The orphan class of biologicals deserves special attention for biosimilar development as they provide necessary treatment to the patient. Orphan-class biosimilars are currently minimally investigated.

Almost 450 orphan drugs have been approved for the market, yet few companies are still considering developing biosimilars to treat rare diseases. In selected cases, it may be scientifically reasonable to request a regulatory waiver for a clinical phase III study of a biosimilar orphan. In addition, the long half-life of biologics requires different approaches to compare the biosimilar and test product for the immunogenicity, safety, and efficacy.