Benzothiazolyl and Benzoxazolyl Hydrazones Function as Zinc Metallochaperones to Reactivate Mutant p53

We identified a set of thiosemicarbazone
(TSC) metal ion chelators
that reactivate specific zinc-deficient p53 mutants using a mechanism
called zinc metallochaperones (ZMCs) that restore zinc binding by
shuttling zinc into cells. We defined biophysical and cellular assays
necessary for structure–activity relationship studies using
this mechanism. We investigated an alternative class of zinc scaffolds
that differ from TSCs by substitution of the thiocarbamoyl moiety
with benzothiazolyl, benzoxazolyl, and benzimidazolyl hydrazones.
Members of this series bound zinc with similar affinity and functioned
to reactivate mutant p53 comparable to the TSCs. Acute toxicity and
efficacy assays in rodents demonstrated C1 to be significantly
less toxic than the TSCs while demonstrating equivalent growth inhibition.
We identified C85 as a ZMC with diminished copper binding
that functions as a chemotherapy and radiation sensitizer. We conclude
that the benzothiazolyl, benzoxazolyl, and benzimidazolyl hydrazones
can function as ZMCs to reactivate mutant p53 in vitro and in vivo.