In this landscape, a conditionally active or masked antibody is a binding molecule engineered so that a peptide, domain or other blocking group prevents target engagement until a specific condition — most often cleavage by a tumor-associated protease — removes the mask. Claims in this space typically cover the masking peptide sequence itself, the protease-cleavable linker joining it to the antibody, or the overall construct and its method of use. The search set behind this page combines masking-peptide design terms with protease-specificity and unmasking-efficiency language to capture that full mechanism, not just antibody sequences generally.

The ranking in this dataset covers 22 companies, and it is heavily front-loaded: the top-ranked assignee holds 55 of the 221 records in scope, and the top five combined account for 67.9% of all records. That concentration means a small number of organizations control most of the foundational masking and protease-activation claims, while the remaining ranked companies each hold comparatively few records. Anyone assessing freedom to operate in this field should start with the leading assignees rather than assume the field is fragmented.

Filing activity grew through the years that can be read reliably, rising from 16 records in 2021 to 21 in 2024, a 31% increase, after an earlier peak of 72 records in 2022. The apparent drop in 2025 and 2026 numbers is not a real slowdown — patent publication typically lags filing by around 18 months, so the most recent one to two years in any dataset are always undercounted. The trend through 2024, the last complete year, points to sustained rather than declining interest.