WASHINGTON - This case raises a critical issue in many antitrust matters—how to define the product market in which businesses compete. Basic antitrust concepts such as monopoly power are meaningful only in relation to a particular product and geographic market. The district court in the case ignored the relevant law and factual allegations before it. Instead of assessing Regeneron's claims on product market definition and allowing it to further develop the factual record on this central question, the district court held that Regeneron's alleged product market was legally deficient and dismissed its complaint.

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