A drug developed to treat allergies has been identified by US researchers as a potential cure for malaria. Tests in mice show that the antihistamine astemizole also kills the malaria parasite. It is already licensed for use in people, so it could be developed for use as a malaria drug in about 12 months. And because it is no longer under patent, it will be possible to manufacture it at rock-bottom prices.

The breakthrough has excited researchers because of the cost of developing other anti-malarial treatments. "Time and money are major roadblocks when it comes to developing new drugs for neglected diseases like malaria," said David Sullivan at the Johns Hopkins Bloomberg school of public health in Baltimore, Maryland, who led the team.

One study of drug development costs during the 1990s estimated that each drug that reached the market cost pharmaceutical companies $802m (in 2000 prices) in research and development. Most of the money goes on the final stages of development and testing in humans. Dr Sullivan's team aimed to minimise this stage by screening medicines already cleared as safe to use.

The team report in the journal Nature Chemical Biology that after good results with astemizole they tested it in mice. Moderate doses of the drug cut parasite numbers by 80%, and even parasites resistant to the malaria drug chloroquine dropped by 40%. Higher doses of the drug removed the malaria parasites completely.

The next step will be to study how to make the drug work best in people. "If it works it could be out in a year's time," said Dr Sullivan, "What we need to do is figure out the optimum dose regimen."

Malaria kills 1 million people a year - mostly children in sub-Saharan Africa.