BERLIN, July 4 (Reuters) - Roche intends to halt a trial for combined lung cancer treatment after results fell short of efficacy targets, the Swiss drugmaker said on Thursday, casting further doubt on an experimental immunotherapy pioneered by the company.

The drug, called tiragolumab, has already

flunked previous trials

although some analysts had seen a chance that it could still score on overall survival.

It is part of a new class of drugs known as anti-TIGIT that has attracted a range of rival drug developers working on similar compounds.

Roche shares were indicated 2.3% lower in Julius Baer pre-market trade following the announcement.

The results of its latest study, dubbed SKYSCRAPER-06, "did not meet the primary endpoints of progression-free survival at primary analysis and overall survival at first interim analysis", the company said in a statement.

The trial evaluated tiragolumab plus Roche's established drug Tecentriq and chemotherapy.

"These results are disappointing as it was our hope that this combination might yield improved outcomes for people living with metastatic non-squamous lung cancer," Chief Medical Officer Levi Garraway said in the statement.

Roche said it would evaluate any relevant changes needed to its ongoing tiragolumab programme. (Reporting by Rachel More; Editing by Kim Coghill and Thomas Seythal)