Multiparameter optimization of broad-spectrum thymidine phosphorylase inhibition, ADMET properties, molecular docking, and DFT screening of novel pyrazole-based thiadiazole/thiazole derivatives

Thymidine phosphorylase (TP) is a key enzyme involved in pyrimidine nucleoside metabolism and plays a significant role in angiogenesis, tumor progression, and metastasis. In this study, we synthesized 12 pyrazole-based thiadiazole and thiazole derivatives and evaluated their <i>in vitro</i> TP inhibitory activity. The compounds exhibited IC₅₀ values ranging from 36.67 ± 3.50 μM to 61.23 ± 3.20 μM, with several derivatives showing comparable or superior activity to the standard inhibitor 7-deazaxanthine (IC₅₀ = 38.68 ± 1.12 μM). Structure-activity relationship (SAR) analysis revealed that electron-withdrawing halogen substituents on the aromatic ring enhanced TP inhibition, likely due to increased binding affinity at the TP active site. Molecular docking studies highlighted interactions, such as hydrogen bonding, π-π stacking, and hydrophobic interactions, which support the observed inhibitory activity. Density Functional Theory (DFT) studies revealed electronic properties consistent with the observed activity, showing that compounds with smaller energy gaps exhibited higher reactivity. These findings suggest that pyrazole-based thiadiazole/thiazole hybrids are lead candidates for the development of novel TP inhibitors with anticancer applications.