Biosimilar vs biological agents in rheumatology: When are biosimilar agents similar enough?

With the introduction of biological agents, over the last two decades treatment prospects in many medical fields including Rheumatology have experienced an exciting revolution. The advent of biological therapy for specifically rheumatic diseases has provided more effective control of both the underlying disease, and sustained amelioration of disease activity, compared to the pre-biological era when only anti-inflammatory and immunosuppressant drugs were available. Although the importance of potential improved clinical outcome cannot be overstated, these efficacious treatments for rheumatic diseases are not without a high cost. Biological agents are expensive and rheumatological diseases are common. The patent and regulatory data protection periods for the first and second waves of biological agents based on recombinant proteins have begun to expire, leaving open the potential for development and regulatory approval of one or more "generic" versions of these biological therapies, termed "biosimilars" or "BSs" in Europe (the term we shall use from henceforth), "subsequent entry biologics" in Canada, or "follow-on-biologics" in US. We aimed to review the critical topics of efficacy, safety and regulatory approach of upcoming biosimilars.