Design, Synthesis, and Biological Evaluation of Novel Activators of Human Caseinolytic Protease P with a Pyrazololactam Scaffold

Based
on D9, a previously reported small-molecule
agonist of hClpP, a class of novel hClpP activators with a pyrazololactam
scaffold was designed and synthesized. Detailed structure–activity
relationship studies (SAR) for this class of compounds led to the
identification of compound 24, which potently activated
recombinant hClpP in a proteolysis assay with submicromolar potency
and effectively inhibited cell growth in a broad panel of cancer cell
lines with IC50 values of 0.1–1 μM. Mechanism
studies indicated that compound 24 can potently bind
to cellular hClpP, effectively promote the formation of the hClpP
tetradecamer, efficiently induce the degradation of hClpP substrates,
robustly upregulate the expression of ATF4, and strongly induce apoptosis
in Molm13 and MDA-MB-231 cells. More importantly, compound 24 has promising PK and safety profiles, and showed potent antitumor
activity in a murine MDA-MB-231 xenograft model.