SLCO1B3-SLCO1B7 is a readthrough transcript on chromosome 12 that encodes OATP1B3-1B7, a novel organic anion transporting polypeptide expressed in hepatocyte endoplasmic reticulum 1. The protein functions as a secondary active transmembrane transporter, facilitating sodium-independent organic anion transport including dehydroepiandrosterone-sulfate (DHEAS) 1. Multiple coding polymorphisms within the SLCO1B7 region significantly reduce DHEAS transport function without affecting transporter expression, with the linked haplotype (884A-1073G-1501C) completely abolishing transport activity 1. Clinically, SLCO1B3-SLCO1B7 variants are associated with clozapine-induced agranulocytosis and neutropenia (CIAG), a serious adverse effect limiting use of this antipsychotic for treatment-resistant schizophrenia 2. The genetic variant rs149104283 is recognized as an independent risk allele; when combined with HLA-DQB1 and HLA-B variants, it increases CIAG detection sensitivity from 36.0% to 43.0% and improves pharmacogenomic-guided treatment cost-effectiveness 3. These findings establish SLCO1B3-SLCO1B7 as clinically relevant for predicting clozapine toxicity and support preemptive genetic testing to enhance treatment safety.