Repositioning approved drugs could speed development of new therapies, researchers say
SATURDAY, Sept. 1 (HealthDay News) -- A drug used as part of a regimen to treat HIV also appears to kill cancer cells, researchers from the U.S. National Cancer Institute report.
Based on this new finding, the HIV protease inhibitor nelfinavir is being used in a phase I clinical trial to determine what might be the safest and most effective dose for cancer patients. This strategy of finding new uses for existing drugs could have a major impact on treating cancer and other diseases, the researchers added.
"This could be a new approach to finding cancer drugs and cut the time for getting them approved," said lead researcher Dr. Phillip A. Dennis. "Repositioning drugs that are already FDA-approved could accelerate the development of new cancer therapies."
The researchers hit upon the idea of testing nelfinavir and other protease inhibitors as cancer drugs, because these drugs block Akt, a protein essential for the development of many types of cancer, including non-small cell lung cancer.
The report is published in the Sept. 1 issue of Clinical Cancer Research.
In experiments with mice, Dennis' team tested six protease inhibitors on non-small cell lung cancer and on 60 human cancer cell types from nine different kinds of malignant tissue.
At doses that are safe in HIV-infected patients, three of the drugs, nelfinavir, ritonavir and saquinavir, blocked growth of non-small cell lung cancer and every other cancer cell type tested, the researchers found.
However, nelfinavir was the most effective of all the drugs tested. It caused cancer cells to self-destruct or become stressed to the point of dying, Dennis said.
In addition, nelfinavir inhibited the growth of both drug-sensitive and drug-resistant breast cancer cells, indicating that it could be used to fight cancer cells that are resistant to common chemotherapy drugs. Nelfinavir may also be able to overcome resistance to radiation, the researchers reported.
Dennis noted that low doses of nelfinavir are used in treating HIV, and even at those low doses, the drug is effective against cancer. The current phase I trial will test higher doses to find the most effective dose with the fewest harmful side effects, he said.
In the trial, patients are already receiving higher doses with no apparent problem, Dennis said.
"If nelfinavir is proven effective in fighting cancer, it would, most likely, be used in combination with other cancer drugs," Dennis said.
One expert thinks this finding could be an important advance in cancer treatment.
"If it is proven that the toxicity levels are manageable in humans, it's going to be a great thing," said Charles Saxe, a scientific program director at the American Cancer Society. "Being able to get these drugs faster to patients by crossing over from one disease to another is going to be a big help."
Saxe noted that nelfinavir's ability to fight cancer in humans still needs to be proven. "But if they are right, and they can keep toxicity at reasonable levels, and they can show an effect at doses HIV patients can handle, that would be really exciting," he said.
In other cancer news, National Cancer Institute researchers report that they have found an extract of the skin of muscadine grapes (MSKE) can cause prostate cancer cells to die without affecting normal cells, according to a report in the Sept. 1 issue of Cancer Research.
The lead researcher noted this extract does not contain significant amounts of resveratrol, another grape skin component that has been linked to preventing the growth of prostate cancer.
"These results show that MSKE may have potent anti-tumor activities in the lab that differ from the effects of resveratrol. Further studies of MSKE will be necessary to determine if this extract has potential as a chemopreventive or therapeutic agent," Dr. Jeffrey E. Green, chief of the Transgenic Oncogenesis and Genomics Section at the Center for Cancer Research, said in a statement.
And in other HIV news, a study in the August issue of AIDS Patient Care and STDs, researchers found that one-fourth of HIV patients feel stigmatized by their doctors.
Most of the patients who felt that way were low-income minorities with poor access to care.
"Whether or not it is actual stigmatization is hard to measure, because it's coming from the patients that we interviewed," lead researcher Janni J. Kinsler, from the University of California, Los Angeles, said in a statement. "The point is that these people feel that way, and that's bad enough, because they're less likely to seek the care they need."
For more on cancer, visit the U.S. National Cancer Institute.
SOURCES: Phillip A. Dennis, M.D., Ph.D., Medical Oncology Branch, Center for Cancer Research, U.S. National Cancer Institute, Bethesda, Md.; Charles Saxe, Ph.D., scientific program director, American Cancer Society, Atlanta; Sept. 1, 2007, Clinical Cancer Research; Sept. 1, 2007, Cancer Research; August 2007, AIDS Patient Care and STDs
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