Forbes tries to answer the question in depth of what will happen when biotech drugs start to become generic:
In a few years, the first blockbusters of the biotech age will begin to face generic competition. Big drugs like Amgen's AMGN +2.54% Epogen and Neulasta, Roche and Biogen Idec's BIIB +2.4% Rituxan, and Erbitux, from Eli Lilly and Bristol-Myers Squibb BMY -0.1%, could eventually face cheaper competitors. But they won’t be exact substitutions, because these drugs will be so much harder to make. Most will not be true generics but biosimilars — products with a similar profile that are still seen as slightly different from the original.
So how quickly will sales erode? It will depend on the disease being treated and whether decisions are being made by physicians and patients or by hospital administrators, according to a new analysis by ZS Associates, a global consultancy.