Why Terminal Disclaimers Matter for Drug Competition
Alex Moss | September 24, 2026
On September 24, PIPLI led a group of public interest organizations and academics in submitting a letter to the House Judiciary Subcommittee on Courts, Intellectual Property, Artificial Intelligence, and the Internet about pharmaceutical patents, terminal disclaimers, and the ETHIC Act.
The letter responds to a September 15 letter from the Council for Innovation Promotion (C4IP) about the Subcommittee's June 4 hearing, “Medicines and IP: Balancing Innovation and Access.” C4IP asked the Subcommittee to disregard testimony describing patents linked by terminal disclaimers as duplicative — arguing that little patent term is at stake, that different claims mean different inventions, and that existing ways of challenging patents are adequate. It cited nothing for any of those claims.
Our letter answers with the record: Federal Circuit case law, the Patent Office's own manual, peer reviewed research, and the USPTO's own data. It was signed by several of the scholars whose work it relies on.
What is a terminal disclaimer?
The patent system generally does not allow someone to receive multiple patents on the same invention simply by filing multiple applications. When the Patent Office finds that a new application is too similar to an earlier patent from the same applicant, it issues what is called an obviousness-type double patenting rejection.
An applicant can usually overcome that rejection by filing a terminal disclaimer — agreeing that the later patent will expire no later than the earlier one.
That may sound like a small technical concession. But the applicant still ends up with a separate, separately enforceable patent. And that is the point. As our letter puts it, what a terminal disclaimer buys is the assurance of another patent to assert against competitors.
The effect is cumulative. Each disclaimer adds another patent to a group covering a single invention family, and a company holding dozens of them can turn one dispute into a war of attrition.
What this looks like in practice
Humira is the clearest example. Its basic patent expired at the end of 2016, but AbbVie obtained many more. One peer reviewed study found that of the 73 patents in Humira's core U.S. portfolio, 59 — roughly 80% — were not directed to new, non-obvious inventions. Another found that the 105 patents asserted in Humira litigation clustered into just 24 groups linked by terminal disclaimers, meaning at most 24 patentably distinct inventions.
The overactive bladder drug mirabegron shows the litigation side of it. Astellas brought five successive lawsuits against generic manufacturers based on child patents tied to the same parent by terminal disclaimers. Those lawsuits ran for ten years, and generic manufacturers ultimately paid Astellas $210 million before they could sell free of infringement liability.
“Just challenge the patents” is not an answer
C4IP argues that if particular patents are invalid, competitors should challenge them through the channels Congress created. That answer assumes those channels work.
District court litigation is the main one, and it is expensive: Hatch-Waxman cases cost generic manufacturers an average of $6.2 million. Congress created inter partes review at the Patent Office as a "quick and cost effective" alternative. But the Patent Office has since narrowed it by administrative action, and by its own data the rate at which it agrees to hear these challenges fell from roughly 65%in October 2024 to roughly 37% in February 2026.
Some of the decisions behind that shift were made by people now at C4IP — including its board co-chair, a former USPTO Director, and its president and CEO, who signed the letter we are responding to.
Requiring a generic or biosimilar manufacturer to knock out dozens of patents one at a time, through a process that has become harder to access, is not a remedy. It is a barrier to entry.
What the ETHIC Act would do
The ETHIC Act does not declare terminally disclaimed patents invalid. It changes how they can be enforced, generally limiting a patent owner to asserting one patent per patent group in an infringement action against a generic or biosimilar manufacturer.
That is a competition measure, not a patent quality measure, and deliberately so. The problem is not that each patent in a thicket is individually indefensible. It is that a company can assemble many patents around one medicine and make the cost of clearing them prohibitive.
Our letter asks the Subcommittee to weigh the evidence and the practical realities of the pharmaceutical market — how patents actually function for the companies trying to bring lower cost medicines to patients.