BEIJING – Chinese state-backed vaccine developer China National Biotec Group (CNBG), of Beijing, said on June 16 night that its inactivated COVID-19 vaccine candidate produced a seroconversion rate of up to 100% in a phase I/II trial that enrolled 1,120 healthy subjects. It is the third piece of positive news on COVID-19 treatment development this week, though full data are yet to be seen.

CNBG’s announcement came a day after researchers from Oxford University said dexamethasone showed a statistically significant impact on mortality, and three days after another Chinese vaccine developer, Sinovac Biotech Ltd., reported a seroconversion rate of more than 90% for its vaccine two weeks after inoculation.

CNBG’s vaccine is being developed by Wuhan Institute of Biological Products, a subsidiary of CNBG, together with the Wuhan Institute of Virology under the Chinese Academy of Science. CNBG is the biological product arm of state-run China National Pharmaceutical Group Corp. (Sinopharm).

The randomized, double-blind, and place-controlled phase I/II trial started in Henan province in April and derived the results in 66 days. CNBG said it is the world’s first clinical trial to obtain safety and efficacy data of a two-dose inactivated COVID-19 vaccine.

In this trial, volunteers, ages 18 to 59, were given two shots of the vaccine at low, middle or high dosage levels. They had the second shot either after 14, 21 or 28 days.

In a brief statement, CNBG said the seroconversion rate was 97.6% for the middle dose group, who received injections on a 14-day and 21-day schedule, and 100% for those who received doses 28 days apart. It added that the vaccine induced high titer antibodies in all inoculated people and demonstrated a favorable safety profile without a single adverse event.

Neither data from the low- and high-dose groups nor any other data were disclosed, though CNBG said the antibody titers were high in different dose groups. The company was not reachable for a comment on the trial results as of press time.

Though more data are to be seen, the company claimed that it is the longest clinical trial of a COVID-19 vaccine and has yielded the most comprehensive data and best results to date.

In the trial, researchers looked at the vaccine’s safety and immunogenicity, with a focus on the changes in cellular immunity after vaccination. They also kept an eye on changes in in vivo antibody levels.

Encouraged by the results, the company revealed plans to actively move the vaccine candidate to phase III trials overseas. It said it has secured cooperative intent from companies and institutes in many countries.

Meanwhile, Sinovac has made public its plan to conduct phase III trials in Brazil in collaboration with the Instituto Butantan for its inactivated vaccine candidate.

CNBG has a second vaccine in human trials. Its subsidiary, the Beijing Institute of Biological Products, is also developing an inactivated COVID-19 vaccine candidate known as BBIBP-CorV together with the National Institute for Viral Disease Control and Prevention. It is undergoing phase II trials following trial approval on April 27.

“BBIBP-CorV induces high levels of neutralizing antibodies titers in animal models,” researchers said in Cell on June 6. “Two-dose immunization with 2 μg/dose BBIBP-CorV efficiently protects rhesus macaques … These results support the further evaluation of BBIBP-CorV in a clinical trial.”

Speaking to the state media, Sinopharm’s chairman, Liu Jingzhen, said more than 2,000 people have received its two vaccine candidates, and they are expected to enter the market in late 2020 or first part of 2021 at the earliest.

More vaccines to enter trials

The company also said its manufacturing facilities are ready to produce adequate COVID-19 vaccines to meet the urgent unmet need. It currently has a production unit that can pump out 100 million to 120 million vaccines per year, and another facility in Wuhan is expected to be completed in the next few weeks. Both facilities together can produce 200 million vaccines annually.

“Several Chinese companies have made impressive progress not only in early discovery but also clinical development,” David Shao, CEO of Beijing-based vaccine developer Yisheng Biopharma Co. Ltd., told BioWorld. “These achievements by Chinese biotech companies could benefit the Chinese population as well as people outside of China.”

Five vaccine candidates are in clinical trials in China. One is a viral vector-based vaccine developed by Cansino, which was the first to enter clinical trials in China. The rest are inactivated vaccines, with two developed by CNBG, one by Sinovac and one by the Institute of Medical Biology Chinese Academy of Medical Sciences.

The Chinese health authority said it expects to see more vaccine candidates entering human trials starting in June. China's CDC director, Gao Fu, even said that a vaccine candidate would hopefully be available for emergency use in September.

To date, more than 10 Chinese companies are known to be developing a COVID-19 vaccine. They include Sinovac Biotech Ltd., Cansino Biologics Inc., Clover Biopharmaceuticals, Stemirna Therapeutics Co. Ltd., Beijing Advaccine Biotechnology, Chongqing Zhifei Biological Products Co. Ltd., Walvax Biotechnology Co., Ltd., Suzhou Abogen Biosciences Co. Ltd., Xiamen Innovax Biotech, Hualan Biological Engineering Inc., Zhejiang Pukang Biotechnology Co., Ltd., Changchun Bcht Biotechnology Co., Wuhan Bravovax Co. Ltd. and Yisheng.

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