Drugs from the sea: conotoxins as drug leads for neuropathic pain and other neurological conditions.

The oceans are a source of a large group of structurally unique natural products that are mainly found in invertebrates such as sponges, tunicates, bryozoans, and molluscs. It is interesting to note that the majority of marine compounds currently in clinical trials or under preclinical evaluation are produced by these species rather than as secondary metabolites by marine algae. Through the combined efforts of marine natural products chemists and pharmacologists a number of promising compounds have been identified that are either already at advanced stages of clinical trials such as the new anti-cancer drug marine alkaloid ecteinascidin 743, or have been selected as promising candidates for extended preclinical evaluation. This is the case for conotoxins, (Table 1) where a number of conopeptides are currently being developed as analgesics for the treatment of neuropathic pain.