P HILADELPHIA - A molecule known for its Texas circumference now appears to be a promising new weapon against cancer . A pilot test of the new metal compound carrying heavy, described here Saturday at the annual meeting of the American Association for the Advancement of Science (which publishes Science NOW), extended the life of people living with brain cancer.
natural pigments called porphyrins, that carry iron in the blood, the home in on the tumors. Jonathan Sessler, a chemist at the University of Texas, Austin, thought that porphyrins could become haul for cancer drugs. Because Sessler said that everything is bigger in Texas, he initially stalled fifth link in the porphyrin molecule, resembling a bracelet of four linked rings. This new molecule "Texas size" - appropriately nicknamed texaphyrin - had a capacity of 20% larger, enough to carry a heavy metal atom of gadolinium. net positive charge of gadolinium would be able to absorb an excess of electrons, which tend to recombine with hydroxyl radicals - corrosive molecules formed during radiation therapy against tumor - and eliminate their carcinogenic killing. Gadolinium, Sessler hoped would prolong the effects of hydroxyl radical and thus increase the power of radiation.
To see if Texaphyrins gravitate to tumors like their cousins are porphyrin, Sessler used magnetic resonance imaging (MRI) to scan cancerous mice before and after an injection of texaphyrin. Gadolinium MRI shows increased sharply. Sessler and colleagues at Pharmacyclics in Sunnyvale, California, found that cancerous cells appeared bright white areas on the MRI, even days after an injection of texaphyrin. When the team irradiated these mice, tumor cells decreased or disappeared and 50% of the mice survived the 140 day study. Only 10% of irradiated mice survived without texaphyrins.
In early clinical trials, Sessler and colleagues treated 39 patients with metastatic brain tumors with Texaphyrins 2 hours before radiotherapy for 10 days. Patients who had a life expectancy of 2 to 4 months, survived an average of 188 days. The patients in the group receiving the highest dose survived an average of 362 days. Although drug studies are not complete, Sessler said, "there are people alive that would normally be dead." The National Cancer Institute has selected Texaphyrins within its network of decision NCI -. A group of what he considers therapies is coming and most promising
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