title: Pharmacokinetic Analysis and in Vivo Antitumor Efficacy of Taccalonolides AF and AJ.
abstract: The taccalonolides are microtubule stabilizers that covalently bind tubulin and circumvent clinically relevant forms of resistance to other drugs of this class. Efforts are under way to identify a taccalonolide with optimal properties for clinical development. The structurally similar taccalonolides AF and AJ have comparable microtubule-stabilizing activities in vitro, but taccalonolide AF has excellent in vivo antitumor efficacy when administered systemically, while taccalonolide AJ does not elicit this activity even at maximum tolerated dose. The hypothesis that pharmacokinetic differences underlie the differential efficacies of taccalonolides AF and AJ was tested. The effects of serum on their in vivo potency, metabolism by human liver microsomes and in vivo pharmacokinetic properties were evaluated. Taccalonolides AF and AJ were found to have elimination half-lives of 44 and 8.1 min, respectively. Furthermore, taccalonolide AJ was found to have excellent and highly persistent antitumor efficacy when administered directly to the tumor, suggesting that the lack of antitumor efficacy seen with systemic administration of AJ is likely due to its short half-life in vivo. These results help define why some, but not all, taccalonolides inhibit the growth of tumors at systemically tolerable doses and prompt studies to further improve their pharmacokinetic profile and antitumor efficacy.
authors.forename: April L
authors.identifier: 0000-0002-4363-3268
authors.initials: AL
authors.lastname: Risinger
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Lin
authors.initials: L
authors.lastname: Du
authors.affiliation: College of Pharmacy, The University of Texas at Austin , Austin, Texas 78712, United States.
authors.forename: Raymond
authors.initials: R
authors.lastname: Benavides
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Robles
authors.forename: Robert H
authors.identifier: 0000-0003-0744-4117
authors.initials: RH
authors.lastname: Cichewicz
authors.affiliation: College of Pharmacy, The University of Texas at Austin , Austin, Texas 78712, United States.
authors.forename: John G
authors.initials: JG
authors.lastname: Kuhn
authors.forename: Susan L
authors.initials: SL
authors.lastname: Mooberry
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000493:pharmacokinetics*; D006801:Humans; D008870:Microtubules / Q000187:drug effects; D015394:Molecular Structure; D013256:Steroids / Q000737:chemistry / Q000493:pharmacokinetics*; D013329:Structure-Activity Relationship; D014404:Tubulin / Q000378:metabolism; D050257:Tubulin Modulators / Q000737:chemistry / Q000493:pharmacokinetics*
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D013256:Steroids; D014404:Tubulin; D050257:Tubulin Modulators; C570720:taccalonolide AF; C570719:taccalonolide AJ