Filing is concentrated at the top: the five most active assignees together account for 37.2% of the 949 records in scope, and the top ten account for 57.4%. Beyond that, the ranked list of 100 companies thins into a long tail of single- or few-filing entrants, which is typical for a field still consolidating around a handful of clinical-stage platforms. Because families rather than raw documents are the fairer comparison, the ranking used here counts patent families, not every published document variant.

Medicinal-preparation claims under A61K cover 81.3% of the 949 records, and therapeutic-activity claims under A61P cover 53.6%, meaning most filings sit on ligand and formulation chemistry rather than hardware. Peptide and protein chemistry (C07K) is present in 41.2% of records, reflecting the weight of receptor-targeting ligand platforms. Radiation-therapy delivery hardware, by contrast, is the thinnest major class at 3.9%, which suggests less crowded claim space there relative to the chemistry.

Yes through the last complete year: filings rose from 67 in 2017 to a peak of 142 in 2024, a 78% increase over the 2021-2024 span alone. Figures for 2025 and 2026 in the raw data appear lower, but that reflects publication lag of roughly 18 months rather than a real slowdown — those years are still filling in as more applications publish. Treat any apparent dip in the most recent one to two years with that caveat rather than as evidence of cooling activity.

The organo-metallic and chelation chemistry class (C07F) sits at only 4.7% of the 949 records and the radiation-therapy/electrotherapy class (A61N) at 3.9%, both far below the 81.3% weight carried by general medicinal-preparation claims. That gap points to under-claimed territory around specific chelator-radionuclide pairings, kidney-protection dosing regimens, and dosimetry methods tuned to newer isotopes. A narrowly drafted claim combining a specific radionuclide-chelator pair with a defined protective-dosing step is more likely to clear prior art than a broad formulation claim in the crowded A61K space.

A 2026 filing from Curium US LLC, US20260077075A1, claims an actinium-225 PSMA I&T radiopharmaceutical composition stabilized with sodium ascorbate and optional hydrochloric acid, targeting improved shelf-life and lower toxicity for prostate-cancer treatment. It illustrates the current direction of filing activity: incremental formulation and stability improvements on established targeted-radionuclide chemistry rather than entirely new mechanisms. That pattern is consistent with the broader dataset, where medicinal-preparation and therapeutic-activity classes dominate over novel delivery hardware.