Wellcome’s patent for the use of AZT for treating HIV infections was subject to consideration by the Supreme Court of Canada in the case of Apotex Inc. v. Wellcome Foundation. The main issue before the court was whether, at the time of filing the application for their patent, Wellcome had met the utility requirements of Canadian patent law. The Supreme Court held that where one was claiming the new use of a known material, as was the case here, to avoid the grant of patents on mere speculation, “the gravamen of the invention, the utility required for patentability must, as of the priority date, either be demonstrated or be a sound prediction based on the information and expertise then available”. The court noted that:

The doctrine of “sound prediction” balances the public interest in early disclosure of new and useful inventions, even before their utility has been verified by tests (which in the case of pharmaceutical products may take years) and the public interest in avoiding cluttering the public domain with useless patents and granting monopoly rights in exchange for misinformation.

The Court set out three requirement for sound prediction: 1) a factual basis for the prediction; 2) the inventor must have at the date of the patent application an articulable and “sound” line of reasoning from which the desired result can be inferred from the factual basis and 3) there must be proper disclosure (by which the court seems to mean disclosure of the reasoning used). The court found that, even though the factual information that Wellcome possessed as of their priority date was only that AZT was active against certain retroviruses and it required subsequent testing at the National Institutes of Health to show activity against HIV, Wellcome had a sufficiently clear understanding as to how this might be relevant to treatment of HIV infections (HIV is a retrovirus) and the mechanism by which this might occur, that a sound prediction was possible. Wellcome’s patent therefore complied with the utility requirement of Canadian law.