Humans have turned to nature for medicines since ancient times. And modern scientists have searched the world’s rainforests for new medicinal compounds. The earth’s oceans may be an even better source, though, and at least 26 drugs that come from marine organisms are currently on the market or in development. A generation of innovative chemists hopes to boost this number.
Chemist Mande Holford has an unusual partner in her hunt for new medicines: a fierce marine snail that eats fish. Her study of the creature, she said, is not entirely scientific.
“I fell in love with snails because their shells are gorgeous,” said Holford.
Their tongue-like proboscides, on the other hand, are deadly. They inject prey with venom that’s made of poisonous chains of amino acids, called peptides.
“I like to say that the snails produce a cluster bomb. Inside [their] venom, you have between 50 to 250 peptides," said Holford. "All target something major in the nervous system. One thing that they hit is a pain signal. When they silence the pain signal, the prey doesn’t go into fight or flight mode.”
Marine research yields major medicines
So the fish stays calmer than it naturally would, even as it’s being eaten. Chemists already have had one major success repurposing the snail’s peptides - a drug called Prialt eases pain for HIV and cancer patients.
“On your neurons, you have these 'gates' that allow things to pass from one side to the other. The gate that controls chronic pain, they’ve found a way to shut it down using one of the peptides,” said said Holford.
Holford may have been drawn to study snails by their beauty. She represents a broader trend, however, toward marine research.
“We’ve found some absolutely fascinating chemistry,” said David Newman, who directs the Natural Products Branch of the U.S. National Cancer Institute. After years of collecting organisms on land, his team now collects only marine life, like sponges or corals. He explains that because these organisms can’t move, they rely on chemical warfare.
“I have been known to say that weapons of mass destruction are alive and well on the coral reef, if you happen to be a fellow sponge who’s trying to encroach, or you’re a starfish that’s trying to eat the sponge. These are extremely toxic agents because of the dilution effect of seawater,” said Newman.
For an organization looking to kill cancerous cells, such potent chemicals are an attractive weapon.
Deep ocean mud loaded with cells
And far below coral reefs, some nine kilometers deep, lies what may be an even more promising source - mud.
“Close to 70 percent of the surface of the earth is really deep ocean mud,” said William Fenical, who directs the Center for Marine Biotechnology and Biomedicine at the Scripps Institute for Oceanography in California. His team focuses on microorganisms living on the sea floor.
“These muds contain about one billion cells in the volume of a sugar cube,” said Fenical.
For comparison, that’s one million times the organic matter you’re likely to find in a similar amount of soil on land. It’s the sheer diversity of this microbial soup that excites Fenical.
“For the last 50 years, microorganisms that occur on land have been exploited for the production of antibiotics, cancer drugs, and cholesterol lowering drugs. What we believe is that the ocean is a completely new resource for such microbial products,” he said.
Fenical’s team already has two drugs in development. He said he sees no end to prospects for ocean-based medicines.