Why do biological medicines differ from chemical medicines?
Biological medicines are far more complex and usually much bigger than chemical medicines, which are produced by chemical synthesis. Size is one of the most obvious distinctions: the molecules of a biological medicine are much larger, more complex, mimicking substances produced by the human body (such as enzymes, insulin, and antibodies) than the small molecules which make up classical drugs (see the picture - molecular weight as an indicator of structure complexity).
Biological medicines are produced using a living system or organism. This means that their manufacturing and precise characterization tends to be more difficult than for chemical medicines, which are more easily identifiable and can be exactly reproduce