Ebola: The race for drugs and vaccines

potential ebola vaccines - graphic Many organisations are working together to find suitable compounds

The race is on to find a cure for the disease that has killed more than 5,000 people in West Africa.

There are no proven treatments for people with the Ebola virus or vaccines to prevent infection in the first place.

However, progress is now being made on an unprecedented scale.

Trials, which would normally take years and decades, are being fast-tracked on a timescale of weeks and months.

Vaccines in development
potential Ebola vaccines The aim is to use the lowest dose of the vaccine that provides protection so several doses will be tried

Vaccines train the immune systems of healthy people to fight off any future infection.

Two Ebola vaccines have been rushed from promising animal studies into human trials.

One is produced by GlaxoSmithKline (GSK) and the National Institutes of Health in the US, and the other was designed by the Public Health Agency of Canada and is being produced by Merck.

GSK has inserted an Ebola gene into a weakened chimpanzee virus, which is unable to replicate in the human body.

Initial tests on 20 volunteers in the US showed it was safe and that the tiny fragment of Ebola's genetic code was enough to generate an immune response.

Further trials are taking place in the UK, US, Switzerland and Mali to see if the immune response is strong enough to fight off an Ebola infection and how long any such protection would last.

potential Ebola vaccines The first volunteer took part in a trial in the US.

The Canadian vaccine is based on adding an Ebola gene to a virus that normally infects livestock.

It is being tested in the US and Switzerland, and there are plans for trials in Gabon and Kenya.

Initial safety results on 34 volunteers in Geneva are promising, according to Swiss scientists. They plan to carry out further checks to see whether the vaccine provokes an immune response before they publish their data in a scientific journal in 2015.

Johnson and Johnson also has a vaccine in the pipeline, and the World Health Organization (WHO) is evaluating developments in Russia and Japan.

Vaccine challenges

The first major issue is running the clinical trials at speed, nothing like this has been done before.

Ethical issues surround testing a vaccine during an outbreak, and researchers face a lack of public trust in some communities

When the trials move to the front line of the Ebola outbreak, then it will be healthcare staff and burial workers who will be immunised.

There are no plans for mass vaccination of the general population before June 2015, but the WHO has not ruled it out.

There are also practical issues to address as both vaccines contains live, but weakened, virus.

It means the shots will have to be kept below minus 80C in hot countries with limited access to electricity.

The drug companies also want indemnity in case something goes wrong when they are asked to rush through a vaccine.

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Promising drugs
Several experimental treatments are under development Several experimental treatments are under development

Drug research is also taking place at pace. Instead of preventing infection like vaccines, these are designed to boost the recovery of those who have been infected.

The WHO says it is getting daily proposals for potential medicine, yet many show no activity against the virus.

Two potential drugs are being tested at Medicins Sans Frontieres facilities.

They both interfere with the way viruses replicate inside our cells:

  • Brincidofovir - up to 140 consenting patients will take the tablets twice a week over a two-week period, and survival rates will be compared with before the trial. This research is led by the University of Oxford in the UK.
  • Favipiravir - is approved in Japan for treatment of the influenza virus and is being tested in Gueckedou, Guinea. The research is being led by the French National Institute of Health and Medical Research (Inserm).

Trials are due to start in December, with the first results expected in February 2015.

Other drugs such as ZMapp have attracted attention during the outbreak.

Two US aid workers and a Briton recovered after taking ZMapp, but a Liberian doctor and a Spanish priest died.

Like all other drugs, there is a lack of clinical evidence about whether it does work and stocks have been extremely limited so trials have been hampered.

Ethical quandary

Drugs trials are even more ethically controversial than vaccine trials in the midst of this outbreak.

Should normal randomised clinical trials take place?

It allows doctors to know for certain whether a drug is effective, but it means withholding a potentially life-saving treatment during a deadly outbreak.

One option being used is to compare survival in the same centres before and after drugs were used.

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Survivor's blood
Blood is screened for diseases before it is transfused Blood is screened for diseases before it is transfused

A different approach to manufacturing a drug is to harness one survivor's immune system to help another who is sick.

The body produces Ebola-fighting antibodies in response to an infection.

So the idea is to purify the blood, extract the antibodies and give those to sick patients.

Studies on the 1995 outbreak of Ebola in Democratic Republic of Congo showed seven out of eight people survived after being given the therapy.

This approach is being trialled in Guinea, led by the Antwerp Institute of Tropical Medicine.

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