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CELLULAR AND MOLECULAR

Mediation of Highly Concentrative Uptake of Pregabalin by L-Type Amino Acid Transport in Chinese Hamster Ovary and Caco-2 Cells

Departments of Molecular Sciences (T.Z.S.), Pharmacology (M.L.W.), and Pharmacokinetics, Dynamics, and Metabolism (M.R.F.), Pfizer Global Research and Development, Ann Arbor, Michigan

Pregabalin (PGB) is a novel drug under development for the treatment of epilepsy, neuropathic pain, fibromyalgia, and generalized anxiety disorder. In this study, we investigated PGB transport in rats, mammalian cell lines, and Xenopus laevis oocytes. In contrast to gabapentin (GBP), PGB absorption in rats showed unique linear pharmacokinetics. PGB entered CHO and Caco-2 cells predominately via Na⁺-independent processes. Uptake of PGB was mutually exclusive with leucine, GBP and 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid, the substrates preferential for system L. The preloaded PGB in CHO cells was exchangeable with leucine, but at a lower exchange rate than that of leucine and GBP. Dixon plots showed competitive inhibition of leucine uptake by PGB, with a K_i value very close to the K_m value for PGB uptake (377 versus 363 µM). At an extracellular concentration of 300 µM, the intracellular PGB concentration in CHO cells reached 1.5- and 23-fold higher than that of GBP and leucine, respectively. In contrast, at clinically relevant concentrations, PGB seemed not to interact with GABA transport in GAT1, GAT2, and GAT3 cell lines, system y⁺, b^0,+, B^0,+, and B⁰ transport activities in Caco-2 and NBL-1 cells, and the b^0,+-like transport activity in rBAT cRNA-injected X. laevis oocytes. Taken together, these results suggest that L-type transport is the major transport route for PGB and GBP uptake in mammalian cells. The differential affinity of PGB and GBP at L-type system leads to more concentrative accumulation of PGB than GBP, which may facilitate PGB transmembrane absorption in vivo.

Address correspondence to: Dr. Ti-Zhi Su, Department of Molecular Science, Pfizer Global Research and Development, 2800 Plymouth Road, Ann Arbor, MI 48105. E-mail: ti-zhi.su{at}pfizer.com

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