UPDATE 2-Zeltia jumps on ovarian cancer drug news

(Adds more company comment, background, updates shares)

MADRID, Aug 7 (Reuters) - Spain's Zeltia (ZEL.MC) will seek regulatory approval to use Yondelis to treat ovarian cancer after good final trial results, it said on Thursday, sending the stock soaring.

Zelia would seek approval for Yondelis in the last quarter of this year in both Europe and the U.S., it said, in a major step towards finally getting the drug, derived from a sea squirt found in the Mediterranean and Caribbean, on pharmacy shelves.

Glenn Chapman, Zeltia's head of capital markets, told Reuters Zeltia had managed to prove that a combination of Yondelis and Johnson & Johnson (JNJ.N) drug Doxil was statistically significantly better than using Doxil alone in stopping cancer tumours growing.

"That should be enough to have the approval," Chapman said.

Analysts estimate a drug that enters Phase III trials has a roughly 60-75 percent chance of final approval, but one that has positive results at Phase III has a 95-98 percent chance, Chapman said.

The firm's stock jumped 18 percent on the news and has now risen 37 percent in the last five sessions on hopes for the adoption of the drug to treat ovarian cancer.

The stock was up 13.8 percent at 5.35 euros at 1246 GMT.

Zeltia estimates that in the European Union alone peak sales of Yondelis for the treatment of ovarian cancer would be around 300 million euros a year, which Chapman said was around five years away.

It already sells Yondelis to treat soft-tissue sarcomas -- a relatively rare cancer that occurs in tissue around organs -- and forecast sales of 30 million euros for this year.

"Pharma Mar, subsidiary of Zeltia, has communicated to the European Medicines Agency (EMEA) that the pivotal Phase III trials in ovarian cancer have had positive results," Zeltia said in a statement earlier.

The company will have a better idea of sales for ovarian cancer when it finishes Phase III trials and determines how many cycles of the drug patients need to stabilise or shrink cancerous tumours. Results are to be published at an oncology conference starting on Sept. 16.

U.S. partner Ortho Biotech Products, a Johnson & Johnson (JNJ.N) subsidiary that also makes existing treatment Doxil, will present the same request to the U.S. Food and Drug Administration (FDA) before the end of the year, Zeltia said. (Reporting by Judy MacInnes; Writing by Ben Harding; Editing by Will Waterman)