*Article* **New** *N***-Substituted-1,2,4-triazole Derivatives of Pyrrolo[3,4-***d***]pyridazinone with Significant Anti-Inflammatory Activity—Design, Synthesis and Complementary In Vitro, Computational and Spectroscopic Studies**


**Abstract:** Regarding that the chronic use of commonly available non-steroidal and anti-inflammatory drugs (NSAIDs) is often restricted by their adverse effects, there is still a current need to search for and develop new, safe and effective anti-inflammatory agents. As a continuation of our previous work, we designed and synthesized a series of 18 novel *N*-substituted-1,2,4-triazole-based derivatives of pyrrolo[3,4-*d*]pyridazinone **4a-c-9a-c**. The target compounds were afforded via a convenient way of synthesis, with good yields. The executed cell viability assay revealed that molecules **4a-7a**, **9a**, **4b-7b**, **4c-7c** do not exert a cytotoxic effect and were qualified for further investigations. According to the performed in vitro test, compounds **4a-7a**, **9a**, **4b**, **7b**, **4c** show significant cyclooxygenase-2 (COX-2) inhibitory activity and a promising COX-2/COX-1 selectivity ratio. These findings are supported by a molecular docking study which demonstrates that new derivatives take position in the active site of COX-2 very similar to *Meloxicam*. Moreover, in the carried out in vitro evaluation within cells, the title molecules increase the viability of cells pre-incubated with the pro-inflammatory lipopolysaccharide and reduce the level of reactive oxygen and nitrogen species (RONS) in induced oxidative stress. The spectroscopic and molecular modeling study discloses that new compounds bind favorably to site II(m) of bovine serum albumin. Finally, we have also performed some in silico pharmacokinetic and drug-likeness predictions. Taking all of the results into consideration, the molecules belonging to series **a** (**4a-7a**, **9a**) show the most promising biological profile.

**Keywords:** cyclooxygenase; 1,2,4-triazole; pyridazinone; SAR; molecular docking; anti-inflammatory activity; antioxidant activity; ADME
