Start with the number everyone watches and the one they miss. The watched number is when the compound patent expires. The missed one is when the method-of-use patents do — and that second date can be later.
A compound patent covers the molecule itself. A method-of-use patent covers using that molecule to treat a particular condition. They're separate claims with separate clocks, and the franchise is protected until the last relevant one lapses.
Lilly's 2025 grants show both layers. The compound side is US12252524B2, covering GIP/GLP1 co-agonist compounds. The method side is US12295987B2, covering a method of using a GIP/GLP1 co-agonist for diabetes. Same mechanism, two kinds of protection.
By the numbers, this is why the incretin cliff is fuzzier than a single date. A generic maker who waits out the compound patent may still face live method-of-use claims on treating specific conditions — and analog patents like US12365716B2 on top of that.
The honest limit: method-of-use patents are narrower and more contestable than compound patents. A generic can sometimes launch for an unprotected use, and courts don't always uphold use claims. They extend the cliff; they don't move it indefinitely.
So the Cliff Watch read: for the incretin franchise, don't quote a single expiry. The effective cliff is set by a stack — compound, method-of-use, analogs — and the 2025 grants show Lilly building all three layers. The molecule's expiry is the floor of the cliff, not the edge.