One assignee leads the ranked field with 394 records, more than five times the count held by the tenth-ranked assignee at 42. The top five assignees combined account for 38.4% of all 2,164 records in scope, and the top ten account for 52.6%. That leaves roughly half the field distributed across a long tail of 90 further ranked assignees, each typically holding a small number of families, so the field is concentrated at the top but not closed to new entrants.

Annual filings rose from 62 in 2017 to a peak of 185 in 2021, then eased to 130 by 2024 — a 30% decline over that three-year span. Figures for 2025 and 2026 appear lower still, but that reflects publication lag of roughly 18 months rather than an actual drop in filing activity, since recent filings have not all published yet. The fairest reading is a field that cooled from an unusually active 2021 rather than one in structural decline.

C12N, covering microorganisms and genetic engineering methods, appears on 90.9% of the 2,164 records in scope, making it by far the dominant class. A61K medicinal preparations follows at 41.5%, with C07K peptides and proteins at 20.2% and A61P therapeutic activity at 17.1%. Because a single record can carry several IPC classes, these percentages add up to more than 100%, which is expected and reflects how differentiation method claims are typically paired with formulation or therapeutic-use claims.

The classes with the lowest density relative to the core method classes are C12M bioreactor and enzyme apparatus at 2.8% of records and A61L sterilising and disinfecting at 1.6%. Both cover practical scale-up and contamination-control problems that manufacturers routinely face, suggesting these branches are either genuinely under-claimed or routed through classes outside this search. Either way, they are worth a dedicated search before assuming freedom to operate in scale-up or process-control claims.

US20050266554A1, covering PDX1-expressing endoderm, is the most-cited record in this dataset at 394 citations, indicating it is treated as a foundational reference across later endoderm and pancreatic differentiation work. High citation counts in a searched corpus tend to favour older filings simply because they have had more time to be cited, so this is best read as a signal of influence on the field's citation graph rather than a statement about current commercial importance. New filings in adjacent lineage-specification work should still expect to be compared against it during prosecution or freedom-to-operate review.