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Biologics are complex molecules, modifying our immune responses to specific chronic inflammatory conditions like rheumatoid arthritis, psoriatic arthritis, or irritable bowel disease. They are manufactured by placing genes into host cells who through transcription and translation provide the core protein. Biosimilars are biologics “generic” equivalents, except they are not.
The reverse engineering of the DNA, choice of a host cell and the subsequent isolation and purification of the core protein make them similar but not identical. In the lock and key world of drugs, where a drug, the key, must fit into another structure, the lock, to be effective, the shape of that key may mean the lock opens, or doesn’t, or even require a bit of twisting and finagling. Biosimilars have an identical primary structure as their biologic but other factors, influencing shape may and do differ
Biosimilars aren’t just similar but are in fact highly similar. While the FDA is not perfect it wouldn’t approve a biosimilar that is simply “similar” to a biologic. This same skepticism surrounded generic drugs in the early 2000s before they eventually took off and now account for 89% of all drugs being dispensed in the USA compared to 60% in 2005. In some cases, the plan sponsor would be wise to forgo the rebates for biologics and instead opt for the lower net cost biosimilars provide. Of course, non-fiduciary PBMs will not push for this if they’re generating revenue from biologic manufacturers for the dispensation of their products.
How the FDA approves these slightly different keys and their impact on the care of our patients, that is the first concern of the rheumatologists; the second is the cost and economics.