Abstract :Biosimilar (follow-on biologic or subsequent entry biologic) are biologic products that are highly similar to an already FDA approved biologic product (reference product) manufactured by a company. Biological products are derived from living organisms such as humans, animals and microorganisms through biotechnology, derived from natural sources or produced synthetically. Biologicals are highly valuable for treatment of rheumatoid arthritis, diabetes, anemia, low white blood cell counts, inflammatory bowel disease, multiple sclerosis, psoriasis and various forms of cancer. Some biosimilars consist of small molecules such as human insulin or erythropoietin but mostly are complex molecules such as monoclonal antibodies. Biosimilars exhibit high molecular complexity unlike generic drugs having small molecular structure. Generic drugs are bioequivalent to the brand-name drugs having identical active ingredient and similar safety, quality and performance characteristics far an intended use.