Previously, the district court conducted a Markman hearing to interpret the claims of the Housey patents. A Markman hearing, typically conducted pre-trial, is when the trial judge hears evidence about the meaning of the asserted patent claim, and then makes a judgement as a matter of law. A narrow claim interpretation can often favour accused infringers because it can allow them to escape literal infringement. On the other hand, the wider the interpretation, the more probable it is that infringers will fall within the claim's limitations. Too broad a claim interpretation, however, can create problems for the patentee by causing the patent claim to be invalid in light of the prior art. Because the meaning of the claims is often central to deciding the case, Markman hearings reduce the number of patent cases that are tried by a jury.
During the hearing, Housey argued for a narrow interpretation, that an 'inhibitor or activator of a protein' was limited to substances that directly interact with — that is, bind to — the target protein. However, the Federal Circuit held that the definition included substances that both directly and indirectly affect a protein of interest, and the patent and its prosecution history clearly supported the broad plain meaning.
