Discovery of a novel diphenyl piperidinone-naphthoquinone STAT3 inhibitor as chemoimmunotherapeutic agent

A series of novel diarylpiperidinone-naphthoquinone hybrids were designed and synthesized. Among these, compound 8d emerged as a potent inhibitor targeting the STAT3 SH2 domain. In vitro evaluation using Cell Counting Kit-8 (CCK-8) assay demonstrated the superior antiproliferative activity of 8d (IC₅₀ = 0.26-0.67 μM) against multiple Cancer cell lines, including SW480, MDA-MB-231, A549, and cisplatin-resistant A549/DDP cells. Compound 8d exhibited 2.7- to 192-fold enhanced potency compared to precursor compounds 4 and 3d, as well as the clinical agents oxaliplatin, doxorubicin, and cisplatin. In vivo antitumor studies in a CT26 tumor-bearing BALB/c mouse model revealed that compound 8d elicited 63.17 % tumor growth inhibition (TGI) at 5 mg/kg. This efficacy significantly surpassed that of precursor compounds 4 (29.60 % TGI) and 3d (31.12 % TGI), as well as their combination (37.06 % TGI). Notably, at 10 mg/kg, 8d achieved 75.62 % TGI, comparable to oxaliplatin (OXA; 76.22 % TGI), while exhibiting superior tolerability. Mechanistic studies revealed that 8d directly binds to the STAT3 SH2 domain, thereby inhibiting STAT3 activation (phosphorylation, p-STAT3) and its downstream signaling. These perturbations subsequently triggered Reactive Oxygen Species (ROS) generation, downregulated Bcl-2 expression, collapsed mitochondrial membrane potential (ΔΨm), inhibited Glutathione Peroxidase 4 (GPX4) activity, and elevated lipid peroxidation (LPO) levels, ultimately inducing both Apoptosis and Ferroptosis in tumor cells. These effects synergistically induced immunogenic cell death (ICD), promoting dendritic cell (DC) maturation and enhancing CD8+ T lymphocyte infiltration into the tumor microenvironment (TME), thereby potentiating antitumor immunity. Collectively, 8d exerted potent antitumor effects through combined chemotherapeutic and immunotherapeutic mechanisms, highlighting its potential as a promising candidate for Cancer therapy.

Chemoimmunotherapy; Diphenyl piperidinone; Naphthoquinone; STAT3 inhibitor.