Experimental Pill Works Against Some Genetic Cancers, Researchers Say

An experimental drug that belongs to a new class of cancer-fighting drugs appears to be successful in slowing the growth of certain inherited tumors that have resisted standard treatments, British researchers say.

The new drug, called olaparib, is a PARP inhibitor – the nickname for a category of drugs that target poly (ADP-ribose) polymerase, an enzyme that helps cancer cells repair DNA damage. PARP inhibitors stop unstable cancer cells from repairing themselves and continuing to spread through the body.

In a recent study by researchers at the Institute of Cancer Research in Sutton, U.K., officials found success in treating patients with olaparib. About 66 percent of 19 patients who had cancer resulting from mutations in the BRCA1 or BRCA2 genes improved after treatment with the drug.

Fifteen of the 19 patients had ovarian cancer, while three had breast cancer and one man had prostate cancer, officials said.

However, the use of olaparib did not improve the condition of 41 other patients with tumors not associated with mutations of the two BRCA genes, researchers noted.

Results of the new study are published in the June 25 issue of The New England Journal of Medicine.

PARP Inhibitors as Cancer Therapy

The success of olaparib is an encouraging sign for PARP Inhibitors, which “will very likely change the way we treat patients” whose tumors are caused by BRCA defects, according to Daniel Silver, MD, PhD, of the Dana-Farber Cancer Institute in Boston and a co-author of an editorial about the study.

PARP inhibitors are so-called smart drugs that more precisely treat cancer by going right at the building blocks of tumor growth while leaving surrounding healthy tissue unharmed. The drugs are favored by many because they generally result in fewer side effects than chemotherapy and other traditional treatments.

In the study of olaparib, the most common side effects were mild fatigue and stomach upset, researchers said. Olaparib, made by drug maker AstraZeneca, is a pill that is taken twice a day.

Broader Use Being Eyed

So far, researchers have focused the use of olparib on cancers involving mutations on specific genes, but the drug and other PARP inhibitors may someday help people suffering from other cancers.

The drugs are now being tested in women battling triple-negative breast cancer, which can be hard to treat since the cancerous tumors do not have receptors for the hormones estrogen and progesterone or the protein HER2. Current cancer therapies target those receptors.

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