Synthesis and biological evaluation of novel naproxen–phenacetin triazole hybrids as promising anti-inflammatory agents with enhanced gastrointestinal tolerability

Traditional nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit both COX-1 and COX-2 isoforms with limited selectivity, often resulting in gastrointestinal (GI) side effects. Compounds that preferentially inhibit COX-2 over COX-1 are believed to pose a lower ulcerogenic risk. To develop GI-safer and cost-effective anti-inflammatory agents, we designed hybrid molecules by combining naproxen and phenacetin with a 1,2,4-triazole-5-thione. The structures of synthesized compounds were confirmed via IR, ¹H/¹³C NMR, and HR-ESI-MS analyses. Among the compounds, ten inhibited COX-2 with IC₅₀ ≤ 0.56 μM, and five exhibited high selectivity (SI ≥ 100). Compounds 46 (IC₅₀ = 0.16 μM, SI = 2.36), 55 (0.19 μM, SI = 2.27), and 59 (0.21 μM, SI = 1.65) demonstrated potency comparable to celecoxib. Three selected compounds were further evaluated in vivo using a carrageenan-induced paw oedema model and for acute gastric toxicity in Swiss mouse (n = 6; Ethics No. 2024/11 08). Orally administered compounds 55 and 64 (20 mg/kg) reduced paw oedema by 61 % and 52 %, respectively, similar to indomethacin (52 %), without causing visible gastric lesions (lesion score ∼ 2 vs. 5 for indomethacin). Molecular docking studies of the active compounds revealed the formation of stable hydrogen bonds with His90 and Arg513 within the COX-2 side pocket, similar to the binding pattern observed in selective COX-2 inhibitors. In silico ADME assessments via SwissADME and PreADMET indicated that these compounds meet Lipinski's rule of five criteria, possess optimal polar surface area and Caco-2 permeability, and show minimal risk for local gastric irritation, suggesting promising oral bioavailability. Overall, the 1,2,4-triazole-thione–naproxen/phenacetin hybrids represent promising lead candidates for the development of GI-safer NSAIDs. Compounds 55 and 64, in particular, merit further optimization and long-term safety evaluation.