CureVac links COVID-19 vaccine to immune response, setting it up to enter pivotal trial

Franz-Werner Haas, interim CEO of CureVac
CureVac CEO Franz-Werner Haas (CureVac)

CureVac has shared phase 1/2 data on its COVID-19 vaccine candidate CVnCoV. The German biotech said the mRNA vaccine dose selected for further development sparked increases in virus-neutralizing antibodies and early indications of T-cell activation.

While BioNTech and Moderna raced mRNA vaccines into the clinic, CureVac advanced its candidate into human testing more slowly, albeit still at a breakneck speed by historical standards. CureVac used the extra time in preclinical to design a differentiated asset. Rather than build upon chemical modification of the RNA, CureVac optimized the nucleic acid itself.

The result is an mRNA vaccine that CureVac expects to generate a balanced immune response and be more straightforward to scale up. The phase 1 data provide an early, incomplete look at whether the candidate can live up to those expectations.

CureVac’s statement focused on the 12-µg dose, which was added to the dose-escalation study after the assessment of the 2-µg, 4-µg and 8-µg doses got underway in June. According to CureVac, the 12-µg dose raised levels of binding and neutralizing antibodies to levels seen in the plasma of a set of 67 seriously ill COVID-19 patients, including around 16 people who were hospitalized. 

The relative proportion of neutralizing to binding antibody levels was similar in the vaccinated and convalescent individuals, CureVac said, providing early validation of the effort to develop a vaccine that generates a balanced immune response comparable to the body’s natural reaction.

CureVac saw “indications of functional T cells confirming activation of cellular immune response” in the data. Analysis of T-cell-mediated immunity is ongoing, and the indications of functional T cells are from early data.

The 12-µg dose was well tolerated, according to CureVac, with no related serious adverse events seen in the study population. Some participants experienced grade 3 fatigue, headache, chills and muscle pain, with a smaller number of people reporting fever. The events primarily happened after the administration of the second dose and usually resolved within 48 hours.

CureVac is yet to share data on the other doses, nor numbers on the 12-µg dose, but the details it has released suggest CVnCoV may work as hoped. A more thorough test of the vaccine is set to start later this year, when CureVac plans to start administering the 12-µg dose to participants in a phase 2b/3 clinical trial.

The timeline means CureVac’s mRNA rivals Moderna and BioNTech, which is developing its vaccine with Pfizer, may have the phase 3 data they need to seek approval, at least on an emergency basis, by the time CVnCoV enters late-stage testing. Even so, CureVac has lined up a deal to sell an initial 225 million doses of CVnCoV to the EU.