ÖOn February 25, the National Institutes of Health discontinued a clinical trial testing the use of convalescent plasma in out-of-hospital COVID-19 patients after an independent advisory board said the treatment was no better than placebo to prevent serious illness or death.
“Even if registration continued, the study was very unlikely to show that convalescent plasma prevented the progression from mild to severe disease,” says Simone Glynn, an epidemiologist at the NIH’s National Heart, Lung and Blood Institute (NHLBI), who said directed the study. According to Glynn, data underlying the decision to discontinue the study are not yet available as patients will be observed for up to 30 days after participating in the study.
The completion of the study is the latest blow to an intervention seen as showing promise to prevent the progression of mild to severe COVID-19 in people who contract the virus.
The principle of infusing antibody-rich plasma from recovered patients into sick patients is more than 100 years old. Based on observational results that plasma prevented cases of severe COVID-19, the U.S. Food and Drug Administration (FDA) issued an Emergency Authorization (EUA) for the treatment of people hospitalized with COVID-19 in August.
Convalescent plasma was a good treatment when we didn’t know how to make virus-specific antibodies. It was in the middle of the pandemic and it served its purpose.
– Miriam Merad, Icahn School of Medicine on Mt. Sinai
Representatives from 47 emergency rooms in the United States participated in the COVID-19 Outpatient Recovery Study (C3PO) clinical trial to test whether recovery plasma is beneficial in outpatient settings, according to the NIH. The NHLBI had enrolled 511 of the 900 patients it wanted to recruit by the end of the study.
Study participants were enrolled in the study when they went to the emergency room after mild or moderate symptoms of COVID-19. All were sick for a week or less and were not hospitalized. Everyone had at least one risk factor, such as obesity or high blood pressure, to develop a serious illness. Half of the participants were to receive a single infusion of plasma donated by COVID-19 survivors and the other half a placebo.
While the monitoring panel concluded that convalescent plasma was safe, they noted that it was no better than placebo in changing patient outcomes. After this decision, NHLBI Director Gary Gibbons stopped the study.
Although data analysis continues, NHLBI officials are confident that the placebo and treatment groups were comparable to each other. “From what we’ve seen so far, all demographics have been balanced,” said Nahed El Kassar, who administered C3PO for the NHLBI.
Convalescent plasma use was quickly politicized during the COVID-19 pandemic, with former President Donald Trump hyping the treatment long before randomized trials were conducted to determine its effectiveness. Trump was on the side of former FDA Commissioner Stephen Hahn when Hahn announced at a press conference the EEA for convalescent plasma, which led to Hahn’s resignation for overestimating the benefits of the treatment.
Against this troubled backdrop, several clinical studies have taken place around the world, some of which have been previously covered The scientist. Together, they seem to dampen hopes for the benefits of convalescent plasma, especially in hospital patients. The NIH decision to stop C3PO comes less than a week after a JAMA A review of 10 clinical trials also found that plasma was no better than placebo at reducing death or improving clinical outcomes. Nine of these studies focused on hospital patients, the other on outpatients.
“Convalescent plasma was a good treatment when we didn’t know how to make virus-specific antibodies. It was in the middle of the pandemic and it served its purpose. But right now I think it’s the end [of convalescent plasma as a viable treatment]and I’m not surprised by that [NIH] Results at all, ”says Miriam Merad, oncologist and immunologist at the Icahn School of Medicine on Mt. Sinai.
Some doctors, like Michael Joyner of the Mayo Clinic, claim that convalescent plasma can be helpful for certain patients. Joyner was one of the leaders in the U.S. expanded convalescent plasma access program last year that prompted the FDA to issue the EEA ratifying the use of convalescent plasma in hospitalized COVID-19 patients. He argues that emerging evidence shows a benefit of convalescent plasma when given at the beginning of a hospital stay in higher doses than those tested by the NIH.
“I’m very happy to say that convalescent plasma is fantastic if you have lymphoma, leukemia, a congenital problem, or are taking an immunosuppressant,” says Joyner. “I’m also really excited to tell people that if they are symptomatic on an outpatient basis, they will be given monoclonals,” adds Joyner. Monoclonal antibodies are tailored to attack the virus’ spike proteins, grabbing receptors on human cells, and causing infection. Two monoclonal drugs from Regeneron and Eli Lilly have received EUAs from the FDA.
According to Merad, monoclonal antibodies are superior to convalescent plasma because they were specially developed for the SARS-CoV-2 virus. Convalescent plasma likely contains some neutralizing antibodies to SARS-CoV-2, she says, but it also contains antibodies to other infections unrelated to the virus. If the problem is with antibody production, use the tool that is best suited to solving that challenge. Merad also notes that there is always a risk of contamination when a blood product is transferred from one person to another.
The debate over the use of convalescent plasma is likely to continue as clinical trials progress. The NIH is sponsoring a study on convalescent plasma use in hospitalized COVID-19 patients, and Johns Hopkins University is sponsoring two studies on use in outpatient settings.