Drug companies are pressing FDA to explain what its new "similar" category of biosimilars, which falls below the statutory "highly similar" measure, means for products that meet the lower bar, reacting to three new categories unveiled in FDA's draft biosimilar guidance on clinical pharmacology. The guidance's suggestion that immunogenicity data could be collected postmarket also has sparked confusion, with originator biologic makers urging FDA to require such data be gathered before biosimilars hit the market. FDA's introduction of the three...