1CAY10649, a thiazolinone compound, directly inhibits 5-lipoxygenase (5-LO) product formation in intact polymorphonuclear leukocytes (PMNL) with an IC50 value of 0.28 μM and in a soluble fraction of an S100 PMNL cell lysate with an IC50 value of 0.09 μM, following stimulation by calcium and arachidonic acid. This activity highlights its potential in mitigating inflammatory responses by targeting the biosynthesis of leukotrienes, substances implicated in various inflammatory processes such as neutrophil chemotaxis, increased vascular permeability, and smooth muscle contraction.