As promising Ebola vaccines from global drugmakers GlaxoSmithKline and Merck & Co. still await official licenses, China has approved its own shot, co-developed by the Chinese Academy of Military Medical Sciences’ Bioengineering Institute and domestic vaccine specialist Tianjin CanSino Biologics.
Dubbed Ad5-EBOV, the recombinant adenovirus vector-based vaccine is the first shot based on the strain behind the recent epidemic in West Africa in 2014—the deadliest outbreak in recorded history. Along with the CFDA decision, the Chinese vaccinemaker revealed (Chinese) a 65,000-square-meter (700,000-square-foot), 70-million-dose-capacity manufacturing site, which the company said is in compliance with the World Health Organization’s cGMP requirement.
The vaccine differs from programs at GSK and Merck because those companies' vaccines are developed to express the glycoprotein of the Ebola virus identified during the disease’s discovery back in 1976. CanSino says the two virus types are very similar, but slight differences could allow its shot to provide better protection in the real world.
Because the Ebola crisis has died down, China’s FDA approved Ad5-EBOV without a phase 3 test after putting the product on its expedited review list in April. CanSino told FiercePharma that the vaccine has also been through a challenge experiment at the microbiology lab at the Public Health Agency of Canada, the original developer of Merck's rVSV-ZEBOV.
In a 500-participant phase 2 trial in Sierra Leone, the results of which were published earlier this year in The Lancet, the vaccine elicited strong antibody responses in volunteers within 28 days. Researchers noted that the responses, though still existent, decreased significantly at day 168, a finding the team said is consistent with previous tests on rVSV-ZEBOV in Africa and Europe.
In a related commentary published alongside the Ad5-EBOV study results, two experts from the Netherlands expressed concerns about the “durability of protection when implementing mass vaccination campaigns in future outbreak settings in Africa.” CanSino, in a written response to FiercePharma, said the product is positioned for emergency use for now; therefore, it's currently not focused on long-term efficacy. The company didn't rule out the possibility for implementing a booster shot in the future.
A recent phase 2 study conducted by a U.S.-Liberia partnership showed that responses to Merck’s and GSK’s shots also peaked after a month, and that most recipients of the two shots still had an antibody response at one year.
CanSino's program further incorporates a freeze-drying technique known as lyophilization, which allows the vaccine to be stored at 4°C (39°F) for a long time, and to remain stable at 37°C (99°F) for about three weeks. The other two candidates, on the other hand, must be stored at -70°C (-94°F) or below, and are stable for only one week at 4°C (39°F). This means CanSino's version could be more suitable for the African region in terms of logistics.