Cancer Therapy: Preclinical Role of ATP-Binding Cassette and Solute Carrier Transporters in Erlotinib CNS Penetration and Intracellular Accumulation

Purpose: To study the role of drug transporters in central nervous system (CNS) penetration and cellular accumulation of erlotinib and its metabolite, OSI-420. Experimental Design: After oral erlotinib administration to wild-type and ATP-binding cassette (ABC) transporter-knockout mice (Mdr1a/b / , Abcg2 / , Mdr1a/b / Abcg2 / , and Abcc4 / ), plasma was collected and brain extracellular fluid (ECF) was sampled using intracerebral microdialysis. A pharmacokinetic model was fit to erlotinib andOSI-420 concentration–time data, and brain penetration (PBrain) was estimated by the ratio of ECF-to-unbound plasma area under concentration–time curves. Intracellular accumulation of erlotinib was assessed in cells overexpressing human ABC transporters or SLC22A solute carriers. Results: PBrain in wild-type mice was 0.27 0.11 and 0.07 0.02 (mean SD) for erlotinib and OSI420, respectively. Erlotinib and OSI-420 PBrain in Abcg2 / and Mdr1a/b / Abcg2 / mice were significantly higher than in wild-type mice.Mdr1a/b / mice showed similar brain ECF penetration as wild-type mice (0.49 0.37 and 0.04 0.02 for erlotinib and OSI-420, respectively). In vitro, erlotinib and OSI-420 accumulation was significantly lower in cells overexpressing breast cancer resistance protein (BCRP) than in control cells. Only OSI-420, not erlotinib, showed lower accumulation in cells overexpressing P-glycoprotein (P-gp) than in control cells. The P-gp/BCRP inhibitor elacridar increased erlotinib and OSI-420 accumulation in BCRP-overexpressing cells. Erlotinib uptake was higher in OAT3and OCT2transfected cells than in empty vector control cells. Conclusion: Abcg2 is the main efflux transporter preventing erlotinib and OSI-420 penetration in mouse brain. Erlotinib and OSI-420 are substrates for SLC22A family members OAT3 and OCT2. Our findings provide amechanistic basis for erlotinib CNS penetration, cellular uptake, and effluxmechanisms. Clin Cancer Res; 17(1); 89–99. 2010 AACR.