Protein-based COVID-19 Vaccine Candidate Narrows Adjuvant Partner

Clover Biopharmaceuticals and Dynavax Technologies Corporation announced their plan to initiate a global Phase 2/3 efficacy trial with the S-Trimer COVID-19 vaccine candidate adjuvanted, with CpG 1018 plus alum in the first half of 2021.

In a press release on February 1, 2021, the companies stated an interim analysis for vaccine efficacy may become available in the middle of 2021.

Clover stated it expects to produce hundreds of millions of vaccine doses in 2021 and up to 1 billion vaccine doses in peak annual production as required by global demand.

Furthermore, the Coalition for Epidemic Preparedness Innovations (CEPI) will continue to support Clover’s COVID-19 vaccine candidate and will fund the development, including the Phase 2/3 trial, through licensure.

In its Phase 1 clinical trial, Clover’s protein-based COVID-19 S-Trimer vaccine candidates combined with adjuvants from either Dynavax or GlaxoSmithKline both performed well and induced high levels of neutralizing antibodies while demonstrating favorable safety and tolerability profiles.

However, according to the press statement, Clover and GSK decided to discontinue their partnership to evaluate the S-Trimer COVID-19 vaccine candidate with GSK’s pandemic adjuvant system.

CpG 1018 is the adjuvant used in HEPLISAV-B® [Hepatitis B Vaccine (Recombinant), Adjuvanted], an adult hepatitis B vaccine approved by the U.S. Food and Drug Administration (FDA). Dynavax developed CpG 1018 to provide an increased vaccine immune response, which has been demonstrated in HEPLISAV-B.

CpG 1018 provides a well-developed technology and a significant safety database to support the rapid development and large-scale manufacturing of a COVID-19 vaccine. Upon completing on-going scale-up activities, the existing equipment capacity for CpG 1018 will be 600 million to 1.2 billion adjuvant doses annually, depending on the final quantity selected.

Joshua Liang, CEO of Clover Biopharmaceuticals, commented, “Given the encouraging results of our adjuvanted S-Trimer COVID-19 vaccine candidate to-date, we are enthusiastic about progressing to a global Phase 2/3 efficacy study utilizing Dynavax’s advanced adjuvant CpG 1018 plus alum.”

“We believe this vaccine candidate could be efficacious while potentially having a differentiated, beneficial reactogenicity and safety profile which could make it attractive for a broad population of peoples. We will continue to work closely with our collaborators and regulatory authorities worldwide to help make our vaccine accessible to those most in need as quickly as possible.”

Utilizing Clover’s proprietary Trimer-Tag© technology, S-Trimer is a trimeric SARS-CoV-2 spike (S)-protein subunit vaccine candidate. Like other enveloped RNA viruses such as HIV, RSV, and Influenza, SARS-CoV-2 is also an RNA virus with a trimeric spike (S) protein on its viral envelope. 

The trimeric S protein of SARS-CoV-2 is responsible for binding to host cell surface receptor ACE2 and subsequent viral entry, making it the primary target antigen for vaccine development. S-Trimer resembles the native trimeric viral spike protein and is produced via a rapid mammalian cell-culture based expression system. S-Trimer is intended to be adjuvanted.

Dr. Richard Hatchett, CEO of CEPI, commented: “Clover’s vaccine candidate has the potential to be manufactured at scale and stored in a regular refrigerator, which makes it suitable for use around the globe, including in low-resource settings.”

“Through this partnership, we hope to make hundreds of millions of doses of this vaccine globally accessible through COVAX if it is proven to be safe and effective.”

China-based Clover Biopharmaceuticals is a global, clinical-stage, research-based biotechnology company focused on discovering, developing, and commercializing transformative biologic therapies, focusing on oncology and autoimmune diseases, as well as viral vaccines. For more information, please visit Clover Biopharmaceuticals.

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