Factbox: China's mRNA COVID vaccine candidates

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A medical worker collects a swab sample from a resident at a makeshift nucleic acid testing site at a residential compound, following new confirmed cases of the coronavirus disease (COVID-19), in Beijing, China January 24, 2022. REUTERS/Tingshu Wang

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BEIJING/SHANGHAI, Feb 28 (Reuters) - China has spent over a year developing Pfizer-type COVID-19 vaccines that may even help it pivot from stringent "zero-COVID" restrictions, but a changed market and the Omicron variant have muddied prospects before efficacy data has even been published. read more

Two foreign COVID-19 vaccines using the novel mRNA technology, one from U.S. Biotech Moderna Inc (MRNA.O) and the other from U.S.-German duo Pfizer Inc (PFE.N) and BioNTech SE , showed better efficacy in preventing symptomatic cases than the most-used Chinese shots based on other technologies in pre-Omicron clinical trials.

Below are the major mRNA COVID-19 vaccine candidates in China.

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FRONT-RUNNER ARCoV

The only candidate being tested in large-scale Phase III clinical trials is the two-dose ARCoV from the Academy of Military Medical Sciences (AMMS), Suzhou Abogen Biosciences Co Ltd and Walvax Biotechnology Co Ltd (300142.SZ).

Walvax in August obtained approval for trials in Indonesia and Mexico, with efficacy results yet to be released. It said in February it has postponed a trial in Nepal after largely finishing the recruitment of overseas Phase III participants.

Vice Chairman Huang Zhen in January said Walvax was working to identify COVID-19 infections among trial participants. He also said Walvax has the annual capacity to make 400 million doses in bulk form, and intended to increase that capacity.

Walvax is also trialling ARCoV in China as a booster for those who have had received certain non-mRNA vaccines.

In February, a small study showed ARCoV's neutralising antibody activity against the Omicron variant was much weaker than against a strain with no major mutation. A booster shot readily induced antibody production in animal tests. read more

Two altered versions of ARCoV targeting Omicron induced antibody levels comparable to those elicited by the original ARCoV in animal tests.

The U.S. Commerce Department in December added AMMS to a trade blacklist that restricts its access to U.S. exports. It is unclear whether that will impact ARCoV's development.

HOW DOES ARCOV DIFFER?

ARCoV has many differences from Moderna and Pfizer/BioNTech vaccines. For example, the Western shots instruct the human body to produce antigens mimicking the coronavirus' spike protein, while ARCoV targets just a specific part of the protein.

Chinese researchers said ARCoV can remain stable at 2-8°C for at least six months. The Pfizer/BioNTech vaccine for those aged 12-plus is approved for storage also at 2-8°C but for only a month.

Moderna's vaccine can also be stored at the same temperature for about a month, and the developer in April said data showed it could be stable for up to three months.

OTHER CHINESE MRNA CANDIDATES AGAINST COVID-19

Stemirna Therapeutics Co Ltd has a candidate designed to target the Delta variant in a mid-stage clinical trial in Laos. It is applying for trials of an updated version that it said showed early promise against variants such as Omicron.

Guangzhou RiboBio Co Ltd began an early stage clinical trial in China in January.

AIM Vaccine Co Ltd in January said its candidate appears safe and able to trigger an immune response based on data from an early-stage Phase I trial. It has not formally published its findings.

RNACure has partnered Walvax to develop mRNA vaccines targeting variants. It said in January it was applying for clinical trials for a candidate that showed broad-spectrum protection against variants in animal tests.

Sinopharm and CanSino Biologics Inc (6185.HK) have said they were working on mRNA COVID-19 vaccines. Sinopharm unit China National Biotec Group Co Ltd said it has designed an mRNA candidate targeting the Omicron variant.

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Reporting by Roxanne Liu in Beijing and David Stanway in Shanghai; Editing by Miyoung Kim and Christopher Cushing

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