Full Definition
A biosimilar is a biologic drug approved by the FDA as highly similar to an already-approved reference biologic (the "originator") with no clinically meaningful differences in safety, purity, or potency. Biosimilars offer significant cost savings — typically 15–35% below the originator — and are increasingly important for employer pharmacy strategy, particularly for high-cost drugs like Humira (adalimumab) and Stelara (ustekinumab).