Moderna Therapeutics (NASDAQ:MRNA) became the first company to take a COVID-19 vaccine into a phase III clinical trial, which will test how safe and effective the inoculation is.

Enrolment of the 30,000 people taking part in the clinical assessment is expected to be completed later this month with results slated for as early as October.

Here we look at the approach taken by the Boston-based biotech and how it differs from the methods deployed by the chasing pack.

Traditional approach

Traditionally, vaccines are made of an inactivated virus, or recombinant proteins that stimulate the immune response.

By providing the body’s defence mechanisms with advanced warning of the virus, they trigger production of the antibodies required to fight real thing when it is contracted.

Moderna’s drug uses different tactics. Driving the process is messenger RNA, or mRNA, which plays a fundamental role in human biology, transferring the instructions stored in DNA to make the proteins required in every living cell.

Medicines based on mRNA instruct a patient’s own cells to produce proteins that could prevent, treat, or cure disease.

Small problem

There’s only one problem — no mRNA drug has ever been approved for human use.

Tal Zaks, the chief medical officer of Moderna, recently explained to Stephen Dubner on the Freakonomics Radio podcast just how and why his team might succeed where it and others have thus far failed.

“I think what we have done uniquely is leverage a decade of engineering and science on top of medicine to sort of break the riddle of how to get an mRNA to make enough protein,” he said.

“And the second element is, we already have proven time and again that we can generate neutralising antibodies with this vaccine.

“So, the question ahead of us is not whether mRNA will work, the question ahead of us is whether neutralising antibodies are going to prevent Covid-19. And I think the likelihood of that answer is very, very high.”

Chasing pack

Not far behind Moderna is another mRNA drug, this one has been developed by Pfizer Inc (NYSE:PFE) and its German partner BioNTech (NASDAQ:BNTX).

There are other vaccine candidates in phase III now that use a DNA mechanism. The charge is being led by Oxford University and the Anglo-Swedish firm AstraZeneca (LON:AZN).

Hard on AZ’s heels is the Chinese firm CanSino Biologics, while Johnson & Johnson (NYSE:JNJ) said its phase III clinical assessment will begin this month, enrolling 60,000 participants.

Among those going the conventional route of using an inactivated virus are Merck & Co Inc (NYSE:MRK) and Sinovac Biotech.

GlaxoSmithKline (LON:GSK) and its partner Vir Biotechnology Inc (NASDAQ:VIR) are developing an antibody-based treatment, as are Eli Lily & Co (NYSE:LLY) and partners Regeneron Pharmaceuticals Inc (NASDAQ:REGN) and Roche Holding AG (SWX:RO).