Ebola: Experimental drugs and vaccines

With hundreds of cases of Ebola in Africa, health experts are looking at whether the use of experimental drugs is justified.
What is the current treatment for Ebola?
There is no licensed treatment or vaccine for the Ebola virus. Hospital treatment is based on giving patients intravenous fluids to stop dehydration and antibio
tics to fight infections. Strict medical infection control and rapid burial are regarded as the best means of prevention.
What about experimental treatments?
Several experimental treatments for Ebola are being developed, which have shown promising results in monkeys when given up to five days after infection. However, they have not been tested in more than a handful of people and none have been licensed.

• Two US aid workers have been given an experimental treatment, known as Zmapp, with “apparently encouraging” signs in one of them, said Prof Tom Solomon, director of the NIHR Health Protection Research Unit in Emerging and Zoonotic infections. The treatment is a mixture of three monoclonal antibodies against the Ebola virus, produced in bioengineered tobacco plants.

• Another experimental drug, developed by Tekmira Pharmaceuticals in Canada, has been tested on monkeys and in a handful of healthy human volunteers. The drug, TKM-Ebola, is designed to target the strands of genetic material of the virus (RNA). A small early safety trial on a small number of human volunteers was put on hold last month when regulators requested further safety data.

• The US-based pharmaceutical company, Sarepta Therapeutics, has developed a similar RNA treatment. It has been tested in healthy human volunteers in early safety trials, but has never been tried in a human patient.

What is serum?
Serum – the part of the blood that contains antibodies – has been used in past Ebola outbreaks. Survivors have high levels of antibodies against the virus in their blood. In one outbreak in 1995 in the Democratic Republic of Congo, seven out of eight patients survived after being treated with serum from survivors, according to Prof Solomon. Reports suggest that the US aid workers who developed Ebola may have been given serum before being flown home from Africa.
What other approaches are being tried?
Scientists have been working on a number of prototype vaccines against Ebola. Most are in very early stages of research in animal models and no vaccine has been licensed.
The Food and Drug Administration in the US says it is fast-tracking a vaccine that has shown encouraging signs in monkeys for phase 1 trials in September.
This type of trial is the earliest study in humans and aims to make sure that drugs are safe and show some chance of working.
What are the chances of success?
Experts say that pharmaceutical companies are unlikely to invest the huge resources needed to develop new drugs when these would likely be used only occasionally in relatively small numbers of people. They say investment is needed from international agencies to have any realistic chance of success in the future.
The use of experimental treatments and vaccines has also raised ethical dilemmas. The World Health Organization (WHO) is convening a panel of medical ethicists to explore the use of experimental treatments.
It says the recent treatment of two health workers with experimental medicine has raised questions about whether medicine that has never been tested and shown to be safe in people should be used in the outbreak and if it is used, who should receive it.
“We are in an unusual situation in this outbreak. We have a disease with a high fatality rate without any proven treatment or vaccine,” says Dr Marie-Paule Kieny, Assistant Director-General at the WHO.