Kynurenine 3-monooxygenase (K3MO) lies on the kynurenine pathway, the major pathway for the catabolism of L-tryptophan. It converts kynurenine to 3-hydroxy kynurenine. Inhibition of K3MO is important in several neurological diseases and there is evidence that inhibition of K3MO could also be targeted for the prevention of multiple organ failure, secondary to acute pancreatitis. A structure activity relationship based upon the 1,2,4-oxadiazoles motif was carried out which revealed amide 207 as an inhibitor of P. fluorescens K3MO. Further structure activity relationships were developed based upon 207. This revealed 3,4-dichloro substitution in 235 and 245 as optimum for inhibition. Co-crystalisation of these inhibitors with P. fluorescens K3MO revealed their interactions with the enzyme. It also highlighted new, potential interactions between the inhibitors and K3MO. This led to the synthesis of 271 and 272, which were also potent inhibitors of K3MO. These amides were successfully co-crystalised with P. fluorescens K3MO. Further development of the amides followed, with amide 282 providing the most potent inhibitor of P. fluorescens K3MO to date (Kᵢ = 29.1 nM).