Quetiapine hemifumarate (ICI-204636), an atypical antipsychotic, is used in the treatment of bipolar I mania, schizophrenia, bipolar II depression, bipolar I depression.

Quetiapine alters the neurotransmitter norepinephrine in the brain's limbic system and the expression of c-fos. It also exhibits antipsychotic activity, diminishing the tendency to induce extrapyramidal symptoms and persistently increase prolactin levels. Its effectiveness in behavioral and biochemical assays mirrors that of clozapine, suggesting it may possess neuroprotective properties.

Quetiapine has an affinity for dopamine-2 receptors similar to that of clozapine, and it exhibits comparable affinity for various neurotransmitter receptors, including serotonin, histamine, dopamine, and adrenergic receptors.

CDK activity assays: CDK assays for IC50 determinations and kinetic evaluation are performed in 96-well filter plates. All CDK-cyclin kinase complexes are expressed in insect cells through baculovirus infection and purified. The substrate for the assays is a fragment (amino acids 792–928) of pRb fused to GST (GST?RB-Cterm). The total reaction volume is 0.1 mL containing a final concentration of 20 mM Tris-HCl, pH 7.4, 50 mM NaCl, 1 mM dithiothreitol, 10 mM MgCl2 25 μM ATP (for CDK4-cyclin D1, CDK6-cyclin D2, and CDK6-cyclin D3) containing 0.25 μCi of [γ-32P]ATP, 20 ng of enzyme, 1 μg of GST?RB-Cterm, and appropriate dilutions of inhibitor. All components except the [γ-32P]ATP are added to the wells, and placed on a plate mixer for 2 min. The reaction is started by adding the [γ-32P]ATP, and incubated at 25℃ for 15 min. The reaction is terminated by addition of 0.1 mL of 20% trichloroacetic acid, and the plate is kept at 4?℃ for at least 1 hr to allow the substrate to precipitate. The wells are then washed five times with 0.2 mL of 10% trichloroacetic acid, and radioactive incorporation is determined with a β plate counter.