HOME ABOUT US RESEARCH NEWS AND EVENTS INTO PRACTICE CONTACT US LINKS |
||
In 1967, Chinese scientists began to search for new malaria treatments by systematically testing plants used in traditional Chinese medicine. By 1972, they had isolated and chemically characterised artemisinin, from the Chinese medicinal plant, Artemisia annua . Artemisinin and its derivatives* produce rapid clearance of malaria parasites from the blood. They kill all Plasmodium species and all stages of the parasite’s life cycle. They are safe, well-tolerated and rapidly eliminated from the human body. Artemisinin is a sesquiterpene lactone containing an unusual trioxane ring, which is thought to be the source of anti-malarial activity. However, the detailed mechanism by which the malarial parasite is killed is still the subject of much scientific debate. In the context of growing resistance to established anti-malarial drugs such as chloroquine, the artemisinin family of drugs is increasingly being relied on as the mainstay of malaria treatment. Artemisinin is also showing promise as a possible anti-cancer compound in in vitro models, and has been proposed for use in the treatment of schistosomiasis, another important parasitic disease of the tropics. (*Artemisinin for clinical use is usually derivatised to improve its stability and solubility. The most common derivatives are dihydroartemisinin, artemether, arteether, artesunate and artelinate.) Artemisinin Combination Therapies (ACTs) Artemisinin and its derivatives should be taken in conjunction with a partner drug as an Artemisinin Combination Therapy (ACT). There are two reasons for this. Firstly, artemisinin drugs do not last long in the human body. Because of this, partnering them with another drug that persists for longer improves treatment efficacy and reduces the duration of the treatment course that is required. Secondly, combining two drugs with different modes of action impedes the development of parasite resistance to either constituent. Artemisinins are a vital part of our defences against malaria and so it is essential that their effectiveness is protected with combination therapies. The first ACT to become available internationally was Coartem™, a combination of artemether and lumefantrine, produced by Novartis. Its introduction to the KwaZulu Natal province of South Africa in 2000 contributed to a dramatic reduction in malaria transmission in conjunction with other measures such as insecticidal spraying and treated bed nets. A full treatment is a three-day course and the number of tablets per dose depends on body weight. It is taken orally with fluids (preferably drinks containing fat, such as milk). Other new ACTs are on the market or in developent. Demand for artemisinin and ACTs The WHO has identified ACTs as the most effective treatments currently available for malaria. As a result, 75 countries have recently adopted them as their drugs of choice. From 2001-2006 demand for artemisinin rocketed from a few hundred thousand courses to around 80 million (see figure). in 2008 the Global Malaria Action Plan was published. Under this plan, demand is predicted to rise again to an estimated 260 million treatments a year by 2011. This level of usage will require around 130 tonnes of artemsinin. ACT use (Graph adapted from one by the WHO Global Malaria Programme) Novartis makes Coartem™ available at-cost for use by public health systems in developing countries, under an agreement with the WHO. Sanofi-Aventis also provides ASAQ on a no-profit basis. Despite these undertakings, ACTs are still more expensive than the medicines they are replacing. Treatment costs 37 - 87 cents with Coartem™ (depending on the age of the patient). This compares with a typical price of 10 -15 cents for treatment with chloroquine. Furthermore, a large proportion of anti-malarial drugs used in Africa are purchased through the private sector, where ACT prices are much higher. In Africa, private sector prices of as much as $12 for an adult ACT treatment were observed in 2007. The price of ACTs is an obstacle to their effective deployment. The situation should be helped by a global subsidy for ACTs, the Affordable Medicines Facility for Malaria (AMFm), which is due to be available globally by 2010. Lower ACT prices are essential to making these drugs accessible in countries where the annual health budget may be less than $4 per capita. The high production costs of artemisinin contribute to problems with expense and availability. Artemisinin production is expensive because of the low yield from Artemisia plants. High food prices make Artemisia an uneconomic choice for farmers. Planting areas are down and there is a fear of shortages. In the past, such shortages have led to price hikes. Alternative sources of artemisinin Artemisia annua is currently the sole source of artemisinin and will continue to be essential to supplies for the foreseeable future. However, alternative sources are being investigated as part of the solution to artemisinin cost and security of supply. For example;
Multiple sources of artemisinin are needed to satisfy projected global demand for ACTs and reduce costs. The CNAP Artemisia Research Project is collaborating with the above projects as the Artemisinin Enterprise for maximum impact on ACT production and to ensure that the new technologies do not enter substandard drug or monotherapy supply chains. Artemisinin resistance and monotherapies The malaria parasite has developed resistance to all classes of anti-malarial drug except artemisinin and this has caused serious problems for malaria control. Scientists have been able to produce artemisinin-resistant strains of Plasmodium falciparum in laboratory models, suggesting that, if artemisinin drugs are used indiscriminately, they too will eventually lose effectiveness as a result of parasite resistance. For this reason, the WHO has called for an immediate halt to the marketing and sale of single drug oral* artemisinin monotherapies, which are likely to hasten the development of such resistance. As of May 2006, 13 pharmaceutical companies had agreed to comply and focus their marketing on ACTs. (*Injectable or suppository formulations of artemisinin monotherapy are still recommended for the treatment of severe malaria.) Poor quality and counterfeit drugs Effective malaria treatment is also threatened by poor quality drugs with incorrect composition or ingredients. This may be due to negligence, error, insufficient resources or counterfeiting. The number and sophistication of fake drugs on the market is increasing and the relatively high market value of ACTs makes them a prime target for counterfeiters. In some areas of Africa, up to 80 percent of the artemisinin drugs sold on the private market have been found to be counterfeited . The WHO estimates that poor quality or incorrectly used malaria drugs are responsible for 200,000 deaths every year.
|
||
 |
 Department of Biology |
Fact sheets 
Artemisinin & ACTs