Clover Biopharmaceuticals Announces Positive Phase 1 Data for its Adjuvanted S-Trimer COVID-19 Vaccine Candidates

Clover Biopharmaceuticals, a global clinical-stage biotechnology company committed to developing transformative biologics as vaccines and therapeutics for the world’s most debilitating diseases, today announced positive clinical data from its Phase 1 trial demonstrating that its protein-based COVID-19 S-Trimer vaccine candidates in combination with adjuvants from either GSK (London Stock Exchange: GSK) or Dynavax (Nasdaq: DVAX) induces strong immune responses, including neutralizing antibodies and cell-mediated immunity, as well as favorable safety and tolerability profiles in 150 adult and elderly participants. The manuscript describing the detailed results will be accessible on an online preprint server shortly.

The Phase 1 trial was a randomized, observer-blind, placebo-controlled study to assess the safety, reactogenicity and immunogenicity of the adjuvanted COVID-19 S-Trimer vaccine candidates formulated with different antigen levels. No serious adverse events related to the vaccine candidates studied were reported. The majority of adverse events were mild and transient. S-Trimer adjuvanted with GSK’s pandemic adjuvant system induced neutralizing antibody titers (seroconversion) in 100% of participants at the selected 9 µg S-Trimer dose in both adult and elderly groups, with geometric mean titers (GMT) greater than 1:1,800. CpG-1018/alum-adjuvanted S-Trimer induced neutralizing antibodies in 100% of adult participants at the selected 30 µg S-Trimer dose with GMT greater than 1:1,000, and seroconversion was observed in 88% (7 out of 8) in elderly. Strong Th1 cell-mediated immune responses were also observed for the vaccine candidates with either adjuvant.

Preliminary results from stability studies have demonstrated that S-Trimer is stable at 2-8^o C for at least six months (longer-term stability studies are ongoing) and stable at room temperature and 40^o C for at least one month, in line with the adjuvants tested. Thus, the ability of Clover’s COVID-19 vaccine candidates to be stored in standard refrigeration temperatures makes them suitable for broad global distribution based on current results.

Based on the positive Phase 1 results reported and the unprecedented need for COVID-19 vaccines, Clover and its partners are confident to enter late-stage clinical development for both adjuvanted vaccines. A global Phase 2/3 efficacy study of the S-Trimer vaccine candidate in combination with GSK’s pandemic adjuvant system is expected to begin in December 2020. Clover intends to initiate a separate pivotal clinical trial of the S-Trimer vaccine candidate in combination with Dynavax’s advanced CpG 1018 adjuvant plus alum in the first half of 2021.