The Ebola outbreak currently plaguing West Africa has resulted in renewed urgency to develop a drug that can treat the disease, which currently has no cure. Although there are a number of experimental drugs, only ZMapp has been prescribed to Ebola patients.
Here are 5 things you should know about experimental drugs for Ebola:
What trial drugs are available?
Some 17 drugs are being developed by various companies and institutions, says BioWorld, a Thomson Reuters publication. But they have yet to go through full clinical and human trials for safety and effectiveness. These trial drugs include:
ZMapp - Manufactured by California-based Mapp Biopharmaceutical, the drug has been tested on laboratory animals, but had never been used on humans until the current outbreak. Only a very limited amount of ZMapp had been produced and the last doses were prescribed last week. The company said it would take several months before the new supplies are ready and it does not have the capacity to produce the drug in huge quantity.
TKM-Ebola - Developed by Canada's Tekmira Pharmaceuticals, it has been found to protect monkeys from lethal doses of a virus related to Ebola. The drug was effective even when given as late as three days after exposure to the Marburg virus.
Avigan - Developed by Japan's Fujifilm Holdings, it is an anti-influenza drug favipiravir that was approved for use in Japan in March and is currently in clinical tests in the United States. A Japanese government spokesman has said Tokyo is ready to offer the drug if the World Health Organisation requests for it. The company has enough stock for more than 20,000 patients.
Sarpeta - US-based pharmaceutical company Sarepta Therapeutics has developed a drug that it says has had success in combatting the deadly disease in primates. The drug's development stopped two years ago when government funding dried up, but the company still has enough of the drug to potentially treat a few dozen patients.
BioCryst - Developed by BioCryst Pharmaceuticals, initial results have shown the drug's effectiveness in treating hemorrhagic fevers in monkeys.
Besides the trial drugs, 12 vaccines are also being developed, says BioWorld. Unlike the drugs, vaccines are administered before a person falls sick to prevent infection. Experts from GlaxoSmithKline, for example, are awaiting approval from the US Food and Drug Administration to begin a human safety trial, possibly as soon as September.
Who have been given ZMapp?
The drug has been given to some 10 people - including two American doctors, one Spanish priest and three doctors in Liberia. The Americans - Dr Kent Brantly and Dr Nancy Writebol who contracted the virus while doing humanitarian work in Africa - recovered after treatment at an Atlanta hospital. Another unnamed health worker also reportedly recovered.
How effective is ZMapp?
Its effectiveness is still unclear, even in the cases of the two Americans who recovered. Dr Bruce Ribner, medical director at Emory hospital who treated the Americans, said it was unclear if the drug had contributed to their recovery. He suggested it may have even delayed their return to health.
Other doctors caution that there is a huge gap between the treatment received by the Americans at Emory hospital, and that in West Africa where even basics such as sterile fluids can be in short supply. Emory hospital's containment unit is specially equipped to care for patients with serious communicable diseases. Even if ZMapp is proven to be effective, there must be strong medical teams and good facilities, among other things, the doctors say.
What do medical ethicists say?
They say there are critical questions to consider. Jonathan Ball, professor of molecular virology at Nottingham University, said: "Not all drugs are safe - that's why we have very stringent clinical trials. One could argue that the current outbreak provides a perfect arena in which to test new drugs, but that isn't without risk. We don't know their safety, we don't know if they are likely to work - sure, they have been tested in animals, but these studies don't always tell us what will happen in humans."
Paul Hunter, professor of health protection at the University of East Anglia, said "the ethical case is unequivocal". He said: "if a patient is likely to die and an experimental therapy has a reasonable chance to prevent death, then it should be given. However, this does not mean that any old drug could be given. For an experimental compound to be given, there should be good prior evidence that the therapy will work, the patient or his relatives should give informed consent wherever possible and whenever the therapy is given proper records must be kept and the outcome reported to WHO," he added.
What does WHO say?
On Aug 11, the World Health Organisation (WHO) convened a panel to assess the ethical implications of using experimental drugs for Ebola. The panel agreed that it is ethical to offer unproven interventions - with as yet unknown efficacy and adverse effects. However, the panel declined to make specific recommendations of who should be first to receive ZMapp. The experts noted that more detailed analysis and discussion are required to arrive at "ethical criteria for achieving fair distribution in communities and among countries, in the face of a growing number of possible new interventions, none of which is likely to meet demand in the short term."
SOURCES: REUTERS, AGENCE FRANCE-PRESSE, NEW YORK TIMES, BBC, HUFFINGTON POST