Drug companies delve deep to advance the battle against cancer

Main Category: Cancer / Oncology
Article Date: 27 Oct 2003 - 0:00 PDT


The diversity of life in the sea is emerging as the most important new source of drugs to fight cancer. The first of a generation of medicines based on marine organisms has been approved by the European Commission for use against ovarian cancer. At least three others are in advanced clinical trials on human patients.

Medical researchers have discovered that sea creatures contain chemical compounds previously unknown to science, a few of which have been shown to be successful in tackling cancers that resist conventional chemotherapies.

Professor Tony Moffat, chief scientist of the Royal Pharmaceutical Society, said: "The oceans are an exciting source of new cancer drugs. Over the last 20 years we have pretty much exhausted the land-based sources in the plant and animal kingdom, so people are trying to find totally new sources of lead compounds. Now we are looking at shellfish, sea anemones, fish of different kinds, things that have never previously been looked at, and we are finding that these creatures contain entirely new chemicals which have never been tried before."

The newly approved treatment is Yondelis, whose active ingredient is based on molecules harvested from a Caribbean sea squirt, Ecteinascidia turbinata. The makers hope that the drug will also be approved for use against soft tissue sarcoma, a rare cancer that affects 1,300 people a year in Britain.

In clinical trials at the Royal Marsden Hospital, in London, Yondelis is said to be proving more successful than two standard drugs.

Roger Wilson, president of Sarcoma UK and a former patient, said: "If I have a recurrence of soft tissue sarcoma, with inoperable lung metastases, this is the one drug which I would want to have. There is talk of people on trials not facing too many side- effects, and of some people having indications of responding to treatment for the first time."

Doctors hope that Yondelis will be useful in treating a wide range of sarcomas, the main group of cancers affecting children and teenagers. Scientists at PharmaMar, the Spanish company that developed the drug, say that the fact that it affects different types of tumour suggests that it is acting in an entirely new way against a growth mechanism common to many cancers.

Another drug that could prove a success story is Kahalalide F, which is based on a protein produced by tiny Hawaiian sea snails. The drug has proved effective in tests on patients with prostate, breast and colon cancers. Clinical trials are about to start on patients with liver cancer, an extremely aggressive tumour that does not respond well to conventional chemotherapy.

APL, a drug produced from a different variety of sea squirt, Aplidium albicans, which is found in the Mediterranean, is now in clinical trials on 230 patients with colorectal and kidney cancers, and cancer of the thyroid. Trials on children with leukaemia are due to start by the end of the year.

Pharmacists at the British Pharmaceutical Conference in Harrogate last month were told that molecules harvested from sea urchins, clams, algae, snails and sea cucumbers found in waters off the coast of Venezuela are also under investigation as potential cancer cures. Laboratory tests showed that minute quantities of substances they produce can kill 50 per cent of cancer cells.

"Some outstanding growth inhibition was observed, suggesting that these organisms could be very promising sources of novel compounds," said Ysabel Campos-Santaella, who is working with a research group at King's College, London.

Not all of the new chemicals derived from the sea relate to cancer treatments. Elan Pharmaceuticals, an Irish drugs company, is waiting for approval from America's Food and Drug Administration for a new treatment for chronic pain called Ziconotide, which is based on a protein produced by cone snails to kill fish.

Reuben Henríquez, director of the technology development at PharmaMar, said: "I would say that the sea could become more important than the rainforest as a potential medicine chest."

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