SCB 2019 is a recombinant S-trimer subunit vaccine being developed by Clover Biopharmaceuticals for prevention of COVID-2019 infections. The company is utilising its patented Trimer-Tag© technology to construct a recombinant protein subunit-trimer vaccine (S-Trimer) and is expected to produce the vaccine via a rapid mammalian cell-culture based expression system. Coronaviruses are positive single-stranded RNA (ssRNA) viruses with a trimeric spike (S) protein on its viral envelope. The trimeric S protein of 2019-nCoV is responsible for binding to host cell surface receptor ACE2 and subsequent viral entry. Preclinical studies are underway in China.
Timer-Tag is a drug development platform which produces covalently-trimerized fusion proteins targeting trimerization-dependent pathways. The platform takes advantage of the C-prodomains of collagen proteins which are capable of efficient self-trimerization. It allows any secreted protein (cytokines, soluble receptors, Fab of mAbs) to be made as covalently linked homo-trimers with greatly increased avidity to their disease-causing targets.
Clover Biopharmaceuticals seeks to advance the development of recombinant subunit-trimer vaccine via partnerships and collaborations (Clover Biopharmaceuticals website, February 2020).
In April 2020, the Coalition for Epidemic Preparedness Innovations entered into a collaboration with Clover Biopharmaceuticals Australia (the wholly-owned subsidiary of Sichuan Clover Biopharmaceuticals,(China) for developing a COVID-19 vaccine. As per the agreement, CEPI will provide initial US$3.5m to Clover Biopharmaceuticals to support preparation and initiation of a phase I trial of Clover’s protein-based COVID-19 S-Trimer vaccine in Australia. 
In March 2020, Clover Biopharmaceuticals and Dynavax Technologies Corporation entered into a research and development agreement to develop a vaccine for COVID-2019 infections. Under the terms of agreement, Dynavax will provide technical expertise and the company’s proprietary toll-like receptor 9 (TLR9) agonist adjuvant, CpG 1018. Financial details of the agreement were not disclosed. 
In February 2020, Clover Biopharmaceuticals entered into a research collaboration with GlaxoSmithKline for its protein-based coronavirus vaccine candidate (COVID-19 S-Trimer). GSK will provide Clover with its pandemic adjuvant system for further evaluation of S-Trimer in preclinical studies. Having one of the largest in-house, commercial-scale cGMP biomanufacturing capabilities in China, Clover could potentially rapidly scale-up and produce large-quantities of the coronavirus vaccine. 
Clover Biopharmaceuticals received exclusive worldwide rights from GenHunter Corporation to utilise Trimer-Tag© technology for the development of drug candidates (Clover Biopharmaceuticals website, December 2017).
Key Development Milestones
As at January 2020, early research and development is ongoing for the subunit trimer vaccine for the prevention of COVID-2019 infections  .
In May 2020, Dynavax Technologies announced its intention to offer and sell shares of its common stock, subject to market and other conditions, in an underwritten public offering. It expects to grant the underwriters a 30-day option to purchase up to an additional 15% of the common stock being offered in the offering. The company intends to use the net proceeds to fund activities, associated with the ongoing commercialisation of adjuvanted Hepatitis B vaccine (recombinant) [see Adis Insight Drug Profile800020941], to advance its CpG 1018 vaccine platform, including any scale up efforts in support of a potential COVID-19 vaccine by Dynavax and its collaborators, and for general corporate purposes, including working capital  .
Clover Biopharmaceuticals has patent protection for Trimer-Tag technology platform in the US, Europe, Japan and China (Clover Biopharmaceuticals website, January 2020)