Preclinical characterization of AMPA receptor potentiator TAK‐137 as a therapeutic drug for schizophrenia

The downregulation of the glutamate system may be involved in positive, negative, and cognitive symptoms of schizophrenia. Through enhanced glutamate signaling, the activation of the α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole‐propionic acid (AMPA) receptor, an ionotropic glutamate receptor, could be a new therapeutic strategy for schizophrenia. TAK‐137 is a novel AMPA receptor potentiator with minimal agonistic activity; in this study, we used rodents and nonhuman primates to assess its potential as a drug for schizophrenia. At 10 mg kg(−1) p.o., TAK‐137 partially inhibited methamphetamine‐induced hyperlocomotion in rats, and at 3, 10, and 30 mg kg(−1) p.o., TAK‐137 partially inhibited MK‐801‐induced hyperlocomotion in mice, suggesting weak effects on the positive symptoms of schizophrenia. At 0.1 and 0.3 mg kg(−1) p.o., TAK‐137 significantly ameliorated MK‐801‐induced deficits in the social interaction of rats, demonstrating potential improvement of impaired social functioning, which is a negative symptom of schizophrenia. The effects of TAK‐137 were evaluated on multiple cognitive domains—attention, working memory, and cognitive flexibility. TAK‐137 enhanced attention in the five‐choice serial reaction time task in rats at 0.2 mg kg(−1) p.o., and improved working memory both in rats and monkeys: 0.2 and 0.6 mg kg(−1) p.o. ameliorated MK‐801‐induced deficits in the radial arm maze test in rats, and 0.1 mg kg(−1) p.o. improved the performance of ketamine‐treated monkeys in the delayed matching‐to‐sample task. At 0.1 and 1 mg kg(−1) p.o., TAK‐137 improved the cognitive flexibility of subchronic phencyclidine‐treated rats in the reversal learning test. Thus, TAK‐137‐type AMPA receptor potentiators with low intrinsic activity may offer new therapies for schizophrenia.