Clover Biopharmaceuticals has achieved a significant regulatory milestone with the U.S. Food and Drug Administration (FDA) clearing its Investigational New Drug (IND) application for SCB-1019, the company's respiratory syncytial virus (RSV) vaccine candidate. The Shanghai-based biotechnology company has also completed enrollment of the first participants in a Phase I revaccination clinical trial evaluating this non-adjuvanted bivalent RSV prefusion-stabilized F (PreF)-Trimer subunit vaccine.
The trial represents an important step in addressing critical gaps in current RSV vaccination strategies, particularly focusing on revaccination efficacy when protection wanes over time. SCB-1019 utilizes Clover's proprietary Trimer-Tag vaccine technology platform, which the company believes offers distinct advantages in the competitive RSV vaccine landscape.
"We are pleased to announce the U.S. IND clearance and revaccination clinical trial initiation, which supports the differentiated global opportunity of Clover's RSV PreF vaccine utilizing our validated Trimer-Tag platform," said Joshua Liang, Chief Executive Officer and Board Director of Clover.
Addressing Critical Gaps in RSV Protection
While current protein-based RSV vaccines have demonstrated safety and efficacy as initial doses, Liang highlighted two persistent challenges in the field: "suboptimal boostability for revaccination when protection against RSV disease wanes, and inability to prevent respiratory disease caused by other viruses related to RSV such as hMPV and PIV3."
RSV remains a significant health concern, particularly for vulnerable populations such as older adults and young children. The virus causes substantial morbidity and mortality worldwide, with limited treatment options once infection occurs, making effective vaccination strategies crucial for public health.
Promising Early Results and Trial Design
In October 2024, Clover reported encouraging Phase I results for SCB-1019 in 70 RSV vaccine-naïve older adults aged 60-85 years. These results indicated a "potential best-in-class combined immunogenicity and tolerability profile" when compared head-to-head with GSK's AS01E-adjuvanted RSV vaccine (AREXVY), which is currently approved and in use.
The newly initiated Phase I revaccination trial in the United States will enroll up to 160 older adults (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
- Saline placebo
The study will comprehensively assess safety, reactogenicity, and immunogenicity parameters to determine SCB-1019's potential as a booster vaccination strategy.
Future Combination Vaccine Development
Beyond the standalone RSV vaccine, Clover is advancing plans to evaluate SCB-1019 as part of a respiratory combination vaccine. This approach would target multiple respiratory pathogens simultaneously, including RSV, human metapneumovirus (hMPV), and potentially parainfluenza virus type 3 (PIV3).
The company confirmed that development of this combination Trimer-Tagged PreF vaccine remains on track for Phase I clinical trial initiation in 2025. Such a combination approach could potentially address multiple respiratory threats with a single vaccination, improving patient convenience and potentially broadening protection against related respiratory viruses.
Technology Platform Advantages
The Trimer-Tag platform that underpins SCB-1019 is designed to produce trimeric fusion proteins that mimic the native structure of viral surface proteins. For RSV specifically, this approach targets the prefusion F protein configuration, which has been shown to elicit potent neutralizing antibodies.
What distinguishes Clover's approach is the non-adjuvanted formulation of SCB-1019, which contrasts with some competitor vaccines that require adjuvants to enhance immune response. The company believes this may offer advantages in terms of tolerability while maintaining strong immunogenicity.
Commercial and Strategic Implications
As a global commercial-stage biotechnology company, Clover Biopharmaceuticals has positioned SCB-1019 as a potential differentiator in the growing RSV vaccine market. The revaccination strategy addresses an important clinical need, as protection from initial RSV vaccination is known to wane over time.
The head-to-head comparison with GSK's AREXVY in both vaccine-naïve individuals and as a heterologous booster represents a bold strategic approach, directly challenging an established market leader. If successful, this could position Clover's vaccine as a preferred option for revaccination strategies.
The company's integrated research, development, and manufacturing capabilities, along with its global partnerships, support its mission to "unleash the power of innovative vaccines to save lives and improve health around the world."
