Clover Biopharmaceuticals, a global clinical-stage biotechnology company focused on discovering and developing transformative biologic therapies and vaccines, today announced positive preclinical data demonstrating that its protein-based COVID-19 S-Trimer vaccine candidate in combination with adjuvants from either GSK or Dynavax  induces a strong immune response and protection against SARS-CoV-2 in animal models. The manuscript describing the results titled “S-Trimer, a COVID-19 subunit vaccine candidate, induces protective immunity in nonhuman primates” has been submitted for peer review and can be accessed on an online preprint server at bioRxiv. 


Joshua Liang, Chief Executive Officer of Clover Biopharmaceuticals, said, “We are excited to share these important preclinical results showing that our S-Trimer COVID-19 vaccine candidate induces immune protection against SARS-CoV-2, and we are also pleased with the progress and preliminary data of our Phase 1 clinical trial evaluating S-Trimer. More than ever, we remain committed to developing a safe, effective and accessible COVID-19 vaccine at a scale that could contribute to the control of the pandemic globally.” 

Thomas Breuer, Chief Medical Officer of GSK Vaccines, commented, “We are pleased with the preclinical results that, together with the preliminary insights from the Phase 1 clinical data, underline expectations that the GSK pandemic adjuvant system combined with Clover’s antigen leads to a substantial strengthening of the immune response with the promise of higher efficacy and dose sparing capabilities. Adjuvants are powerful tools in the global fight against the COVID-19 pandemic, and we are looking forward to seeing the progress of the vaccine candidate using GSK’s pandemic adjuvant technology.” 

Rob Janssen, Chief Medical Officer of Dynavax, commented, “We are pleased with the strong preclinical results observed when Dynavax’s advanced adjuvant CpG 1018 plus alum was combined with Clover’s S-Trimer antigen. We are especially encouraged by the absence of measurable viral load in lung tissue as well as other clinical measures in non-human primates challenged with SARS-CoV-2, and by the Th1-polarized T cell response in rodents. These data demonstrate CpG 1018’s potential to significantly increase efficacy by rapidly controlling infection. We are proud to be collaborating with Clover on the development of this vaccine for COVID-19, and are committed to supporting Clover in making the vaccine available globally.” 

Dr. Peng Liang, Founder and Chairman of Clover and inventor of Trimer-Tag© technology, added, “Together with an accompanying manuscript entitled ‘Cryo-EM structure of S-Trimer, a subunit vaccine candidate for COVID-19’ which discloses that our S-Trimer resembles the native SARS-CoV-2 spike antigen in atomic resolution, our complete preclinical studies validate Trimer-Tag© as a potential platform technology for subunit vaccine development against current and future enveloped RNA viruses.” 

Clover’s COVID-19 S-Trimer vaccine was developed by combining the trimeric SARS-CoV-2 spike (S)-protein with the company’s proprietary Trimer-Tag© technology. In preclinical studies, adjuvanted S-Trimer induced strong humoral and Th1-biased cell-mediated immune responses in mice, rats and monkeys, with levels of neutralizing antibodies at or higher than levels observed in human convalescent sera. Rhesus macaques that received the vaccine and were subsequently challenged with SARS-CoV-2 virus were protected against infection, as demonstrated by clinical observations (protection from body weight loss and increases in body temperature) and significant reduction in viral loads in lung tissues and swabs, with no signs of disease enhancement. Strong immune responses and protection were observed when the S-Trimer was administered with either GSK’s pandemic adjuvant system or Dynavax’s CpG 1018 adjuvant plus alum. These positive preclinical data supported the decision to progress adjuvanted vaccine candidates using both adjuvants into Clover’s ongoing Phase 1 clinical study of S-Trimer in healthy adult and elderly participants. 

In June 2020, Clover announced the start of a Phase 1 clinical trial. The trial is a randomized, observer-blind, placebo-controlled study to assess the safety, reactogenicity and immunogenicity of the adjuvanted COVID-19 S-Trimer vaccine at multiple dose levels. The study has completed enrollment of 150 adult and elderly participants. Preliminary results show that the vaccine is likely to be safe and well-tolerated, with high levels of neutralizing antibodies observed. Based on these preliminary results, an additional 200 participants will be enrolled in a Phase 1 dose-expansion study at the selected S-Trimer dose-level and adjuvanted with either GSK’s pandemic adjuvant or Dynavax’s advanced adjuvant CpG 1018 plus alum. Clover intends to initiate a global Phase 2/3 vaccine efficacy study before the end of 2020. Detailed Phase 1 data will be made available in a peer-reviewed publication in the near future. The clinical trials and Clover’s COVID-19 vaccine program are being supported by funding and collaboration with the Coalition for Epidemic Preparedness Innovations (CEPI).

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