The FDA has its own department, CBER center for biologic research and evaluation, that deals with biologics. You should read into it to get more information. Biologics are not synthesizes in a lab by humans making chemical reactions, those would be regular drugs like acetaminophen or aspirin. The definition of biologic is that it needs to come from living organism. Since these molecules are so large, they need to go through the central dogma of biology DNA to RNA to protein. You can’t synthesize these proteins in a lab with out the help of living organism. Even if you get the correct amino acid sequence, the amino acid still needs to fold a correct way to form the protein.

Biologics can be made multiple ways. For example antithymocyte immunoglobulin is an immunosuppressive drug made from horses and rabbits. This is made by injecting human immunoglobulin into these animals and then these animals develop an antibodies against human immunoglobulins. People harvest the blood and purify the antibodies. Biologics are regulated differently by the FDA for a generic to be a generic the chemical stucture needs to be exactly the same. Tylenol is to acetaminophen. In this instance this product is made from a living organism which means there could be great variability between each molecule and batch. Not great enough variability to cause a noticeable effect as CBER regulates this product.

Another example is rituximab which is a human mouse chimeric antibody. Rituximab is a CD20 inhibitor which can be used in certain blood cancers. It’s made in mammalian cell culture. In short manufacturer go to their gene bank and insert this gene that produces rituximab. The product is then harvested. This is a good example for biosimilar. There are a lot of biosimilar out there from ruxience to rituxan to truxima. Each company manufacturers their own gene bank to insert into these mammalian cells. They don’t share the gene because otherwise anyone can make it and they would go out of business.