Blow to Roche's cancer immunotherapy prospects as 2nd trial fails

* Drug candidate tiragolumab previously flunked trial in March

* Anti-TIGIT class of drugs has attracted several rivals

* Roche says trial will continue after disappointing interim data (Adds pre-market stock price indication, background on immune therapy)

By Ludwig Burger

May 11 (Reuters) - Development of a new cancer immunotherapy pioneered by Roche was thrown in doubt on Wednesday when the drug, tiragolumab, failed to slow progression of lung cancer in a second trial.

In a study, a combination of tiragolumab and Roche's established Tecentriq drug did not slow disease progression in newly diagnosed cases of advanced non-small-cell lung cancer when compared with patients on Tecentriq only, the company said.

That was after tiragolumab in March failed to slow progression of a different, more aggressive form of lung cancer.

Roche shares were seen 2.2% lower in bank Julius Baer's pre-market trading.

The setback will likely give pause to more than half a dozen companies working on similar compounds in a class of drugs called anti-TIGIT. Merck & Co (MRK) has been seen as closest behind Roche in that race.

Roche added that the trial would continue after the disappointing interim readout to gather more data on tiragolumab's ability to prolong the lives of trial participants.

"While these results are not what we hoped for in our first analysis, we look forward to seeing mature overall survival for this study to determine next steps," said Roche Chief Medical Officer Levi Garraway.

TIGIT is a receptor found on immune system cells as a backstop to prevent misguided immune attacks against normal body tissue. Some cancer types, however, exploit TIGIT to grow unnoticed by cell-killing immune cells.

A similar mode of action is behind a blockbuster class of immune drugs known as PD-1 and PD-L1, such as Merck & Co's (MRK) Keytruda and Bristol-Myers Squibb's (BMY) Opdivo.

That multi-billion-dollar success has pushed the industry to explore similar anti-cancer concepts, such as anti-TIGIT, typically tested in a drug cocktail with established PD-1 or PD-L1 drugs.

Gilead Sciences (GILD) last November exercised an option to collaborate with Arcus Biosciences (RCUS) on the anti-TIGIT drug domvanalimab.

GlaxoSmithKline (GSK) in June 2021 struck a licensing deal worth up to $2 billion with iTeos Therapeutics Inc (ITOS) for an anti-TIGIT candidate.

Bristol-Myers Squibb (BMY) and Agenus Inc are collaborating on a drug under a May 2021 partnership.

Coherus BioSciences (CHRS) in January exercised an option to licence a drug candidate by Shanghai Junshi Biosciences for the U.S. and Canadian markets.

For Roche, which is seeking to offset a decline in sales due to competition from cheaper copies of a trio of established cancer drugs, more hope rests now on an experimental Alzheimer's drug for which trial results are expected later this year. (Reporting by Ludwig Burger in Frankfurt Additional reporting by John Revill in Zurich; Editing by Tom Hogue)