title: In vitro and in vivo characterization of XR11576, a novel, orally active, dual inhibitor of topoisomerase I and II.
abstract: XR11576, a novel phenazine, was developed as an inhibitor of both topoisomerase I and II. This study characterized the ability of XR11576 to inhibit both enzymes, and determined its in vitro and in vivo antitumor efficacy against a number of murine and human tumor models. XR11576 was a potent inhibitor of purified topoisomerase I and IIalpha, and exhibited similar potency for both enzymes. The compound stabilized enzyme-DNA cleavable complexes indicating that it acted as a topoisomerase poison. The DNA cleavage patterns obtained with XR11576 were different from those induced by camptothecin and etoposide, which are topoisomerase I and II poisons, respectively. XR11576 demonstrated potent cytotoxic activity against a variety of human and murine tumor cell lines (IC50=6-47 nM). Its activity profile was comparable to or better than that of many widely used anticancer drugs. Moreover, XR11576 was unaffected by multidrug resistance (MDR) mediated by overexpression of either P-glycoprotein or MDR-associated protein, or by down-regulation of topoisomerase II. The latter property supports the dual inhibitory mechanism of action of the compound. XR11576 exhibited a similar pharmacokinetic profile in mice and rats after either i.v. or p.o. administration. In vivo XR11576 showed marked efficacy against a number of tumors including sensitive (H69/P) and multidrug-resistant (H69/LX4) small cell lung cancer and the relatively refractory MC26 and HT29 colon carcinomas following i.v. and p.o. administration. The efficacy of XR11576 was at least comparable to that of TAS-103, originally proposed as a dual inhibitor of topoisomerase I and II. These results suggest that XR11576 is a promising new antitumor agent with oral and i.v. activity, and warrants further development.
authors.affiliation: Xenova Ltd, Slough SL1 4NL, UK. prakash_mistry@xenova.co.uk
authors.forename: Prakash
authors.initials: P
authors.lastname: Mistry
authors.forename: Alistair J
authors.initials: AJ
authors.lastname: Stewart
authors.forename: Wendy
authors.initials: W
authors.lastname: Dangerfield
authors.forename: Mark
authors.initials: M
authors.lastname: Baker
authors.forename: Chris
authors.initials: C
authors.lastname: Liddle
authors.forename: Douglas
authors.initials: D
authors.lastname: Bootle
authors.forename: Bettina
authors.initials: B
authors.lastname: Kofler
authors.forename: Deanne
authors.initials: D
authors.lastname: Laurie
authors.forename: William A
authors.initials: WA
authors.lastname: Denny
authors.forename: Bruce
authors.initials: B
authors.lastname: Baguley
authors.forename: Peter A
authors.initials: PA
authors.lastname: Charlton
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000284:Administration, Oral; D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D001835:Body Weight / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects*; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000201:enzymology; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007275:Injections, Intravenous; D008297:Male; D020714:Maximum Tolerated Dose; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D009374:Neoplasms, Experimental / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology; D010619:Phenazines / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000627:therapeutic use*; D051381:Rats; D017208:Rats, Wistar; D014018:Tissue Distribution; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors; D014407:Tumor Cells, Cultured / Q000187:drug effects
chemical_list: C446952:4-methoxybenzo(a)phenazine-11-carboxylic acid (2-(dimethylamino)-1-methylethyl)amide; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D010619:Phenazines; D059004:Topoisomerase I Inhibitors; D059005:Topoisomerase II Inhibitors