ZURICH, June 2 (Reuters) - An experimental drug from Novartis significantly improved the length of time that patients lived with a type of bone marrow cancer without the disease worsening, according to a late-stage study presented on Monday.

The Phase III trial in patients with relapsed or relapsed and refractory multiple myeloma was presented at the American Society of Clinical Oncology (ASCO) meeting in Chicago.

Results of the study involving 768 patients found those taking the Novartis drug LBH589 in combination with bortezomib and dexamethasone went for an extra four months on average without a worsening of the disease, compared with those taking bortezomib and dexamethasone alone.

Multiple myeloma is a form of cancer that starts in plasma cells in bone marrow and disrupts the production of normal blood cells. It affects approximately one to five people in every 100,000 worldwide each year and typically occurs in those aged over 50.

"Almost all patients with multiple myeloma ultimately relapse and become resistant to treatment, so new therapies are critical for continuing to manage the disease and improve outcomes," said study investigator Paul Richardson of the Jerome Lipper Multiple Myeloma Center at Dana-Farber Cancer Institute.

LBH589 in May was granted priority review status by U.S. health regulators - a designation that aims to fast-track the development and review times of drugs for serious or life-threatening conditions.

Novartis believes the drug has the potential to become one of the first in a new class of treatments for the incurable disease and said global regulatory filings were underway.

"We see this data as quite competitive, because this is the first prospective study run in this special population," said Alessandro Riva, global head of Novartis oncology development and medical affairs.

"This regime will be the first regime available to patients after the failure of first-in-line therapy."

The drug works by blocking a key cancer cell enzyme, which causes cell stress and leads to death of these cells.

German Biotech company MorphoSys and Celgene are also working on treatments for multiple myeloma.

(Reporting by Caroline Copley; editing by Jane Baird)