From How Healthcare Legislation Can Ensure Patient Safety and Spur Innovation:

Size and Complexity of Drug Molecules
Size and Complexity of Drug Molecules

To give a sense of size, same-scale computer models of three drugs—aspirin (a small molecule), somatropin (human growth hormone), and Herceptin (an antibody)—are presented as an example of the relative complexity: The molecules are to scale and the objects are not, but the objects (bike, car, private jet) indicate relative size and complexity of these molecules.
Used with Permission. Source: Genetech

http://www.gene.com/gene/about/views/followon-biologics.html