A clinical trial looking at whether blood plasma from coronavirus patients can help those who are seriously ill does not appear to work in intensive care patients, researchers have said.
The REMAP-CAP trial, which is testing the effects of convalescent plasma in Covid-19 patients, has paused enrolment for those who are severely ill needing intensive support in intensive care units (ICUs).
But donors are still being urged to come forward for work on less severely ill patients to see whether they can benefit from the plasma.
A statement from researchers behind the REMAP-CAP trial said the decision to stop recruiting severely ill patients was based on initial analysis of the data.
The statement said: “This analysis showed that convalescent plasma did not improve outcomes in this group.
“There was no evidence of harm associated with the administration of convalescent plasma.
“The trial is continuing to recruit hospitalised Covid-19 patients who are moderately unwell and are not requiring intensive care. Senior investigators are asking people to continue donating plasma.”
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The latest analysis looked at data from a subset of 912 people who were severely ill. More than 2,000 patients are taking part in the trial overall.
The analysis found that, overall, convalescent plasma was unlikely to be beneficial.
Experts found there was “a very low probability” (2.2%) that plasma decreased the number of days that severely ill patients required intensive care support or risk of death by more than 20%.
But they said: “Whether the use of convalescent plasma leads to better outcomes in hospitalised patients with less severe disease remains a very important question. Recruitment of such patients will continue in the trial.”
Manu Shankar-Hari, professor of critical care medicine at Guy’s and St Thomas’ NHS Foundation Trust in London, which is in the trial, said: “We are publicly sharing the preliminary data to ensure that learning happens at pace for determining best treatments for Covid-19.
“Further data on all the trial participants, including whether particular patient subgroups may benefit, will be forthcoming.
“We are incredibly grateful to all the trial participants, plasma donors, clinicians, blood bank services, and research staff who help us understand the best treatments for Covid-19.
“It is biologically plausible that patients who are not producing antibodies at the time of convalescent plasma therapy and those patients with excess virus may benefit more than others.”
A separate RECOVERY trial is looking at a range of treatments for coronavirus including plasma. It works closely with investigators from the REMAP-CAP trial.
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Peter Horby, professor of emerging infectious diseases and global health from the University of Oxford, and chief investigator for RECOVERY, said: “We don’t yet know if convalescent plasma works as a treatment for Covid patients, but if it does it would have a major impact worldwide.
“Plasma from patients who have recovered from Covid-19 contains antibodies that may help to speed up clearance of the virus from those who are suffering from the disease and improve their chances of recovery, particularly if they are treated before they become severely ill.
“By volunteering to donate plasma you will ensure we complete the study and provide the evidence we need to improve care for Covid patients and save lives.”
Anthony Gordon, professor of anesthesia and critical care at Imperial College London, which takes part in REMAP-CAP, said: “I am glad REMAP-CAP has been able to provide important evidence about which patients might benefit from convalescent plasma.
“Although it is disappointing that all critically ill patients don’t appear to gain any benefit, this is still vitally important to know.
“Convalescent plasma is a precious resource, and we can now continue to focus on identifying exactly which patients might benefit the most from treatment – maybe people earlier in their illness or those with weak immune systems.”
Dr Gail Miflin, chief medical officer for NHS Blood and Transplant, said: “REMAP-CAP is now in the analysis phase and is exploring whether subgroups of people in intensive care benefit from plasma. The final results are not yet known.
“We urgently need people to continue donating thousands of units of plasma every week for the larger RECOVERY trial which is using plasma from when people come into hospital.
“Antibodies work by stopping the virus, not by treating the symptoms.
“The emerging evidence from international studies is that use before intensive care may prove to be more effective.”
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