Restricted brain penetration of the tyrosine kinase inhibitor erlotinib due to the drug transporters P-gp and BCRP.
OBJECTIVE
Erlotinib (Tarceva®, OSI-774) is a small molecule inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase. As high-grade gliomas frequently show amplification, overexpression and/or mutation of EGFR, this drug has been tested in several clinical trials with glioblastoma patients, but unfortunately, with little success. As erlotinib is a known substrate of P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) we have investigated the effect of these ABC-transporters on the brain penetration of erlotinib.


METHODS
Erlotinib (50 mg/kg) was given by i.p. administration to wild-type (WT), Mdr1ab(-/-) (single P-gp knockout), Bcrp1(-/-) (single Bcrp1 knockout) and Mdr1ab(-/-)Bcrp1(-/-) (compound P-gp and Bcrp1 knockout) mice. Drug levels in plasma and tissues were determined by reversed-phase high-performance liquid chromatography.


RESULTS
Relative to Mdr1ab(-/-)Bcrp1(-/-) mice that are deficient for both drug transporters, the area under the concentration time curve in brain tissue (AUC)(brain) of erlotinib decreased significantly by 1.6-fold in Mdr1ab(-/-) mice where Bcrp1 is present (49.6 ± 3.95 versus 31.1 ± 1.7, μg/g*h; P < 0.01). In Bcrp1(-/-) mice, were P-gp is present, a more pronounced 3.8-fold decrease to 13.0 ± 0.70, μg/g*h (P < 0.01) was observed, which is close to the 4.5-fold decrease in the AUC(brain) of erlotinib found in WT mice where both drug transporters are present (11.0 ± 1.35, P < 0.01). The plasma clearance of erlotinib was similar in mice deficient for P-gp and/or Bcrp1 compared with wild-type mice. In all other tissues the differences between the genotypes were negligible.


CONCLUSIONS
Both P-gp and Bcrp1 reduce the brain penetration of erlotinib. Although P-gp appears to be the most effective factor limiting the brain penetration of erlotinib, the highest brain accumulation was observed when Bcrp1 was also absent. Strategies to inhibit P-gp/BCRP in patients to improve delivery of (novel molecular-targeted) substrate agents, such as erlotinib, to the brain may be required for treatment of intracranial malignancies.
Department of Clinical Chemistry, The Netherlands Cancer Institute, Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
Nienke A
NA
de Vries
Tessa
T
Buckle
Jin
J
Zhao
Jos H
JH
Beijnen
Jan H M
JH
Schellens
Olaf
O
van Tellingen
D018435:ATP Binding Cassette Transporter, Subfamily B / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D019540:Area Under Curve; D001812:Blood-Brain Barrier / Q000378:metabolism*; D002199:Capillary Permeability; D002851:Chromatography, High Pressure Liquid; D056148:Chromatography, Reverse-Phase; D000069347:Erlotinib Hydrochloride; D005260:Female; D007274:Injections, Intraperitoneal; D008657:Metabolic Clearance Rate; D051379:Mice; D018345:Mice, Knockout; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D011799:Quinazolines / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D014018:Tissue Distribution; D000097202:ATP-Binding Cassette Sub-Family B Member 4
D018435:ATP Binding Cassette Transporter, Subfamily B; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000970:Antineoplastic Agents; D000069347:Erlotinib Hydrochloride; D047428:Protein Kinase Inhibitors; D011799:Quinazolines; D000097202:ATP-Binding Cassette Sub-Family B Member 4; C501412:Abcg2 protein, mouse; C095122:multidrug resistance protein 3