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What happened

After the company offered more details on data from a phase 3 trial of niraparib in ovarian cancer patients, shares in Tesaro, Inc. (NASDAQ: TSRO) are rallying 20% today.

So what

In June, management announced that niraparib significantly improved progression-free survival (PFS) in relapsing/recurring ovarian cancer patients with a specific genetic makeup.

Specifically, the company reported that progression-free survival in patients who didn't receive niraparib was 5.5 months, but that progression-free survival in carriers of the germline BRCA mutation who received niraparib was a median 21 months.

The company offered a more comprehensive look at the trial data over the weekend at the congress of the European Society for Medical Oncology, and the data continue to show that niraparib is both effective and well-tolerated.

Of particular interest is niraparib's efficacy in non-BRCA ovarian cancer patients. Median progression-free survival in BRCA-negative patients was 9.3 months, versus 3.9 months in the placebo group; that suggests that niraparib could eventually play an important role in treating all patients who become resistant to platinum therapy. Said Dr. Mansoor Raza Mirza, principal investigator on the trial:

The effectiveness of platinum-based chemotherapy diminishes over time, and PFS and platinum-free intervals generally become shorter after each round of platinum treatment. In addition, the incidence of infection and risk of neuropathy and hypersensitivity with certain chemotherapy agents rises with subsequent cycles. An oral maintenance treatment that could lengthen the PFS interval between rounds of platinum-based chemotherapy would be very meaningful for patients with ovarian cancer, who often live with a fear of recurrence after ending active treatment.

Now what

Tesaro plans to complete its rolling filing for FDA approval of niraparib this quarter; that timeline could lead to this drug reaching the market next year.

Since up to 85% of ovarian cancer patients see their cancer return and ovarian cancer remains the second most deadly cancer in women, niraparib could reshape patient treatment and deliver hundreds of millions of dollars in sales to Tesaro's top line in the process.

The jump in shares, however, gives this stock a market cap greater than $6 billion, and that's arguably a bit pricey. Therefore, investors might want to add this stock to a watch list, and focus on other ideas to buy right now.