China's RSV Vaccine Posts Positive Phase 1 Results

Clover Biopharmaceuticals, Ltd. today announced positive preliminary immunogenicity and safety data in the older adult cohort from its Phase 1 clinical trial evaluating SCB-1019, the company's bivalent RSV prefusion-stabilized F (PreF)-Trimer subunit vaccine candidate, which is based on Clover's Trimer-Tag vaccine technology platform.

Results indicate that SCB-1019 could potentially have a differentiated and favorable safety and reactogenicity profile compared to currently approved oil-in-water adjuvanted4 and/or mRNA5-based RSV vaccines.

"As the first RSV PreF vaccine candidate developed in China to enter the clinical trial stage and generate clinical data, SCB-1019 .... demonstrate broad and significant neutralizing antibody responses against both RSV-A and RSV-B as well as a favorable tolerability profile," said Joshua Liang, Chief Executive Officer & Board Director of Clover, in a press release on June 18, 2024.

"We look forward to the full clinical readout by the end of 2024 to support further development and strengthen our potentially differentiated profile for markets globally."

Preliminary results for RSV-neutralizing antibodies (nAbs) and safety for SCB-1019 at the selected dose level are summarized below:

Immunogenicity Results:

RSV-A nAbs: SCB-1019 induced geometric mean titers (GMTs) in RSV-A nAbs of up to 7,906 IU/mL compared to 1,078 IU/mL for placebo at Day 28.

RSV-B nAbs: SCB-1019 induced GMTs in RSV-B nAbs of up to 46,674 IU/mL compared to 12,185 IU/mL for placebo at Day 28.

Geometric Mean Fold Rise (GMFR): High baseline nAb titers at Day 0 (pre-vaccination), especially to RSV-B, were observed, potentially reflecting recent outbreaks near the clinical trial sites.

Thus, sub-analysis in subjects with the lowest quartile baseline nAb titers was performed: GMFRs for SCB-1019 were up to 8-fold for RSV-A nAbs and 11-fold for RSV-B nAbs at Day 28 compared to Day 0 (pre-vaccination). No increases in RSV-A or RSV-B nAbs were observed for the placebo on Day 28.

nAb results across both RSV-A and RSV-B appear to be in line or potentially favorable compared to other protein subunit RSV PreF vaccines.

Given that other monovalent RSV-A vaccines have previously observed lower immune responses and/or efficacy against RSV-B, we continue to support Clover's bivalent RSV-A/B approach, wrote the company.

Results further confirm that Clover's PreF antigens in SCB-1019 are in the stabilized prefusion and trimeric fo. This is additionally supported by exploratory immunogenicity results demonstrating significant increases in Site Ø and Site V nAb-competitive titers.

Safety & Reactogenicity Results: SCB-1019 was generally well-tolerated. Local and systemic adverse events (AEs) were generally mild and comparable to saline placebo. No serious adverse events, adverse events of special interest, or AEs leading to discontinuation were observed.

These preliminary results in older adults & elderly cohort (aged 60-85) are consistent with the positive results in younger adults (aged 18-59) announced earlier this year. 

As of June 18, 2024, the U.S. FDA has approved three RSV vaccines and one monoclonal antibody (Beyfortus) for infants for the 2024-2025 RSV season.