Clover Biopharmaceuticals has received U.S. FDA IND clearance and completed enrollment of the first participants in a Phase I revaccination clinical trial for SCB-1019, its non-adjuvanted bivalent RSV vaccine candidate. The milestone represents a significant step forward for the company's respiratory vaccine program, which aims to address critical gaps in current RSV vaccination strategies.
Head-to-Head Comparison Shows Promise
The advancement builds on positive Phase I results announced in October 2024, where SCB-1019 demonstrated comparable immunogenicity to GSK's AS01E-adjuvanted AREXVY while showing superior tolerability. In the 70-participant study involving older adults aged 60-85 years who were RSV vaccine-naïve, SCB-1019 induced geometric mean titers in RSV-A neutralizing antibodies of approximately 30,500 IU/mL compared to approximately 26,700 IU/mL for AREXVY at Day 28.
For RSV-B neutralizing antibodies, SCB-1019 achieved approximately 32,000 IU/mL compared to approximately 37,700 IU/mL for AREXVY, with no statistically significant differences observed between the two vaccines.
Superior Safety Profile Demonstrated
The safety profile emerged as a key differentiator for SCB-1019. The non-adjuvanted vaccine showed significantly lower rates of local adverse events at 16.7% compared to 76.7% for AS01E-adjuvanted AREXVY. Local and systemic adverse events for SCB-1019 were generally mild and comparable to saline placebo, with no vaccine-related serious adverse events, adverse events of special interest, or adverse events leading to discontinuation observed.
Addressing Revaccination Challenges
The ongoing Phase I revaccination trial addresses a critical unmet need in RSV prevention. According to Joshua Liang, Chief Executive Officer and Board Director of Clover, "While currently approved protein-based RSV vaccines are safe & effective when given as an initial dose, critical gaps persist globally: (1) suboptimal boostability for revaccination when protection against RSV disease wanes, and (2) inability to prevent respiratory disease caused by other viruses related to RSV such as hMPV and PIV3."
The revaccination study will enroll up to 160 older adults aged 60-85 years who previously received an initial dose of GSK's AREXVY at least two seasons prior. Participants will be randomized to receive either a heterologous revaccination dose of SCB-1019, a homologous AREXVY revaccination dose, or saline placebo. The study will assess safety, reactogenicity, and immunogenicity.
Broader Respiratory Vaccine Strategy
SCB-1019's bivalent design targeting both RSV-A and RSV-B strains showed potential advantages in breadth of immunity. The vaccine demonstrated an approximately 1.5-fold higher trend in antibodies against a potent RSV-B specific neutralization epitope in Site V compared to AREXVY's monovalent RSV-A formulation, based on an exploratory competitive-ELISA assay.
Clover plans to expand SCB-1019's application as part of a respiratory combination vaccine targeting RSV, human metapneumovirus (hMPV), and potentially parainfluenza virus type 3 (PIV3). This combination approach utilizing Clover's Trimer-Tag vaccine technology platform is on track for Phase I clinical trial initiation in 2025.
Technology Platform Validation
SCB-1019 is based on Clover's Trimer-Tag vaccine technology platform and represents a non-adjuvanted bivalent RSV prefusion-stabilized F (PreF)-Trimer subunit vaccine candidate. The positive clinical results support the platform's potential for developing next-generation respiratory vaccines that could address multiple pathogens simultaneously while maintaining favorable safety profiles.
