Survivors' plasma fails Ebola treatment

A treatment once considered among the most promising for Ebola patients was not found to be effective in a study performed in Guinea, researchers reported in The New England Journal of Medicine on Wednesday.

The experimental treatment involved transfusions of blood plasma collected from Ebola survivors, whose immune systems develop antibodies to neutralise the virus. But the survival rate among the 84 patients in the study who received such transfusions last year was not significantly better than for previous patients who had not received transfusions. Still, the researchers held out some hope for the treatment, known as convalescent plasma.

“We can only say the way plasma was used didn’t show the effect we’d hoped for,” said the study’s lead author, Dr Johan van Griensven, who leads the unit for HIV and neglected tropical diseases at the Antwerp Institute of Tropical Medicine.

The plasma treatment was at one point the top experimental therapy recommended by the WHO for testing during the Ebola outbreak in West Africa, which has killed more than 11,000 people. Van Griensven said there was still a possibility that the treatment could be effective in certain circumstances.

For example, an unusually high proportion of young children and pregnant women who received it during the study survived. However, because only a small number of them were part of the study, conclusions could not be drawn, he said.

It is also possible that only plasma with very high levels of the active antibodies might be effective. Researchers had plan-ned to quantify those levels in a specialised laboratory in France, but samples have yet to be analy-sed because it took many mont-hs to gain approval to ship them.

Another report in the same journal found a survival advantage for Ebola patients in Liberia who received an antimalarial treatment containing the drug amodiaquine. The finding was serendipitous: A Doctors Without Borders treatment centre ran out of a standard malaria treatment and for 12 days used the substitute with amodiaquine. Patients given the substitute drug had a 31 per cent lower risk of death once the data were adjusted for other factors that could affect survival.

Doctors discovered the effect only months later, when they re-viewed patient records after no-ting that amodiaquine had sho-wn anti-Ebola activity in a la-boratory study published 2013. The study cautioned, however, that the survival difference could also have been explained by a negative effect of the standard malaria treatment.

Experts not involved in the two papers said the researchers demonstrated the ability to collect important data in an emergency situation. Some had questioned whether Ebola survivors in Guinea would volunteer to participate in the plasma study, noting that the very idea of blood donations from strangers is alien to most people there.

“If somebody gets ill, a family member will come to the centre here and donate blood,” said Dr Nyankoye Haba, who directs the country’s national blood transfusion centre and is an author of the study.

Lack of randomisation
A major limitation of the plasma study was a lack of randomisation. In the most rigorous studies, an experimental treatment is given only to a subset of patients whose outcomes are compared with patients not receiving the therapy. But because plasma was perceived to be so promising, and unlikely to cause harm, the researchers deemed it unacceptable to deprive some patients of the opportunity to receive it.

Patients receiving the plasma transfusions were instead compared with those who had previously undergone treatment at the same Doctors Without Borders centre. This was problematic, because survival rates fluctuated throughout the epidemic though any causes are not known.

Thus, definitive conclusions about the effectiveness of plasma treatment cannot yet be drawn, said Dr Luciana Borio, the acting chief scientist at the Food and Drug Administration, who was not involved in the study. Borio wrote in an email that dedicated investigators working with the community had performed “important clinical research,” but that the international community now needed to “further improve the quality of clinical trials done during a public health emergency.”

The study itself, which involved a coalition of more than a dozen international and local institutions, is likely to leave a positive effect on Guinea. “We really have strengthened the competences of the staff in the transfusion centre,” Haba said.