Drug-to-antibody ratio (DAR)

The drug-to-antibody ratio, or DAR, is the number of payload molecules attached to each antibody in an antibody-drug conjugate, typically between 2 and 8. A higher DAR delivers more drug per binding event, as with T-DXd at roughly 8 and sacituzumab at about 7.6, but it increases hydrophobicity, aggregation and clearance unless hydrophilic linkers compensate. Site-specific conjugation gives a homogeneous DAR, which improves pharmacokinetics. The term belongs to the Antibody-drug conjugate (ADC) and Site-specific conjugation & linker chemistry technologies, is picked up by the Hydrophilic next-generation linkers term, and appears in the DESTINY-Breast03 paper and the idea on ADC dose and schedule optimisation trials.