Sanofi and GlaxoSmithKline (GSK) announced a delay in their adjuvanted recombinant protein-based COVID-19 vaccine program to improve immune response in older adults. A Phase 1/2 study interim results showed an immune response comparable to patients who recovered from COVID-19 in adults aged 18 to 49 years, but a low immune response in older adults likely due to an insufficient concentration of the antigen, according to a press release.
The companies said they plan a Phase 2b study, which is expected to start in February 2021 with support from the Biomedical Advanced Research and Development Authority (BARDA), part of the Department of Health and Human Services’ Office of the Assistant Secretary for Preparedness and Response (ASPR). The study will include a proposed comparison with an authorized COVID-19 vaccine. If data are positive, a global Phase 3 study could start in Q2 2021. Positive results from this study would lead to regulatory submissions in the second half of 2021, delaying the vaccine’s potential availability from mid-2021 to Q4 2021.
The interim Phase 1/2 results showed a level of neutralizing antibody titers after two doses comparable to sera from patients who recovered from COVID-19, a balanced cellular response in adults aged 18 to 49 years, but insufficient neutralizing antibody titers in adults over the age of 50. The candidate showed transient but higher than expected levels of reactogenicity likely due to the suboptimal antigen formulation, with no serious adverse events related to the vaccine candidate. The most favorable results were observed in the group that tested the highest antigen concentration, combined with the GSK adjuvant, showing neutralization titers in 88 percent of participants.
The Phase 1/2 clinical study is a randomized, double blind and placebo-controlled study designed to evaluate the safety, reactogenicity and immunogenicity (immune response) of the COVID-19 vaccine candidate. A total of 440 healthy adults participated in the study, across 10 investigational sites in the United States. The participants received one or two doses of the vaccine candidate, or placebo at 21 days apart.
Sanofi’s recombinant technology and GSK’s pandemic adjuvant are established vaccine platforms that have been used in vaccines against influenza. The companies said the recombinant technology offers the advantages of stability at temperatures used for routine vaccines, the ability to generate high and sustained immune responses, and the potential to prevent virus transmission.
