Placental alkaline phosphatase (PLAP) is highly expressed in primate placental tissue. Its biological function and relevance are still unknown, but PLAP-like enzymes are detected in serum of patients with primary testicular tumors, in particular seminoma and other cancers. Consequently, the identification of PLAP-specific inhibitors with selectivity over tissue non-specific alkaline phosphatase (TNAP) and intestinal alkaline phosphatase (IAP) may provide the necessary tools to characterize its biological role. Currently, inhibitors of PLAP lack either potency or selectivity. The small molecule probe ML095 (CID-25067483) is a biochemical inhibitor of PLAP, and will be useful to elucidate the key biological functions and natural substrates of human PLAP.