One assignee holds 362 of the 762 records in scope, far ahead of the rest of the ranked field of 88 companies. The next four filers combine with the leader for 491 records, or 64.4% of all records in scope. Below the top ten — which together hold 591 records, 77.6% of the total — the field thins quickly into single-digit filers, so due diligence should focus heavily on the leading handful of assignees rather than treating this as evenly distributed.

Accelerated blood clearance (ABC) is the phenomenon where a first dose of a PEGylated or lipid nanoparticle formulation triggers antibody or complement responses that cause a second dose to be cleared from circulation much faster, undermining repeat-dosing efficacy. It is a central reactogenicity concern for LNP-based vaccines and therapeutics that require multiple doses. Several of the most-cited records in this landscape, including the top-cited WO2017099823A1, explicitly claim compositions designed to avoid triggering this response.

The classification data suggests polymer-chemistry claims — covering condensation polymers (C08G), acyclic and carbocyclic compounds (C07C), and polymer compositions (C08L) — appear on only 5-11% of the 762 records in scope, well below the 88.3% carrying medicinal-preparation claims. That gap does not guarantee an open path, since some of the largest filers likely hold foundational lipid-composition claims that touch adjacent polymer chemistry, but it does indicate the PEG-alternative space is comparatively less densely claimed and worth a focused freedom-to-operate check.

Filings peaked at 95 in 2019 and fell to 28 by 2024, a decline that includes a documented 66% drop between 2021 and 2024. Some of this reflects a genuine cooling as core compositional claims around early mRNA-LNP platforms matured and were filed. However, publication lags filing by roughly 18 months, so the 2025-26 counts in this dataset are still incomplete and should not be read as continuing evidence of decline until later data cuts confirm it.

WO2017099823A1, assigned to ModernaTX and cited 647 times, claims lipid-based and lipid nanoparticle compositions for delivering nucleic acids and proteins in vivo that are specifically designed to avoid triggering accelerated blood clearance and to carry an improved toxicity profile. Anyone filing lipid nanoparticle compositions with similar ABC-avoidance or toxicity claims needs to review this family's claim scope closely, since it is the single most-cited record in this landscape and predates most of the field's later filings. Designing around it typically means differentiating on lipid structure, PEG-alternative chemistry, or a distinct mechanism for avoiding the immune response rather than the same compositional approach.