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Wagner, C C; Bauer, M; Karch, R; Feurstein, T; Kopp, S; Chiba, P; Kletter, K; Löscher, W; Müller, M; Zeitlinger, M; Langer, O (2009). A pilot study to assess the efficacy of tariquidar to inhibit P-glycoprotein at the human blood-brain barrier with (R)-11C-verapamil and PET. Journal of Nuclear Medicine, 50(12):1954-1961.

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Tariquidar, a potent, nontoxic, third-generation P-glycoprotein (P-gp) inhibitor, is a possible reversal agent for central nervous system drug resistance. In animal studies, tariquidar has been shown to increase the delivery of P-gp substrates into the brain by severalfold. The aim of this study was to measure P-gp function at the human blood-brain barrier (BBB) after tariquidar administration using PET and the model P-gp substrate (R)-(11)C-verapamil. METHODS: Five healthy volunteers underwent paired (R)-(11)C-verapamil PET scans and arterial blood sampling before and at 2 h 50 min after intravenous administration of tariquidar (2 mg/kg of body weight). The inhibition of P-gp on CD56-positive peripheral lymphocytes of each volunteer was determined by means of the (123)Rh efflux assay. Tariquidar concentrations in venous plasma were quantified using liquid chromatography/mass spectrometry. RESULTS: Tariquidar administration resulted in significant increases (Wilcoxon test for paired samples) in the distribution volume (DV, +24% +/- 15%) and influx rate constant (K(1), +49% +/- 36%) of (R)-(11)C-verapamil across the BBB (DV, 0.65 +/- 0.13 and 0.80 +/- 0.07, P = 0.043; K(1), 0.034 +/- 0.009 and 0.049 +/- 0.009, P = 0.043, before and after tariquidar administration, respectively). A strong correlation was observed between the change in brain DV after administration of tariquidar and tariquidar exposure in plasma (r = 0.90, P = 0.037). The mean plasma concentration of tariquidar achieved during the second PET scan (490 +/- 166 ng/mL) corresponded to 100% inhibition of P-gp function in peripheral lymphocytes. CONCLUSION: Tariquidar significantly increased brain penetration of (R)-(11)C-verapamil-derived activity due to increased influx. As opposed to peripheral P-gp function, central P-gp inhibition appeared to be far from complete after the administered tariquidar dose.


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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > University Hospital Zurich > Clinic and Policlinic for Internal Medicine
Dewey Decimal Classification:610 Medicine & health
Deposited On:15 Mar 2010 09:46
Last Modified:05 Apr 2016 13:54
Publisher:Society of Nuclear Medicine
Publisher DOI:10.2967/jnumed.109.063289
PubMed ID:19910428

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