The new generation of anti-cancer drugs are able to target only the body's cells that are cancerous -- hence the term "cell-targeted therapies" or "smart bombs." This is an advance from chemo that killed both cancerous and healthy cells - and sometimes was called "carpet bombing" because it led to so much collateral damage.
The older generation of anti-
cancer drugs (like chemo) were made by synthesizing different chemicals and in
no way relied on living organisms in the process. This produced less complex structures that sometimes are called "Small Molecules."
Drugs made by the biotechnology industry are derived from living things (like animals or microscopic organisms)
and the drugs are grown in specially engineered cells. What results are new molecules which are very complex and
so sometimes are called "Big Molecules."