The Hatch-Waxman Act seeks to balance the competing interests of encouraging the development of pioneering drugs while enabling low-cost, generic versions of these drugs to efficiently enter the market when the patents on the drugs expire. To this end, patent infringement was defined in 35 U.S.C. § 271(e)(2) to include the act of submitting an ANDA to the FDA with the intent to market a drug that is protected by product or use patents before their expiration. This is an artificial act of infringement that gives pioneer drug makers the chance to litigate their patents before the generic drug is actually marketed. In such cases, infringement is based on how the generic drug is described in the ANDA and the approved uses on the label, not whether or not the generic drug as it is manufactured actually embodies any of the claims in the patent.
Pioneer drug patents are listed in the FDA's Orange Book. To avoid being sued under § 271(e)(2), a generic drug maker scours its ANDA specification and label to remove any statements that fall within the scope of the patents in the Orange Book. This can be a tricky process. Under FDA labeling rules, with limited exception, the language on a generic drug's label must be identical to the language on the pioneer drug's label. FDA rules are not so clear, however, when it comes to generic drug specifications.
Please read "Hatch-Waxman Developments: Artificial Infringement by Artificial Drugs" for more information.