A biodrug (or biopharmaceutical) is a medicine whose active substance has a biological origin and is not produced nor obtained by chemical synthesis like most of the current pharmacopoeia’s molecules. Biodrugs, by being macromolecules, differ from small chemical molecules on many aspects.
Small molecules are composed of 20 to 100 atoms and are typically produced by chemical synthesis. Biodrugs range from a few hundred atoms (e.g. hormones) to 25,000 atoms for antibodies. They are typically produced by a living cell system.
As for the delivery system, small molecules are administered orally. They have a higher cell permeability and can reach intracellular regions through cell membranes. In some cases, they can even cross the blood-brain barrier (BBB). Biodrugs, being larger in size and sometimes more unstable in structure, are administered by injection. Many therapeutic targets are not accessible to biomedical drugs because of the BBB or the plasma membrane for example.
This difference between the two types of drugs affects the mode of delivery: by blood circulation for small molecules, and by blood and lymphatic route for biomedical drugs.
As for the targeted pathologies, small molecules address a wide spectrum of pathologies. This is also the case for biopharmaceuticals, but these drugs dominate in oncology, inflammation, infections, metabolic and cardiovascular diseases.
From a medico-economic standpoint, small molecules benefit from low prices thanks to their simpler and cheaper development process. However, they suffer from greater competition, largely linked to the generic’s economy. Biodrugs undergo a much more complex and expensive development process, resulting in high prices when it comes to marketing. The equivalent of generics for biodrugs is called biosimilars. However, demonstrating the bioequivalence between two biodrugs is practically impossible, given the physicochemical complexity of these products and the high technicity of their bioprocess. The goal here is to prove that the drugs are comparable on their therapeutic usage, their structure and bioprocess.