(Adds shares, background on Bristol-Myers' deals)

Nov 10 (Reuters) - Bristol-Myers Squibb Co said on Thursday its blockbuster immunotherapy Opdivo helped patients with advanced stomach cancer live longer in a late-stage study, becoming the first drug of its kind to show a survival benefit in these patients.

Opdivo met the main study goal of overall survival in patients who failed to respond to or are intolerant of standard chemotherapy, the company said.

New York-based Bristol-Myer's shares inched up 1.1 percent to $56.90 in premarket trade.

The trial was conducted by Bristol-Myers' partner, Japan's Ono Pharmaceutical Co Ltd in Japan, Korea and Taiwan, and compared the effect of Opdivo to a placebo.

Stomach cancer, also known as gastric cancer, is the third leading cause of cancer-related death in the world, and kills more than 720,000 every year, Bristol-Myers said.

Opdivo, like Merck & Co Inc's Keytruda, belongs to a new class of medicines called PD-1 inhibitors that help the immune system unmask hidden cancer cells.

Both drugs have secured regulatory approval for several types of cancer, but lung cancer is considered by far the biggest market for cancer drugs.

Opdivo and Keytruda are both used in previously-treated lung cancer patients, but Merck's supremacy in this class of drugs was confirmed when Keytruda last month won approval for untreated lung cancer patients, significantly expanding its addressable population.

Swiss drugmaker Roche Holding AG's Tecentriq is another major immunotherapy that has only recently won approvals for multiple types of cancer.

As competition heats up, Bristol-Myers has orchestrated a string of deals to strengthen its pipeline.

On Wednesday, it announced a collaboration to test Opdivo in combination with an experimental drug from Infinity Pharmaceuticals Inc in patients with advanced solid tumors.

Separately on Thursday, Bristol-Myers agreed to pay Japan's Nitto Denko Corp $100 million up front for the right to its early-stage drug for liver fibrosis due to incurable fatty liver disease NASH or hepatitis C.

(Reporting by Natalie Grover in Bengaluru; Editing by Sai Sachin Ravikumar)