Phenylacetamide derivatives P10, P15, P21 potently inhibit STAT3 dimerization, showing selectivity over DNA binding

The Signal Transducer and Activator of Transcription 3 (STAT3) is a pivotal transcription factor within the JAK-STAT signaling pathway, widely recognized as a compelling anti-cancer drug target. Despite its critical role in cell proliferation, survival, and immune response, including its dysregulation in psoriasis and spinal cord injury (from domain context), no direct STAT3 inhibitors have yet achieved clinical approval. Current drug development strategies primarily focus on targeting the STAT3 SH2 domain to prevent dimerization or the DNA-binding domain to block gene transcription, highlighting a significant unmet need for selective and potent inhibitors.

Researchers designed and synthesized a series of novel compounds featuring a phenylacetamide core, subsequently evaluating their biological activity against STAT3. Two distinct fluorescence polarization (FP) assays were employed: a STAT3:DNA FP assay to quantify inhibition of STAT3's DNA-binding potential, and a STAT3:phosphopeptide FP assay to assess the abrogation of STAT3 dimerization. Additionally, molecular docking simulations were performed to predict the binding modes and interactions of the most potent compounds within the STAT3 protein structure.

The phenylacetamide derivatives demonstrated a clear propensity to inhibit STAT3 dimerization rather than its DNA-binding activity, indicating selectivity for the STAT3 SH2 domain. Among the synthesized compounds, P10, P15, and P21 emerged as particularly potent inhibitors of STAT3 dimerization. Their FP-determined IC50 values were approximately 15.6 μM for P10, 29.4 μM for P15, and 6.49 μM for P21, showcasing significant inhibitory strength. Molecular docking analysis suggested that P10, P15, and P21 bind specifically between the Linker and SH2 domains of STAT3, forming potential hydrogen bonds within this binding pocket. Predictions of drug-likeness and physiochemical properties further support the potential of these three compounds for future investigation.

Compound P21 exhibited the highest potency, inhibiting STAT3 dimerization with an IC50 of approximately 6.49 μM.