Synthetic peroxides as antimalarizals

The discovery of artemisinin in 1971 initiated a new era in antimalarial chemotherapy. Although the clinically useful semisynthetic artemisinin derivatives are rapid acting and potent antimalarial drugs, they have short half-lives and must be administered over a period of 5-7 days, leading to noncompliance and recrudescence. With this in view, many synthetic antimalarial peroxides have been prepared. Yet, identification of orally active synthetic peroxide drug development candidates that are easily synthesized, inexpensive, and with good biopharmaceutical properties has been surprisingly difficult. In this review, we document the pitfalls and progress made in this endeavor. For each of 15 synthetic peroxide structural classes, we note highlights of the synthetic routes, product stereochemistry, and origin of the peroxide O atoms. Both in vitro and in vivo antimalarial data are then discussed and any SAR noted. Available data indicates that several synthetic 1,2,4-trioxanes are only marginally less effective than the semisynthetic artemisinins. Within a given peroxide chemical family, the more lipophilic members are more potent and possess better oral antimalarial activity in animal models than their more polar counterparts. This poses a challenge to identify peroxide structures with suitable "drug-like" physicochemical properties. Nonetheless, substantial progress has been made in the identification of a new generation of synthetic antimalarial peroxides.