Clover Biopharmaceuticals (HKEX: 02197), a Shanghai-based biotechnology company, reported additional Phase I data for its RSV prefusion F protein vaccine candidate, SCB-1019, evaluating re-vaccination in older adults aged 60 to 85 who had previously received GSK's AREXVY at least two seasons prior, the company said on March 24. The updated analysis included 62 participants, up from 34 in an October 2025 readout, and reported immunogenicity findings described by the company as preliminary and exploratory.
Among the 62 participants randomized across three arms — 30 receiving SCB-1019, 26 receiving AREXVY, and 6 receiving saline placebo — heterologous re-vaccination with SCB-1019 induced RSV-A and RSV-B neutralizing antibody geometric mean titers approximately 60–80% higher than those observed with homologous AREXVY re-vaccination, according to the company. No changes in neutralizing antibodies were observed in the placebo group. A separate exploratory cross-trial comparison suggested that SCB-1019 re-vaccination restored neutralizing antibody titers to approximately 120–135% of peak levels seen after an initial AREXVY dose, while AREXVY re-vaccination restored titers to roughly 75% of those peak levels. The company also reported that homologous AREXVY re-vaccination induced an approximately 40-fold increase in antibodies against the T4-foldon trimerization tag used in AREXVY's construct. No safety data were disclosed in the announcement, and the company did not report the timepoint at which immunogenicity was assessed or provide dosing details for SCB-1019.
The randomized, placebo-controlled Phase I trial enrolled older adults in the United States who had received a prior AREXVY dose. The study was designed to assess safety, reactogenicity, and immunogenicity, though only immunogenicity findings were reported in this release. The data remain preliminary and are based on a small sample of 62 participants with unequal group sizes. Efficacy data were not reported, and no information on blinding status or independent data monitoring was disclosed. The cross-trial comparison to previously vaccinated individuals from a separate Clover study introduces additional uncertainty regarding assay standardization and population comparability.
SCB-1019 is a prefusion F protein-based RSV vaccine candidate. Clover is developing combination vaccines incorporating RSV with human metapneumovirus and parainfluenza virus type 3 antigens, with a Phase II trial that began enrollment in January 2026. AREXVY, GSK's approved RSV vaccine, demonstrated 82.6% efficacy against RSV-associated lower respiratory tract disease in its pivotal Phase III trial in adults 60 and older, though re-vaccination data have not supported policy recommendations for repeat dosing. Cross-trial comparisons are limited by differences in study design, duration, and patient populations.
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