China's Clover says its coronavirus vaccine candidate showed promise in animal test

FILE PHOTO: A woman holds a small bottle labeled with a "Vaccine COVID-19" sticker and a medical syringe in this illustration taken April 10, 2020. REUTERS/Dado Ruvic/Illustration//File Photo

BEIJING (Reuters) - An experimental coronavirus vaccine developed by China’s Clover Biopharmaceuticals appeared to be safe and able to trigger immune responses in animal tests, researchers have said.

The result of the study on monkeys comes months after Clover began an early stage human trial in Australia in June, as global drug makers race to develop a safe and effective vaccine that can protect people from the COVID-19 pandemic that has killed nearly 1 million people.

Clover’s vaccine candidate, which is partly funded by a global vaccine research coalition, uses adjuvants, ingredients that could boost immune responses, from Britain’s GlaxoSmithKline and U.S.-based Dynavax Technologies.

Two doses of the candidate with GSK's adjuvant induced antibody levels in monkeys that are higher than those seen in the blood of patients recovering from COVID-19, researchers at Clover and other Chinese institutes said in a paper published on Thursday ahead of peer-review.

Antibody levels triggered by two doses of the vaccine with Dynavax’s adjuvant, plus alum, were similar to those observed in convalescent patients’ serum, they said.

Adjuvants could reduce the amount of antigen, the substance that triggers immune responses, required in each vaccine dose, allowing manufacturers to make more doses.

The candidate, called S-Trimmer, did not cause a disease enhancement effect when tested in monkeys, a scenario where the vaccine-generated immunity worsens the disease instead of preventing subjects from getting sick, which experts worry may happen to coronavirus vaccines.

Vaccinated animals appeared to be protected from weight loss, fever and organ damage when challenged with the virus after inoculation, the study said.

No vaccine candidate has yet been proved to be effective and safe to protect humans from the coronavirus, but at least nine candidates are in the final stage of clinical trials to test their efficacy and safety.

Reporting by Roxanne Liu and Tony Munroe in Beijing; Editing by Miyoung Kim and Raju Gopalakrishnan