The Ebola outbreak has been contained with a lot of effort and some luck. But, despite months of work, we still don’t have a drug or vaccine to treat the deadly virus. Instead we have relied on supportive care and quarantines. The outbreak has starkly shown that we are not prepared to deal with such a nightmare scenario on a global scale.

One of the biggest challenges is the development of effective treatments to counter a new threat. That is because drug development is a genuinely hard problem. Even if drug candidates are found within weeks of an emergency, it can take months before those treatments are tested and manufactured to be available on the ground.

In the recent Ebola outbreak, the World Health Organization (WHO) declared an emergency in August. Within weeks, some of the drugs that had been sitting on shelves in pharma companies were being manufactured for trials and those companies began recruiting volunteers. In two months, completely new treatments had been found in the lab and were being shipped to Africa for trials. But even today, nearly 10 months after the emergency was declared, there are still no approved drugs or vaccines for treating Ebola.

What’s already on the shelf?

An alternative approach is to check whether already-approved drugs could be used to treat the new disease. This process is called “drug repurposing” or “drug repositioning,” and the US Army Medical Research Institute of Infectious Diseases has applied it to find new drugs for Ebola. In a study just published in Science Translational Medicine, they report finding two such drugs that could be used in Ebola treatment soon.

To do this, the researchers took 2,600 approved drugs and biologically active probes and subjected each of them to an “assay.” These assays involve pitting the drug against the Ebola virus, which has been engineered to produce green fluorescent proteins if the drug manages to control the virus.

After this first step, the researchers found that 171 chemicals—80 of them approved drugs—showed some activity against the virus. Next they tested a subset of the most active drugs on rodents infected with Ebola virus. In the end two drugs—Zoloft and Vascor—appeared to have the potential to become treatments for humans.

Zoloft (generic name sertraline) is an antidepressant that was launched by Pfizer in 1991. And Vascor (generic name bepridil) is used to treat chest pain, but is not sold in the US anymore. Their development had nothing to do with Ebola, but researchers believe that both these drugs affect the virus by stopping it from entering and hijacking cells to multiply and cause the disease.

If a disease spreads around the world too quickly, repositioned drugs could be our best against it. That’s because these drugs have already passed a slew of safety tests in humans, which will reduce the time required for them to be approved for a second disease. And they are already being manufactured at a large scale and distributed globally.

The pharma paradox

This seems like promising news, but only drug trials will show whether these medications work to cure or prevent the disease in humans. And those trials are something that pharmaceutical companies aren’t likely to invest in, because both the drugs are off-patent.

“If the drug patent has expired, pharma companies won’t make money from it and thus won’t invest any money required for trials,” Jonathan Corcoran, a professor at Kings College London who has worked on drug repositioning, tells Quartz.

When a drug patent expires, no single company has an exclusive right over its sale. Thus, if one pharma company invests the millions required to run a human trial, other companies can then gin up their own generic version and profit from it, dividing up the market.

So as promising as this strategy seems, it likely could only work if government or philanthropical organizations invest money in the trials. Quartz has reached out the US Army Medical Research to find out whether it will find funding for human trials, and we will update this post with any response.

This article is published in collaboration with Quartz. Publication does not imply endorsement of views by the World Economic Forum.

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Author: Akshat Rathi is a reporter for Quartz in London. 

Image: Pharmaceutical tablets and capsules in foil strips are arranged on a table in this picture illustration taken in Ljubljana September 18, 2013. REUTERS/Srdjan Zivulovic.