Writer: Researchers have reported promising results in a new type of cancer treatment during preliminary drug trials on inherited tumors that often defy standard treatment. The experimental anticancer pill called olaparib is a member of a new class of drugs called PARP inhibitors that prevent unstable cancer cells from repairing themselves.

The study, led by the Institute of Cancer Research, with the pharmaceutical company AstraZeneca is featured in the New England Journal of Medicine.

19 patients with inherited forms of advanced breast (3), ovarian (15) and prostate (1) cancers caused by mutations of the BRCA1 and BRCA2 genes were given olaparib. In 12 of these patients the researchers found that the tumors shrank or were stabilized where no other treatment had earlier worked. Two years later one of the first patients to be given the treatment is still in remission.

Researcher Johann de Bono, MD, PhD, of the Institute of Cancer Research in Sutton, U. K. said patients experienced very few side effects while on the experimental drug and some reported the treatment was "much easier than chemotherapy".

De Bono said, "This drug showed very impressive results in shrinking patients' tumours. It's giving patients who have already tried many conventional treatments long periods of remission, free from the symptoms of cancer or major side-effects."

He added that the drug should now be tested in larger trials.

Women with defects in the BRCA1 and BRCA2 genes are at increased risk of developing aggressive cancers of the breast and ovaries at a young age while BRCA2 gene mutations raise a man's risk of prostate cancer. However the drug, olaparib did not help 41 other patients with tumors that were not associated with BRCA mutations, said de Bono.

PARP is short for poly (ADP-ribose) polymerase, an enzyme used by cancer cells to repair DNA damage.

Cancerous and healthy cells all have multiple systems for DNA repair and even if one pathway is turned off, most cells can survive.

In the case of people with BRCA mutations, one pathway is shut down and the drug olaparib, eliminates the cancer cells by shutting down a key enzyme called PARP leaving the healthy cells unscathed as they are controlled by their healthy BRCA genes.

Professor Stan Kaye, who also worked on the study said, "The next step is to test this drug on other more common types of ovarian and breast cancers where we hope it will be just as effective."

Dr Peter Sneddon, of the charity Cancer Research UK said, "Although development of this drug is in its early stages, it is very exciting to see that it has the potential to work when other treatment options have failed."

According to James Carmichael, MD, global medical director for olaparib, drug maker AstraZeneca, who helped to fund the work, plans to continue studying the drug.