* Analysts say failure puts approval at risk
* Chemotherapy outperformed Swiss company's star drug
* Roche says sticks by Tecentriq, will analyse results (Adds analyst comment, company comment and details throughout)
By John Miller
ZURICH, May 10 (Reuters) - Roche's Tecentriq immuno-oncology drug failed a late-stage follow-up trial against advanced bladder cancer, the Swiss drugmaker said on Wednesday, raising questions about whether regulators could scale back their approval of the medicine.
Roche, the world's biggest maker of cancer drugs, had won fast-track approval last May in the United States for Tecentriq against bladder cancer but full approval hinged on further trials.
Roche said a phase III IMvigor211 study that evaluated the drug in people with locally advanced or metastatic urothelial cancer whose disease progressed during or after treatment with chemotherapy "did not meet its primary endpoint of overall survival compared to chemotherapy."
The Swiss company's shares fell nearly 2 percent.
Roche said it was sticking by Tecentriq.
"We believe that Tecentriq will continue to play an important role in the treatment for people with advanced bladder cancer, and will discuss these data with health authorities," a company spokesman said on Wednesday.
The drug, also already approved for lung cancer, is a pillar of Roche's cancer drug strategy and is seen by its scientists as a backbone for multiple combinations with other drugs to fight various forms of the disease. The company has more than 30 trials ongoing with Tecentriq.
In the first quarter, sales of Tecentriq, also known as atezolizumab, hit 113 million Swiss francs ($112.45 million), more than the 103 million estimate in a Reuters poll.
"This puts the existing U.S. bladder cancer approval in serious doubt, and will also, of course, raise market concerns about Tecentriq's efficacy in other cancer types," Kepler Cheuvreux analyst David Evans wrote in a note to investors.
Deutsche Bank analysts said the failure placed up to $1 billion in peak sales at risk, though they also said more important would be late-stage trial data, expected after July, about Tecentriq's performance in the larger, more-lucrative lung cancer setting.
The failure also comes as more of Roche's rivals enter the market for treating bladder cancer.
U.S. health regulators on Tuesday granted accelerated approval for Pfizer Inc's immuno-oncology drug Bavencio to treat advanced bladder cancer, marking the second approval in less than two months for the treatment developed along with Germany's Merck KGaA.
The IMvigor211 study had been meant to confirm a previous trial, called IMvigor210, that was central to the U.S. Food and Drug Administration's accelerated approval last year of Tecentriq against bladder cancer.
While Tecentriq's results in Imvigor211 were consistent with its previous study, Roche said, patients getting chemotherapy in the latest trial survived longer than anticipated.
"We will apply insights to the continued development of Tecentriq," Roche said.
The failure of Tecentriq is the latest instance where cancer immunotherapies have not lived up to their promise of revolutionising treatment.
Tecentriq belongs to a class of drugs called PD-1 inhibitors, which help the immune system to fight cancer by blocking a mechanism that tumours use to evade attack.
Last year, Bristol Myers-Squibb's Opdivo failed to do better than older chemotherapies. ($1 = 1.0049 Swiss francs) (Reporting by Michael Shields; editing by Brenna Hughes Neghaiwi and Jane Merriman)