Relación Costo – Beneficio a lo largo de todo el proceso.

The selectivity towards A2780 cells over healthy cells for the pyridyl complexes followed the order19>18>20(SF = 2.1, 1.1 and 0.9, respectively). There is a trend in selectivity with greater stability of the pyridyl monodentate ligand resulting in a more selective complex. However, parent chloride complex 13 showed the best selectivity (SF = 3.9), despite containing the more labile chlorido ligand. Therefore, no enhancement in selectivity occurs by replacement of the chlorido ligand with the more stable pyridyl ligands, in contrast to iridium complex [(η5-CpxBiPh)Ir(2- PhPy)pyridine]PF6 vis-a-vis its chloride analogue (SF of 13 vs 4).17 This may

indicate that the presence of the CpxBiPhcapping ligand may play a role in governing the selectivity of the complex in parallel with the choice of monodentate ligand.

4.5

Conclusions

The importance of incorporating different monodentate ligands in chelated half- sandwich complexes is evident, with not only modulation of reactivity18,31 but also cell transport mechanisms being affected.16

In this Chapter, the monodentate ligands pyridine, 4-(dimethylamino)pyridine and 4-(trifluoromethyl)pyridine were used to replace the chlorido ligand in the potent complex [(η5-Cp*)Ir(2-(2ˈ-methylphenyl)pyridine)Cl] 13to investigate the effects on aqueous stability, reactivity towards potential biological targets and biological behaviour, with the aim of increasing potency and selectivity.

The pyridyl containing complexes 18-20 all exhibit enhanced stability in aqueous solution (76-85%) compared to parent chlorido complex13(28%) with respect to the release of the monodentate ligand. The rate at which the pyridyl ligands dissociate from the complexes are also dramatically slowed compared to the quickly reached

(within 15 min) equilibrium between Ir-Cl and Ir-OD2/OD for 13. Upon release of

the pyridyl ligand, the formation of the aqua complex13Adoes not appear to be the new species (as determined by 1H NMR spectroscopy), although the identity of the new species was not determined. The pyridyl complexes also resist conversion to the parent complex in concentrations of chloride mimicking biologically relevant conditions.

Complexes 18-20 show less binding to the guanine derivative 9-EtG (22-38%) than the chlorido complex (100%), and an electron-donating -NMe2 substituent on the

pyridine ligand enhances the stability towards reaction with GSH. The general trend in stability follows the order of 19 (Py-NMe2) > 18 (Py)> 20 (Py-CF3)> 13 (Cl-),

which correlates with the type of monodentate ligand present on the complex. The electron-donating -NMe2 group in 19 stabilises the bonding of the monodentate

ligand, whereas the electron-withdrawing –CF3group in20decreases the stability of

the bond. This shows that modulation of chemical reactivity at the monodentate site can be achieved by careful selection of the ligands used.

Although the products of the reaction with GSH are independent of the monondentate ligand, these complexes show the interesting property of promoting the oxidation of the sulfur atom in the presence of O2. The formation of glutathione

sulfenate and glutathione sulfinate adducts, which have been shown to be more labile than metal-SG adducts in Ru(II) arene systems,28may allow the complex to perform its antiproliferative mechanism without being deactivated.

Replacement of the chlorido ligand with pyridine derivatives can result in the enhancement of antiproliferative activity.17,18 In this work, the potency after 0 h recovery time is directly related to the stability of the Ir bond to the monodentate

apoptosis, potentially demonstrating cytostatic activity. The activity after 72 h recovery time shows no correlation with stability. The generation of ROS is likely to be a contributing factor to the antiproliferative activity of all of the complexes during the initial 24 h incubation. The cell recovery time does not affect the potency of complexes 18 and 20, but prolonged recovery decreases the activity of 19 and enhances the activity of13. Induction of apoptosis is only observed after 24 h for18- 20, suggesting that they cause cell death at a faster rate than the parent complex 13. Therefore, these monodentate ligands can play a dramatic role in the biological behaviour of half-sandwich iridium(III) complexes.

Intriguing differences in the biological behaviour observed for these structurally similar Cp* iridium(III) complexes arise from the use of different monodentate ligands. The antiproliferative activity can be partially rationalised by the greater stability of the pyridyl complexes, but further study is warranted to understand fully the biological behaviour of these complexes.

4.6

References

(1) Tönnemann, J.; Risse, J.; Grote, Z.; Scopelliti, R.; Severin, K. Eur. J. Inorg. Chem.2013,2013, 4558.

(2) Babak, M. V.; Meier , S. M.; Legin, A. A.; Adib Razavi, M. S.; Roller, A.; Jakupec , M. A.; Keppler , B. K.; Hartinger , C. G. Chem. Eur. J2013,19, 4308.

(3) Mitra, R.; Das, S.; Shinde, S.; Sinha, S.; Somasundaram, K.; Samuelson, A. G.Chem. Eur. J2012,18, 12278.

(4) Ludwig, G.; Ranđelović, I.; Maksimović-Ivanić, D.; Mijatović, S.; Bulatović, M. Z.; Miljković, D.; Korb, M.; Lang, H.; Steinborn, D.; Kaluđerović, G.

(5) Ludwig, G.; Mijatović, S.; Ranđelović, I.; Bulatović, M.; Miljković, D.; Maksimović-Ivanić, D.; Korb, M.; Lang, H.; Steinborn, D.; Kaluđerović, G. N. Eur. J. Med. Chem.2013,69, 216.

(6) Kilpin, K. J.; Crot, S.; Riedel, T.; Kitchen, J. A.; Dyson, P. J. Dalton Trans.2014,43, 1443.

(7) Govender, P.; Sudding, L. C.; Clavel, C. M.; Dyson, P. J.; Therrien, B.; Smith, G. S.Dalton Trans.2013,42, 1267.

(8) Renfrew, A. K.; Juillerat-Jeanneret, L.; Dyson, P. J. J. Organomet. Chem.2011,696, 772.

(9) Vock, C. A.; Scolaro, C.; Phillips, A. D.; Scopelliti, R.; Sava, G.; Dyson, P. J.J. Med. Chem.2006,49, 5552.

(10) Scolaro, C.; Bergamo, A.; Brescacin, L.; Delfino, R.; Cocchietto, M.; Laurenczy, G.; Geldbach, T. J.; Sava, G.; Dyson, P. J.J. Med. Chem.2005,48, 4161. (11) Kurzwernhart, A.; Kandioller, W.; Enyedy, E. A.; Novak, M.; Jakupec, M. A.; Keppler, B. K.; Hartinger, C. G.Dalton Trans.2013,42, 6193.

(12) Wang, F.; Habtemariam, A.; van der Geer, E. P. L.; Fernández, R.; Melchart, M.; Deeth, R. J.; Aird, R.; Guichard, S.; Fabbiani, F. P. A.; Lozano-Casal, P.; Oswald, I. D. H.; Jodrell, D. I.; Parsons, S.; Sadler, P. J. Proc. Nat. Acad. Sci. USA2005,102, 18269.

(13) Lippert, B. Cisplatin: chemistry and biochemistry of a leading anticancer drug; Helvetica Chimica Acta: Würzburg, 1999.

(14) Fu, Y.; Romero, M. J.; Habtemariam, A.; Snowden, M. E.; Song, L.; Clarkson, G. J.; Qamar, B.; Pizarro, A. M.; Unwin, P. R.; Sadler, P. J. Chem. Sci.

2012,3, 2485.

(15) Fu, Y.; Habtemariam, A.; Basri, A. M. B. H.; Braddick, D.; Clarkson, G. J.; Sadler, P. J.Dalton Trans.2011,40, 10553.

(16) Romero-Canelon, I.; Pizarro, A. M.; Habtemariam, A.; Sadler, P. J. Metallomics2012,4, 1271.

(17) Liu, Z.; Romero-Canelón, I.; Qamar, B.; Hearn, J. M.; Habtemariam, A.; Barry, N. P. E.; Pizarro, A. M.; Clarkson, G. J.; Sadler, P. J.Angew. Chem. Int. Ed.2014,53, 3941.

(18) Liu, Z.; Romero-Canelón, I.; Habtemariam, A.; Clarkson, G. J.; Sadler, P. J.Organometallics2014,33, 5324.

(19) Liu, Z.; Habtemariam, A.; Pizarro, A. M.; Clarkson, G. J.; Sadler, P. J.Organometallics2011,30, 4702.

(20) Peacock, A. F. A.; Habtemariam, A.; Fernández, R.; Walland, V.; Fabbiani, F. P. A.; Parsons, S.; Aird, R. E.; Jodrell, D. I.; Sadler, P. J. J. Am. Chem. Soc.2006,128, 1739.

(21) Berners-Price, S. J.; Kuchel, P. W.J. Inorg. Biochem.1990,38, 327. (22) Betanzos-Lara, S.; Liu, Z.; Habtemariam, A.; Pizarro, A. M.; Qamar, B.; Sadler, P. J.Angew. Chem. Int. Ed.2012,51, 3897.

(23) Jungwirth, U.; Kowol, C. R.; Keppler, B. K.; Hartinger, C. G.; Berger, W.; Heffeter, P.Antioxid. Redox Signaling2011,15, 1085.

(24) Kandioller, W.; Balsano, E.; Meier, S. M.; Jungwirth, U.; Goschl, S.; Roller, A.; Jakupec, M. A.; Berger, W.; Keppler, B. K.; Hartinger, C. G. Chem. Commun.2013,49, 3348.

(25) Liu, Y.; Zhang, X.; Zhang, R.; Chen, T.; Wong, Y.-S.; Liu, J.; Zheng, W.-J.Eur. J. Inorg. Chem.2011,2011, 1974.

(26) Peacock, A. F. A.; Habtemariam, A.; Moggach, S. A.; Prescimone, A.; Parsons, S.; Sadler, P. J.Inorg. Chem.2007,46, 4049.

(27) Pizarro, A.; Habtemariam, A.; Sadler, P. In Medicinal Organometallic Chemistry; Jaouen, G., Metzler-Nolte, N., Eds.; Springer Berlin Heidelberg: 2010; Vol. 32, p 21.

(28) Wang, F.; Xu, J.; Habtemariam, A.; Bella, J.; Sadler, P. J. J. Am. Chem. Soc.2005,127, 17734.

(29) Liu, Z.; Habtemariam, A.; Pizarro, A. M.; Fletcher, S. A.; Kisova, A.; Vrana, O.; Salassa, L.; Bruijnincx, P. C. A.; Clarkson, G. J.; Brabec, V.; Sadler, P. J. J. Med. Chem.2011,54, 3011.

(30) Helm, L.; Merbach, A. E.Coord. Chem. Rev.1999,187, 151.

(31) Betanzos-Lara, S.; Salassa, L.; Habtemariam, A.; Novakova, O.; Pizarro, A. M.; Clarkson, G. J.; Liskova, B.; Brabec, V.; Sadler, P. J. Organometallics2012,31, 3466.

(32) Hassner, A. In Encyclopedia of Reagents for Organic Synthesis; John Wiley & Sons, Ltd: 2001.

(34) Heffeter, P.; Jungwirth, U.; Jakupec, M.; Hartinger, C.; Galanski, M.; Elbling, L.; Micksche, M.; Keppler, B.; Berger, W. Drug. Resist. Update.2008,11, 1.

(35) Reedijk, J.Proc. Nat. Acad. Sci. USA2003,100, 3611.

(36) Goto, S.; Iida, T.; Cho, S.; Oka, M.; Kohno, S.; Kondo, T. Free Radical Res.1999,31, 549.

(37) Wexselblatt, E.; Gibson, D.J. Inorg. Biochem.2012,117, 220.

(38) Schluga, P.; Hartinger, C. G.; Egger, A.; Reisner, E.; Galanski, M.; Jakupec, M. A.; Keppler, B. K.Dalton Trans.2006, 1796.

(39) Dougan, S. J.; Habtemariam, A.; McHale, S. E.; Parsons, S.; Sadler, P. J.Proc. Nat. Acad. Sci. U.S.A.2008,105, 11628.

(40) Liu, Z.; Sadler, P. J.Inorg. Chem. Front.2014,1, 668.

(41) Liu, Z.; Deeth, R. J.; Butler, J. S.; Habtemariam, A.; Newton, M. E.; Sadler, P. J.Angew. Chem. Int. Ed.2013,52, 4194.

(42) Maenaka, Y.; Suenobu, T.; Fukuzumi, S. J. Am. Chem. Soc. 2011, 134, 367.

(43) Soldevila-Barreda, J. J.; Bruijnincx, P. C. A.; Habtemariam, A.; Clarkson, G. J.; Deeth, R. J.; Sadler, P. J.Organometallics2012,31, 5958.

(44) Yan, Y.; Melchart, M.; Habtemariam, A.; Peacock, A. A.; Sadler, P. J. Biol. Inorg. Chem.2006,11, 483.

(45) Fish, R. H.Aust. J. Chem.2010,63, 1505.

(46) Liu, Z.; Sadler, P. J.Acc. Chem. Res.2014,47, 1174. (47) Halliwell, B. IneLS; John Wiley & Sons, Ltd: 2001.

(48) Morgan, M. J.; Kim, Y.-S.; Liu, Z.-g.Cell Res.2008,18, 343.

(49) Chen, Y.; Azad, M. B.; Gibson, S. B. Cell Death Differ. 2009, 16, 1040.

(50) Chen, Y.; McMillan-Ward, E.; Kong, J.; Israels, S. J.; Gibson, S. B.J. Cell Sci.2007,120, 4155.

(51) Farrell, N.; Povirk, L. F.; Dange, Y.; DeMasters, G.; Gupta, M. S.; Kohlhagen, G.; Khan, Q. A.; Pommier, Y.; Gewirtz, D. A. Biochem. Pharmacol.

Chapter 5