Clover Biopharmaceuticals (Clover) released additional interim data from its ongoing U.S. Phase I study comparing heterologous revaccination with its RSV PreF candidate SCB-1019 against homologous revaccination with GSK’s AREXVY in adults aged 60–85 years who had received an initial AREXVY dose at least two seasons earlier.
The analysis covers 62 participants: 30 received SCB-1019, 26 received AREXVY, and 6 received saline placebo. Key findings include:
• Immunogenicity: SCB-1019 heterologous revaccination produced approximately 60–80% higher geometric mean titers (GMTs) of RSV-A and RSV-B neutralizing antibodies (nAbs) versus AREXVY homologous revaccination, while the placebo group showed no meaningful change.
• Benchmark comparison: Cross-trial evaluation against Clover’s previous study in RSV vaccine-naïve older adults indicated SCB-1019 restored RSV-A and RSV-B nAb GMTs to roughly 120–135% of the peak levels achieved after an initial AREXVY dose. In contrast, AREXVY revaccination recovered only about 75% of those peak titers.
• Off-target response: AREXVY homologous revaccination triggered an approximately 40-fold rise in antibodies targeting the T4-foldon trimerization tag incorporated in the GSK vaccine; SCB-1019 showed no such increase.
Market context underscores the potential impact: over 40% of U.S. adults aged 60 and above—about 15.00 million doses—have already received a protein-based RSV vaccine, yet no formal revaccination guidance exists despite evidence of waning protection. Clover’s data suggest its RSV+hMPV±PIV3 combination candidates could address both durability and breadth of protection; these candidates entered Phase II testing in January 2026.
Clover advises shareholders and prospective investors to exercise caution when trading the company’s shares.
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