Following is a fact file on the main drugs to tackle the Ebola virus, which has claimed more than 1,400 lives in five African countries since December.
No licensed drug exists for treating Ebola. Several prototypes are in the pipeline, one of which has been fast-tracked for use in the outbreak, although whether it works is unknown.
According to University of Oxford epidemiologist Oliver Brady, up to 30,000 people would have required drugs, either to combat or prevent infection, as of August 20.
ZMapp: a cocktail of three antibodies that cling to the virus and inhibit its reproduction, developed by Mapp Biopharmaceutical Inc. of San Diego, California, partly in conjunction with the US Army.
It has been tested successfully on lab monkeys but not evaluated on humans.
After the World Health Organisation said on 12 August that it was ethical to use experimental treatment in the crisis, ZMapp was given to seven infected frontline workers.
Of these, two American doctors have recovered; a Liberian doctor and a Spanish priest have died; and a doctor and a nurse, both Liberian, and a British nurse, who has been flown to London from Sierra Leone, are still in treatment.
Stocks of ZMapp, which is derived from tobacco leaves and is hard to produce on a large scale, are exhausted, the company said on 12 August. It is likely to take several more months "to get even a modest amount," according to Anthony Fauci, director of the US National Institute for Allergy and Infectious Diseases (NIAID).
TKM-Ebola: Drug under development by Tekmira Pharmaceuticals Corp. of Vancouver, Canada, under a $140-million (105-million-euro) contract with the Pentagon.
The drug, using a technique called RNA interference, is designed to throw a genetic switch causing the death of cells infected by the virus.
Tests on a small group of monkeys have shown it provides 100 percent protection against an otherwise lethal dose of the virus.
It is currently in a Phase I trial, the first step in the three-phase test process. In this phase, a drug is evaluated on healthy non-infected humans to see whether it is safe. Further phases test it for safety and effectiveness.
Tekmira said on August 14 that it was in contact with government agencies, NGOs and the WHO "on the potential use" of TKM-Ebola in west Africa.
Anti-viral drugs: Several proposed treatments for mitigating Ebola started out as drugs to inhibit replication of the influenza virus.
They include Avigan, a Japanese anti-flu tablet drug developed by Fujifilm Holdings Corp. that was approved in Japan on March 24 and is currently undergoing clinical trials in the United States. Japan said on August 25 it is ready to ship the drug to Ebola-hit areas if the WHO requests.
But it is unclear whether Avigan -- lab name T-705 -- will work on Ebola, which is part of a different viral family called filoviruses. No tests of T-705 have been done on Ebola-infected lab animals or humans.
Vaccines: There are two main candidates, but both face extensive trials and neither is likely to be available before 2015 even if they are fast-tracked.
The British company GlaxoSmithKline (GSK) says a prototype vaccine may enter Phase I clinical trials among a small group of human volunteers "later this year." The formula comprises an adenovirus -- a virus group best known for causing the common cold -- into which two Ebola genes have been slotted.
The virus penetrates a cell and delivers its payload, which produces a protein that triggers an immune response to recognise and destroy an invading virus.
The adenovirus is designed not to replicate further, thus preventing any spread of the Ebola genes.
The other is a vaccine by Johnson & Johnson subsidiary Crucell, designed to combat Ebola and its cousin filovirus the Marburg virus.
Tests on monkeys found the formula to be completely protective in a single dose.
A Phase I trial, launched in 2006 with 32 volunteers, found the drug was safe. Another Phase I trial, with the drug tweaked to widen protection against the spectrum of viral strains, is planned for late 2015 or early 2016.
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Updated Date: Aug 27, 2014 11:55:51 IST