For decades, researchers have looked to the seas as a source for new drugs. Some of those efforts are beginning to pay off.
Prialt, a medication derived by mimicking the deadly toxin of the cone snail, went on the market earlier this year to treat the "phantom" pain that amputees suffer in limbs that have been removed. Advocates say it's 30 times more potent than morphine, without its addictive qualities.
FOR THE RECORD - An article about marine research in Friday's Health & Science section misspelled the name of Margo Haygood, a biologist at the Scripps Institute of Oceanography. The Sun regrets the error.
Meanwhile, some 20 compounds derived from sponges, mollusks, microbes and other aquatic creatures are currently in clinical trials. Some may soon be the basis for treatments of ailments that range from cancer and depression to asthma, arthritis, Alzheimer's and general pain.
And scientists continue to study the immune systems of sea creatures, the toxins they produce and their symbiotic relationships with bacteria that feed off them.
"The drug companies are looking everywhere for possible therapies," said Bert Spilker, a Bethesda-based pharmaceutical consultant. "It's not as if suddenly everyone is going out and searching, but there's been a steady interest in it for years."
Since 1960, at least seven drugs based on compounds found in plants, soils and other terrestrial sources have been approved by the Food and Drug Administration, including paclitaxel, approved in 1992 as a treatment for breast, ovarian and some types of lung cancer, according to the National Cancer Institute.
But experts say the oceans are still a relatively untapped resource.
"There's a phenomenal number of microbes living in the seas, and we're constantly searching, but we really have no idea what we're going to find," said David Newman, an expert on marine products at the National Cancer Institute. "There's immense potential there, but it's a long process."
This week, a biologist at George Washington University published findings showing that the immune system of the purple sea urchin produces a surprisingly complex response when threatened by infection.
Associate professor L. Courtney Smith found that when she injected sea urchins with a bacterial agent, the urchins produced an unexpectedly diverse range of proteins. The findings were published in Physiological Genomics.
Smith said that understanding the sea urchin's immune system may have medical applications if it turns out that the animal's relatively simple immune system uses mechanisms that perform functions similar to our own.
"Basically, there's a lot more going on than we thought," Smith said.
Elsewhere, much research has focused on coral reefs, which are among the most poisonous environments on Earth. In fact, corals have survived for thousands of years precisely because they've developed such effective toxins to ward off predators. Along with sponges, sea squirts and snails, the world's reefs may be a treasure chest of medical possibilities, scientists believe.
"Think about a microorganism living on a coral. It can't run away from its enemies, and it generally can't hide, so it puts out toxins that make it poisonous to fish. Those toxins have to be exquisitely potent because they're being diluted by being released in seawater," Newman said. "In nature, the creature with the best chemistry set wins."
The National Cancer Center has gathered thousands of samples of coral reef organisms, but its collection is still far from complete, Newman says.
As potentially exciting as the oceans are, it typically takes five to 15 years to bring any drug derived from a natural source to market, Newman said. Still, he noted, almost two-thirds of anti-cancer agents investigated as drug treatment candidates between 1981 and 2002 were derived from natural products.
One of them, bryostatin, (the name for a family of compounds produced by a stringy brown critter that swims in the Pacific) is currently the focus of dozens of clinical trials as a potential treatment for combating leukemia, lymphoma and several other cancers.
Experts credit another sea creature - a Caribbean sea sponge called Cryptotheya crypta - with producing the raw materials that proved to be a model for an antiviral compound used to treat herpes, called Ara A , and another compound used to combat cancerous tumors, called Ara C.
The quest for a medically useful, ocean-based organism generally starts with divers who probe the depths of the sea, looking for something unusual.
"If they see something they haven't seen before, that will be what attracts their interest," said Mark Schrope, a spokesman for the Harbor Branch Oceanographic Institution in Fort Pierce, Fla.
The research and educational center has a submersible craft that routinely probes to depths of 3,000 feet, looking for potential cures. In 1987, the institute discovered a sea sponge that has become the basis for discodermolide, a cancer therapy now in clinical trials.