Last week, FDA released draft guidance titled “Scientific Considerations in Demonstrating Biosimilarity to a Reference Product: Updated Recommendations for Assessing the Need for Comparative Efficacy Studies.” This draft guidance reflects an evolution in FDA’s approach to determining whether a comparative clinical study with efficacy endpoints (a comparative efficacy study or CES) is necessary to support a demonstration of biosimilarity. Specifically, the agency notes that a comparative analytical assessment (CAA) is generally more sensitive when it comes to detecting differences between products than a CES.