title: Pharmacodynamic evaluation of the target efficacy of SB939, an oral HDAC inhibitor with selectivity for tumor tissue.
abstract: SB939 is an oral histone deacetylase (HDAC) inhibitor currently in phase II clinical trials potently inhibiting class I, II, and IV HDACs with favorable pharmacokinetic properties, resulting in tumor tissue accumulation. To show target efficacy, a Western blot assay measuring histone H3 acetylation (acH3) relative to a loading control was developed, validated on cancer cell lines, peripheral blood mononuclear cells (PBMC), and in animal tumor models. Exposure of cells to 60 nmol/L (22 ng/mL) SB939 for 24 hours was sufficient to detect an acH3 signal in 25 μg of protein lysate. AcH3 levels of liver, spleen, PBMCs, bone marrow and tumor were measured in BALB/c mice, HCT-116 xenografted BALB/c nude mice, or in SCID mice orthotopically engrafted with AML (HL-60) after oral treatment with SB939. AcH3 could only be detected after treatment. In all tissues, the highest signal detected was at the 3-hour time point on day 1. On day 15, the signal decreased in normal tissues but increased in cancerous tissues and became detectable in the bone marrow of leukemic mice. In all tissues, acH3 correlated with SB939 dose levels (r(2)=0.76-0.94). When applied to PBMCs from 30 patients with advanced solid malignancies in a phase I clinical trial, a dose-dependent (10-80 mg) increase in relative acH3 was observed 3-hour postdose on day 1, correlating with C(max) and AUC of SB939 concentrations in plasma (r=0.97, P=0.014). Our data show that the favorable pharmacokinetic and pharmacodynamic properties of SB939 are translated from preclinical models to patients.
authors.affiliation: S*BIO Pte. Ltd., 1 Science Park Rd, #05-09 The Capricorn, Singapore Science Park II, Singapore 117528. veronica_diermayr@sbio.com
authors.forename: Veronica
authors.initials: V
authors.lastname: Novotny-Diermayr
authors.forename: Nina
authors.initials: N
authors.lastname: Sausgruber
authors.forename: Yung Kiang
authors.initials: YK
authors.lastname: Loh
authors.forename: Mohammed Khalid
authors.initials: MK
authors.lastname: Pasha
authors.forename: Ramesh
authors.initials: R
authors.lastname: Jayaraman
authors.forename: Hannes
authors.initials: H
authors.lastname: Hentze
authors.forename: Wei-Peng
authors.initials: WP
authors.lastname: Yong
authors.forename: Boon-Cher
authors.initials: BC
authors.lastname: Goh
authors.forename: Han-Chong
authors.initials: HC
authors.lastname: Toh
authors.forename: Kantharaj
authors.initials: K
authors.lastname: Ethirajulu
authors.forename: Joy
authors.initials: J
authors.lastname: Zhu
authors.forename: Jeanette Marjorie
authors.initials: JM
authors.lastname: Wood
mesh_terms: D000818:Animals; D001562:Benzimidazoles / Q000493:pharmacokinetics / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004305:Dose-Response Relationship, Drug; D005260:Female; D045325:HCT116 Cells; D018922:HL-60 Cells; D056572:Histone Deacetylase Inhibitors / Q000493:pharmacokinetics / Q000494:pharmacology*; D006655:Histone Deacetylases / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism; D057230:Limit of Detection; D051379:Mice; D008807:Mice, Inbred BALB C; D008819:Mice, Nude; D016513:Mice, SCID; D009369:Neoplasms / Q000201:enzymology*; D015398:Signal Transduction / Q000187:drug effects; D023041:Xenograft Model Antitumor Assays
chemical_list: D001562:Benzimidazoles; D056572:Histone Deacetylase Inhibitors; D006657:Histones; C557525:SB939 compound; D006655:Histone Deacetylases