ExpreS2ion Biotech Holding AB's affiliate ExpreS2ion Biotechnologies ApS announced that additional positive results for the ABNCoV2 vaccine, that is being developed as a universal booster vaccine, has been presented from the Phase II clinical trial conducted by Bavarian Nordic. The full study data confirms that existing levels of SARS-CoV-2 neutralizing antibodies increased by 2-40-fold, depending on the initial levels of antibodies, with no serious adverse events reported. Based on this excellent outcome, Bavarian Nordic plans to initiate a Phase III study in the first half of 2022.

As reported previously by ExpreS2ion, the data from the first study group of 103 subjects demonstrated that a single booster dose with the ABNCoV2 vaccine raised the neutralizing antibodies against the original variant and peaked at two weeks with a 2-40-fold increase depending on the initial antibody levels. The same trend was observed for all other SARS-CoV2 variants tested, namely Alpha, Beta and Delta. All subjects were boosted to absolute antibody levels reported to be associated with a very high efficacy against SARS-CoV2.

The additional results reported on February 28, 2022 from a group of 66 seropositive subjects who received one lower dose of ABNCoV2 confirm similar high neutralizing antibody levels against the same SARS-CoV-2 variants of concern as observed with the higher dose. Taking the pre-booster levels and/or time since the last vaccination into account, the higher booster dose of ABNCoV2 trended towards inducing stronger levels of neutralizing levels against SARS-CoV-2. Furthermore, a group of 28 seronegative subjects, who had not been previously vaccinated or infected with SARS-CoV-2, received 2 doses of the 100 µg formulation of ABNCoV2 4 weeks apart. The neutralizing antibody levels against the Wuhan variant were elevated to levels reported to be highly efficacious against SARS-CoV-2 also for this group.

The vaccine was generally well-tolerated, with no related serious adverse events reported and no relevant difference in the safety profile between subjects receiving either the low or high dose of ABNCoV2. While the 50 µg dose has shown positive results, it has been decided to use the 100 µg dose in the Phase III trial to maximize the likelihood of success. The Phase III trial is planned to be initiated in the first half of 2022.

It will include approximately 4,000 seropositive study participants who will receive a booster vaccination with 100 µg ABNCoV2 or an mRNA-based vaccine, aiming to demonstrate non-inferiority of ABNCoV2 to the licensed mRNA vaccine. An overall agreement has been made with regulatory authorities on the trial design, and manufacturing of vaccine bulk for the trial has been completed, pending filling at Bavarian Nordic's manufacturing line in the near future.