"Interchangeable status" refers to the high regulatory standard by which the biosimilar can be expected to produce the same clinical result as the branded biologic drug being copied.

Without interchangeable status, doctors would have to specifically prescribe the biosimilar drug and switching between the copy and the branded version would not be allowed.

The biotech industry has generally argued against interchangeability because it believes biologic drugs are unique and cannot be copied.

The uniqueness of biologic drugs and the absence of generic competition has been a boon to the biotech industry, which typically charges premium prices for its biologic drugs. The drugs Genzyme makes for the treatment of rare genetic diseases, for example, can cost upwards of $200,000 a year. Treatment with Roche's cancer drug Avastin can cost about $100,000, while Biogen's multiple sclerosis drug Avonex, which patient must take for their entire lives, costs about $20,000 per year.

The eventual approval and launch of biosimilar drugs, therefore is a potential threat to the biotech sector, which could face lower-priced competition for its drugs similar to what has happened to large pharmaceutical companies.

The FDA's public hearing on biosimilars follows the agency's decision in August to approve a biosimilar version of the Sanofi-Aventis ( SNY) anticoagulant Lovenox developed by Momenta Pharmaceuticals ( MNTA) and Novartis ( TEVA).

In Europe, the approval and commercial presence of biosimilars is much further along, although the difficulties and high cost in making biologic drugs has minimized price erosion that usually comes with generic competition.

Among the biologic drugs most susceptible to biosimilar competition include the anemia drugs Epogen and Procrit sold by Amgen and Johnson & Johnson ( JNJ), respectively, Amgen's rheumatoid arthritis drug Enbrel, Roche's cancer and rheumatoid arthritis drug Rituxan and Biogen multiple sclerosis drug Avonex.

Teva Pharmaceuticals ( TEVA) has already announced its intention to move aggressively into the market for biosimilar drugs.

--Written by Adam Feuerstein in Boston.

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Adam Feuerstein writes regularly for TheStreet.com. In keeping with TSC's editorial policy, he doesn't own or short individual stocks, although he owns stock in TheStreet.com. He also doesn't invest in hedge funds or other private investment partnerships. Feuerstein appreciates your feedback; click here to send him an email.

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