(Corrects first name of Roche Chief Medical Officer in third paragraph)
* Data shows Tecentriq helped breast cancer patients
* Survival data is immature, but Roche optimistic
* Trailing rivals, Roche seeking immunotherapy niches
By John Miller and Ludwig Burger
ZURICH/MUNICH, Oct 20 (Reuters) - An immunotherapy cocktail from Roche helped slow a type of breast cancer where new treatments have proven elusive, data released on Saturday showed, offering positive news for the Swiss drugmaker as it chases medicines produced by its rivals.
Women with advanced triple-negative breast cancer lived a median 7.2 months without their disease worsening (PFS) with Roche's Tecentriq plus chemotherapy as an initial treatment, compared with 5.5 months for those getting chemotherapy alone.
Overall survival (OS) data from the IMpassion 130 study is not yet mature, but Roche Chief Medical Officer Sandra Horning told Reuters she had reason for optimism.
Patients getting the Tecentriq cocktail lived a median 21.3 months, so far, compared to 17.6 months for those on chemotherapy, she said.
Horning said these results offered new hope for people struggling with a difficult disease where patients and doctors desperately need new treatment options.
"It's really extraordinary to see a survival benefit of any kind in triple-negative breast cancer," she said. "We're quite excited about the degree of effect."
Tecentriq's benefit was greater among the roughly 40 percent of triple-negative breast cancer patients in its study whose tumours had high levels of a protein known as PD-L1, that helps tumours avoid immune system detection, Horning added.
Interim OS data for that group showed patients lived a median of 25 months, compared to just 15.5 months on chemotherapy.
Roche has filed with regulators for approval.
Triple-negative tumours, which affect 15 percent of breast cancer patients, have no hormone receptors or HER2 receptors, so patients do not benefit from hormone therapy or HER2-targeting drugs like Roche's $7 billion-per-year blockbuster Herceptin or GlaxoSmithKline's Tykerb.
Standard treatments include surgery, radiation and chemotherapy.
Roche in July announced the 902-patient study had showed Tecentriq to chemotherapy boosted outcomes, but the specific data was released at the European Society for Medical Oncology's annual conference in Munich on Saturday.
With Roche's Tecentriq trailing immunotherapies from Merck and Bristol-Myers Squibb in the main form of lung cancer, Chief Executive Severin Schwan is pursuing smaller but still lucrative treatment areas where he can gain an approval head start.
So far, Tecentriq's sales are up 50 percent over the first nine months to 524 million Swiss francs ($528 million), but that is a fraction of sales generated by blockbuster checkpoint inhibitors from Merck's Keytruda and Bristol's Opdivo.
Triple-negative breast cancer offers an opportunity, as does small cell lung cancer, where Roche also has a chance to be first to win the blessings of the regulators.
"Roche has more of a niche approach and is seeking to have clearly defined markets with dedicated studies," Gregoire Biollaz, fund manager at Pictet Asset Management, told Reuters.
Roche, the biggest maker of cancer drugs, needs Tecentriq to be a success. Roche's three biggest cancer drugs Avastin, Herceptin and Rituxan earn $21 billion in annual sales, but patent expirations are already exposing them to competition from cheaper copies made by rivals.
Rivals are also pressing on with cancer drug development. Merck and Bristol-Myers Squibb are testing their own immunotherapy combinations against triple-negative disease, including with partners.
$1 = 0.9929 Swiss francs Reporting by John Miller Editing by Edmund Blair/Adrian Croft