The generic manufacturers claimed that the patent did not satisfy the utility requirement. Justice Binnie, for the Court, considered the doctrine of sound prediction to determine whether the invention was useful. There are three elements. First, there must be a factual basis for the prediction at the date that it was filed. Second, the inventor must have a sound line of reasoning from which the desired result can be inferred from the factual basis. Third, there must be proper disclosure. As Justice Binnie believed that predictability is a question of fact, he relied on the trial judge's findings and determined that all three requirements for sound prediction were satisfied. At the time the patent application was filed, Glaxo Wellcome knew that AZT was suitable for prolonged treatment of humans, that compounds of its class could act as chain terminators, and that in vitro efficacy had been shown in human cells.
