ProstaglandinsIn 1969 it was established that Plexaura homomalla, a common coral found in the Caribbean and the western Atlantic, is a rich natural source of prostaglandins. Prostaglandins are important hormones produced from tissues that control essential body functions such as blood clotting and extremely complex inflammatory responses. The coral prostaglandins from Plexaura homomalla and other species have been researched exhaustively and have provided vital knowledge on the prostaglandin metabolism of humans. No drugs have yet resulted from this research.
9.5 > Cone snails such as Conus textile mainly inhabit tropical marine areas. They inject venom into their prey with a harpoon-like tooth. Scientists have succeeded in deriving a very effective painkiller from this venom.
9.6 > Moss animals are tiny animals that live in branch and leaf-like colonies. Bryostatin – an inhibitor of tumour cell growth – is extracted from the bryozoan Bugula neritina. It is probably produced by bacteria on the surface of the colony.
PeptidesIt took nearly 30 years after the development of Ara-C for the next marine-derived substance to be approved for the treatment of human medical conditions. This was the peptide Ziconotide (Prialt®), which is derived from the venom of various species of marine cone snail. Peptides are large protein components. Accordingly, the cone snail toxin consists of a highly complex mix of different protein components called conotoxins. These conotoxins attack the metabolism of animals and humans at different points. In their natural environment the toxins paralyse their prey by blocking ion channels in the cell membrane – small apertures that are important to the transmission of nerve impulses. Instead of the pure snail venom, a modified version of the venom cocktail is used to treat severe chronic pain. The drug Ziconotide prevents ions from entering pain-sensing nerve cells. By doing so it blocks the nerves in the spinal cord that send pain signals to the brain. This drug is used for patients whose pain is so severe that it cannot be controlled by morphine medication. It is also used in cases of morphine-intolerance.
AlkaloidsEcteinascidin 743 (also known as trabectidin) is an alkaloid, or nitrogen-containing organic compound marketed under the brand name of Yondelis®. It is the latest marine-derived compound and was originally extracted from the tunicate Ecteinascidia turbinata, a simple filter feeder living on the sea floor. The substance was only approved as a drug in 2008. Ecteinascidin 743 interferes with a complex metabolic mechanism that confers drug resistance on cancer cells. It binds in the minor groove of DNA, slightly distorting the shape of the DNA, which obstructs the metabolism of the cancer cell. In greater detail, ecteinascidin 743 unites with the DNA repair protein TC-ER, then links with the DNA, thus preventing the MDR1 gene (MDR = multi drug resistance) – vital to the cancer cell – from being selected. This gene contains the blueprint for the MDR1 protein, the function of which is to discharge toxins and exogenous substances from cells. In cancer therapy, therefore, its effect is counterproductive because it also discharges medication from the tumour cells. This can ultimately lead to resistance and failure of the therapy. Ecteinascidin 743 blocks the production of MDR1 and thus prevents it from discharging the drug. Scientists hope that ecteinascidin 743 will reinforce the potency of other chemotherapy drugs by preventing resistance. Yondelis® has so far been approved for the treatment of soft tissue sarcomas – rare, malignant connective-tissue tumours. >