WASHINGTON – The Food and Drug Administration on Friday cleared the first treatment for patients with advanced breast cancer caused by BRCA mutations, which are genetic defects that raise the risk of malignancies.

The drug, called Lynparza, already is approved for certain patients with advanced ovarian cancer associated with the same mutations. Richard Pazdur, director of the FDA’s Oncology Center of Excellence, said in a statement that expanding the approval to breast-cancer patients “demonstrates the current paradigm of developing drugs that target the underlying genetic causes of a cancer, often across cancer types.”

Lynparza belongs to a class of drugs called PARP inhibitors that block an enzyme involved in repairing damaged DNA. By blocking the enzyme, the DNA in cancer cells may be less likely to be fixed, leading to the death of those cells and potentially a slowdown or halt in tumor growth, the FDA said.

The drug, also known as olaparib, is marketed by AstraZeneca and Merck.

The agency said its approval was based on a randomized clinical trial of more than 300 advanced breast cancer patients with BRCA 1 or BRCA 2 mutations. The trial found that the length of time during which the tumors did not grow significantly, a measure called progression-free survival, was a median of 7 months for patients treated with Lynparza compared to 4.2 months for patients receiving chemotherapy only.

When those results were published last June, Mark Robson, an oncologist at Memorial Sloan Kettering Cancer Center who led the multisite trial, described the treatment as “an early chapter in a woman’s journey” in dealing with breast cancer – one that can delay the start of chemotherapy and help preserve her quality of life. He also said it was important for researchers to determine whether the results could be improved if the medication were used in combination with other treatments.

The FDA on Friday also approved Myriad Genetics’ diagnostic test, called BRACAnalysis CDx, as a companion to Lynparza. The test, which was previously cleared for ovarian cancer patients, identifies which breast cancer patients have BRCA mutations.

The National Cancer Institute estimates that about 253,000 women will be diagnosed with breast cancer this year and that more than 40,000 will die of the disease. About 5 percent to 10 percent of patients with breast cancer have a BRCA mutation.