The corpus shows filing concentrated among a small group of repeat assignees with long co-filing histories, alongside a much larger long tail of single- or few-filing entrants. The most-cited foundational documents in this dataset date from the late 1990s and early 2000s, covering base coating chemistry and non-thrombogenic surface treatments, and much of the newer filing activity builds refinements on top of that earlier architecture rather than replacing it. Anyone assessing freedom to operate should treat those early, heavily-cited coating patents as the starting point for a clearance search, since later filings tend to layer on top of them rather than around them.

No — filings peaked at 24 in 2018 and had fallen to around 4 by the 2022 midpoint, which is a declining rather than a flat or growing trend. That said, publication typically lags actual filing by about 18 months, so the last one to two years in any chart will understate true activity until later data catches up. Even accounting for that lag, the multi-year decline from the 2018 peak points to a field where the core claim space has been substantially staked out rather than one still expanding.

US8845716B2, assigned to Osstem Cardiotec, claims a three-layer stent coating structure: a polymer base layer, a second layer combining a biocompatible or bioabsorbable polymer with one drug, and a third layer adding a different second drug on top. The design purpose is to sequence the release of two distinct therapeutic substances while suppressing the early burst release that single-layer coatings are prone to. Anyone designing a multi-drug or multi-layer eluting coating needs to check this claim scope specifically, since it covers the layering architecture rather than any single drug or polymer in isolation.

The United States carries by far the deepest filing density in this dataset at 340 receiving-office filings, ahead of the EPO at 197 and WIPO PCT filings at 139. Canada, Australia and India each sit well below that at under 50 filings apiece, making them comparatively lighter-filed jurisdictions for this specific technology. A clearance search that starts with US prior art and the EPO will cover the large majority of the relevant claim landscape before extending to smaller markets.

Relative to the dense core claims around implant structure (A61F) and general coating processes (A61L), sub-areas like peptide- and protein-based eluting coatings (C07K, 50 records), sequenced multi-drug layer release, and degradation-rate-tuned topcoats show comparatively thinner filing density. That does not guarantee those areas are unclaimed, but it does mean the prior art a new filer has to design around is shallower there than in the core mechanical and single-drug coating claims. A targeted novelty search in those specific sub-areas is a reasonable next step before committing significant R&D spend.