Tesaro (TSRO) won U.S. approval Monday for its PARP inhibitor niraparib as a new maintenance treatment for ovarian cancer patients responsive to platinum-based chemotherapy.

The new Tesaro drug, to be marketed under the brand name Zejula, was granted a broad treatment label by the FDA, including patients with ovarian cancer containing a mutation to a tumor suppressor gene known as BRCA, as well as patients who lack the mutation.

Zejula's approval also came early. FDA has until June 30 to render its decision.

Tesaro shares were halted at $156.73 ahead of the FDA's approval announcement. The stock rose 6% to $165.60 once the halt was lifted.

The company is waiting to disclose Zejula's price at commercial launch in late April.

"Maintenance therapy is an important part of a cancer treatment regimen for patients who have responded positively to a primary treatment," said Dr. Richard Pazdur, M.D., acting director of the FDA's Office of Hematology and Oncology Products. "Zejula offers patients a new treatment option that may help delay the future growth of these cancers, regardless of whether they have a specific genetic mutation."

Zejula belongs to a class of oral drugs known as PARP inhibitors. The drugs work by blocking an enzyme, poly (ADP-ribose) polymerase, that cancer cells use to repair their DNA after being damaged by chemotherapy. Mutations in the BRCA gene are correlated with a higher risk for breast and ovarian cancers. But BRCA mutations also inhibit DNA repair, which is why PARP inhibitors are thought to work better in these types of tumors.

Tesaro conducted a clinical trial in women with ovarian cancer put into remission by platinum-based chemotherapy. The study was designed to measure the length of time the patients' tumors did not grow after treatment (progression-free survival) in patients with and without the BRCA mutation. The median progression-free survival for patients taking Zejula who had a germline BRCA mutation was 21 months compared to 5.5 months for similar patients on placebo. The median progression-free survival for patients taking Zejula who did not have a germline BRCA mutation was 9.3 months compared to 3.9 months for the similar placebo patients.

AstraZeneca's (AZN - Get Report) PARP inhibitor Lynparza is already approved in the U.S. as a treatment for ovarian cancer patients with BRCA mutant tumors no longer responsive to three or more prior therapies. The company recently presented its own ovarian cancer maintenance therapy data and expects to seek an expanded approval soon, although its data only covers tumors that carry the BRCA mutation.

Last December, Clovis Oncology (CLVS - Get Report) secured FDA approval for Rubraca, another PARP inhibitor, to treat BRCA-mutant ovarian cancer no longer responsive to two or more prior therapies. Clovis is also conducting a clinical trial to test Rubraca as an ovarian cancer maintenance therapy, with results expected in the third quarter.

Adam Feuerstein writes regularly for TheStreet. In keeping with company editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.