Article About the Latest Trend of Using Metals in Medicine
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Medicine Mines Metals to Heal And Cure
By Sharman Esarey
LONDON (Reuters) - The basic building block of life is carbon. Or is it? If a living organism gets a disease, the answer is organic. Isn't it?
The Oxford dictionary says life is the condition that distinguishes active animals and plants from inorganic, or non-carbon, matter. But medical researchers differ.
``Life is not just organic. For a chemist, organic chemistry is the chemistry of carbon -- but life is certainly inorganic as well as organic,'' said Dr. Peter Sadler, professor of chemistry at the University of Edinburgh in Scotland.
``In fact there are about 23 elements other than carbon needed for daily life. Life depends on inorganic elements,'' he said.
And here a growing number of scientists envision a potential treasure chest in the metals neatly lined up in the Periodic Table of Elements.
These metals might help unlock treatments or tests for medical conditions ranging from cancer to arthritis to Alzheimer's disease (news - web sites), heart attacks and microbial or viral infections.
Most drugs on the market make use of different combinations of just a half-dozen or so of the 110 elements in the table.
``Why are there so few drugs on the market that do include metal ions? We have carbon, hydrogen, nitrogen, oxygen, and sulphur, but not very many elements of the Periodic Table, said Dr. Peter Preusch, a scientist and program director at the U.S. National Institutes of Health (news - web sites) (NIH), which has just launched a grants offer to stimulate such research.
``Are we missing opportunities?'' asked Preusch, of the National Institute of General Medical Sciences.
METALS USED IN MEDICINE SINCE ANTIQUITY
Though doctors have used metals in therapy through the ages and some traditional healing systems also employ them, research in the field really took off in the last two decades after a fortuitous discovery and two runaway successes.
``The use of metals in medicine goes back to antiquity, but mercury and arsenic and such were used, most of which were toxic,'' said Dr. Michael Abrams, president and CEO of AnorMED, a Canadian company which researches and licenses metal-based therapeutic products.
``The reason there is a lot more interest in the last 10 to 20 years is that metals can let you do things that conventional organics cannot...They can accomplish medical tasks that can't be accomplished by conventional organics.''
The two dazzling successes that have researchers' attention are a drug and a diagnostic tool.
The metal gadolinium is the contrast agent that makes Magnetic Resonance Imaging, a diagnostic tool that has revolutionized imaging, work. The magnetic property of the metal gives you more information more quickly and has fewer side effects than prior technologies.
Several decades ago, Michigan State University researcher Barnett Rosenberg was testing the effects of an electric field on a strain of bacteria -- when it inexplicably stopped dividing.
After months of study, he traced the phenomenon to a platinum electrode created by the electrolysis, and thus was born an $800 million market and the world's largest-selling anti-cancer drug.
``There are a couple of very successful metal-containing drugs on the market: Cisplatin and Generation 2 carboplatin that have clearly been successful in a disease niche. The question is: Is that a fluke?'' said Preusch.
WHAT CAN METALS DO?
``The National Cancer Institute (news - web sites) has studied a large number of compounds for their potential activity against cancer or the HIV virus (news - web sites). They found that the frequency of success among metal-containing compounds was similar to that of organic compounds,'' Preusch added.
Some researchers are looking at those metals that naturally occur in the body and their metabolism -- how they are absorbed and released, where they are found in the cell and what varying functions they fulfill, such as regulating oxygen levels or controlling major biochemical pathways within enzymes.
Others are examining metals not needed for daily life, such as platinum, to see what they might do for us, said Edinburgh's Sadler.
Still others are looking at illnesses, like malaria, which is difficult to treat, to see what metals might offer. Some are researching ways to block iron or zinc's pathway into bacteria.
``There are pathogenic bacteria that cause meningitis. (Bacteria) must get iron. If they don't get iron, they die. They are clever at finding iron and getting it away from us,'' he said.
Still others are looking at radioactive metals for diagnostic equipment.
THE QUALITIES OF METALS
For AnorMED there are a number of interesting quirks to metals that give them potential.
Metals have diverse, three-dimensional structures that provide novel shapes for fitting into biological targets, which are not easily duplicated by simple organic molecules.
This is especially true of the platinum cancer-fighting drugs, which AnorMED has helped develop. It has licensed its ZDO473, a new platinum-based anti-cancer agent designed to overcome platinum drug resistance, to Anglo-Swedish drug group AstraZeneca.
Metal ions also tend to attach themselves to biological molecules, which can be harnessed to scavenge and remove unwanted compounds from the body.
Using this ability, AnorMED has developed drug Foznol, which it has licensed to U.K.-based Shire Pharmaceutical. Foznol is used to help control phosphate levels in end-stage kidney disease patients.
Researchers also note that metal compounds, unlike most common organic molecules, are capable of losing or adding electrons, so-called oxidation and reduction reactions. In diseased environments, these reactions could help inspire new drugs.
But scientists say much more basic research must be done on the metals to see how they behave.
``The more we understand about the nuts and bolts of how it (the interactions of metals with living cells) works, the more opportunities might present themselves,'' Preusch said, adding that interest in the field was growing.
``In response to the NIH program announcement, I have received a reasonable number of inquiries. I expect we will receive over one hundred applications over the next three years. The amount of money we will invest in the area will depend on the number of applications that are received and how well they do in the peer review,'' he said.
Edinburgh's Sadler sees a bright future for the field.
``People are looking for dazzling treatments (but) there is a need for more research. Slowly, slowly this will make a big contribution,'' he said. |
