Accord Healthcare Limited & Ors v The Regents of the University of California & Anor

This appeal came out of a high-stakes pharmaceutical patent dispute. The patent owners and licensee held rights over enzalutamide, a treatment for prostate cancer, and the generic challengers wanted those rights revoked. If they succeeded, that could help clear the path for market entry.

The appeal was narrower than the original trial. The challengers had run several validity arguments below, but by the time the case reached the Court of Appeal they focused only on obviousness. Their case was that two earlier public disclosures, referred to as the Poster and the Slides, made the patented compound obvious to the skilled team working in this field.

That mattered because the patent did not maintain priority from earlier applications, so the relevant date was the filing date of 29 March 2006. The earlier materials had been made public before then and could therefore be used as prior art. Both materials described related research by the inventors and disclosed a compound called RD162. The patented compound, RD162', differed in one identified structural feature.

The commercial significance is easy to see. In sectors such as medicines, a patent challenge is often part of launch planning. But this case shows that even where prior art looks close, the court still asks a disciplined question: would the claimed step really have been obvious to the skilled team at the time?

The core dispute was not whether the earlier materials existed or whether they disclosed related compounds. The real fight was whether the move from RD162 to the patented compound RD162' was an obvious one. The Court of Appeal recorded that the only difference identified between the two compounds was at a position on the molecule called position X: RD162 had a cyclobutyl group, while RD162' had a geminal dimethyl substituent.

The challengers said that this was an obvious modification in light of the Poster and, separately, the Slides. The court treated those two items of prior art separately, which is important. A business cannot simply bundle different disclosures together unless the legal test allows it. Here, the parties accepted that the Poster and the Slides had to be considered on their own terms.

The judgment also explains why the technical background mattered. The skilled team would include both a cancer biologist and a medicinal chemist. They would be trying to develop a new androgen receptor antagonist for prostate cancer, with attention not only to activity but also to drug-like properties such as pharmacokinetics and lipophilicity. So the question was not just whether a chemist could imagine the change, but whether the skilled team would see it as an obvious way forward in the real research setting.

The legal issue was whether the trial judge had been wrong to reject the obviousness challenge. More specifically, the Court of Appeal had to decide whether the judge had made an error of principle by placing weight on the lack of proper “context” in the challengers’ expert evidence and by concluding that hindsight had affected that evidence.

The challengers argued, in substance, that if a technical step is obvious, the law does not require a separate motive for taking it. They relied on the idea that technicians may make small changes to known products to achieve essentially the same result. The Court of Appeal did not reject that general proposition. But it agreed with the trial judge that everything depends on the facts, and that in medicinal chemistry a structurally small change does not necessarily mean an obviously immaterial one.

So the issue became practical and evidential: had the challengers shown, through credible expert evidence, the real scenario in which the skilled team would have chosen this exact modification as an obvious route forward? The court said that question mattered, and that the trial judge was entitled to treat the omission as significant.

The Court of Appeal dismissed the appeal. It held that the trial judge had been entitled to conclude that the challengers had not proved obviousness over either the Poster or the Slides. The court stressed that obviousness is a highly fact-dependent evaluative decision, especially in a specialist technical area where the trial judge has heard the expert evidence in detail.

On the Poster, the court accepted that the judge was entitled to find the challengers’ expert evidence infected by hindsight. A central problem was that the expert had focused on the specific change from cyclobutyl to dimethyl without clearly explaining the practical objective or research context in which the skilled team would have made that move. The court said that the focus on close analogues appeared to be driven by knowledge of the patent claim.

On the Slides, the challengers came closer, and the trial judge had even changed his mind more than once. But the same evidential weakness remained. The Court of Appeal agreed that the judge was entitled to find that there was not enough primary evidence to establish obviousness. In short, the appeal failed because the challengers did not show a sufficiently clear, non-hindsight route from the prior art to the claimed compound.

This decision is most useful for businesses whose product plans depend on someone else’s patent position. That includes generic suppliers, life sciences startups, manufacturers entering regulated markets, and investors assessing whether a launch window is realistic. The case is a reminder that patent risk is not just a legal filing issue. It is a commercial planning issue.

If your strategy assumes that a competitor’s patent is weak because the claimed product looks like a small variation on earlier work, be careful. The court may still uphold the patent if the evidence does not show that the variation was an obvious route for the skilled team at the relevant date. In technical sectors, courts look closely at the real development pathway, not just side-by-side structural comparisons.

This also matters for budgeting. A validity challenge can involve extensive expert evidence, trial time and appeal risk. If your business model depends on a successful challenge, you need to pressure-test the scientific narrative early. Ask not only “Can we describe the difference?” but also “Can we prove why the skilled team would have made that move then, for that purpose, without knowing the patent outcome?”

If your business is developing, sourcing or launching a product in a patent-sensitive market, use this case as a planning prompt. The lesson is not that obviousness challenges never work. It is that they need a disciplined factual foundation. A thin theory built around a known target can unravel if the court sees it as hindsight.

For smaller businesses, the practical answer is early coordination between commercial, technical and legal teams. Product managers may focus on launch timing, scientists on technical feasibility, and lawyers on infringement and validity. This case shows why those streams need to meet early. The strongest position usually comes from aligning the product roadmap with a realistic freedom-to-operate review and a tested evidence strategy.