Development of a Highly In Vivo Efficacious Dual Antitumor and Antiangiogenic Organoiridium Complex as a Potential Anti-Lung Cancer Agent

While the phenomenal clinical success of blockbuster platinum (Pt) drugs is highly encouraging, the inherent and acquired resistance and dose-limiting side effects severely limit their clinical application. To find a better alternative with translational potential, we synthesized a library of six organo-IrIII half-sandwich [(η5-CpX)Ir(N∧N)Cl]+-type complexes. In vitro screening identified two lead candidates [(η5-CpXPh)Ir(Ph2Phen)Cl]+ (5, CpXPh = tetramethyl-phenyl-cyclopentadienyl and Ph2Phen = 4,7-diphenyl-1,10-phenanthroline) and [(η5-CpXBiPh)Ir(Ph2Phen)Cl]+ (6, CpXBiPh = tetramethyl-biphenyl-cyclopentadienyl) with nanomolar IC50 values. Both 5 and 6 efficiently overcame Pt resistance and presented excellent cancer cell selectivity in vitro. Potent antiangiogenic properties of 6 were demonstrated in the zebrafish model. Satisfyingly, 6 and its nanoliposome Lipo-6 presented considerably higher in vivo antitumor efficacy as compared to cisplatin, as well as earlier reported IrIII half-sandwich complexes in mice bearing the A549 non-small lung cancer xenograft. In particular, complex 6 is the first example of this class that exerted dual in vivo antiangiogenic and antitumor properties.