Although the U.S. Food and Drug Administration (FDA) recently awarded convalescent plasma emergency use authorization (EUA), investigators at the University of New Mexico (UNM) recently stopped a clinical trial earlier in the month after discovering no benefit to COVID-19 patients with the use of convalescent plasma obtained from donors who survived the condition. Dr. Michelle Harkins, division chief of Pulmonary Critical Care and Sleep Medicine at UNM, recently shared concerns based on the FDA award and comments out of the White House describing convalescent plasma as a “Very powerful treatment.” The UNM findings should be at least understood for further research involving convalescent plasma.
Stopping the Study
By August 14, the University of New Mexico investigators identified possible serious shortcoming in the use of so-called “convalescent plasma,” reporting that none of 12 patients at University of New Mexico Hospital who received the treatment received any benefit whatsoever.
Dr. Harkins reported, “We stopped after we enrolled 13 patients after we got some strong data back showing that most of the convalescent plasma had little to no neutralizing antibodies in it and actually didn’t help them improve their antibody levels.” The team’s study was published in the Journal of Infectious Diseases and represents a unique collaboration between multiple departments within UNM.
No Positive Results
The study showed no evidence that convalescent plasma had triggered any strong immune response in the hospitalized patients. Moreover, after the investigators and staff tested the plasma from multiple donors they found a wide difference in the concentrations of the neutralizing antibodies.
The team also measured levels of Immunoglobulin M (IgM) antibodies, that is, the first to be produced in the body when the immune system detects an infection, as well as Immunoglobulin G (IgG) antibodies, which trigger a longer-lasting immune response. They found that the presence of IgG doesn’t translate to high levels of neutralizing antibodies.
Concentrations of Neutralizing Antibodies Vary
The UNM team suspects, based on their observations, that the concentrations of neutralizing antibodies in convalescent plasma may very well vary depending on the severity of the donor’s illness and how much time actually elapsed prior to the donation. This study out of UNM underscores the need to test concentrations of neutralizing antibodies prior to administering convalescent plasma to patients.
Moreover, although each patient received a standardized 200 milliliters of plasma, the difference in patient weight, age and size suggests that the amount of plasma administered must be matched to each patient’s body size.
Dr. Michelle Harkins, division chief of Pulmonary Critical Care and Sleep Medicine at UNM
Call to Action: Although this UNM study only involved 12 patients, its findings nonetheless should be considered in any convalescent research moving forward. If anything else, more research into the varying concentrations of antibodies in convalescent plasma must be better understood. Researchers will need to better pre-screen convalescent plasma donations to identify those samples with higher antibody levels.