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Table 1 Key characteristics of biologics versus small molecules

From: What is the future of targeted therapy in rheumatology: biologics or small molecules?

  Biologics Small molecules
Chemical composition Protein Organic small molecule
Structure Known sequence, variable three-dimensional structure and glycosylation Well-defined structure
Molecular weight >1 kDa <700 Da
Stability Protease and heat-sensitive Mostly stable
Administration Parenteral Oral
In vivo half-life (Usually) Long (Usually) Short
Target Extracellular Intracellular
Mechanism of action (Usually) Blocking, depletion (Usually) Enzyme inhibition
Specificity High Low/variable
Manufacturing cost High Low/variable
Degradation Catabolism Metabolism
Generics Biosimilar Identical
  1. The table highlights selected typical key characterisitics of biologic therapeutics and small-molecule anti-rheumatic agents. Specific drugs may deviate from the typical features. Further differences, such as costs and standards of manufacturing, regulatory requirements, registration path, supply chain logistics, and so on have been omitted.