A randomized, double-blind phase I clinical trial of two recombinant dimeric RBD COVID-19 vaccine candidates: safety, reactogenicity and immunogenicity

  1. Sonia PĂ©rez-RodrĂ­guez
  2. Meiby de la Caridad Rodríguez-González
  3. Rolando Ochoa-Azze
  4. Yanet Climent-Ruiz
  5. Carlos Alberto González-Delgado
  6. Beatriz Paredes-Moreno
  7. Carmen Valenzuela-Silva
  8. Laura RodrĂ­guez-Noda
  9. Rocmira Perez-Nicado
  10. Raúl González-Mugica
  11. Marisel MartĂ­nez-PĂ©rez
  12. Belinda Sánchez-Ramírez
  13. Tays Hernández-García
  14. Alina DĂ­az-Machado
  15. Maura Tamayo-RodrĂ­guez
  16. Alis MartĂ­n-Trujillo
  17. Jorman Rubino-Moreno
  18. Anamary Suárez-Batista
  19. Marta Dubed-EchevarrĂ­a
  20. MarĂ­a Teresa PĂ©rez-Guevara
  21. Mayté Amoroto-Roig
  22. Yanet Chappi-Estévez
  23. Gretchen Bergado-Báez
  24. Franciscary Pi-Estopiñán
  25. Guang-Wu Chen
  26. Yuri Valdés-Balbín
  27. Dagmar GarcĂ­a-Rivera
  28. Vicente VĂ©rez-Bencomo
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Abstract

Background

The Receptor Binding Domain (RBD) of the SARS-CoV-2 spike protein is the target for many COVID-19 vaccines. Here we report results for phase 1 clinical trial of two COVID-19 vaccine candidates based on recombinant dimeric RBD (d-RBD).

Methods

We performed a randomized, double-blind, phase I clinical trial in the National Centre of Toxicology in Havana. Sixty Cuban volunteers aged 19-59 years were randomized into three groups (20 subjects each): 1) FINLAY-FR-1 (50 mcg d-RBD plus outer membrane vesicles from N. meningitidis ); 2) FINLAY-FR-1A-50 mcg d-RBD (three doses); 3) FINLAY-FR-1A-25 mcg d-RDB (three doses). The FINLAY-FR-1 group was randomly divided to receive a third dose of the same vaccine candidate (homologous schedule) or of FINLAY-FR-1A-50 (heterologous schedule). The primary outcomes were safety and reactogenicity. The secondary outcome was vaccine immunogenicity. Humoral response at baseline and following each vaccination was evaluated using live-virus neutralization test, anti-RBD IgG ELISA and in-vitro neutralization test of RBD:hACE2 interaction.

Results

Most adverse events were of mild intensity (63.5%), solicited (58.8%), and local (61.8%); 69.4% with causal association with vaccination. Serious adverse events were not found. The FINLAY-FR-1 group reported more adverse events than the other two groups. After the third dose, anti-RBD seroconversion was 100%, 94.4% and 90% for the FINLAY-FR-1, FINLAY-FR-1A-50 and FINLAY-FR-1A-25 respectively. The in-vitro inhibition of RBD:hACE2 interaction increased after the second dose in all formulations. The geometric mean neutralizing titres after the third dose rose significantly in the group vaccinated with FINLAY-FR-1 with respect to the other formulations and the COVID-19 Convalescent Serum Panel. No differences were found between FINLAY-FR-1 homologous or heterologous schedules.

Conclusions

Vaccine candidates were safe and immunogenic, and induced live-virus neutralizing antibodies against SARS-CoV-2. The highest values were obtained when outer membrane vesicles were used as adjuvant.

Trial registry

<ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://rpcec.sld.cu/en/trials/RPCEC00000338-En">https://rpcec.sld.cu/en/trials/RPCEC00000338-En</ext-link>

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