Liz Szabo

USA TODAY

The first human trials of a Canadian Ebola vaccine began Monday, part of a flood of experimental therapies rushed into testing to battle the Ebola epidemic.

Although the world has been fighting Ebola since 1976, major drugmakers showed little interest in the disease because outbreaks were small and sporadic, said Thomas Geisbert, a professor at the University of Texas Medical Branch, who has studied Ebola and tested drugs against it for many years.

Ebola research got a jump-start after the terrorist attacks in 2001 as the government funded studies to prepare for possible bioterror attacks, said Anthony Fauci, director of the National Institute for Allergy and Infectious Diseases.

Only the current Ebola outbreak in West Africa, the biggest in history, has succeeded in moving experimental drugs and vaccines into larger clinical trials. There are no approved drugs or vaccines on the market, so several Ebola patients have received experimental medications.

Though some of these drugs are in short supply, experts say other approaches could be put to much greater use. Here's a summary of promising potential therapies:

BLOOD TRANSFUSIONS

The World Health Organization has said researchers should make blood transfusions a priority for testing. Although there's no definitive proof that blood transfusions work, the goal is to give blood from an Ebola survivor to a patient in the hope that the donor's antibodies could help a patient's immune system fight the Ebola virus.

Ebola survivor Kent Brantly, a doctor with the missionary group Samaritan's Purse, received a blood donation from a teenage survivor before he was evacuated from Liberia.

Brantly survived and has since donated blood to three other Americans infected with the virus, including missionary doctor Richard Sacra, NBC cameraman Ashoka Mukpo and Dallas nurse Nina Pham. Sacra recovered. Mukpo and Pham are hospitalized.

Transfusing whole blood from one patient to another has drawbacks, but there is great potential for giving immune globulin, or purified antibodies, said Peter Hotez, dean of the National School of Tropical Medicine in Houston. Unlike whole blood, these purified antibodies could be given to anyone, regardless of blood type, Hotez said.

They would not provoke an immune reaction. And they would not risk exposing people to other blood-borne diseases, such as malaria or HIV. Any facility with the ability to do blood banking could handle these procedures. That could allow the therapy to offered across much of Africa, using survivors' blood.

VACCINES

Two types of vaccines are being tested. A vaccine developed by the Public Health Agency of Canada began testing Monday at the Walter Reed Army Institute of Research in Silver Spring, Md.

The vaccine uses a vesicular stomatitis virus (VSV) to deliver its payload and offers promise for preventing and treating Ebola, Hotez said.

A second type of vaccine, which uses an adenovirus, is being developed by pharmaceutical giant GlaxoSmithKline. A clinical trial of that vaccine began at the National Institutes of Health in Bethesda, Md., last month. Another trial of this vaccine began in the West African country of Mali last week.

Although Mali has had no Ebola cases, it shares a border with Guinea, where the current outbreak started. Liberia and Sierra Leone also are battling Ebola epidemics. Even under the best circumstances, vaccines won't be ready to use for several months.

ANTIVIRAL DRUGS

The Japanese company Fujifilm has said it has 20,000 doses of an influenza drug called fabipiravir. The drug was given to a French nurse infected with Ebola in Africa and evacuated to France for treatment. That nurse, a volunteer with Doctors Without Borders, has recovered from Ebola and was released from a hospital. As with any experimental Ebola treatments, doctors can't say whether the new drug is responsible for curing the nurse. Without larger trials, it's impossible to know whether the nurse was cured by the drug or simply by good supportive care at the French hospital.

Brincidofovir is an antiviral drug that has been given to Ebola patient Ashoka Mukpo, who is being treated at the Nebraska Medical Center in Omaha, as well as Thomas Eric Duncan, the Liberian national who died in Dallas.

Brincidofovir has a limited track record against Ebola and has been tested against the virus only in laboratory dishes, not animals or people, Fauci said.

On the plus side, brincidofovir has a good safety record in humans, and there are supplies available, Fauci said. Brincidofovir has been tested in more than 1,000 people in clinical trials that tested the drug against other diseases, such as cytomegalovirus, which causes a syndrome similar to mononucleosis.

MAN-MADE ANTIBODIES

ZMapp, made by Mapp Biopharmaceutical of San Diego, contains man-made antibodies against Ebola. About seven Ebola patients have been treated with ZMapp. Brantly received ZMapp, as did missionary Nancy Writebol, who also survived. A Spanish priest and a Liberian health worker who received ZMapp died.

Mapp Biopharmaceutical has said supplies of ZMapp are exhausted. Producing the drug, which is grown in tobacco plants, takes months.

PREVENTING EBOLA REPRODUCTION

TKM-Ebola, made by a Canadian company called Tekmira Pharmaceuticals, has been given to a handful of Ebola patients, including Sacra. The drug keeps Ebola from reproducing and protected 100% of monkeys tested. Concerns over the drug's safety led the Food and Drug Administration to put a temporarily hold on an early human trial.