Clover Bio-B announced positive additional data from its Phase I clinical trial in the United States for its respiratory syncytial virus (RSV) prefusion F protein (PreF) vaccine candidate, SCB-1019. The trial enrolled elderly subjects (aged 60–85) who had received GSK's RSV vaccine, AREXVY, at least two respiratory seasons prior to enrollment. It directly compared the effects of a booster dose of SCB-1019 against a booster dose of AREXVY. Subjects were randomized to receive either the heterologous booster candidate SCB-1019 (Clover's prefusion F protein), the homologous booster vaccine AREXVY (GSK's prefusion F protein), or a saline placebo. The study evaluated safety, reactogenicity, and immunogenicity. The newly released data is based on 62 subjects, whereas results from October 2025 were based on 34 subjects. Immunogenicity analysis for all enrolled subjects is complete. A summary of preliminary and exploratory results from the 62 subjects (30 receiving SCB-1019, 26 receiving AREXVY, and 6 receiving placebo) is as follows: Compared to the homologous AREXVY booster, the SCB-1019 heterologous booster group showed an approximate 60–80% increase in geometric mean titers (GMT) of RSV-A and RSV-B neutralizing antibodies (nAb). No significant changes in RSV neutralizing antibodies were observed in the placebo group. An exploratory cross-trial comparison with Clover's prior study of a first dose of AREXVY in RSV vaccine-naïve elderly individuals indicated that the SCB-1019 heterologous booster restored RSV-A and RSV-B neutralizing antibody GMTs to approximately 120%–135% of the peak level seen after the first AREXVY dose. In this same exploratory comparison, the homologous AREXVY booster only restored levels to about 75% of the peak. The homologous AREXVY booster induced an approximately 40-fold increase in "non-specific antibodies" originating from its T4-foldon trimer tag structure. Currently, among US adults aged 60 and over who are eligible for RSV vaccination, more than 40% have received an initial protein-based RSV vaccine dose (totaling approximately 15 million doses). While protection following the initial dose is observed to wane over time, clinical data for currently approved RSV vaccines does not yet support policy recommendations for booster vaccinations. Existing clinical data from Clover suggests that the company's RSV+hMPV±PIV3 combination vaccine candidate has the potential to restore RSV protection in this population while also extending protection to include hMPV and potentially PIV3. Clover's RSV+hMPV±PIV3 candidate completed enrollment of its first subject in January 2026 and is currently in Phase II clinical trials.
Comments