{"entity":{"id":"hydrazone","kind":"term","name":"Acid-labile hydrazone (AcBut)","aka":["acid-cleavable linker"],"tldr":"The hydrazone linker is acid-sensitive and breaks in the lysosome's low pH. It was used in the calicheamicin ADCs, but is too leaky for most modern designs.","summary":"The acid-labile hydrazone linker, known as AcBut, breaks in the low pH of the lysosome and was the chemistry used in the calicheamicin ADCs. Hydrazones hydrolyse at pH 4 to 5 but are relatively unstable in plasma, and that leakiness contributed to the off-target toxicity of first-generation ADCs, which is why most modern designs avoid it. Gemtuzumab ozogamicin and inotuzumab ozogamicin use a hydrazone combined with a disulfide. The linker belongs to the Antibody-drug conjugate (ADC) technology and the Linker (ADC) term, is associated with the payload Calicheamicin, and is referenced by the drug record for Gemtuzumab ozogamicin.","asOf":"2026-09-09","wikipedia":"https://en.wikipedia.org/wiki/Hydrazone","links":[{"label":"Wikipedia","url":"https://en.wikipedia.org/wiki/Hydrazone"}],"tags":[],"related":["calicheamicin"],"cancers":[],"sections":[],"technologies":["adc"],"targets":[],"drugs":["gemtuzumab-ozogamicin"],"companies":[],"institutions":[],"pathways":[],"terms":["linker"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"category":"ADC chemistry"},"route":"/terms/hydrazone/","neighbours":{"term":[{"id":"calicheamicin","kind":"term","name":"Calicheamicin","route":"/terms/calicheamicin/"},{"id":"linker","kind":"term","name":"Linker (ADC)","route":"/terms/linker/"}],"technology":[{"id":"adc","kind":"technology","name":"Antibody-drug conjugate (ADC)","route":"/technologies/adc/"}],"drug":[{"id":"gemtuzumab-ozogamicin","kind":"drug","name":"Gemtuzumab ozogamicin","route":"/drugs/gemtuzumab-ozogamicin/"}]}}