The development of new chemotherapeutic agents.

There is a great need for new drugs to treat the increasing numbers of patients with disseminated cancers. Many of the known anticancer drugs, including the taxoids, docetaxel (Taxotere) and paclitaxel (Taxol), are derived from natural products and there will be many more active compounds to be discovered amongst the 300000 plant species available for evaluation. Cytotoxic agents may kill cancer cells by a variety of means. Thymidilate synthase inhibitors such as LY231514 and raltitrexed (Tomudex) have shown activity against a variety of solid tumours including colorectal cancer. The antifolate, trimetrexate, and the nucleoside analogue, gemcitabine, have also shown anticancer activity. Amongst the topoisomerase I inhibitors, CPT-11 is being developed for use against colorectal cancer. Non-cytotoxic agents which interfere with processes such as angiogenesis may also have a role in future treatments for disseminated cancers.