One of the key questions is whether the patent was going to survive. Most seem to assume that if a company pays to settle, then the patent was likely going to be invalidated. That's where the draft, Maintaining the Balance: An Empirical Study on Inter Partes Review Outcomes of Orange Book-Listed Drug Patents and its Effect on Hatch-Waxman Litigation, by Tulip Mahaseth (a recent Northwestern Law grad) comes in. Here is the abstract from SSRN:
The Hatch-Waxman Act intended to strike a delicate balance between encouraging pioneer drug innovation and promoting market entry of affordable generic versions of pioneer drugs by providing a streamlined pathway to challenge validity of Orange Book patents in federal district courts. In 2012, the America Invents Act introduced Inter Partes Review (IPR) proceedings which provide a faster, cheaper pathway to challenge Orange Book patents than Hatch-Waxman district court litigation. IPRs also have a lower evidentiary burden of proof and broader claim construction standard, which should make it easier, in theory, to obtain patent invalidation in IPRs as compared to Hatch-Waxman litigation. This empirical study on IPR outcomes of Orange Book patents in the past six years shows that both generic manufacturers and patent owners obtain more favorable final decisions in IPRs as compared to their Hatch-Waxman litigation outcomes because the rate of settlement in IPRs is much lower than in Hatch-Waxman litigation. Moreover, generic manufacturers do not appear to be targeting Orange Book patents in IPRs during their drug exclusivity period. Only 2 out of more than 400 IPRs against Orange Book patents were filed by generic petitioners during the patents’ New Chemical Entity exclusivity period. About 90% of the 230 Orange Book patents challenged in IPR proceedings were also challenged in Hatch-Waxman litigation. It is likely that generic manufacturers are not deterred from Hatch-Waxman litigation because of the lucrative 180-day exclusivity period, which gives the first generic filer 180 days to exclusively market their generic version without competition from other generics when the Orange Book drug patent is successfully invalidated in a subsequent district court proceeding. Therefore, IPR proceedings do not appear to be disrupting the delicate balance sought by the Hatch-Waxman Act. Instead, the IPR process has provided generic manufacturers a dual track option for challenging Orange Book patents by initiating Hatch-Waxman litigation in district courts and also pursuing patent invalidity in IPRs before the Patent Trial and Appeal Board, which has reduced rate of settlements resulting in more patents being upheld and invalidated.There's a lot of great data in this paper, comparing Orange Book IPRs with non-Orange Book IPRs, including comparison of win rates and settlement rates.
But I want to focus on one seemingly minor point: as the number of IPRs has increased, the rate of settlement has decreased. And, more important, the decreasing rate of settlement has led to more invalidation and more affirmance of patents.
This result gives a nice window into how we might view settlements. Traditional Priest-Klein analysis says that this is exactly what we should see - that the previously settled cases were 50/50. But proving this is harder, and this data set would allow for a nice differences-in-differences analysis in future work.
Additionally, a split among outcomes implies that the settlements were not necessarily because the patentee believed the patent was at risk. If anti-competitive settlements were ruling the day, I would have predicted that most of the (recent) non-settlements would have resulted in patent invalidation. Then again, it is possible that a 50% chance was risky enough to merit a reverse payment settlement in the past. Regardless of how one comes out on this issue, this study provides some helpful details for the argument.