* Sees low single-digit rise in 2018 sales vs flat before
* Q1 sales of multiple sclerosis drug Ocrevus top forecast
* Sales of cancer drug Rituxan drop on biosimilar challenge(Adds analyst comment, shares)
By John Miller
ZURICH, April 26 (Reuters) - Cheaper copies of Roche'sRituxan toppled the blood cancer drug from its perch asthe Swiss company's top seller in the first quarter, unsettlingsome investors despite a stronger-than-expected performance fromnew medicines.
Robust demand for new treatments such as Ocrevus formultiple sclerosis and Hemlibra for haemophilia A helped theworld's biggest cancer drugs maker to nudge up its full-yearsales and profit forecasts on Thursday.
However, an 8 percent drop in Rituxan sales, including a44-percent plunge in Europe, rattled some analysts, particularlywith a biosimilar copy of Roche's blockbuster breast cancer drugHerceptin expected later this year.
"The key focus for today looks likely to be the big hit frombiosimilars versus the decent performance from Ocrevus andHemlibra, with the former likely to dominate," Credit Suisseanalyst Tim Race said, calling Rituxan's drop in Europe"stunning".
Roche shares were flat at 1015 GMT, lagging a Europeanblue-chip index up 0.4 percent.
Roche Chief Executive Severin Schwan remained upbeat.
"I am very confident that we can grow in spite of the entryof biosimilars," he told reporters.
First-quarter sales rose 6 percent to 13.6 billion Swissfrancs ($13.8 billion), compared with analysts' average estimateof 13.3 billion francs in a Reuters poll.
The company now expects a low single-digit percentage risein sales at constant exchange rates this year, after previouslywarning revenue could be flat. Core earnings per share shouldgrow broadly in line with sales, it added.
Ocrevus sales easily topped estimates, hitting 479 millionfrancs versus the 406 million expected in the Reuters poll.
Hemlibra, approved for haemophilia A late last year, came inat 23 million francs. Analysts said that was a good start asRoche moves in on rivals like Shire.
Sales of cancer drug Avastin fell 2 percent to 1.6 billionfrancs, while Herceptin, now Roche's top-selling drug, held itsown, rising 2 percent to 1.8 billion francs.
Rituxan, Herceptin and Avastin currently produce $21 billionin annual sales, but their patents have expired or will soon.
Roche shares have fallen 11 percent in two years amidscepticism new drugs will be able to replace its ageing cancerdrug portfolio.
Analysts also saw immunotherapy Tecentriq as a first-quarterblemish, with revenue of 139 million francs lagging the 154million poll estimate and just above the 132 million of thefourth quarter.
Roche pharmaceuticals chief Dan O'Day remained confidentongoing Tecentriq trials against numerous cancers were reasonsto believe the immunotherapy's best days are ahead, despitemore-established medicines like Keytruda from Merck orBristol-Myers Squibb's Opdivo.
($1 = 0.9826 Swiss francs)(Reporting by John Miller; Editing by Michael Shields and MarkPotter)
