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Fox News medical contributor Dr. Marc Siegel joined "Tucker Carlson Tonight" Wednesday to discuss three hopeful developments in the fight against the coronavirus.

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The first development that Siegel spoke of involves a San Francisco bioengineer's effort to re-engineer antibodies to attack COVID-19.

"Back in January, Netflix, ironically, released a documentary called 'Pandemic.'" Siegel explained. "And one of the scientists they featured, an immunologist bioengineer from San Francisco, Jacob Glanville, has now gone on since that film to be working on ... several antibodies that he took from another coronavirus, SARS, from 2003.

"And he's re-engineered these antibodies so that they literally attack... the virus by blocking its entry into the cell," Siegel went on. "He's got it to the point now where he's handing it over to Army research. The Army research laboratories are going to test it and see how effective it is. And from there, [they'll] go on to human trials."

Siegel described Glanville's would-be treatment as "very, very interesting," noting that "it has been used in the past, using targeted antibodies to go after a virus. It may not be a cure, but it can certainly decrease symptoms."

The second development involves using tobacco plants to develop antibodies.

"Tobacco is actually a plant that we use to grow vaccines, to grow the proteins that we then use to challenge your immune system to create an antibody," Siegel told Carlson. "A tobacco plant is now being injected with a protein from this coronavirus to see if they can develop a vaccine.

"So not only are they making tobacco that puts our lungs at risk for this virus, but they're also working on a vaccine against the virus," the doctor added.

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The third development involves a Harvard study shedding light on what could be a key symptom of the virus.

"Harvard has been looking at the symptoms we see from COVID-19, and they've discovered something we've been talking about recently, which is the [loss of] sense of smell called Anosmia," Siegel said. "And when you lose your sense of smell ... it's because this virus seems to attack the skin inside the nose and it gives you a loss of sense of smell and a loss of sense of taste.

"That's a characteristic finding ... if I see it with people that come in with a little bit different symptoms," the doctor added. "Maybe [they have] cough, maybe shortness of breath, maybe fever, maybe not. But if they have that loss of sense of smell, I think, 'Well, this could be COVID-19.' It's very helpful diagnostically."