The Food and Drug Administration is reviewing research data on what could become the first U.S.-approved "biosimilar" drug, a cheaper, sort-of generic version of a biologic drug.

Nearly five years after Congress passed a law enabling future approval of biosimilars, for the first time the FDA has accepted an application to sell a similar, but not identical, version of a biologic drug.

The FDA is evaluating Swiss drugmaker Novartis AG's application to sell a biosimilar version of Neupogen, which brought maker Amgen Inc. $1.4 billion in sales last year. Neupogen, known chemically as filgrastim, treats a dangerous decrease in infection-fighting white blood cells, common in cancer patients getting certain treatments.

Sandoz, the generic division of Novartis, already sells three biosimilar drugs, including filgrastim, in about 60 other countries.

The FDA should make its decision after a standard 10-month review, a spokeswoman said.

"Biosimilars have been successfully used in Europe and other markets for years," Ralph Neas, CEO of the Generic Pharmaceutical Association, said in a statement. "Filgrastim's filing acceptance moves us closer to the day when U.S. patients that currently must rely on costly brand biologics for treatment will have more choices."

Biologic drugs are powerful, injected medicines produced in living cells. They are much more expensive to produce than traditional pills made by mixing chemicals. Some newer ones cost more than $100,000 per treatment course, making copayments unaffordable for many patients.

That also adds up to billions in annual costs for insurance companies and government health programs, which are trying to rein in spending. Thus the Affordable Care Act, which President Obama signed into law early in 2010, includes the Biologics Price Competition and Innovation Act's requirements for approval of cheaper biosimilars.

When a traditional drug loses patent protection, multiple companies start selling copycat pills at up to 90 percent less than the brand-name medicine. That's why nearly 85 percent of prescriptions dispensed in the U.S. are generic pills.

To gain approval, generic drugmakers need only prove to the FDA that their pills are chemically identical to the original drug.

Companies wanting FDA approval to make biosimilars must prove their product is "highly similar" to the original medicine--and also conduct expensive studies, first in animals and then in patients, to prove its safety, purity and potency. They'll still be costly to manufacture, so biosimilar drugs likely will only cost about a third less than the original biologic medicine.

Still, Express Scripts, the country's largest prescription benefit manager, last year estimated the U.S. could save $250 billion between 2014 and 2024, if biosimilar versions of filgrastim and 10 other likely drug candidates hit the market.

--Associated Press