In what is being called a “landmark clinical trial” of genetic oncology, UK researchers have discovered that AstraZeneca’s Lynparza (olaparib), approved in 2015 to treat ovarian tumors in women, can benefit men suffering from prostate cancer.

Encouraged by the positive results, a second study has been initiated. If it reproduces the earlier findings, the researchers believe olaparib could become a standard treatment for advanced prostate cancer in certain cases.

The first trial carried out by the Institute of Cancer Research in London, in cooperation with the Royal Marsden hospital and backed by a number of financial supporters, showed that the AstraZeneca drug helped 25-30% of patients with advanced prostate cancer – all of whom carried specific genetic mutations that affect their cells’ ability to repair damaged DNA.

Among the 49 men in the trial who had terminal prostate cancer that was hitherto unresponsive to treatment, 14 – all with detectable DNA repair mutations – are said to have survived much longer than expected for patients with such advanced disease. Joaquin Maleo, lead author of the study, said it appears that olaparib further disrupts the repair mechanism by causing so much damage that tumour cells can no longer survive.

In the second trial, only patients whose DNA shows detectable repair mutations will receive olaparib, a Parp inhibitor approved for women with ovarian cancer who inherited mutations in their so-called BRCA genes.

“We are finding that similar mutations affecting DNA repair are also present in other genes in other cancers,” Maleo said, adding that genomic research suggests that beyond prostate, ovarian and breast cancer sufferers, some people with gastric cancer — one of the most difficult tumors to treat — may benefit from a course of a Parp inhibitor such as olaparib.

Although the drug has been approved by regulators in Europe and the US, AstraZeneca has expressed disappointment that the UK’s National Institute for Health and Care Excellent (Nice) and the Cancer Drugs Fund have not agreed to fund the use of olaparib in the National Health Service (NHS), citing its high price tag of £43,000 for a full 11-month course.