The health reform legislation that was recently signed into law contains a provision that creates a pathway to enable the US Food and Drug Administration (FDA) to approve biosimilars - generic versions of biologic drugs. Unlike generic small molecule drugs, which is the synthetic chemical compounds, the complexity of biologic drugs makes it questionable whether a generic company could produce an identical biologic product. WSJ recently reported that Merck decided to end efforts to copy Amgen's blockbuster Aranesp anemia drug, which showed how the emerging field of developing generic versions of biotechnology therapies won't be easy to enter. For small molecule chemical compounds, once the patent is expired, the generic companies can start to manufacture the same ingredients (active pharmaceutical ingredients (APIs)) for the generic version of the brand products. The approval of the generic version typically requires only the bioavailability/bioequivalence tests in healthy volunteers. For biological products, it is typically the large proteins with 3-D or 4-D structures. The same protein with different 3-D structure may have different functions. This makes the biosimilars very difficult to copy - similarity does not mean the same therapeutic effects. When we deal with the proteins, we will always need to deal with the issues of immunogenicity. Some of the biological products (for example the plasma-derived products) can not be tested in the healthy volunteers. If a bioequivalence study is required, it is typically done in real patients, which makes the trial much more expensive than typical bioavailability/bioequivalence trial in healthy volunteers.