Gene-targeted olaparib proves effective against prostate cancer

Dec. 3 (UPI) -- A gene-targeting therapy already being used in breast and ovarian cancer may also be effective in prostate cancer, a new study has revealed.

In research published Monday in The Lancet Oncology, the drug olaparib, which is marketed under the name Lynparza, was effective at slowing disease progression in more than 80 percent of men with prostate cancer whose tumors had mutations in the BRCA gene.

If the drug continues to prove effective in subsequent trials, researchers say, it could become the first-ever gene-targeted therapy in prostate cancer.

"Our trial has shown that men with prostate cancer who were selected for faults in DNA repair genes responded very well to the targeted drug olaparib, especially where they had BRCA mutations in their tumors," study leader Professor Johann de Bono, Regius Professor of Cancer Research at The Institute of Cancer Research, London, said in a statement. "This study and another phase III trial place olaparib on the verge of becoming the first genetically targeted treatment in prostate cancer."

Olaparib is already approved by the U.S. Food and Drug Administration for the treatment of certain types of ovarian cancers -- namely, those caused by tumors with mutations in the BRCA genes. BRCA genes are integral to cell growth and DNA repair. Mutations can mean that DNA damage in cells to go unrepaired, which increases the chance that a person will develop cancer.

For the Phase II study published in The Lancet Oncology, researchers gave olaparib to 98 men with advanced prostate cancer at either 300 mg or 400 mg twice daily in four-week cycles at 17 U.K. hospitals.

In all, 40 percent of men with BRCA mutations enrolled in the study remained free of disease progression for more than a year, and some 20 percent of patients with other DNA repair gene alterations also responded to the drug.

Median overall survival with olaparib was 17.7 months for patients with BRCA mutations. Patients treated with olaparib whose prostate cancers had DNA repair defects lived for more than 13 months on average. Overall, the authors found that 47 percent of men with these DNA repair defects responded to olaparib, halting disease progression for an average of 5.5 months

The findings echoed those of an earlier trial, which tested use of olaparib in a group of men with advanced prostate cancer who weren't selected for treatment based on gene mutations. That study highlighted that those whose tumors had mutations in a range of genes involved in repairing damage to DNA could benefit most from the drug.

Based on their findings to date, the researchers believe men with advanced prostate cancer should now routinely have their tumors tested for DNA repair defects such as BRCA mutations.

"Precision medicines targeted to specific genetic faults are transforming treatment for many different cancers, and with this new research it looks like we will soon be able to add prostate cancer to that list," said Paul Workman, chief executive at The Institute of Cancer Research, London. "It's exciting to see a drug which the ICR helped pioneer having such widespread benefits for both women and men with cancer.

"The next step is to work out how to combine olaparib with other drugs to keep cancer at bay for much longer," Workman added.