Microbially Derived Semisynthetic Artemisinin

Artemisinin is a sesquiterpene lactone endoperoxide with potent antimalarial properties, recommended by the World Health Organization for the treatment of malaria in artemisinin combination therapies (ACTs). It is extracted from the plant Artemisia annua, but its supplies are limited and its price is volatile. In order to increase supply and stabilize the price of artemisinin, a semisynthesis has been developed, whereby an artemisinin precursor (amorpha-4,11-diene) is produced in microbes and the isolated precursor converted chemically to artemisinin. Escherichia coli has been engineered to produce amorpha-4,11-diene by the expression of a heterologous mevalonate pathway along with amorpha-4,11-diene synthase (ADS) from A. annua. Development of the E. coli platform to increase production of amorpha-4,11-diene from 24 mg/L to >25 g/L is described. ADS has also been expressed in the yeast model system Saccharomyces cerevisiae which, following manipulation of the mevalonate pathway, produced 150 mg/L of amorpha-4,11-diene. The cDNAs encoding the cytochrome P450 that oxidizes amorpha-4,11-diene to artemisinic acid, CYP71AV1, and its cognate reductase were isolated from A. annua and expressed in amorpha-4,11-diene-producing E. coli and yeast, leading to the production of >1 g/L artemisinic acid from both organisms. A route for the chemical conversion of artemisinic acid to artemisinin is described. Production of semisynthetic artemisinin may lead to the development of a second source of the drug for incorporation into ACTs.