As cases of SARS-CoV-2 continue to rise, with close to 1.9 million cases worldwide, the race is on to find a vaccine. Countries and companies around the world have risen to the call, with over 30 vaccines already in development. Four of which have already moved on to clinical trials.
US-based company Moderna was the first to move to trial with its messenger RNA-based vaccine. With approval from the NIH in early March, the first study participants were dosed less than two weeks later. The company plans to enroll a total of 45 healthy volunteers for its Phase 1 trial.
RNA vaccines are a fairly new development, and so far, none have been approved for clinical use. Interestingly, mRNA-1273 was not tested in animals before moving on to human trials.
China was the second country to receive approval for human trials. The day after the first trial started in the US, China’s Academy of Military Sciences and biotech firm CanSino Biologics received approval to begin testing Ad5-nCoV. Their vaccine candidate has a genetically engineered adenovirus-based that expresses SARS-CoV-2 spike proteins.
Coronaviruses get their name from the crown-like protein projections on their surface. These “projections” are called spike proteins, or S proteins. These proteins bind to host receptors, allowing the virus to fuse with cell membranes. Hopefully, by creating a vaccine based on these S proteins we can induce antibodies to block the virus from ever entering a host’s cell, neutralizing its ability to infect and replicate.
The University of Oxford began enrolling patients for their Phase I/II trial on March 30th. Their vaccine candidate, ChAdOx1 nCoV-19, also targets the S protein and was again not tested in animals before being approved for human testing. A Phase I trial using the same vector against MERS is currently ongoing though.
They intend to enroll over 500 patients and anticipate the study participants will be enrolled for six months before moving on to Phase III trials.
US-based company Inovio is the latest to start clinical trials of their SARS-CoV-2 candidate, INO-4800. The first participants were dosed on April 6th with the new DNA-based vaccine candidate. The company expects to have the first safety and efficacy data by late summer.
Like RNA vaccines, no DNA vaccine has yet been approved for human use, but some have been approved in animals. DNA vaccines use a plasmid containing DNA sequences that encode the target virus. Once incorporated, the cell will start to produce the encoded antigens, which the body will see as inappropriate gene expression and will begin producing an immune response. The research so far shows that this type of vaccination might produce an even stronger response than a traditional vaccine.
Inovio has already produced thousands of doses to support their Phase I and II trials and plans to have millions ready by the end of the year for emergency use.
While final approval of a vaccine is still 12-18 months away, the speed at which many country’s pharmaceutical and government agencies are working brings hope that there is light at the end of the tunnel for this pandemic.