A new medication that helps women fight advanced ovarian cancer has been approved three months early by federal drug regulators because of its capacity to keep the disease at bay — but it is not a cure, doctors said Tuesday.

The medication, to be sold starting next month under the brand name Zejula, is a so-called PARP-inhibitor and was tested at the Northwell Cancer Institute in Lake Success as part of a major nationwide clinical trial.

The medication is the third PARP-inhibitor to be approved in recent months. However, it is the only one that can be prescribed to the vast number of patients whose cancers are considered “sporadic,” meaning there is no definable reason why the cancer occurred. The other two recently approved PARP inhibitors are for patients with either of the two BRCA gene mutations, said Dr. Veena John, a medical oncologist at Northwell Cancer Institute.

BRCA mutations predispose carriers to breast, ovarian and other cancers. BRCA mutations account for 15 percent to 20 percent of ovarian cancers. In men, a BRCA-2 mutation enhances the likelihood of breast and prostate cancers. About 22,000 women develop ovarian cancer annually in the United States.

The new drug works, John said, by interfering with an enzyme involved in the repair of damaged DNA in tumor cells. When the tumor can’t repair its DNA, it no longer possesses instructions to function. The tumor dies. The term PARP stands for poly ADP-ribose polymerase.

“It’s an exciting option and I am glad that it got approval,” John said in an interview Tuesday.

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She said results of the clinical trial, which included 553 patients nationally, were reported in the New England Journal of Medicine in December. The compelling findings led the U.S. Food and Drug Administration to approve the medication three months ahead of schedule. Along with ovarian cancer patients, the clinical trial included those with fallopian tube peritoneal cancers.

Before its approval, Dr. Edward A. Jiménez, a gynecologic oncologist at Winthrop University Hospital in Mineola, said he obtained the drug on a compassionate-use basis for Winthrop patients. He said the PARP-drug approach has helped doctors better understand the biology of the disease.

“It is a step forward,” but not a cure, Jiménez said Tuesday. “A significant proportion of patients experience recurrences,” he said. “Each year over 14,000 women die of ovarian cancer,” the highest for any gynecologic cancer, he said.

The medication extends the period of time that doctors refer to as “progression free survival,” which basically means the months to years without a cancer recurrence. It is not yet known if the drug extends overall survival, Jiménez said.

In the study, patients with BRCA mutations experienced progression-free survival of 21 months with the drug compared with only 5.5 months for those on placebo, which was standard therapy. For women without BRCA mutations, progression-free survival was 9.3 months compared with 3.9 months for those on placebo.

The new drug is taken in capsule form at dosage of 300-milligrams, John said. Tesaro, the medication’s Massachusetts-based maker has not released the launch price, but the other two PARP drugs, prescribed to patients with BRCA mutations, cost more than $12,000-a-month, according to multiple financial news reports on the medications’ pricing.

Ovarian cancer is considered among the most lethal malignancies because it produces only vague symptoms in its earliest stages, lacks a general population screening test and too often is detected late in its evolution. Most difficult for patients, the disease is marked by remissions and recurrences in its advanced stages, John said.

Zejula is known as “maintenance therapy,” which means that it can be prescribed to patients who have responded well to platinum-based chemotherapy, a commonly used treatment for the cancer. The new drug helps maintain remission and delay recurrences.

“Maintenance therapy is an important part of a cancer treatment regimen for patients who have responded positively to a primary treatment,” Dr. Richard Pazdur, acting director of the Office of Hematology and Oncology Products at the FDA said in a statement.