U.S. regulators have approved the first drug aimed at women with advanced breast cancer caused by an inherited flawed gene.

The Food and Drug Administration on Friday approved AstraZeneca PLC's Lynparza for patients with inherited BRCA gene mutations who have undergone chemotherapy.

The drug has been on the market since 2014 for ovarian cancer, and is the first in a new class of medicines called PARP inhibitors to be approved for breast cancer. PARP inhibitors prevent cancer cells from fixing problems in their DNA.

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Lynparza will cost $13,886 per month without insurance, according to AstraZeneca. The company is offering patients financial assistance.

"While there is currently no cure for metastatic breast cancer, today's approval offers a new, targeted option that may help to delay disease progression for these patients," Dr. Susan M. Domchek at the University of Pennsylvania's Abramson Cancer Center said in a statement.

Until recently, cancer medicines targeted the disease based on where in the body it occurs.

This is a new approach to "target the underlying genetic causes of a cancer," the FDA's Dr. Richard Pazdur said in a statement.

The agency also approved a companion blood test from Myriad Genetic Laboratories Inc. for detecting BRCA mutations and determining which patients likely would benefit from Lynparza.

About 250,000 people each year are diagnosed with breast cancer and just over 40,000 die from it, according to the National Cancer Institute. About 20 percent to 25 percent of patients with hereditary breast cancers have a BRCA mutation. BRCA-related breast cancer often strikes younger people and is harder to treat than other breast cancers.

The latest approval was based on a study of 302 women with cancers that have spread beyond the breast and who had a BRCA gene mutation.

Lynparza modestly delayed the time until cancer worsened — 7 months versus 4 months for women given one of three commonly used chemotherapies. About half the study participants responded to Lynparza compared with about a quarter of those only treated with chemotherapy. It's unknown whether treatment increases survival.

Possible side effects are less severe than for chemotherapy, but serious problems can include blood and bone marrow cancers. Common side effects include nausea, fatigue, respiratory infections and blood count problems.

Lynparza is marketed jointly by UK-based AstraZeneca and Merck & Co., which is based in Kenilworth, New Jersey.