* 245 companies developing or already selling biosimilars
* 700 biosimilars approved or moving through pipeline
* Leading role for South Korea, Brazil: BioWorld report
By Ben Hirschler
Sept 29 (Reuters) - Hundreds of companies around the world are chasing an emerging market for cheaper copies of costly biotech drugs, with more than 700 so-called biosimilars now in development or already approved, according to a major study of the sector.
Biotech medicines - made from proteins and other large molecules - account for six of the 10 biggest-selling drugs in the world today, led by AbbVie's $12 billion-a-year rheumatoid arthritis injection Humira.
The total market for such biological medicines could exceed $250 billion by 2020 but many of today's top-sellers, such as Roche's cancer drugs Rituxan and Herceptin, are now losing patent protection or will do so in the next few years.
That has opened up an opportunity for companies with the technical ability to make copycat versions - something that is easier said than done, since such drugs are produced in living cells and imitations can only ever be similar, not identical.
Despite the hurdles, a total of 245 companies in different countries have now jumped on the bandwagon as developers, manufacturers and suppliers of biosimilars or follow-on biologics, the study compiled by Thomson Reuters BioWorld found.
Major companies involved in the emerging biosimilars sector include leading generics players such as Novartis's Sandoz unit and Teva ; innovative pharmaceutical groups like Pfizer and Amgen ; and scores of smaller drugmakers and regional businesses.
In all, biosimilars are expected to account for approximately one quarter of the $100 billion worth of sales stemming from off-patent biological drugs by the end of the decade, the study said.
South Korea and Brazil stand out as pioneers of biosimilar drug development, with India's large pharmaceutical sector also anticipating a thriving market for such products.
While biosimilars could slash the cost of treating diseases like cancer and rheumatoid arthritis in much the same way that generics have curbed spending on traditional medicines, the impact is likely to be more gradual for several reasons.
In the first place, such copycat medicines are typically offered at a 20 to 30 percent discount to innovator brands - rather than the 90 percent or so seen with conventional generics - and many doctors are cautious about their use as they may vary slightly from the original product.
What is more, the regulations surrounding biosimilars have, until recently, been unclear. Europe approved the first biosimilar drug in 2006 but the United States is only now considering the first applications.
The first official application for a biosimilar was filed in the United States in July by Sandoz, which wants to sell a copy of Amgen's Neupogen for patients with low white blood cell counts.
This was followed a few weeks later by an application from South Korea's Celltrion for an imitation of Johnson & Johnson and Merck & Co's arthritis drug Remicade. (Editing by Susan Thomas)