Ebola: Experimental drugs and vaccines
With hundreds of cases of Ebola in Africa, a panel of World Health Organization (WHO) experts has declared it is ethical to use experimental drugs in this current outbreak.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 antibiotics 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 has been licensed.
- Two US aid workers had 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 that attack proteins on the surface of the virus.
- 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 strands of genetic material of the virus (RNA). The drug interrupts the genetic code of the virus and prevents it from making disease-causing proteins. 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 Fcompany is hopeful that it may get the go-ahead to continue the trial and is willing to make the drug available.
- 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.
Serum - the part of the blood that contains antibodies that can target and neutralise the disease - 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. The WHO says serum could be used as a potential treatment in this current outbreak if methods are developed to collect and administer it safely.What other approaches are being tried?
Scientists have been working on a number of prototype vaccines against Ebola. The WHO says further trials would start soon and potential vaccines may be available in 2016.
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 pharmaceutical companies are unlikely to invest the huge resources needed to develop new drugs when these would probably 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.