Rational biosynthetic engineering for optimization of geldanamycin analogues

A rational biosynthetic engineering approach was applied to the optimization of the pharmacological properties of the benzoquinone ansamycin, geldanamycin. Geldanamycin and its natural or semisynthetic derivatives have the potential to serve as anticancer chemotherapeutic agents. However, these first-generation Hsp90 inhibitors share an unfavorable structural feature that causes both reduced efficacy and toxicity during clinical evaluation. We report the rationally designed biosynthesis of C15 hydroxylated non-quinone geldanamycin analogues by site-directed mutagenesis of the geldanamycin polyketide synthase (PKS), together with a combination of post-PKS tailoring genes. A 15-hydroxyl-17-demethoxy nonquinone analogue, DHQ3, exhibited stronger inhibition of Hsp90 ATPase activity (4.6-fold) than geldanamycin. Taken together, the results of the present study indicate that rational biosynthetic engineering allows the generation of derivatives of geldanamycin with superior pharmacological properties.