On January 12, the Food and Drug Administration (FDA) approved Lynparza (olaparib) for people with breast cancer that has spread beyond its original site (a process known as metastasis) and who carry BRCA gene mutations.

Women with inherited (also known as “germline”) BRCA gene mutations are at higher risk for breast and ovarian cancers. Around half of women who carry these mutations will develop breast cancer during their lifetime, according to the National Cancer Institute.

Lynparza, from AstraZeneca, is a targeted therapy that works by blocking poly (ADP-ribose) polymerase, or PARP proteins, which play a role in DNA repair. Inhibiting PARP leads to more DNA breaks in cancer cells, which can halt cell division. People with BRCA mutations do not make proteins that fix this kind of DNA damage, so BRCA-related cancers are particularly susceptible to these drugs. Lynparza was previously approved in 2014 for the treatment of advanced ovarian cancer in women with BRCA mutations.

Breast cancer is classified by the kind of receptors it expresses. A majority of breast tumors carry hormone receptors for estrogen or progesterone (known as HR-positive) and can be treated with hormone-blocking drugs. Other tumors express a receptor called HER2 (human epidermal growth factor receptor 2) and can be treated with HER2 inhibitors. Triple-negative breast cancer doesn’t express any of these receptors and is harder to treat.

Lynparza is now indicated for the treatment of patients with germline BRCA-mutated HER2-negative metastatic breast cancer who were previously treated with chemotherapy. Patients with HR-positive breast cancer should have been treated with prior hormone or endocrine therapy or be considered inappropriate for endocrine treatment.

The FDA also expanded the approval of the BRACAnalysis CDx assay, a diagnostic test to accompany Lynparza, for the detection of BRCA mutations in blood samples from patients with breast cancer.

The new approval was supported by data from the Phase III OlympiAD trial, which evaluated Lynparza in more than 300 people with HR-positive or triple-negative metastatic breast cancer and BRCA1 or BRCA2 gene mutations. Participants were randomly assigned to receive Lynparza tablets or standard chemotherapy.

As reported at the 2017 American Society of Clinical Oncology annual meeting and in The New England Journal of Medicine, Lynparza led to longer survival, fewer serious side effects and better quality of life. The overall response rate—meaning complete or partial tumor shrinkage—was 60 percent in the Lynparza group, compared with 29 percent in the chemotherapy group.

The median duration of progression-free survival—meaning that patients were still alive with no worsening of disease—was 7.0 months in the Lynparza group and 4.2 months in the chemotherapy group, representing a 42 percent improvement. However, overall survival ended up being similar (19.3 months versus 19.6 months, respectively) as cancer cells developed resistance to Lynparza.

Severe side effects were reported less often in the Lynparza group than in the chemotherapy group (37 percent versus 51 percent). Common side effects included nausea, vomiting and anemia.

“This class of drugs has been used to treat advanced BRCA-mutated ovarian cancer and has now shown efficacy in treating certain types of BRCA-mutated breast cancer,” Richard Pazdur, MD, director of the FDA’s Oncology Center of Excellence, said in an FDA news release. “This approval demonstrates the current paradigm of developing drugs that target the underlying genetic causes of a cancer, often across cancer types.”

Click here to read the FDA press release about Lynparza approval.

Click here to see the full prescribing information for Lynparza.