CV7202 elicited unacceptably high reactogenicity we subsequently tested 1 and 2 mu g doses which were better tolerated. No vaccine-related serious adverse events or withdrawals occurred. Low, dose-dependent VNT responses were detectable from Day 15 and by Day 29%, 31% and 22% of 1, 2 and 5 mu g groups, respectively, had VNTs >= 0.5 IU/mL, considered an adequate response by the WHO. After two 1 or 2 mu g doses all recipients had titers >= 0.5 IU/mL by Day 43. Day 57 GMTs were not significantly lower than those with Rabipur, which elicited adequate responses in all vaccinees after two doses. CV7202-elicited VNT were significantly correlated with RABV-G-specific IgG antibodies (r( )(2)= 0.8319, p < 0.0001).Conclusions: Two 1 mu g or 2 mu g doses of CV7202 were well tolerated and elicited rabies neutralizing antibody responses that met WHO criteria in all recipients, but 5 mu g had unacceptable reactogenicity for a prophylactic vaccine. (C) 2020 Published by Elsevier Ltd.