A New Treatment for Malaria: Artemisinin
Prof. Dr. Talal Aburjai
Overview
• Malaria• Problems associated with the disease• Actions taken in dealing with the
problems• Artemisinin
• Background information• Mechanism of action
Introduction on Malaria
• ~40% of population at risk• India, Indonesia, Latin America and
Africa• ~500 million cases of malarial illness
per year• ~1.5 million deaths • Total cost of malaria is approximately
$1,800 million US dollars
What is the Cause of Malaria?
• Malaria caused by four major Plasmodium parasites:• Plasmodium vivax• Plasmodium malariae• Plasmodium ovale• Plasmodium falciparum
• Plasmodium falciparum is the most prevalent parasite species
General Symptoms
• Fever and flu-like illness• Shaking chills• Headache• Muscle aches• Tiredness
• Nausea, vomiting and diarrhea may also occur
Classification of Malaria
• Uncomplicated Malaria• Cold stage (sensation of cold, shivering)• Hot stage (fever, headaches, vomiting;
seizures in young children)• Sweating stage (sweats, return to normal
temperature, tiredness)
Classification of Malaria
• Severe Malaria– Cerebral malaria (seizures, coma)– Severe anemia– Hemoglobinuria– Abnormalities in blood coagulation– Cardiovascular collapse and shock
Life Cycle of Malaria Parasite
Conventional Treatment
• Use of insecticide such as DDT• Use of quinoline-based antimalarial
drugs
Malaria Parasite Resistance
• Mechanism of resistance is due to genetic mutations in malaria parasite
Resistance
Delayed Response
Recurrence of Infection
Increased GametocyteIncrease Transmission
Increased Clinical Cases
More Drug Used
“Roll Back Malaria”
• Currently courses of actions being explored:• Development of drug combinations• Search for effective vaccine • Genomic approach• Search for new antimalarial drugs
ARTEMISININ
Artemisia annua
• Also known as sweet wormwood
• Origin from northern parts of China
• Artemisinin present in leaves and flower of the plant in 0.01-0.08% dry weight
Artemisia annua
• Used in Traditional Chinese Medicine for more than 2000 years
• Earliest record found in the “Fifty Two Prescription”
• First antimalarial application described in “The Handbook of Prescriptions for Emergencies” in the 4th century by a Chinese alchemist
Artemsia annua
• Li Shizhen, a great Chinese herbalist
• Use of wormwood is also recorded in the “Great Compendium of Herbs” in 1596
“take a handful of sweet wormwood, soak it in a sheng (liter) of water, and squeeze out the juice and drink it all”
Artemisinin
• One of the most novel discoveries in recent medicinal plant research
• 1967- extracts of Artemisia was found to have antimalarial activity
• 1972- artemisinin isolated from the plant
• 1979- structure of artemisinin determined by X-ray analysis
Chemical Structure
Structure of Artemisinin
Structure of Artemisinin Derivatives
Sesquiterpene Trioxane Lactone
Key Features
• Rapid onset of actions• Effective against severe malaria
• Rapid clearance rate• Slow development of artemisinin
resistance• Frequent recurrence of infections
Site of Action
Artemisinin
Artemisinin
Conventional Treatment
Mechanism of Action
• Killing of malaria parasite is mediated by production free radicals– Artemisinin derivatives lacking
endoperoxide bridge are devoid of antimalarial activity
– Addition of free radical generating compounds enhances antimalarial activity
– Antioxidants block antimalarial activity
Mechanism of Action
• Heme/iron mediates breakage of endoperoxide bridge– Chloroquine antagonizes the antimalarial
activity– Iron chelators antagonize antiparasitic
effect of artemisinin
• Artemisinin-derived free radicals bind to protein through alkylation
Mechanism of Action
Mechanism of Action
• Inhibit homozoin biosynthesis or cause hemozoin degradation
• Inhibit hemoglobin digestion by malaria parasites
• Forms covalent adducts with malarial proteins
Adverse Reactions
• Very few adverse reactions• Common side effects include
– Nausea– Vomiting– Anorexia– dizziness
• Safe for pregnant women
Resistance
• Currently no evidence for clinically relevant artemisinin resistance
• Reasons for delay of artemisinin resistance:– Short half-life– Reduces transmission potential – Used in combination with other
antimalarial drugs
Combination Therapy
• Use of artemisinin-based combined therapies would help delay antimalarial drug resistance
Summary
• Artemisinin induce rapid killing of parasites
• Fast clearance rate• Very few side effects• Artemsinin-resistant parasites have
not been identified• Should be used in combination with
other antimalarial drugs
Discussion
• What is your opinion about integration of Complementary and Alternative Medicine with Western Medical Practices?– Do you think this integration process will
benefit the patients?– What would be your concerns if you’re
asked to take Traditional Chinese Medicine?