Biotech Drugs Still Won't Copy by Christopher Weaver, Jeanne Whalen and Jonathan D. Rockoff.  The Wall Street Journal.  February 26, 2013.

Conventional drugs can be duplicated by reproducing the formula.  Biotech drugs are products of living  cells with altered DNA and are more difficult to reproduce.  The difference between conventional and biotech has significance when patent protection of a drug expires and when generics move into the gap.    While generics of conventional drugs are identical to the original, the similarity of the generics of biotech drugs is more difficult to assess.  The article present issues involved in biosimilar drugs, or the generic equivalent of the biotech drugs.