An international team led by Texan researchers is using arsenic as a powerful tumor imaging agent. In fact, they are using a drug called bavituximab, 'an antibody that homes in on a specific molecular target on the blood vessels that feed tumors.' By linking this drug to very small doses of arsenic -- about one-millionth of what could be considered as poison -- they think it could allow physicians to detect hard-to-find tumors in a near future. The combination has already successfully tested with rats affected by prostate tumors. And it could soon be used on on humans to image breast tumors. But read more...
The Bavituximab drug is a monoclonal antibody analog which is used to potentially treat cancers and viral infections. (Credit: Wikipedia) It has been licensed by Peregrine Pharmaceuticals, Inc. from UT Southwestern Medical Center. As you can see above on the left, Bavituximab can be used as an anti-cancer drug, "Bavituximab binding to the tumor blood vessel cells alerts the body's immune system to attack the tumor and its blood supply" (Credit: Peregrine). But it also can be used as an anti-viral drug as you can see on the right. "After binding to these infected cells, the drug alerts the body's immune system to attack the infected cells" (Credit: Peregrine).
Binding tiny doses of arsenic to bavituximab is a project led by Dr. Philip Thorpe, professor of pharmacology at the University of Texas Southwestern Medical Center, and by Dr. Ralph Mason, professor of radiology and director of the UT Southwestern Cancer Imaging Program.
So why did these scientists decide to hire arsenic for help? The first reason is because "arsenic-labeled bavituximab appears to be safe." The second one is because it works. "In the study, Dr. Thorpe and his colleagues injected radioarsenic-labeled bavituximab into rats with prostate tumors. When the bavituximab bound to its target on the the tumor blood vessels, the tag-along arsenic created a 'hot spot' that researchers then imaged using positron emission tomography methods. The radioactivity levels produced by the arsenic are comparable to those used in standard, routine imaging procedures in humans. The technique allowed them to locate and capture unusually clear images of the tumors. They also discovered that there was little or no detectable uptake of bavituximab by normal organs, including the liver, a common site where drugs become entrapped."
Here is a quote from Thorpe. "We hope to use this technique to detect early tumor deposits that are not visible using other imaging techniques. The images we obtain are so clear that we may be able to see secondary tumors that have spread from the original tumor mass and lodged in distant organs."
This research work is scheduled to appear in the March 1, 2008 issue of Clinical Cancer Research under the name "Vascular Imaging of Solid Tumors in Rats with a Radioactive Arsenic-Labeled Antibody that Binds Exposed Phosphatidylserine." Unfortunately, the journal site gives access to its February 15, 2008 issue and gives a preview of its March 15, 2008 issue, but doesn't show anything about its March 1, 2008 issue.
But for more information, you can read a March 3, 2008 news release from Peregrine Pharmaceuticals, which states that Bavituximab can successfully target tumor blood vessels. Here is a quote. "In the study, researchers administered radiolabeled bavituximab to rats with prostate tumors and then conducted molecular imaging studies of the rats over the next several days. The results showed that radiolabeled bavituximab localized to the tumor blood vessels with great specificity. In these subjects, 22 times as much bavituximab localized to the tumor compared to the liver when measured 72 hours post-injection. The study further showed no specific localization of bavituximab to blood or other tissues including the heart, kidney, intestine, muscle, bone and brain. The tumor blood vessel-selective targeting observed in vivo in the study was confirmed by further bio-distribution analyses and by histology studies."
So are you ready for arsenic? Drop me a note if you think it's a good -- or bad -- idea.
Sources: University of Texas Southwestern Medical Center news release, March 1, 2008; and various websites
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