Dec 242013




206873-63-4 CAS NO

XR 9576;XR9576;D06008.

Molecular Weight (MW) 646.73






Xenova (Originator), QLT PhotoTherapeutics (Licensee)
Modulators of the Therapeutic Activity of Antineoplastic Agents, Multidrug Resistance Modulators, ONCOLYTIC DRUGS, P-Glycoprotein (MDR-1) Inhibitors

Tariquidar (XR9576) is a potent and selective noncompetitive inhibitor of P-glycoprotein with Kd of 5.1 nM, reverses drug resistance in MDR cell Lines. Phase 3.

Tariquidar (INN/USAN) is a P-glycoprotein inhibitor[1] undergoing research as an adjuvant against multidrug resistance in cancer.

Tariquidar is a P-glycoprotein inhibitor undergoing research as an adjuvant against multidrug resistance in cancer. Tariquidar non-competitively binds to the p-glycoprotein transporter, thereby inhibiting transmembrane transport of anticancer drugs. Inhibition of transmembrane transport may result in increased intracellular concentrations of an anticancer drug, thereby augmenting its cytotoxicity


The resistance of tumours to treatment with certain cytotoxic agents is an obstacle to the successful chemotherapeutic treatment of cancer patients. A tumour may acquire resistance to a cytotoxic agent used in a previous treatment. A tumour may also manifest intrinsic resistance, or cross-resistance, to a cytotoxic agent to which it has not previously been exposed, that agent being unrelated by structure or mechanism of action to any agent used in previous treatments of the tumour.

Analogously, certain pathogens may acquire resistance to pharmaceutical agents used in previous treatments of the diseases or disorders to which those pathogens give rise. Pathogens may also manifest intrinsic resistance, or cross resistance, to pharmaceutical agents to which they have not previously been exposed. Examples of this effect include multi-drug resistant forms of malaria, tuberculosis, leishmaniasis and amoebic dysentery. These phenomena are referred to collectively as multi-drug resistance (MDR).

The most common form of MDR is caused by over-production in the cell membrane of P-gp, a protein which is able to reduce the accumulation of drugs in cells by pumping them out. This protein has been shown to be a major cause of multidrug resistance in tumour cells (Beck, W. T. Biochem. Pharmacol, 1987, 36,2879-2887).

In addition to cancer cells, p-glycoprotein has been found in many normal human tissues including the liver, small intestine, kidney, and blood-brain endothelium. P-gps are localised to the secretory domains of the cells in all these tissues. This localisation suggests that P-gp may play a role in limiting the absorption of foreign toxic substances across biological barriers.

Consequently, in addition to their ability to increase the sensitivity of cancer cells to cytotoxic agents, P-gp inhibitors are expected to increase the net oral absorption of certain drugs and improve the transport of drugs through the blood-brain barrier. Indeed, administration of cyclosporin, a P-gp inhibitor, has been shown to increase the intestinal absorption of acebutolol and vinblastine in rats by 2.6 and 2.2-fold respectively (Tereo, T. et al. J. Pharm. Pharmacol, 1996, 48, 1083-1089), while mice deficient in mdr la P-gp gene exhibit up to 100-fold increased senstivity to the centrally neurotoxic pesticide ivermectin (Schinkel, A. H. et al Cell 1994, 77, 491-502). Besides increased drug levels in the brain, the P-gp deficient mice were shown to have elevated drug levels in many tissues and decreased drug elimination.

Disadvantages of drugs which have so far been used to modulate MDR, termed resistance modifying agents or RMAs, are that they frequently possess a poor pharmacokinetic profile and/or are toxic at the concentrations required for MDR modulation.

It has now been found that a series of anthranilic acid derivatives have activity as inhibitors of P-gp and may therefore be used in overcoming the multi-drug resistance of tumours and pathogens. They also have potential utility in improving the absorption, distribution, metabolism and elimination characteristics of certain drugs.

  1.  Robey RW, Shukla S, Finley EM, Oldham RK, Barnett D, Ambudkar SV, Fojo T, Bates SE. Inhibition of P-glycoprotein (ABCB1)- and multidrug resistance-associated protein 1 (ABCC1)-mediated transport by the orally administered inhibitor, CBT-1((R)). Biochem Pharmacol 2008;3:1302-12. PMID 18234154.
  2. Contino M, Zinzi L, Cantore M, Perrone MG, Leopoldo M, Berardi F, Perrone R, Colabufo NA. Activity-lipophilicity relationship studies on P-gp ligands designed as simplified tariquidar bulky fragments. Bioorg Med Chem Lett. 2013 Jul 1;23(13):3728-31. doi: 10.1016/j.bmcl.2013.05.019. Epub 2013 May 16. PubMed PMID: 23726026.
  3. Matthew D. Hall, Kyle R. Brimacombe, Matthew S. Varonka, Kristen M. Pluchino, Julie K. Monda, Jiayang Li, Martin J. Walsh, Matthew B. Boxer, Timothy H. Warren§, Henry M. Fales, and Michael M. Gottesman.Synthesis and Structure–Activity Evaluation of Isatin-β-thiosemicarbazones with Improved Selective Activity toward Multidrug-Resistant Cells Expressing P-Glycoprotein, J. Med. Chem., 2011, 54 (16), pp 5878–5889.

EP 0934276; GB 2334521; JP 2001502683; US 6218393; WO 9817648

Bioorg Med Chem Lett1999,9,(4):595




4,5-Dimethoxy-2-nitrobenzoic acid (I) was converted to the corresponding acid chloride (II) upon treatment with SOCl2, and this was further coupled to aniline (III), producing amide (IV). Catalytic hydrogenation of the nitro group of (IV) afforded amine (V). Acid chloride (VII) –obtained by chlorination of 3-quinolinecarboxylic acid (VI) with SOCl2– was then condensed with amine (V) to furnish the title diamide.





Figure US06218393-20010417-C00318



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