* Q3 sales 13.1 billion francs vs 13.04 billion estimate
* Ocrevus sales 308 mln francs, Rituxan up 1 pct to 1.78 bln
* Rituxan sales fall 16 percent in Europe
* Roche shares down 0.6 pct (Adds Roche, analyst comments, shares and details throughout)
By John Miller
ZURICH, Oct 19 (Reuters) - Roche's sales rose 6 percent in the third quarter as new multiple sclerosis drug Ocrevus offset the initial blow to the Swiss-based company from copies of older, patent-expired drugs in Europe.
Roche is banking on new drugs as older medicines' patents expire and expose them to encroachment by "biosimilars", rival treatments that are as effective as the original but cheaper.
Group sales of 13.1 billion Swiss francs ($13.4 billion) narrowly beat the 13.04 billion average estimate by analysts in a Reuters poll.
Ocrevus sales reached 308 million francs, ahead of the poll average of 228 million, while sales of Rituxan, Roche's top seller, rose 1 percent to 1.78 billion francs, dented by biosimilar versions from rivals including Novartis and Celltrion which trimmed European revenue 16 percent.
Competition is growing fiercer, Roche drugs unit chief Dan O'Day said on Thursday, with Rituxan copies to be joined by rival versions of Roche's breast cancer medicine Herceptin in Europe this year.
"We will continue to see an increased effect of biosimilars," O'Day said. "We're focused on launching the new and innovative medicines in markets around the world as soon as we can."
Roche shares fell 0.6 percent by 0830 GMT. Since August the stock is down 1.3 percent, against the STOXX Europe Health Care Index's 3.6 percent rise, as the looming biosimilars threat prompted some analysts to take a dim view of Roche's mid-term prospects.
"The example of Rituxan in Europe shows the significant negative impact of biosimilars, and that's going to be accentuated in the fourth quarter," wrote Zuercher Kantonalbank analyst Michael Nawrath, who has a "market weight" rating.
Annual sales of Rituxan, Herceptin and cancer medicine Avastin top $21 billion, or more than half of Roche's pharmaceuticals business.
Sales of Herceptin from July through September were flat at 1.69 billion francs, Roche reported, while Avastin revenue slipped 4 percent to 1.59 billion.
As biosimilars bite, the trio's combined sales are expected to fall more than 40 percent by 2022, according to analyst forecasts compiled by Thomson Reuters.
"These products present an unsettling vision for the years ahead," wrote Bernstein analyst Tim Anderson.
For 2017, however, Roche still expects sales to grow at a mid single digit rate at constant exchange rates, Chief Executive Severin Schwan said. Core earnings per share are seen growing broadly in line with sales.
Sales of Tecentriq, Roche's new immunotherapy for bladder and lung cancer, doubled to 118 million francs from the year-ago period but fell from the previous quarter after failing a bladder cancer study.
Roche is counting on trials of Tecentriq in combination with other medicines to arrest the decline, with initial results from one closely watched study in early lung cancer treatment (called Impower 150, that mixes Tecentriq, Avastin and chemotherapy) due by year end.
"We continue to see the Impower 150 study in lung cancer decisive for Tecentriq and Roche's top-line growth," said Bruno Bulic, a Baader Helvea analyst. ($1 = 0.9801 Swiss francs) (Reporting by John Miller; Editing by Michael Shields and David Holmes)