An analysis finds that pharmas frequently file multiple similar patents on drugs, then use them as the basis for questionable litigation against would-be competitors.
A four-decade-old framework intended to simplify generic drugmakers’ path to market is now “increasingly exploited” to maintain long-term exclusivity for brand-name pharmas, a new analysis finds.
The work, led by Sean Tu of the University of Alabama School of Law, appeared in Health Affairs Scholar in December 2025. It cites multiple examples of pharmas using what the authors term serial litigation to stave off would-be competitors for years, allowing them to keep prices high.
Generic drugmakers facing this strategy might well develop a sense of deja vu. “I’m litigating. I think the litigation is done. And then I get sued again,” Tu said. “And I do the litigation. And I think the litigation is done. And I get sued again. And it’s really problematic when it’s these patents that are really the same.”
Use of the strategy is “certainly something that we’ve watched progress probably over the last decade, decade and a half,” notes Julia Pike, the global head of IP at generics maker Sandoz. This increase comes as brand-name drugmakers face patent cliffs that could see them lose billions in revenue in the coming years. According to analysts at William Blair, the lost exclusivity will affect assets that accounted for more than 30% of the collective revenues from Bristol Myers Squibb, Pfizer, AstraZeneca, Novartis and Regeneron in 2024.
A Hatch-Waxman Loophole
Pharmas are able to employ the serial litigation strategy because of the way the Hatch-Waxman Act is structured, Tu explained. Prior to that landmark 1984 legislation, generic drugmakers needed to run their own clinical trials in order to get the FDA’s nod to go to market, even when a brand-name version of their product had already been approved.
The act removed the need for this duplicate effort by requiring the sponsor of the original drug to list all patents related to it with the FDA. Generics companies can then file an Abbreviated New Drug Application (ANDA) with the agency that includes certifications regarding each of the relevant patents. These certifications might note that a patent is expired, for example, or assert that it is invalid.
The brand-name drugmaker then has an opportunity to sue for patent infringement. Doing so triggers a 30-month stay on the FDA’s ANDA decision and engages the generics company in a costly legal battle.
The act worked as intended for about two decades after its passage, Tu said. “You would see one or two patents per drug. People would challenge these patents. They would invalidate them. And then they would be able to go on the market, and the prices would drop by, like, 50% the next day” due to the new competition.
But then, “in 2010, you saw this real huge uptake in the just number of patents per drug,” Tu noted—a trend he’s previously documented. Many of these are what’s known as continuation patents, meaning that they’re essentially identical to an existing patent. These are allowed, Tu explained, for cases in which companies want to get a product to market quickly, and thus elect to file a relatively narrow and easily-defended patent initially, with the option to file a broader version later.
With multiple continuation patents on the books for a single drug, pharmas can choose to sue a generics maker for infringing one, and then, if the second company successfully defends against the suit, sue again under a different patent.
“If we stop competition, that’s a win for brand companies, right? That means that we’re going to have higher drug prices for longer periods of time,” Tu said. “How do I get less competitors? I make it riskier. I make it more expensive. I force them to come on the market later. All of that I can do through patents.”
Costs Pile Up
Pike said the uptick in continuation patents and serial litigation is a costly trend for generics companies like hers. She cited an industry group estimate that each round of Hatch-Waxman litigation costs more than $6 million. “So you can imagine if we’ve been sued three, four, five times in a row, that accumulates fairly quickly,” she said.
That’s not a hypothetical for Sandoz. In its attempt to market a generic version of Allergan’s Bimatoprost, for example, a medication for glaucoma and high eye pressure, “We’ve been in four waves of litigation on that case since 2011. And that case continues,” Pike notes.
Sandoz was also one of several generic makers embroiled in litigation with Astellas over the right to make their own versions of the overactive bladder drug Myrbetriq, a story cited by Tu and his colleagues as an exampleof the serial litigation strategy. Astellas has so far filed five rounds of lawsuits over the drug, the paper notes, and of the original nine companies vying to make generics, all but two have settled, including Sandoz.
Pike called the saga “a textbook example of serial patent litigation.” But, she added, “It’s not an Astellas strategy. It’s a broader industry strategy.”
Astellas did not respond to a request for comment on this story.
The cost of defending such lawsuits outstrips the cost of developing a drug, Pike noted. “Before you’ve even set foot in the U.S., you’re anticipating that the cost of developing that product is going to double just because of the first round of litigation.”
“People say, ‘oh, this guy doesn’t like patents,’” Tu said of himself. “That’s not true. Patents are very effective at promoting innovation. . . . But your patents shouldn’t last for forever. And we’re asking the patent system to do something now that it was never intended to do, which is extend monopoly power.”
