Bivalent COVID-19 Vaccine ARCT-2301 Shows Superiority

Meiji Seika Pharma Co., Ltd. has announced positive results from a Phase III study of a bivalent version of Kostaive®, a self-amplifying mRNA vaccine against COVID-19. The study, conducted in Japan, compared the immunogenicity and safety of the bivalent version of Kostaive® (ARCT-2301) with COMIRNATY® RTU (Bivalent: Ancestral strain and Omicron BA.4-5 subvariant) in healthy Japanese adults aged 18 years or older who had previously received three to five doses of mRNA COVID-19 vaccine.

The study confirmed the non-inferiority of ARCT-2301 to COMIRNATY (BA.4/5) in terms of the geometric mean titer (GMT) ratio and seroresponse rate (SRR) difference of neutralizing antibodies against SARS-CoV-2 (Omicron strain BA.4/5), meeting the primary endpoint. Additionally, the bivalent version of Kostaive® demonstrated superiority over COMIRNATY (BA.4/5) for both SARS-CoV-2 (Omicron strain BA.4/5 and Wuhan strain).

The study also reported no causally-associated severe or serious adverse events with ARCT-2301, supporting its immunogenicity and safety. These results enable Meiji Seika Pharma to release an updated version of Kostaive® against novel variants of concern in 2024 in Japan.

The study was conducted in collaboration with Arcturus Therapeutics and under an exclusive partnership with CSL Seqirus for the distribution of Kostaive® in Japan.

The bivalent version of Kostaive® utilizes self-amplifying messenger RNA (sa-mRNA) vaccine technology, which not only instructs cells in the body to make a specific protein but also makes copies of these instructions, leading to the production of more protein compared to an equivalent amount of standard mRNA. This allows for lower doses of the vaccine to be used. Sa-mRNA also has the potential to prompt a potent and durable cellular immune response in addition to producing effective antibodies against the targeted virus.

Meiji Seika Pharma's partnership with CSL Seqirus, a subsidiary of CSL Limited, and Arcturus Therapeutics, a global messenger RNA Medicines Company, has enabled the development and potential release of an updated version of Kostaive® against COVID-19 variants in Japan.

These results demonstrate the potential of the bivalent version of Kostaive® and sa-mRNA technology in providing effective and safe booster vaccination options against COVID-19 variants, contributing to the ongoing efforts to combat the pandemic. Today the company's shares have moved 3.5% to a price of $34.3. Check out the company's full 8-K submission here.

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