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U.S. Patent Awarded for Prodrug Cancer Imaging, Treatment

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30 July 2014. A new patent was awarded for a technology that detects and treats solid tumor cancers with a prodrug, a precursor compound activated inside the body — made by GenSpera Inc., a biotechnology company in San Antonio. U.S. patent number 8,772,226 was awarded on 8 July to inventors Samuel Denmeade and John Isaacs of Johns Hopkins University and Søren Brøgger Christensen at University of Copenhagen in Denmark, and assigned to Johns Hopkins University. GenSpera, founded by Denmeade and Issacs, licenses the technology from Johns Hopkins.

The patent covers the use of thapsigargin, a substance derived from the thapsia plant, a weed grown in Mediterranean regions and toxic to sheep and cattle. GenSpera synthesizes a form of thapsigargin that remains dormant until activated by enzymes associated with the targeted cancers, both to attack the tumor as well as the supporting blood supply.

The patent also covers the activation mechanisms when thapsigargin comes into contact with the enzymes prostate specific membrane antigen (PSMA), prostate specific antigen (PSA), and human glandular kallikrein 2 (hK2). One or more of these enzymes are associated with liver, breast, brain, renal, and colon, as well as prostate cancer. The activation process employs peptides that in the presence of these enzymes open up to release the thapsigargin payload. Thapsigargin, says the company, kills tumor and supporting cells independently of the rate of cell division, and thus can be used to treat both slow and fast-growing cancers.

This activation process can be applied as well to detecting cancer, particularly in early stages or when tumors are growing slowly. Current imaging methods such as trans-rectal ultrasound or magnetic resonance spectroscopy are established  techniques for detecting prostate cancer, for example, which provide images of regions where the cancer may occur.

The patent instead describes a process for detecting and highlighting cancer cells rather than regions. The techniques in the patent label the prodrugs with radioactive isotopes, such as tritium, which in contact with the enzymes emit rays that illuminate to allow for imaging and detection.

GenSpera’s lead product, code-named G-202, is in intermediate-stage clinical trials as a treatment for liver cancer and glioblastoma, a form of brain cancer. A trial testing G-202 with prostate cancer completed early-stage trials.

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