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Trial to Test Convalescent Antibodies for Covid-19

SARS-Cov-2 virus

Scanning electron microscope image of SARS-Cov-2 virus, in orange, emerging from cells (NIAID, Flickr)

7 April 2020. A group of Canadian academic labs and hospitals will begin a clinical trial testing antibodies from recovered Covid-19 patients as a treatment for the disease. The Convalescent Plasma for Covid-19 Research or Concor trial is expected to enroll 1,000 patients with Covid-19 infections at some 40 hospitals in Canada.

Plasma is the clear part of human blood that contains white blood cells including those used by the immune system to fight infections. In people who recovered from Covid-19, white blood cells also contain antibodies to protect the individual from further infections from the SARS-CoV-2 virus. In some cases, those antibodies neutralize, while other antibodies stimulate a response from other immune-system cells, or simply bind to the virus without affecting its infectiousness.

The plasma with antibodies from recovered Covid-19 patients is called convalescent plasma and is considered a potential source of treatments for the disease. U.S. Food and Drug Administration on 3 April issued updated regulatory guidance for convalescent plasma’s use in clinical trials and expanded authorized emergency access for seriously ill patients for whom clinical trials are not feasible. However, clinical evidence is sketchy, limited to small sample tests with no placebos and mixed outcomes.

“While there have been reports of people trying this with some success, all of these involved only handfuls of patients and that is all we have to go on,” says hematologist Donald Arnold at McMaster University in Hamilton, Ontario, the clinical trial leader, in a university statement. “We really don’t know if this is truly an effective therapy.”

“When people have recovered from Covid-19 infection,” Arnold adds, “we are hoping they will donate a unit of plasma which is essentially the clear portion of blood where all the antibodies are. Presumably those antibodies helped them fight off their Covid-19 infection and allowed them to get better.”

The Concor trial plans to enroll 1,000 Covid-19 patients at some 40 hospitals in every Canadian province and most territories, randomized two-to-one to receive plasma or standard care. Arnold, with trial co-leaders allergist Philippe Bégin at University of Montreal and pathologist Jeannie Callum at University of Toronto, enlisted the help of Canadian blood banks to supply the plasma. The study team is looking primarily at death rates of participants, but also need for mechanical ventilation, length of hospitalization, and need for intensive care, as well as reports of adverse effects.

Arnold says the project came together quickly, after a conference call on 29 March, and merging a similar study planned in Quebec. The trial’s start date will depend on the amount of time for collecting donated plasma, with six to 10 months needed for the study itself. He also hopes to provide interim findings in three to four months.

Richard Carl, a recovered Covid-19 patient in Toronto, tells the Toronto Globe and Mail, “There is a real feeling of helplessness in the world today. The thought of asking someone to help fix this thing; I couldn’t say yes fast enough.” Carl is a patient representative on a committee advising the clinical trial.

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