UNLOCKING THE OCEAN'S MEDICINE CABINET

Material derived from articles written by Bryan Christie, Health Correspondent for The Scotsman newspaper

Drugs derived from primitive sea creatures dredged up from waters of the Caribbean are being used for the first time in the world on cancer patients in Scotland. The sponge-like organisms produce powerful compounds which have been shown in laboratory research to combat a range of human cancers. Now the first trials have started on patients at the Western General hospital in Edinburgh in a move which, if successful, could lead to a weapon being created in the continuing battle against cancer. It is part of a £6.5 million investment being made by the Imperial Cancer Research Fund over the next five years in research at Edinburgh University’s department of clinical oncology at the hospital.

A Spanish company, Pharma Mar, has developed a drug, Ecteinascidin 743, from a creature called Ecteinascidia turbinata, part of a family of sponge like-organisms called tunicates found on the roots of mangrove trees or shrubs that lie along the coast of warm water Caribbean islands. Sea squirts, as they are more commonly known, are bag-like with two small openings out of which water is squirted in fine jets. Such organisms cannot move and have to protect themselves. They have developed poisons which they release into the water around them if they are under threat. It is these toxins which are being developed to fight human cancer.

Professor John Smyth, who leads the unit, said: “He hoped the drug would prove useful in small cell lung cancer, melanoma and breast cancer. It has a potency and an order of magnitude greatly different from the compounds we already use.” The first trials taking place at the moment will cover a group of about two dozen patients for whom other treatments have been unsuccessful. These are designed to test the safety of the drugs and determine any side effects.

The Edinburgh unit is also to investigate the effects of another group of compounds known as dolastatins - a different group of unique substances extracted from the seahare Dolabella auricularia found in the Indian Ocean. These have also shown potential in the laboratory but have yet to be tested in patients.

Most of the anti-cancer drugs available are synthetic chemicals but increasing interest is being shown in what the natural world has to offer. Edinburgh was one of a number of centres around the world involved in testing drugs derived from the yew tree. These have since been licensed and are being used to help in the treatment of ovarian and breast cancer.

Potential for over-exploitation

Marine scientists are now going to spectacular lengths - and depths - to find cures for what ails humankind. “No matter how creative a chemist can be ... nature is much more creative,” says Dr Shirley Pomponi, the director of biomedical marine research at the Harbor Branch Oceanographic Institution, a leading United States ocean research group. The peculiarities of predators, pressure and salinity prod sea organisms to manufacture unique toxic chemicals for self-defence. Creation of these chemicals, known as “natural products”, mimics the manufacture by coffee plants of caffeine, which scientists think is created as a pesticide.

Medical science has long sought radical remedies in the world’s rainforests. Yet biomedical exploration of the oceans, which cover 70 per cent of the earth’s surface, is in its infancy. Scientists have catalogued perhaps 10,000 marine organisms, the barest fraction of what may lie in the depths. Already scientists have isolated a series of compounds called topsentins that may become a treatment for arthritis and a chemical called discodermolide that works against breast and ovarian cancer.

One of the most promising sea chemicals is found in the previously mentioned sea squirt from which Pharma Mar has already developed a drug. But its promise illustrates a troubling aspect of marine-based drugs - mass production. It takes a tonne of sea squirts to produce a gram of the chemical compound, stirring fears of over-harvesting of wild organisms. Another difficulty is that the search for new marine compounds can be a long and financially perilous quest, says Bill Fenical, of the Scripps Institution of Oceanography, near San Diego, California. Most drugs take at least ten years from discovery to production, during which the compound could be overtaken by better drugs or fail due to late-developing side effects. “It is really risky. It has big potential profits but big potential losses,” says Fenical.