By the year 2010, $20 billion worth of protein pharmaceuticals will be off patent and in a market open to generic manufacturers. Subtle changes, such as in glycosylation or formulation, may show dramatic effects, or no effect, on efficacy and safety.

What analytical or clinical validation should be required of biogenerics (biosimilars or follow-on biologics)? What metrics can be developed and validated to detect variation, determine its significance, and to monitor quality? How should we weigh uncertainty in risk against the public health benefits of reducing drug costs?