UPDATE 1-Amgen CEO says threat from biosimilars not absolute

* Smart biotechs may stem damage from biosimilars

* Sensipar kidney drug could get big boost from study

(Adds details on Amgen, rival drugs, byline)

NEW YORK, May 18 (Reuters) - The chief executive of Amgen Inc AMGN.O forecast on Monday that "smart" biotechnology companies may be able to retain up to half the sales of their drugs once they face competition from cheaper so-called biosimilars.

Kevin Sharer, speaking to investors at Deutsche Bank AG’s annual healthcare conference, said he believed that longer- term, some biotechnology companies “can sustain 30 percent to 50 percent of cash flow from products if they’re smart competitors.”

He said that was considerably better than conventional medicines facing generic competition, meaning pills made of chemicals combined together rather than grown from living cells -- as is the case with biotechnology drugs.

Conventional drugs can lose up to 90 percent of their sales within a year once they face generic competition, in part because many companies often begin selling heavily discounted copycat formulations. By contrast, relatively few companies are now capable of making generic forms of biotech drugs, referred to as biosimilars or biogenerics.

European regulators recently approved biosimilar forms of two Amgen drugs, Epogen for anemia and Neupogen, used to boost infection-fighting white blood cells in patients on chemotherapy. The two drugs are not facing biosimilar competition in the lucrative U.S. market.

Sharer did not forecast how well Epogen and Neupogen would fare as competition from the biosimilars intensified this year, but his comments suggested he is confident they would not fall off the map.

The first-quarter global sales of Epogen, an older version of Amgen’s Aranesp brand used primarily in kidney dialysis patients, rose 2 percent to $565 million. But that was still well below the $607 million analysts were expecting.

Combined global sales of Neupogen and Amgen’s newer white blood cell booster, Neulasta, fell 1 percent to $1.07 billion, shy of Wall Street estimates of $1.17 billion.

Sharer said the company’s Sensipar drug for kidney failure patients could get a big sales lift if it proves able in an ongoing study to reduce calcification in blood vessels.

Sensipar now has sales potential “close to a blockbuster drug,” Sharer said, meaning annual sales could approach $1 billion. But he said its sales could grow far beyond that if the anti-calcification study succeeds.

Sensipar sales rose 11 percent in the first quarter to $148 million. (Reporting by Ransdell Pierson; Editing by Andre Grenon)