In this landscape, site-specific conjugation refers to methods that attach a payload to a defined position on an antibody rather than to whichever lysine or cysteine residue happens to react, and the search was anchored specifically to filings that also claim homogeneity, conjugation efficiency, manufacturability or control of residual free payload. That combination excludes general ADC chemistry patents that do not address the manufacturability angle. Common technical routes covered include engineered cysteine conjugation, enzymatic conjugation such as sortase-based tagging, and photocrosslinking peptide approaches.

The assignee ranking for this scope returns seven companies, with the leading assignee holding 9 of the ranked records and the fifth-placed assignee holding 2. That is a meaningfully concentrated lead rather than an even spread, so a competitive review should start with the top assignee's full portfolio before working down the shorter tail. The ranking is the complete set returned for this search scope, not a filtered top-50 or top-100 list.

Yes, based on the trend data: filings rose from 3 in 2017 to a peak of 9 in 2021, then fell to 0 by the 2022 midpoint and have stayed low through the most recent years captured. Because patent publication typically lags filing by around 18 months, the very last one or two years in any dataset understate true activity, so some of the apparent drop-off may still reverse as pending applications publish. Even accounting for that lag, the collapse from a 2021 peak to zero by 2022 is early enough that it likely reflects a real slowdown, not just a reporting artefact.

The IPC composition shows heavy concentration in A61K (94.7% of the 19 records) and C07K (89.5%), meaning most claims sit on the drug-conjugate composition and the antibody or peptide scaffold itself. C12P, covering fermentation and enzymatic synthesis, appears in only 5.3% of records, suggesting that claims narrowly tied to the enzymatic production step, as opposed to the resulting conjugate, are comparatively under-filed. Non-cysteine engineered handle chemistries and residual free-payload quantification methods are other areas with thin direct representation in this set.

US20220047711A1, assigned to Genentech, Inc. and published 2022-02-17, claims peptides bearing a photocrosslinking moiety used to synthesise antibody-drug conjugates, along with methods of making and using them. It sits alongside an earlier related filing, WO2020123275A1, on the same photocrosslinking approach, and both are among the most-cited records in this scope. Anyone developing a photocrosslinking-based site-specific conjugation method should review this family closely before finalising a chemistry route, since it defines the specific peptide-based crosslinking mechanism rather than antibody conjugation in general.