CLOVER BIO-B(02197) announced that the Phase I clinical trial in the United States for repeated administration of RSV vaccine in elderly population has obtained more positive data.

CLOVER BIO-B (02197) announced that its respiratory syncytial virus (RSV) pre-fusion F protein (PreF) candidate vaccine (SCB-1019) has obtained additional positive data from a Phase I clinical trial conducted in the United States. The clinical trial targeted elderly subjects (60-85 years old) who had received the GSK RSV vaccine AREXVY at least two seasons before enrollment, and compared the efficacy of repeated doses of SCB-1019 and AREXVY head-to-head. Subjects were randomly assigned to receive either the heterologous repeat candidate vaccine SCB-1019 (Clover Bio's pre-fusion F protein), the homologous repeat vaccine AREXVY (GSK pre-fusion F protein), or a saline placebo. The study evaluated safety, reactogenicity, and immunogenicity. The clinical data presented in this announcement are based on 62 subjects, while results from October 2025 were from 34 subjects. Immune response analysis has been completed for all enrolled subjects, and preliminary and exploratory results summary for 62 subjects (30 who received SCB-1019, 26 who received AREXVY, and 6 who received saline placebo) are as follows: Compared to homologous repeat with AREXVY, the heterologous repeat group with SCB-1019 showed an approximately 60-80% increase in geometric mean titers (GMT) of neutralizing antibodies (nAb) for RSV-A and RSV-B; no significant changes in RSV neutralizing antibodies were observed in the placebo group; exploratory cross-trial comparisons with Clover Bio's previous clinical study of initial dose of AREXVY in elderly individuals not previously vaccinated against RSV showed that heterologous repeat with SCB-1019 could restore the neutralizing antibody GMT levels for RSV-A and RSV-B to approximately 120%-135% of the peak levels after initial dose of AREXVY, while homologous repeat with AREXVY in this exploratory cross-trial study could only restore to about 75% of peak levels; homologous repeat with AREXVY could result in a 40-fold increase in "non-specific antibodies" induced by the T4-foldon trimer tagging construct. Currently, over 40% of adults in the United States aged 60 and older who are eligible for RSV vaccination have received a first dose of protein-based RSV vaccine (total dose of approximately 15 million doses). Observations show a gradual decrease in protective efficacy after the first dose, and current clinical data on RSV vaccines do not support recommendations for repeated vaccination. Clover Bio's existing clinical data suggest that their RSV+hMPVPIV3 combined vaccine has the potential to restore RSV protective efficacy in this population, while also expanding protection against hMPVPIV3. The RSV+hMPVPIV3 combined vaccine has enrolled its first subjects in January 2026 and is currently in Phase II clinical trials.