Acylfulvenes are a family of antitumor agents derived from the natural product illudin S. One member of this family, (-)-(hydroxymethyl)acyfulvene, is currently in phase II clinical trials for a number of cancers. Mechanistic studies indicate that acylfulvenes are bioactivated by reductive cytosolic enzymes including alkenal/one oxidoreductase (AOR), leading to a reactive intermediate that can further alkylate cellular macromolecules. However, the detailed mechanisms underlying the high therapeutic index for acylfulvenes are poorly understood, and alkylation targets have not been characterized chemically. In an effort to define the mechanism by which acylfulvenes induce apoptosis, we synthesized four acylfulvene analogs: (-)-acylfulvene (AF), (+)-AF, (-)-(hydroxymethyl)acylfulvene (HMAF), and (+)-HMAF. These compounds were obtained either by a chiral resolution method or by asymmetric synthesis. The relative toxicities of these compounds in (define the cells somehow) were compared. Additionally, kinetic parameters for AOR-catalyzed activation were determined using purified enzyme. Cell toxicity studies indicate the absolute configuration of acylfulvene analogs has a significant influence on cytotoxicity. (-)-HMAF is 25 times more potent than (+)-HMAF in cells transfected with an AOR overexpression vector. However, the rates of AOR-mediated activation are more strongly dependent on acylfulvene substitution than on absolute stereochemistry. These results indicate that AOR-mediated metabolism, as well as other biochemical factors, contributes to the relative toxicities of acylfulvene analogs.
[Proc Amer Assoc Cancer Res, Volume 47, 2006]