The FDA’s draft guidance proposing to remove routine comparative efficacy studies (CES) for most biosimilars in favor of comparative analytical assessments (CAA) has sparked debate across the industry. Biosimilar trade groups largely support the shift to CAAs as the new default, arguing it reduces redundant clinical testing and accelerates market entry. Innovator company representatives including PhRMA urged caution and want CES retained for complex modalities like multispecific antibodies and ADCs. Comments from both sides requested clearer criteria for when CES would still be required and how CAAs should be validated. The outcome will materially affect development costs and timelines for biosimilar sponsors and could change the competitive dynamics in biologics markets.