Convalescent Plasma Did Not Prevent Disease Progression in High-risk Covid Patients: US Study

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Convalescent plasma did not prevent disease progression in a high-risk group of outpatients with COVID-19 when administered within the first week of their symptoms, according to final results of the clinical trial funded by US medical agency.

The study funded by the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health, and by the Biomedical Advanced Research and Development Authority (BARDA), part of the Office of the Assistant Secretary for Preparedness and Response at the US Department of Health and Human Services, was published in an online issue of The New England Journal of Medicine.

The Convalescent Plasma in Outpatients (C3PO) trial was stopped in February due to lack of efficacy based on a planned interim analysis, according to the official statement. "We were hoping that the use of COVID-19 convalescent plasma would achieve at least a 10% reduction in disease progression in this group, but instead the reduction we observed was less than 2%," said Clifton Callaway, MD, PhD, the contact principal investigator for the C3PO trial and professor of emergency medicine at the University of Pittsburgh. "That was surprising to us. As physicians, we wanted this to make a big difference in reducing severe illness and it did not."

COVID-19 convalescent plasma, also known as "survivor's plasma," is blood plasma derived from patients who have recovered from COVID-19. Last year, the US Food and Drug Administration issued an Emergency Use Authorisation (EUA) to allow use of convalescent plasma in hospitalised patients with Covid-19.

India

In India, the government revised the clinical guidance for Covid-19 treatment in May, dropping the off-label use of convalescent plasma as it was found not beneficial in reducing the progression to severe disease or death. The previous guidelines recommended off-label use of plasma therapy at the stage of early moderate disease, that is, within seven days of the onset of symptoms and if there is availability of a high titre donor plasma.

Research

Researchers wanted to know whether administering convalescent plasma might also be beneficial in persons who were recently infected with SARS-CoV-2 and prevent progression to severe Covid-19 illness.

The randomized, controlled clinical trial involved adult outpatients who presented to emergency departments with mild COVID-19 symptoms during their first week post-infection. The trial was conducted by the SIREN clinical trials network, and enrolled more than 500 participants from 48 emergency departments across the United States.

The participants were racially and ethnically diverse with a median age of 54 years, and slightly more than half were women. Participants also had at least one risk factor for progression to severe COVID-19, such as obesity, hypertension, diabetes, heart disease, or chronic lung disease.

The researchers randomly assigned the participants to receive treatment with either high-titer COVID-19 convalescent plasma (containing anti-COVID-19 antibodies) or placebo (salt solution infused with multivitamins and lacking antibodies).

Results

The researchers found no significant difference in disease progression between the two groups. Of the 511 participants, disease progression occurred in 77 (30%) in the COVID-19 plasma group compared with 81 patients (31.9%) in the placebo group. The plasma intervention did not cause harm, the researchers found.

"The results show that convalescent plasma does not appear to benefit this particular group," said Nahed El Kassar, MD, PhD., one of the study's co-authors and medical officer in the Blood Epidemiology and Clinical Therapeutics branch of the NHLBI's Division of Blood Diseases and Resources. "But the findings answer an important clinical question and may help bring researchers a step closer to finding more effective treatments against this devastating disease."

The reason the intervention did not produce the expected results is unclear, Callaway said. Researchers are continuing to look at possible explanations, including insufficient plasma dose, timing of plasma administration, host-related factors, or other aspects of the host tissue responses to the infection, he added.

Additional studies of COVID-19 convalescent plasma are ongoing or planned in different populations.

"We need the results of these other convalescent plasma studies to get a clearer, more conclusive picture of its value for future treatments of COVID-19," said Simone Glynn, MD, MPH, chief of the NHLBI's Blood Epidemiology and Clinical Therapeutics branch, who is coordinating the trial.

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