Staff reviewers at the U.S. Food and Drug Administration recommended approval of Novartis AG's copy of Amgen Inc's blockbuster cancer drug Neupogen.

Novartis's drug is the first to be reviewed in the United States under the so-called biosimilar pathway.

The reviewers found no "clinically meaningful differences" between the two drugs, the FDA said. (1.usa.gov/1DoT7eb)

The injectable biotech medicine is designed to prevent infections in breast cancer patients undergoing chemotherapy, which reduces white blood cells, giving rise to a condition called neutropenia.

The Swiss drugmaker sells copies of Neupogen, made by its generics arm Sandoz, under the brand name Zarzio in over 40 countries.

Biosimilars are yet to make inroads in the United States as the country has lagged in establishing a regulatory framework for them.

Data from a late-stage trial showed last month that Novartis's drug had similar efficacy and safety as Neupogen, which raked in nearly $1.4 billion in global sales in 2013 - nearly 84 percent from the United States.

The reviewers recommended that Novartis's copy should be approved for all the five indications for which Neupogen is approved, the FDA said on Monday.

Independent experts are scheduled to meet on Wednesday to recommend whether the copy should be approved.

Biotech medicines, or biologics, account for six of the world's 10 biggest-selling drugs today.

These drugs have safer profiles and stronger efficacy in the treatment of cancers and immunological diseases and consequently carry hefty price tags, limiting their use.

Biosimilars, which typically cost 20-30 percent less than their reference biologic, are expected to account for about one quarter of the $100 billion sales stemming from off-patent biologics by the end of the decade, according to Thomson Reuters BioWorld.

Biologics are made from living cells and creating their copies is an arduous process, which can give unpredictable results. Therefore, unlike knockoffs of simple chemical drugs, biologic copies can only be "similar", never identical.

Drugmakers including Novartis, Teva Pharmaceutical Industries Ltd and South Korea's Celltrion Inc are racing to develop biosimilars ahead of the looming expiry of patents on some big-ticket biologics.

The market for these copies has huge potential as cash-strapped healthcare systems look to curb spending.

Meanwhile, Amgen and Sandoz are embroiled in a legal dispute related to the interpretation of patent litigation provisions of the U.S. biosimilar pathway, first issued in 2012.