Two major studies into the potential benefits of treating hospitalised Covid-19 patients with convalescent plasma have found no evidence to support the treatment’s benefit.
The NIHR-supported REMAP-CAP and RECOVERY trials have been highly publicised and were set up to test if plasma transfusions from someone who has recovered from the coronavirus might be able to help improve outcomes for Covid-19 patients struggling to develop antibodies.
Convalescent plasma treatments had shown to have positive effects for patients during a SARS outbreak in the early 2000s - with SARS being a different variant of the coronavirus virus type.
However, preliminary analysis of data from almost 10,500 patients randomised in the convalescent plasma arm of the RECOVERY study showed no significant difference was found in the primary endpoint of 28-day mortality (18% with convalescent plasma treatments vs 18% with usual care alone).
The study has therefore now closed recruitment to its convalescent plasma treatment arm for all patients hospitalised with Covid-19.
The Data Monitoring Committee found no convincing evidence that further recruitment would be conclusive proof of worthwhile mortality benefit - either overall or in any particular subgroup of patients.
Follow up observations of existing patients is ongoing and analysis continuing, with the final results to be published in due course.
Similar early findings from the REMAP-CAP trial also found that treating critically ill Covid-19 patients in intensive care with blood plasma had limited impact on patient outcomes.
Analysis of its findings showed a low probability - just 2.2% - that convalescent plasma decreased the number of days that patients required intensive care support or death by more than 20%.
No evidence of harm was found as a result of convalescent plasma treatment, but based on the initial analysis of 912 patients. Investigators have now paused recruitment of severely ill Covid-19 patients in intensive care to this arm of the study.
The trial is continuing to analyse data in case there is evidence of benefit in a subgroup, and to see whether patients who haven’t started making their own antibodies may still benefit from the treatment.
Professor Anthony Gordon, Chief Investigator of REMAP-CAP said: “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.”
Professor Nick Lemoine, Medical Director of the NIHR Clinical Research Network, added: “Despite the negative convalescent plasma results from RECOVERY and REMAP-CAP, both studies demonstrate the huge importance of randomised clinical trials. Convalescent plasma was once widely considered a therapeutic option with a high potential for treating Covid-19 - yet NIHR-supported research has shown plasma transfusion to be ineffective overall.
“While disappointing, data from these vital studies will allow clinicians the world over to focus treatment decisions on proven therapeutic options.
“We want to say an enormous thank you to everyone who has taken part in these urgent public health studies - as well as to all those who have so kindly donated their blood plasma through NHS Blood and Transplant, having had this dreadful disease.”
Following the initial results from the RECOVERY and REMAP-CAP trials, NHS Blood and Transplant has temporarily halted the collection of plasma from people who have had Covid-19.