[Taxol (paclitaxel), first molecule of a new class of cytotoxic agents: taxanes].

Taxol is the first of the taxanes, a new class of cytotoxic agents whose cellular target is the microtubules network. Taxol induces the polymerisation of the alpha and beta sub-units of the tubulin. This mechanism of action which is different from the vinca-alkaloids explains the main cytotoxic activity of paclitaxel through the formation of abnormal and stable bundles of microtubules. Severe hypersensitivity reactions which were seen in early phase I studies are prevented by an oral corticosteroids and H1 and H2 blockers premedication. Profound neutropenia is frequent but of short duration explaining that infectious manifestations are rare and neutropenia not cumulative. Thrombopenia and anemia are rare. Neurotoxicity is dose related but severe peripheral neuropathy is rare. Conduction abnormalities are mainly asymptomatic bradycardias. In second line ovarian cancer and breast metastatic cancer a noticeable level of activity has been observed, and in lung and head and neck cancer Taxol has proved to be effective.