On Mar. 24, 2021, Clover Biopharmaceuticals and Dynavax Technologies announced the first participants had been dosed in Clover’s SPECTRA trial (Study Evaluating Protective-Efficacy and Safety of Clover’s Trimeric Recombinant Protein-based and Adjuvanted COVID-19 Vaccine), a global Phase 2/3 clinical trial evaluating the efficacy, safety and immunogenicity of Clover’s protein-based S-Trimer COVID-19 vaccine candidate adjuvanted with Dynavax’s CpG 1018 plus alum.

The global Phase 2/3 trial was a double-blind, randomized, controlled study of the adjuvanted S-Trimer COVID-19 vaccine candidate in a two-dose regimen, given 21 days apart. The study was expected to enroll over 22,000 adult and elderly participants at multiple sites across Latin America, Asia, Europe and Africa. An independent external Data Safety Monitoring Board (DSMB) provided safety oversight throughout the program by regular review of available efficacy and safety data. An interim analysis of the primary endpoint was expected in the middle of 2021, depending on trial enrollment and occurrence of COVID-19 cases in the study.

SPECTRA was fully funded by the Coalition for Epidemic Preparedness Innovations (CEPI). Through this collaboration, hundreds of millions of adjuvanted S-Trimer vaccine doses will potentially be made available for procurement and allocation through the COVAX Facility to protect the most at-risk populations in participating countries.

In December 2020, Clover reported positive clinical data from its Phase 1 trial demonstrating that its protein-based COVID-19 S-Trimer vaccine candidate in combination with Dynavax’s CpG 1018 induces strong immune response, including neutralizing antibodies and cell-mediated immunity, as well as favorable safety and tolerability profiles in the adult and elderly participants. The vaccine candidate was expected to be stable long term under standard refrigeration conditions and has demonstrated stability at room temperature for at least two months, making it suitable for global distribution.  The Phase 1 data was shared in The Lancet in early 2021.

Utilizing Clover’s proprietary Trimer-Tag^© technology, S-Trimer is a trimeric SARS-CoV-2 spike (S)-protein subunit vaccine candidate. Similar to other enveloped RNA viruses such as HIV, RSV and Influenza, SARS-CoV-2 is also an RNA virus that has 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.