An Old Source for Potential New Covid-19 Drugs: Blood Serum

On February 27, researchers in China published a short note in the journal Lancet Infectious Diseases citing some evidence of the success of convalescent plasma in treating Ebola and previous respiratory viruses, including SARS, MERS, and influenza H1N1. That same day, Arturo Casadevall, an infectious disease expert at Johns Hopkins School of Public Health, published an op-ed in The Wall Street Journal about the use, to treat measles in the 1930s, of what was then called convalescent serum. Take the blood of people who’ve recovered, let the red blood cells clot and remove them, and transfuse what’s left—the “serum”—into people in the early stages of the disease. (You have to match their blood types.) Not only does this process ease symptoms and potentially save lives, it accelerates the path to immunity, like something in between a drug and a vaccine. In addition to measles, it was used against polio, mumps, and even the 1918 influenza pandemic.

“When serum was used way back then, they didn’t have the same understanding of antibodies. Antibodies hadn’t really been purified the same way,” says Liise-anne Pirofski, chief of the infectious disease division at Albert Einstein College of Medicine and Montefiore Medical Center, and one of the first advocates for using plasma on Covid-19. She’s also a longtime colleague of Casadevall, a fellow advocate of the approach. “Here we are in this crisis, and something that was used 100 years ago is something that could save us now. I just think that’s very cool,” she continues.

Casadevall’s op-ed reawakened the interest of infectious disease experts and other scientists. Colleagues started pinging him saying they wanted to turn the idea into a project. Casadevall and Pirofski were already at work on an article to that end for the Journal of Clinical Investigation: “The Convalescent Sera Option for Containing Covid-19.” Since then, that loose group has grown to perhaps as many as 100 researchers. Casadevall has since tweeted that the Covid-19 Convalescent Plasma Project even has the support of the National Academies of Sciences, Engineering, and Medicine.

Their idea is simple: develop, simultaneously, both studies and arguments for “compassionate use” to give serum antibodies to people with early Covid-19 symptoms. Compassionate use, the Food and Drug Administration’s term for special permission to administer experimental treatments, usually gets invoked for people who are at immediate risk of dying, or who have a disease for which no cure or better treatment exists. In this case, they’d give convalescent plasma to Covid-19 patients the same way doctors have used plasma for decades—with the goal of keeping people in the emergency room from ending up in the intensive care unit, breathing with a ventilator.

As a second possibility, researchers will try testing post-exposure prophylaxis, giving the antibodies to people who might be exposed to the virus, like health care workers, to induce immunity for as long as the foreign antibodies last in their bodies. This “passive immunity” wouldn’t be permanent like a vaccination, but it could keep these workers healthy and at work.

“And there’s a third potential use case, which is Hail Mary-ing people who are really sick,” says Michael Joyner, a physiologist at the Mayo Clinic and one of the group’s organizers. Nobody knows yet if that approach will work at all. But Joyner says it’s an option worth testing. “In an emergency situation like this, the enemy of good is better.” Joyner isn’t an infectious diseases specialist; he’s a physiologist who studies how oxygen moves in the body. But he’s a networker, and he wanted to be part of the mobilization of scientists fighting the pandemic.

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