Lu AF90103 (Compound 42e) is a methyl ester prodrug of compound 42d capable of penetrating the blood–brain barrier. Compound 42d acts as a partial agonist of the GluN1/GluN2B complex, exhibiting 24% efficacy, and has an EC 50 value of 78 nM. Lu AF90103 plays an important role in neuropsychiatric diseases research.