Passive immunotherapy- the use of donor antibodies from those either recovered from infection or who have been immunised to produce protective antibodies has been used for many decades for conditions where no drug treatment is available. Pooled human plasma can be used "as is" or treated to isolate the antibody-containing gammaglobulin fraction (giving a low volume, "hyperimmune" globulin formulation). A more modern twist is to use manufactured antibodies of a single specificity (monoclonal antibodies), either on their own or combined as a cocktail.
Passive immunotherapy works and is logistically simple (plasma collection on an industrial scale is routine) and hence an obvious choice for evaluation in COVID-19 treatment.
First results from a (very) small Chinese study of five critically ill (ventilator dependent) COVID-19 patients hint at benefit from convalescent plasma transfusion, with three patients taken off mechanical ventilation within 2 weeks of treatment. Three were discharged after hospital stays of 51-55 days, the other two being in stable condition 37 days after transfusion.
Several industrial and academic groups are pursuing hyperimmune globulin approaches (Takeda, Vir Biotech, Lilly, Celltrion), with others, including Regeneron, looking to monoclonal therapies.
Treatment of 5 Critically Ill Patients With COVID-19 With Convalescent Plasma
Shen C et al. JAMA. Published online March 27, 2020. https://tinyurl.com/tj52h3j
More on US plans for the use of convalescent plasma here:
How blood from coronavirus survivors might save lives. Maxmen A. Nature online 23rd March 2020 https://tinyurl.com/s6e9ndy
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