Differences between small molecule therapies and biologics

Compare and contrast the differences between small molecule therapies and biologics (e.g. peptides/proteins, antibodies, cytokines, enzymes).
In addition to advantages and disadvantages of each, some items/issues to discuss may include physical properties (and consequences), administration, manufacturing, selectivity, and preclinical and clinical development design.
Google, Wikipedia, Online newspaper articles are not considered legitimate references. DO NOT just quote from abstract of scholarly article. Include quotes from published FDA guidelines and scientific journals.

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