Although we have been advocating for continued research into new antimalarial drugs, David Smith of the University of Florida’s Emerging Pathogens Institute says that, “We don’t have anything in the pipeline after ACTs, and it’s basically just a matter of time until drug resistance evolves and artemisinin also fails. So the question becomes how do we keep ACTs in our arsenal for as long as effectively possible?”
Smith, a co-author on a study that is scheduled to publish online this week in the Proceedings of the National Academy of Sciences pointed out that, “The models indicate that we can slow the evolution of resistance to current artemisinin-based therapies if nations use them in combination with two or more partner drugs. Currently, most nations don’t do this. They use one therapy at a time, wait for it to fail, and then switch to a different therapy.”
Issues of cost, logistics and policy implementation are at the root of the problem. In Nigeria, for example, monotherapy artemesinin-based drugs are still available in shops, although the National Agency for Food and Drug Administration is no longer granting new licenses for monotherapies. Some of the old licenses have a few years left, unfortunately.Â ACTs brought in through donor programs like the Global Fund have been targeted free for children, which leaves the door open for ‘leakage’ to the adult population who may take lower than effective doses and promote drug resistance.
The upcoming article in PNAS will explain that, “The researchers’ models also show that cycling through single drugs accelerated the rate at which malaria parasites evolved drug resistance. Smith said this occurred because cycling a single drug degraded the parasite’s average fitness, which made it easier for drug-resistant genes to spread throughout the parasite population.”
The contrast still persists with free or subsidized ACTs in the public sector, often aimed only at children and expensive ACTs in the private sector for adults. Unless a comprehensive national malaria drug policy can be implemented throughout all elements of the health sector, the threat of developing resistance to aretesinim-based medicines will persist.