Convalescent Plasma: Another COVID Dud

By Josh Bloom — Aug 19, 2021
As was the case with other "instant therapies" for COVID, convalescent plasma showed no utility whatsoever in a well-designed randomized controlled trial, something that should come as no surprise to anyone who has ever waded in the treacherous waters of drug discovery research. Another one bites the dust.
Image: Wikipedia

One of the many lessons learned from COVID is that it's not trivial to come up with new drugs or therapies that will tackle a new virus. Chemistry blogger Derek Lowe, who started his unparalleled "In the Pipeline" blog two decades ago, explained just this in a recent Bloomberg Opinion piece.

A recently discovered cure for hepatitis C is a rare exception, along with the drug cocktail that prevents HIV infections from progressing to AIDS. There are drugs that can control but not cure herpes.

Derek Lowe in Bloomberg Opinion, July 14,2021

So, it isn't the least bit surprising that early "promising" drugs like hydroxychloroquine and remdesivir (among others) failed to provide a substantial benefit to patients with COVID (1)

Now, another one bites the dust. It was reasonable to try convalescent plasma (aka "survivor's plasma), which was taken from people who caught and recovered from Covid-19. But reasonable doesn't mean successful. The survivor's plasma did not survive the trial.

The "Clinical Trial of COVID-19 Convalescent Plasma in Outpatients" aka C3PO (clever, no?) studied the effect of early administration (1) of convalescent plasma in a group of high-risk patients who sought treatment in an emergency department but were not admitted. Unfortunately, there wasn't any.

Depressing Details

  • The sponsors of the C3PO trial, which began in August 2020, were the National Heart, Lung, and Blood Institute (part of NIH) and BARDA (2)
  • The desired endpoint was a 10% reduction in disease progression.
  • More than 500 participants from 48 EDs in the US were enrolled.
  • High-risk patients were defined as having at least one of the following risks: high blood pressure, obesity, chronic lung disease, and heart disease. 
  • The trial was a randomized controlled trial; half the participants received plasma containing antibodies, the other half got a placebo. 
  • COVID progression was seen in 77 of the 511 participants (31.9%) who got plasma and 81/511 (30%).
  • The observed reduction in disease progression was less than 2% in the patients given the plasma. 
  • If this isn't a complete flop, then I don't know what is. 

The "Good" News

Although the plasma wasn't helpful, at least it didn't harm anyone. 

“The results show that convalescent plasma does not appear to benefit this particular group... 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.” [emphasis mine]

Nahed El Kassar, M.D., Ph.D, et. al. "NIH study shows no significant benefit of convalescent plasma for COVID-19 outpatients with early symptoms."

I don't get it. Aside from knowing not to use convalescent plasma, it is difficult to see how this trial will leave researchers a step closer to anything whatsoever. 


(1) Early administration means within one week of the beginning of symptoms. 

(2) BARDA is an acronym for the Biomedical Advanced Research and Development Authority


Josh Bloom

Director of Chemical and Pharmaceutical Science

Dr. Josh Bloom, the Director of Chemical and Pharmaceutical Science, comes from the world of drug discovery, where he did research for more than 20 years. He holds a Ph.D. in chemistry.

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