A common pharmacophore for cytotoxic natural products that stabilize microtubules

Taxol (paclitaxel), a complex diterpene obtained from the Pacific yew, Taxus brevifolia, is arguably the most important new drug in cancer chemotherapy. The mechanism of cytotoxic action for paclitaxel—i.e., the stabilization of microtubules leading to mitotic arrest—is now shared by four recently identified natural products, eleutherobin, epothilones A and B, and discodermolide. Their ability to competitively inhibit [(3)H]paclitaxel binding to microtubules strongly suggests the existence of a common binding site. Recently, we have developed nonaromatic analogues of paclitaxel that maintain high cytotoxicity and tubulin binding (e.g., nonataxel). We now propose a common pharmacophore that unites paclitaxel, nonataxel, the epothilones, eleutherobin, and discodermolide, and rationalizes the extensive structure–activity relationship data pertinent to these compounds. Insights from the common pharmacophore have enabled the development of a hybrid construct with demonstrated cytotoxic and tubulin-binding activity.