In-Depth: Plant-based COVID vaccine enters final stage of testing

Plant-based COVID vaccine
Posted at 4:35 PM, Apr 16, 2021
and last updated 2021-04-17 18:04:13-04

SAN DIEGO (KGTV) -- Researchers are conducting a late-stage clinical trial on a new kind of COVID-19 vaccine: one that’s grown in plants.

The vaccine was developed by Canada-based biopharma Medicago and GlaxoSmithKline. Sites around the U.S., including San Diego, are currently enrolling volunteers for a 30,000-person Phase 3 trial.

The two-dose vaccine uses particles grown in plants that closely mimic the shape of the coronavirus to train the immune system.

“It's a mirror image,” said Dr. Denis Tarakjian, who is leading the San Diego arm of the trial at the Medical Center for Clinical Research.

Although similar in structure, these virus-like particles are empty shells that do not contain genetic information and cannot cause an infection, he said.

Medicago’s vaccine does not need to be frozen like the ones from Pfizer or Moderna. It can be stored at refrigerator temperatures similar to the shot from Johnson & Johnson, making it easier to transport and deploy.

All of the authorized COVID-19 vaccines on the market train the immune system with a fragment of the coronavirus: the spike protein. Instead of a fragment, Medicago’s virus-like particles are designed to closely resemble the overall structure of the pathogen.

“The whole point is that it looks like a virus to your immune system so that you develop a really nice, robust response against it,” said Dr. Christian Ramers of Family Health Centers of San Diego.

Researchers have been experimenting with virus-like particles since the 1960s. The Food and Drug Administration approved the first vaccines using the platform in the 1980s to fight Hepatitis B.

But the big breakthrough happened in the late 2000s, said UC San Francisco infectious disease expert Dr. Peter Chin-Hong, when regulators licensed two vaccines for human papillomavirus or HPV.

“In the HPV world, it's done wonders. It's gone gangbusters,” he said. “More than 90 percent efficacy in HPV so they're hoping that it will do the same in COVID.”

If approved, a spokesperson for Medicago said its COVID vaccine could become the first-of-its-kind grown in plants. Past VLP vaccines were grown in bacteria, yeast or certain cells.

A small Phase 1 study found one formulation of Medicago’s COVID vaccine produced 10 times as many antibodies compared to people infected with the real coronavirus. Results from a Phase 2 study are expected to be released this month.

The primary challenge facing researchers will be to enroll enough volunteers for the 30,000 person trial now that anyone 16 and older can book a vaccination appointment in California.
Researchers need volunteers who are 18 or older, have not received a COVID-19 vaccine, and have not had COVID.

“Just because we have something today doesn't necessarily mean we can't find something better tomorrow,” said Dr. Tarakjian. He said the world needs as many vaccine options as possible to fight off variants.

“It's an opportunity for you to be a part of a cutting-edge technology and be the solution to a problem that is devastating this whole world,” he said.

Medicago is hoping to complete the trial and submit results to regulators for review later this year.