Design, Synthesis, and Structure-Activity Relationships of Novel Piperidine-Fused Imidazolone ClpP Activators as Potential Anti-Cancer Agents.

Caseinolytic protease P (ClpP) is essential for maintaining mitochondrial protein homeostasis, and its activation has emerged as an attractive cancer therapeutic strategy. However, ONC201 is currently the only approved ClpP activator, and its low potency leads to high clinical doses, driving an urgent demand for highly potent agents. In this study, utilizing a ring-opening-based molecular simplification strategy, we identified a class of activators based on a novel piperidine-fused imidazolone scaffold. Through side-chain optimization, we ultimately obtained CLPP-3036 as a highly potent compound. CLPP-3036 exhibits nanomolar enzymatic potency (EC50 = 6.02 nM, 146-fold more potent than ONC201) and excellent antiproliferative activity (MV4-11 IC50 = 1.13 nM). Importantly, CLPP-3036 demonstrates significantly superior inhibitory activity compared to ONC201 across multiple hematologic and solid tumor cell lines, such as Raji cells (IC50 = 9.8 nM, nearly 1260-fold more potent). Furthermore, CLPP-3036 promotes the degradation of ClpP substrate proteins and effectively triggers apoptosis in MV4-11 cells. Collectively, CLPP-3036 is a potent piperidine-fused imidazolone ClpP activator and represents a promising lead compound worthy of further study.