Seattle’s HDT Bio to start U.S. clinical trials of its COVID-19 vaccine candidate

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Steve Reed, CEO of HDT Bio. (HDT Bio Photo)

An experimental COVID-19 vaccine in development by Seattle-based HDT Bio will enter early-stage clinical trials in the U.S., the company announced yesterday after the U.S. Food and Drug Administration cleared the trial to go forward.

The phase 1 trial will enroll 60 volunteers and will assess safety and the strength of the immune response against the vaccine.

HDT Bio’s vaccine is based on RNA, like the approved vaccines from Moderna and Pfizer. But the HDT RNA is additionally powered to make multiple copies of itself, which has the potential to yield a more potent shot with lower doses, and at lower costs.

The RNA in the HDT Bio vaccine attaches to the outside of a nanoparticle the company developed that improves the vaccine’s stability and also amplifies the immune response. The immune system raises a response against the proteins encoded by the RNA, and the nanoparticle boosts the response.

“We think there’s a good chance our vaccine will have efficacy after just a single shot and may be evaluated for such in trials,” said HDT Bio co-founder and COO Christopher Pirie. He added: “We expect doses will be eventually shipped at refrigerator temperatures.”

In August the company published early promising results from its tests of the vaccine in mice and non-human primates, in Science Translational Medicine.

An easy-to-manufacture, stable, one-shot vaccine could be the answer to easier roll-out and global vaccine coverage. The company began trials in May testing a similar vaccine in India with its development partner Gennova Biopharmaceuticals, based in Pune, India.

“An important part of HDT’s mission is establishing value-sharing partnerships with drug companies in historically underserved countries.  Our goal is to empower our partners to produce and distribute innovative medicines at affordable prices,” said HDT Bio CEO and president Steve Reed in a statement announcing the India collaboration.

Reed, former head of Seattle’s Infectious Disease Research Institute, has developed leprosy and leishmaniasis vaccines, and a lead vaccine candidate for tuberculosis. HDT Bio, founded in 2019 by Reed, Pirie, André Lieber and Michael Gale and Darrick Carter, is additionally developing vaccines for cancer and other infectious diseases, including AIDS.

As more people worldwide become vaccinated with existing vaccines, HDT is preparing for the pool of volunteers for trials to shrink in some regions. “We’ll be tailoring our studies to accommodate the vaccine status of each territory we work in,” said Pirie.

“Locally, that will probably mean moving towards boosting already vaccinated individuals for improved protection against diverse variant strains,” added Pirie. The company will be testing the vaccine, designed to work against multiple viral variants, in partnership with Kaiser Permanente in Seattle, and will release details about trial recruitment soon.

HDT Bio has received an $8.2 million contract from the National Institute of Allergy and Infectious Disease at the National Institutes of Health to support development of its COVID-19 vaccine, and it also recently raised $6 million in seed financing for the vaccine effort, led by Zoic Capital.

Another experimental vaccine developed at the Institute for Protein Design at the University of Washington is also currently in human testing. The vaccine design, developed by Seattle biotech company Icosavax and SK bioscience in South Korea, consists of a nanoparticle scaffolding studded with copies of a key region of the virus’ spike protein, mimicking the shape of the coronavirus.

Editor’s Note: This story was updated to more precisely describe the company’s trial and with information about the founders.