"Smart" Drug Targets Experimental Prostate Cancer
The drug is activated by prostate specific antigen

By Will Boggs, MD

Thursday, March 20 (Reuters Health) - A potent chemo drug that is activated by prostate specific antigen, or PSA, shows high activity against prostate cancer implanted in mice, researchers report.

They designed a precursor of the anticancer drug doxorubicin that binds to a common protein, albumin, in the body, and is then cleaved by PSA, which is produced in the prostate, so releasing doxorubicin at the tumor site. The idea is to limit the effects of the drug in normal tissue, but to have high levels accumulate in the prostate, the team explains in the International Journal of Cancer.

Dr. Felix Kratz from the Tumor Biology Center in Freiburg, Germany, colleagues then compared the effect of the novel formulation with that of free doxorubicin in experiments with mice.

Free doxorubicin and the albumin bound-doxorubicin precursor drug both markedly reduced the growth of prostate cancer implants in the mice. Tumor growth resumed following discontinuation of doxorubicin, but remained stable after the new agent was discontinued.

Free doxorubicin treatment reduced prostate tumor size by 33 percent, the researchers note, whereas the albumin-doxorubicin product reduced prostate tumor size by 62 percent.

Although the results are promising "and show an improvement compared to the free drug, we need to achieve complete remissions in pre-clinical models before advancing to the clinic," Kratz said.

His team is currently investigating other PSA-cleavable combinations of proteins and potent anticancer drugs "for the potential treatment of prostate cancer."

SOURCE: International Journal of Cancer, March 1, 2008.

Copyright © 2008 Reuters Limited. All rights reserved. Republication or redistribution of Reuters content, including by framing or similar means, is expressly prohibited without the prior written consent of Reuters. Reuters shall not be liable for any errors or delays in the content, or for any actions taken in reliance thereon. Reuters and the Reuters sphere logo are registered trademarks and trademarks of the Reuters group of companies around the world.

Would you like to receive prostate cancer news by email? Subscribe to NewsPulse