(Reuters) - A federal judge in San Diego has rejected claims by some 1,500 plaintiffs in a multidistrict litigation that several similar type 2 diabetes drugs increase the risk of pancreatic cancer.

U.S. District Judge Anthony Battaglia on Tuesday granted summary judgment to AstraZeneca PLC's Amylin Pharmaceuticals, Eli Lilly and Co, Merck & Co Inc and Novo Nordisk Inc, finding the plaintiffs' claims preempted by federal law.

Hunter Shkolnik of Napoli Shkolnik, a lawyer for the plaintiffs, did not immediately respond to a request for comment.

"We are extremely happy with the court's ruling," said Raymond Williams of DLA Piper, a lawyer for Novo Nordisk.

Lilly, which is represented by Barry Boise of Troutman Pepper Hamilton Sanders, declined to comment.

The other drugmakers and their attorneys - Paul Boehm of Williams & Connolly for Merck and Amy Laurendeau of O'Melveny & Myers for AstraZeneca - did not immediately respond to requests for comment.

The litigation, which began in 2013, involves AstraZeneca's Byetta, co-marketed with Lilly before 2011; Merck's Januvia and Janumet; and Novo Nordisk's Victoza. All of the drugs work similarly, by mimicking the gut hormone incretin.

Plaintiffs brought state law claims accusing the companies of failing to warn of the drugs' risk of pancreatic cancer, after a study found that patients using them had precancerous pancreatic cells.

The drugmakers moved for summary judgment, citing an article by Food and Drug Administration officials in a medical journal dismissing a link between incretin drugs and cancer. That showed that the agency would not have approved a cancer warning on the drugs' labels, meaning the plaintiffs' claims were preempted, they argued.

Battaglia agreed, granting the defendants summary judgment on preemtion grounds, but the 9th Circuit U.S. Court of Appeals vacated that ruling, finding the plaintiffs should have been allowed more discovery.

Following the remand, the defendants again sought summary judgment, both on the grounds that the case was preempted and that the plaintiffs had failed to establish general causation.

This time, the plaintiffs, citing newly discovered evidence, countered that their claims were not preempted because the drugmakers failed to submit relevant safety information about the drugs to the FDA. Had they done so, the plaintiffs said, the FDA would have approved pancreatic cancer warnings for the drugs, meaning there was no conflict between state and federal law.

Battaglia rejected that argument, finding the information cited by the plaintiffs was not relevant and that the FDA had carefully monitored incretin-based drugs' safety without requiring a cancer warning.

"Quite the contrary, the FDA has published its findings regarding the pancreatic safety of incretin mimetics, commented on the adequacy of the drug labeling, and maintained its position that scientific evidence of a causal association between incretin-based therapies and pancreatic cancer is indeterminate," he wrote.

Battaglia further found that the plaintiffs' experts looked at data selectively and did not practice "good science." Without the experts, the judge said, the plaintiffs could not establish general causation, and he granted summary judgment to the defendant on those grounds as well.

The case is In re Incretin-Based Therapies Products Liability Litigation, U.S. District Court, Southern District of California, No. 3:13-md-02452.

For plaintiffs: Hunter Shkolnik of Napoli Shkolnik, Jacob Plattenberger of TorHoerman Law and Michael Johnson of Johnson Becker

For Merck: Paul Boehm of Williams & Connolly

For Novo Nordisk: Raymond Williams of DLA Piper

For AstraZeneca: Amy Laurendeau of O'Melveny & Myers

For Eli Lilly: Barry Boise of Troutman Pepper Hamilton Sanders