PF-04859989

PF-04859989 is a potent, brain-penetrant, and irreversible small molecule inhibitor of kynurenine aminotransferase 2 (KAT2), the primary enzyme responsible for the synthesis of kynurenic acid (KYNA) in the mammalian brain. KYNA acts as an endogenous antagonist at both the N-methyl-D-aspartate (NMDA) receptor and the alpha-7 nicotinic acetylcholine receptor (α7nAChR). Elevated levels of KYNA have been implicated in the pathophysiology of psychiatric disorders, including schizophrenia and bipolar disorder, where they are thought to contribute to cognitive deficits and sleep architecture disturbances. Developed by Pfizer, PF-04859989 was investigated in Phase 1 clinical trials to evaluate its safety and ability to modulate brain KYNA levels. While it is no longer prominently featured in active clinical development pipelines, it remains a widely utilized pharmacological tool in preclinical research for exploring the kynurenine pathway's role in neurobiology.