In the study, all of the ferrets were infected with canine distemper virus, which is closely related to measles. When treated with the drug, known as ERDRP-0519, the ferrets survived the normally fatal infection and levels of the virus were sharply reduced.
All of the animals remained disease-free and developed immunity to the virus. The findings were reported in the journal Science Translational Medicine. "The emergence of strong antiviral immunity in treated animals is particularly encouraging, since it suggests that the drug may not only save an infected individual from disease but contribute to closing measles immunity gaps in a population," Dr. Richard Plemper of Georgia State University said in a statement.
Plemper helped develop the drug with colleagues at the Emory Institute for Drug Discovery and the Paul-Ehrlich Institute in Germany.
The drug was developed specifically for measles. It works by interfering with the ability of the virus to make copies of itself.
Plemper said it wasn't possible to test the drug against the measles virus because there is no model that replicates human measles in animals. But, he said, tests of the drug in tissue cultures showed the measles virus was five times more sensitive to the drug than the canine virus.
It will take years of additional testing to determine whether a measles pill can be used in humans. The drug must first prove effective in monkeys. Then it needs to be tested in a small trial of healthy people to see if it causes any side effects.
If it passes all of those hurdles, it could be tested in larger human trials. Plemper thinks the ideal user of the drug would be unvaccinated adolescents and teens who have been exposed to measles and are at greater risk of spreading the virus. Plemper said vaccines are still the best way to protect against measles, a highly contagious virus that kills around 50,000 people per year.
Before widespread vaccination, which started in the 1980s, measles caused an estimated 2.6 million deaths each year, according to the World Health Organization.
In developing countries, lack of access to the vaccine remains a problem. In developed countries, especially in Europe, fears over the potential side effects of vaccines, fueled by now debunked science suggesting a link to autism, have led parents to refuse to vaccinate their children, resulting in a resurgence of measles.
In a conference call with reporters, Plemper acknowledged that the availability of a measles pill could encourage more parents to decide not to get their child vaccinated, putting even more people at risk. He said it is crucial that people become educated about the need for vaccination, especially in resource-rich countries where it is widely available.
In the United States, outbreaks have been occurring in pockets of unprotected individuals. In a recent example, some two dozen people were infected with the virus in New York City last month. Most U.S. outbreaks have been triggered by unvaccinated people traveling to the country.
In December, the U.S. Centers for Disease Control and Prevention said there were 175 reported measles cases last year, three times the annual average. Of those, 172 were traced to overseas travel.