Although the '482 patent does not expire until 2017, generic gabapentin has been on the market since 2004, when Teva first launched its generic product. This was shortly followed by the launch of other generic competitors. Understandably, the disputant patent has been the subject of many court decisions, most notably last year, when a district court granted summary judgement — a decision made without a trial when there is no dispute as to the facts of the case — in favour of the generics companies, which included Teva, Purepac, Watson, Ivax, Apotex and Eon. In that case, the lower court ruled that Pfizer had failed to prove that the generic product made by Teva infringed on the '482 patent. Pfizer's appeal forms the basis of the current case.
The '482 patent states that under certain conditions, gabapentin has a tendency to form a lactam, which makes the drug unstable, and is linked to causing seizures rather than preventing them. Because of this, the '482 patent teaches that gabapentin must be highly purified before formulation, and that the proportion of anion of a mineral acid present should not exceed 20 ppm. It is this claim that formed the major dispute in this case. The generics manufacturers argued that because the Teva product contained greater than 20 ppm of hydrochloride, it did not infringe on the '482 patent.
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