title: A method for quantification of exportin-1 (XPO1) occupancy by Selective Inhibitor of Nuclear Export (SINE) compounds.
abstract: Selective Inhibitor of Nuclear Export (SINE) compounds are a family of small-molecules that inhibit nuclear export through covalent binding to cysteine 528 (Cys528) in the cargo-binding pocket of Exportin 1 (XPO1/CRM1) and promote cancer cell death. Selinexor is the lead SINE compound currently in phase I and II clinical trials for advanced solid and hematological malignancies. In an effort to understand selinexor-XPO1 interaction and to establish whether cancer cell response is a function of drug-target engagement, we developed a quantitative XPO1 occupancy assay. Biotinylated leptomycin B (b-LMB) was utilized as a tool compound to measure SINE-free XPO1. Binding to XPO1 was quantitated from SINE compound treated adherent and suspension cells in vitro, dosed ex vivo human peripheral blood mononuclear cells (PBMCs), and PBMCs from mice dosed orally with drug in vivo. Evaluation of a panel of selinexor sensitive and resistant cell lines revealed that resistance was not attributed to XPO1 occupancy by selinexor. Administration of a single dose of selinexor bound XPO1 for minimally 72 hours both in vitro and in vivo. While XPO1 inhibition directly correlates with selinexor pharmacokinetics, the biological outcome of this inhibition depends on modulation of pathways downstream of XPO1, which ultimately determines cancer cell responsiveness.
authors.affiliation: All authors are current or former employees of Karyopharm Therapeutics Inc., Newton, MA, 02459 U.S.A.
authors.forename: Marsha L
authors.initials: ML
authors.lastname: Crochiere
authors.affiliation: All authors are current or former employees of Karyopharm Therapeutics Inc., Newton, MA, 02459 U.S.A.
authors.forename: Erkan
authors.initials: E
authors.lastname: Baloglu
authors.affiliation: All authors are current or former employees of Karyopharm Therapeutics Inc., Newton, MA, 02459 U.S.A.
authors.forename: Boris
authors.initials: B
authors.lastname: Klebanov
authors.affiliation: All authors are current or former employees of Karyopharm Therapeutics Inc., Newton, MA, 02459 U.S.A.
authors.forename: Scott
authors.initials: S
authors.lastname: Donovan
authors.affiliation: All authors are current or former employees of Karyopharm Therapeutics Inc., Newton, MA, 02459 U.S.A.
authors.forename: Diego
authors.initials: D
authors.lastname: Del Alamo
authors.affiliation: All authors are current or former employees of Karyopharm Therapeutics Inc., Newton, MA, 02459 U.S.A.
authors.forename: Margaret
authors.initials: M
authors.lastname: Lee
authors.affiliation: All authors are current or former employees of Karyopharm Therapeutics Inc., Newton, MA, 02459 U.S.A.
authors.forename: Michael
authors.initials: M
authors.lastname: Kauffman
authors.affiliation: All authors are current or former employees of Karyopharm Therapeutics Inc., Newton, MA, 02459 U.S.A.
authors.forename: Sharon
authors.initials: S
authors.lastname: Shacham
authors.affiliation: All authors are current or former employees of Karyopharm Therapeutics Inc., Newton, MA, 02459 U.S.A.
authors.forename: Yosef
authors.initials: Y
authors.lastname: Landesman
mesh_terms: D000178:Acrylamides / Q000737:chemistry / Q000494:pharmacology; D000179:Acrylates / Q000737:chemistry / Q000494:pharmacology; D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D019921:Biotinylation; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects* / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004353:Drug Evaluation, Preclinical / Q000379:methods; D005231:Fatty Acids, Unsaturated / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology; D045325:HCT116 Cells; D006801:Humans; D006834:Hydrazines / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D028884:Karyopherins / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D015394:Molecular Structure; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D015203:Reproducibility of Results; D013844:Thiazoles / Q000737:chemistry / Q000494:pharmacology; D014230:Triazoles / Q000737:chemistry / Q000493:pharmacokinetics / Q000494:pharmacology*; D000097606:Exportin 1 Protein
chemical_list: D000178:Acrylamides; D000179:Acrylates; D000903:Antibiotics, Antineoplastic; D005231:Fatty Acids, Unsaturated; D006834:Hydrazines; D028884:Karyopherins; D018160:Receptors, Cytoplasmic and Nuclear; D013844:Thiazoles; D014230:Triazoles; D000097606:Exportin 1 Protein; C576639:KPT-185; C586831:KPT-276; C585161:selinexor; C000593855:verdinexor; C038753:leptomycin B
keywords: cancer; export; occupancy; resistance; selinexor