Extended Immunity with sa-mRNA COVID-19 Vaccines from CSL and Arcturus

In a recent study conducted by Meiji Seika Pharma in Japan, the sa-mRNA COVID-19 vaccine, ARCT-154, developed by CSL and Arcturus Therapeutics, has shown promising results in terms of providing a longer duration of immunity compared to conventional mRNA vaccines. The Phase 3 study's follow-up analysis revealed that ARCT-154, administered at a lower dose than Comirnaty®, induced a more sustained immune response against both the Wuhan strain and the Omicron BA.4/5 variant of the virus.

The six-month data report from the randomized, double-blind, active-controlled trial, which took place across 11 sites in Japan, demonstrated that ARCT-154 maintained a higher geometric mean titer (GMT) ratio compared to Comirnaty® at various intervals post-booster. Notably, at one month post-booster, ARCT-154 showed a GMT of 5390, compared to Comirnaty®'s 3738, with a ratio of 1.44. This advantage was sustained, with ARCT-154 maintaining a GMT ratio of 2.21 over Comirnaty® at 181 days post-booster.

The study also highlighted the slower decline in neutralizing antibodies against the Omicron BA.4/5 variant in recipients of ARCT-154. At Day 91, the GMTs for ARCT-154 were significantly higher than those for Comirnaty®, and this difference was maintained until Day 181, with ARCT-154 showing a GMT ratio of 2.26 in favor.

Self-amplifying mRNA vaccines, like ARCT-154, work differently from standard mRNA vaccines by instructing the body to produce more mRNA and protein, thereby enhancing the immune response. CSL, a global biotechnology company, has a diverse portfolio of life-saving medicines and vaccines, and is committed to protecting public health through innovative technologies. Arcturus Therapeutics, a company with enabling technologies for mRNA medicines and vaccines, has developed the world's first approved sa-mRNA COVID vaccine and continues to collaborate globally for innovative mRNA vaccines.

The results of this study are significant as they suggest that sa-mRNA technology could offer substantial improvements over traditional mRNA vaccines, including the potential for longer-lasting protection at lower doses. This advancement is a step forward in the ongoing efforts to combat viral respiratory diseases and protect public health on a global scale.