Small molecule medicines: Most medicines, such as acetylsalicylic acid (aspirin), are small molecule products. This means that they have simple molecular structures with low molecular weight. These small structures are easy to produce or copy. Once a patent expires, other manufacturers can make copies of small molecule medicines by reproducing the exact same active ingredient, which they can then sell as a generic copy.
Biological medicines: By comparison, biological medicines are very large and have complex molecular structures, created by living cells, from specialised ingredients, using an intricate biotechnology process. It is impossible to produce an exact copy of a biological medicine without using the exact same ingredients, the same living cell lines, and identical manufacturing conditions. In fact, it is not even possible to demonstrate that a batch of any biologic is identical to previous batches of the same biologic.
Biosimilars: The first biological medicine of its kind is called the reference or innovator medicine. Once a patent expires for a reference biologic, other manufacturers are able to copy it. However, the innovator company doesn’t have to share its patented manufacturing processes (which may include the room temperature, the type of cells that produce the biologic, and the food the cells used to grow it), and since there is always variability in a live biological system, it is impossible to create an identical medicine. But they are able to create a copy that is highly similar, with a different brand name; these are known as biosimilars.
To be approved for use in New Zealand by Medsafe, the manufacturer must demonstrate that their biosimilar has no clinically meaningful differences to the reference medicine in quality, safety and efficacy.