Brain Penetration of WEB 2086 (Apafant) and Dantrolene in Mdr1a (P-Glycoprotein) and Bcrp Knockout Rats

Abstract

Transporter gene knockout rat models are attracting increasing interest for mechanistic studies of new drugs as transporter substrates or inhibitors in vivo. However, limited data are available on the functional validity of such models at the blood-brain barrier. Therefore, the present study evaluated Mdr1a [P-glycoprotein (P-gp)], Bcrp, and combined Mdr1a/Bcrp knockout rat strains for the influence of P-gp and breast cancer resistance protein (BCRP) transport proteins on brain penetration of the selective test substrates [ .5-fold in double Mdr1a/Bcrp knockouts, and 7.3-fold in zosuquidar-treated wild-type rats, but was unchanged in Bcrp knockout rats. Mean BPR of dantrolene increased 3.3-fold in Bcrp knockouts and 3.9-fold in double Mdr1a/Bcrp knockouts compared with wild type, but was unchanged in the Mdr1a knockouts. The human intestinal CaCo-2 cell bidirectional transport system in vitro confirmed the in vivo finding that [ 14 C]WEB 2086 is a substrate of P-gp but not of BCRP. Therefore, Mdr1a, Bcrp, and combined Mdr1a/Bcrp knockout rats provide functional absence of these efflux transporters at the blood-brain barrier and are a suitable model for mechanistic studies on the brain penetration of drug candidates.

Differential role of P-glycoprotein and breast cancer resistance protein in drug distribution into brain, CSF and peripheral nerve tissues in rats

“…It was previously reported that dantrolene brain exposure increased 3-and 6-fold in Abcg2(À/À) mice following an IV bolus dose or IV infusion, respectively (Enokizono et al, 2008;Xiao et al, 2012). In the Abcg2(À/À) rats, C b /C p of dantrolene increased 2-fold in our study and 3-fold in the study recently reported by Fuchs et al (2014). This small difference in dantrolene brain exposure observed between rats and mice was probably due to experimental variations.…”

The Use of Transporter Probe Drug Cocktails for the Assessment of Transporter-Based Drug–Drug Interactions in a Clinical Setting—Proposal of a Four Component Transporter Cocktail

“…). It was confirmed that ZSQ (1 μM) and FTC (1 μM) are selective P‐gp and BCRP inhibitors, respectively, and MK‐571 (50 μM) is a nonselective inhibitor of P‐gp and BCRP . Using these three chemical inhibitors, the contribution of P‐gp, BCRP, and other transporters that potentially could be inhibited by MK‐571 was evaluated.…”

Peripherally Selective Cannabinoid 1 Receptor (CB1R) Agonists for the Treatment of Neuropathic Pain

“…34 Given the very low aqueous solubility of PRCBs, their relative lack of BBB permeability suggests that they may be substrates for active drug efflux transporters such as P-glycoprotein or multidrug resistance proteins. Future studies using selective inhibitors of such transporters (e.g., ref 35) or transporter knockout rodents (e.g., ref 36) should help identify precisely the efflux transporters for which PRCBs serve as substrates.…”