In this study, we provide insight into the metabolic profile of a series of piperazin-1-ylpyridazines suffering from rapid in vitro intrinsic clearance in a metabolic stability assay using liver microsomes (e.g. compound 1 MLM/HLM t1/2 = 2/3 min). Aided by empirical metabolite identification and computational predictive models, we designed the structural modifications required to improve in vitro intrinsic clearance by more than 50-fold (e.g. compound 29 MLM/HLM t1/2 = 113/105 min).