Next, de Bono's team tried the drug on a smaller group of patients, all of whom were confirmed carriers of the BRCA1 or BRCA2 mutation. Those patients received 200 milligrams of olaparib twice a day.
The researchers found that olaparib was absorbed quickly, was eliminated from the body quickly, and had mild side effects. In addition, among people with the BRCA mutations the drug shrunk tumors in breast, ovarian and prostate cancer.
"Olaparib has few of the adverse effects of conventional chemotherapy, inhibits PARP, and has anti-tumor activity in cancer associated with the BRCA1 and BRCA2 mutation," the team concluded.
Iglehart thinks that combining a PARP inhibitor with chemotherapy drugs that damage DNA might make the drug even more effective. "You might then push cancers over the cliff that would be only susceptible to a PARP inhibitor," he said.
In addition, "PARP inhibitors may be used for tumors that Herceptin or tamoxifen are totally incapable of treating," he said. "That's true for ovarian cancer, too. There is nothing to treat that disease."
Two other trials of PARP inhibitors, which were reported on during the American Society of Clinical Oncology annual meeting in June, also found that they were effective in treating breast cancer.
In one trial where PARP inhibitors were combined with standard chemotherapy, there was almost a doubling of survival -- from 5.7 months with chemo alone to 9.2 months when the PARP inhibitor BSI-201 was added, as well as about a 60 percent reduction in the risk of dying from the disease. There were also no additional side effects.
The second PARP inhibitor trial involved 54 women with advanced breast cancer who carried the BRCA mutations. In this trial, 41 percent of patients saw their tumors disappear. There was a slightly lower response rate in the lower-dose group. Mild nausea and fatigue were the most common side effects.
"The drugs are
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