Tesaro Inc. shareholders can be forgiven if they feel like they won the lottery.

The stock more than doubled Wednesday, adding $1.8 billion in market value, after the Waltham company reported its experimental drug slowed ovarian cancer progression in a late-stage clinical trial.

Tesaro is testing its drug candidate, called niraparib, in women whose ovarian cancer returned after taking other drugs. Rival drug maker AstraZeneca PLC last year won approval for an ovarian cancer drug treating patients with a particular mutation, but Tesaro’s treatment targets a potentially broader set of patients.

The clinical findings met Tesaro’s primary goal of extending progression-free survival in women with recurrent ovarian cancer. Its drug is part of a new class of medicines known as PARP inhibitors that work by preventing cancer cells from replenishing their DNA.

“We’re extremely gratified,’’ Tesaro chief executive Lonnie Moulder said in an interview. “We’ve been developing niraparib since the early days of the company. These results could make a substantial difference in controlling the disease in ovarian cancer patients.’’

The results sent Tesaro’s stock surging $40.19 a share to $77.40, the highest price since the company went public in June 2012. The company’s market value climbed to $3.55 billion.

Bolstered by the clinical findings, Moulder said six-year-old Tesaro planned to file new drug applications for niraparib in the United States and Europe by the end of the year. In the United States, he said, the company will seek a priority review, potentially speeding up approval.

“We would be prepared to get the product on the market as early as next year,’’ Moulder said.

If the drug gets the green light from regulators, it would be Tesaro’s second marketed medicine. Last year, the Food and Drug Administration approved Varubi, a “cancer support’’ therapy developed by Tesaro to treat nausea and vomiting induced by chemotherapy in patients with lung, breast, and ovarian cancers, helping them to tolerate their treatments.

Tesaro was founded in 2010 by Moulder and Mary Lynne Hedley, its president and chief operating officer, with financial backing from New Enterprise Associates, a venture capital firm based in Menlo Park, Calif. The company raised $81 million in the 2012 initial public offering and has now raised more than $1 billion in public and private capital.

It has about 350 employees, including about 250 in Waltham, and recently opened a European office outside Zurich.

Robert Weisman can be reached at robert.weisman@globe.com. Follow him on Twitter @GlobeRobW.