The limitation that matters in an ADC claim is the linker. US12622977B2, "Antibody drug conjugate" (Chia Tai Tianqing, issued May 12, 2026; CPC A61K 47/6855), like the broader ADC genre, recites three parts: an antibody that targets a tumor antigen, a cytotoxic drug, and a linker connecting them. The antibody is often a known binder and the payload is often a known cytotoxin; what the claim hinges on is the chemistry in between.
Why the linker carries the weight: it has to do two contradictory things. In the bloodstream it must hold the toxin firmly to the antibody, so the cytotoxin does not release prematurely and poison healthy tissue. Inside the target cell, it must release the toxin efficiently. Cleavable versus non-cleavable linkers, and the specific cleavage trigger, are therefore the claim limitations that define both the invention and its scope. A claim reciting a particular cleavable linker is narrower — and often more defensible — than one gesturing at "a linker."
Construe the conjugation site, too. ADC claims frequently recite where and how the linker attaches to the antibody (lysine residues, engineered cysteines, site-specific conjugation) and the drug-to-antibody ratio. These are not incidental; they are limitations that a competitor's ADC either meets or does not. Reading US12622977B2, the CPC tags (A61K 47/6855, A61K 47/65, A61K 47/6803) point to the conjugate and linker classifications — the patent office's own signal that the conjugation chemistry is the claimed core.
Separate the three components when assessing infringement. A competitor using the same target antigen but a structurally different linker may not infringe a linker-specific claim; one using the same linker chemistry with a different antibody might. Because the ADC field is enormous — Genentech alone holds well over a thousand grants touching ADCs, with Immunomedics, Novartis, and others close behind — the practical question is rarely "is this an ADC?" but "does this linker-conjugation chemistry read on the asserted claim?"
The genus-versus-species tension applies. Broad ADC claims that recite "a cleavable linker" functionally risk written-description and enablement challenges, especially given the crowded prior art; narrow claims reciting a specific linker structure are more durable but easier to design around. The inventive specificity tends to live in the species claims on particular linker chemistries, which is where the modern ADC filings concentrate.
The teardown conclusion: do not describe an ADC patent by its target or its drug. Describe it by its linker and conjugation chemistry, because that is the limitation the independent claim almost always turns on. The antibody points and the payload kills; the linker is the invention, and construing it precisely — cleavable or not, what trigger, what attachment, what ratio — is how you read the claim's true scope.