Abstract 1535: Development of a fluorescent analog of BCR-ABL kinase inhibitor, Tasigna® (AMN-107, nilotinib) to study its interaction with ABC drug transporters
Authors: Shukla Suneet , Skoumbourdis Amanda P. , Wu Chung-Pu , Hartz Anika M.s. , Bauer Björn , Thomas Craig J. , Ambudkar Suresh V. 
Published: February 2011

Abstract
Development of a fluorescent analog of BCR-ABL kinase inhibitor, Tasigna® (AMN-107, nilotinib) to study its interaction with ABC drug transporters
Tasigna® (AMN107, nilotinib) is a recently approved BCR-ABL kinase inhibitor for the treatment of drug-resistant chronic myelogenous leukemia (CML). One possible mechanism for the development of resistance to Tasigna could be the active efflux by ATP binding cassette (ABC) drug transporters. The literature regarding tyrosine kinase inhibitors being effluxed by two major ABC drug transporters, P-glycoprotein (Pgp) and ABCG2 is contradictory. We report here synthesis of a fluorescent derivative of Tasigna, BODIPY® FL Tasigna, which can be used as a probe in in vivo and in vitro assays to monitor the levels, localization and activity of this drug. BODIPY® FL Tasigna inhibited the BCR-ABL kinase activity in K562 cells suggesting that the fluorescent derivative was active as parent drug in inhibiting the target kinases. BODIPY® FL Tasigna was effluxed by Pgp- and ABCG2-expressing cultured cell lines and was also demonstrated to be actively pumped out in an ex vivo blood-brain barrier model which is well-known to physiologically express both Pgp and ABCG2. This transport of BODIPY® FL Tasigna was inhibited in both brain capillaries and cultured cells by 5 μM PSC833 or FTC, which are specific inhibitors of Pgp and ABCG2, respectively. In addition, Tasigna also inhibited the brain uptake of Pgp and ABCG2 substrates, NBD-CsA (IC50: 3.46 µM) and Bodipy-prazosin IC50: 93.2 nM), respectively in brain capillaries suggesting that it may influence the activity of blood brain barrier function in CML patients. In biochemical assays similar to Tasigna, BODIPY® FL Tasigna, interacted at the substrate binding pocket of the transporter, as was evident from its inhibitory effect on [125I]-Iodoarylazidoprazosin (IAAP) binding to Pgp and ABCG2 and by stimulation of Pgp- and ABCG2-mediated ATP hydrolysis. A direct evidence of reduced efficacy of Tasigna in ABC transporters expressing cells was demonstrated by the fact that Tasigna was 4 to 5-fold less effective at inhibiting the phosphorylation of Crkl (P-Crkl), its target in CML cells, in Pgp-expressing and ABCG2-expressing K562 cells. Taken together, these data for the first time provide direct evidence that Tasigna is a transport substrate of the major ABC drug transporters Pgp and ABCG2, which may be linked to the development of resistance to this drug in CML patients. In addition, we propose that BODIPY® FL Tasigna can be used as an in vivo probe to study Tasigna in imaging and other preclinical studies.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1535.