The biopharmaceutical company CureVac has begun a phase 2b/3 clinical trial of its mRNA-based COVID-19 vaccine candidate CVnCoV. The study plans to enroll around 36,500 participants from Europe and Latin America.
CureVac’s mRNA vaccine harnesses the potency of untranslated regions to optimize the RNA rather than make chemical modifications. The approach has created a candidate that triggers immune responses at a 12-µg dose, compared to the 100 µg used by Moderna in its mRNA vaccine candidate. This could enable CureVac to make more doses of the vaccine.
The phase 2b portion of the clinical trial will randomize 4,000 subjects across two age cohorts—18 to 60 years and 61 years and older—to take two doses of CVnCoV or placebo four weeks apart. Around 800 to 1,000 of the participants will be aged 61 years and older.
Once at least 1,000 subjects have a one week of follow-up after the first vaccination, the Data and Safety Monitoring Board will review the safety, reactogenicity and immunogenicity data and make a decision to proceed on to the phase 3.which will recruit 32,500 subjects.
CureVac is also aiming to trigger balanced immune responses. Based on the available data, the vaccine has a somewhat less tolerability profile compared to other vaccines. A higher proportion of subjects who received 12 µg of CVnCoV had moderate to severe fever, headache and fatigue than was seen in the BioNTech-Pfizer phase 3, although the CureVac results come from a small cohort presented last month.