Azide-PEG3-Val-Cit-PAB-MMAF is an enzyme-cleavable ADC linker featuring an azide, a hydrophilic PEG spacer, a Val-Cit-PAB dipeptide, and an MMAF warhead. Azides are click chemistry groups which readily react with terminal alkynes or strained cyclooctynes. The Val-Cit-PAB is cleaved by cellular proteases for efficient release of the MMAF payload to the cell.