Aryl Sulfate is a Useful Motif for Conjugating and Releasing Phenolic Molecules: Sulfur Fluorine Exchange Click Chemistry Enables Discovery of Ortho-Hydroxy-Protected Aryl Sulfate Linker

A new self-immolative linker motif, Ortho Hydroxy-Protected Aryl Sulfate (OHPAS), was devised, and OHPAS-containing antibody drug conjugates (ADC) were tested in vitro and in vivo. Conveniently synthesized using Sulfur Fluorine Exchange (SuFEx) chemistry, it is based structurally on diaryl sulfate, with one aryl acting as a payload and the other as a self-immolative sulfate unit having a latent phenol function at the ortho position. The chemically stable OHPAS linker was stable in plasma samples from 5 different species, yet it can release the payload molecule smoothly upon chemical or biological triggering. The payload release proceeds via intramolecular cyclization, producing a cyclic sulfate coproduct that eventually hydrolyzes to a catechol monosulfate. A set of OHPAS-containing ADCs based on Trastuzumab were prepared with a drug to antibody ratio of ∼2, and were shown to be cytotoxic in 5 different cancer cell lines in vitro and dose-dependently inhibited tumor growth in a NCI-N87 mouse xenograft model. We conclude that OHPAS conjugates will be of considerable use for delivering phenol-containing payloads to tissues targeted for medical intervention.