Impact of ABCC2 genotype on antiepileptic drug response in Caucasian patients with childhood epilepsy.

BACKGROUND

Antiepileptic treatment response has been suggested to be modulated by genetic polymorphisms of drug efflux transporters, in particular ABCB1. Recently, we found a significant association of ABCC2 -24C>T with nonresponse, primarily in the context of generalized epilepsy. Moreover, ABCC2 1249G>A was reported to alter transmembranal carbamazepine transport. Therefore, we aimed to confirm the association of ABCC2 variants with pharmacotherapy-resistance in Caucasians mainly affected by partial epilepsy.

PATIENTS AND METHODS

A total of 208 patients (114 male; age: 11.3±5.9 years) were genotyped for three putatively functionally relevant polymorphisms of ABCC2 (-24C>T, 1249G>A, 3972C>T). Genotype and haplotype frequencies were compared between responders and nonresponders to first-line antiepileptic treatment.

RESULTS

Carriers of the ABCC2 1249G>A variant (417V>I) were more frequent among responders [odds ratio (OR)=2.68 (1.25-5.78); P=0.010]. This association remained significant after adjusting for age, sex and seizure type, [OR=2.88 (1.23-6.73); P=0.015]. The impact of 1249G>A was more pronounced among 64 patients receiving carbamazepine or oxcarbazepine (P=0.005), but nonsignificant in patients receiving other anticonvulsants. ABCC2 -24C>T and 3972C>T showed lack of association to therapy response. Haplotype analyses revealed that haplotype H2 containing solely the 1249A variant allele was more frequent in the responder group [OR=2.98 (1.38-6.44); P=0.004].

DISCUSSION

These data argue for a greater probability of antiepileptic drug response among carriers of the ABCC2 1249A variant that is associated with reduced carbamazepine transport. Although we could not confirm an impact of ABCC2 -24C>T, these results suggest that ABCC2 genotype may also modulate the response to anticonvulsants besides the extensively studied ABCB1 (P-glycoprotein).