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Absorption, Metabolism, Excretion, and the Contribution of Intestinal Metabolism to the Oral Disposition of [14C]Cobimetinib, a MEK Inhibitor, in Humans S

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Absorption, Metabolism, Excretion, and the Contribution of Intestinal Metabolism to the Oral Disposition of [14C]Cobimetinib, a MEK Inhibitor, in Humans S Supplemental material to this article can be found at: http://dmd.aspetjournals.org/content/suppl/2015/10/08/dmd.115.066282.DC1 1521-009X/44/1/28–39$25.00 http://dx.doi.org/10.1124/dmd.115.066282 DRUG METABOLISM AND DISPOSITION Drug Metab Dispos 44:28–39, January 2016 Copyright ª 2015 by The American Society for Pharmacology and Experimental Therapeutics Absorption, Metabolism, Excretion, and the Contribution of Intestinal Metabolism to the Oral Disposition of [14C]Cobimetinib, a MEK Inhibitor, in Humans s Ryan H. Takahashi, Edna F. Choo, Shuguang Ma, Susan Wong, Jason Halladay,1 Yuzhong Deng, Isabelle Rooney, Mary Gates, Cornelis E.C.A. Hop, S. Cyrus Khojasteh, Mark J. Dresser,2 and Luna Musib Departments of Drug Metabolism and Pharmacokinetics (R.H.T., E.F.C., S.M., S.W., J.H., Y.D., C.E.C.A.H., S.C.K.,), Product Development Oncology (I.R.), Early Clinical Development (M.G.), and Clinical Pharmacology (M.J.D, L.M.), Genentech, South San Francisco, California Received July 14, 2015; accepted October 7, 2015 Downloaded from ABSTRACT The pharmacokinetics, metabolism, and excretion of cobimetinib, cobimetinib had been well absorbed (fraction absorbed, Fa =0.88). a MEK inhibitor, were characterized in healthy male subjects (n =6) Given this good absorption and the previously determined low following a single 20 mg (200 mCi) oral dose. Unchanged cobime- hepatic clearance, the systemic exposures were lower than tinib and M16 (glycine conjugate of hydrolyzed cobimetinib) were expected (bioavailability, F = 0.28). We hypothesized that intestinal dmd.aspetjournals.org the major circulating species, accounting for 20.5% and 18.3% of metabolism had strongly attenuated the oral bioavailability of the drug-related material in plasma up to 48 hours postdose, cobimetinib. Supporting this hypothesis, the fraction escaping respectively. Other circulating metabolites were minor, accounting gut wall elimination (Fg) was estimated to be 0.37 based on F and for less than 10% of drug-related material in plasma. The total Fa from this study and the fraction escaping hepatic elimination (Fh) recovery of the administered radioactivity was 94.3% (61.6%, S.D.) from the absolute bioavailability study (F =Fa 3 Fh 3 Fg). with 76.5% (62.3%) in feces and 17.8% (62.5%) in urine. Metabolite Physiologically based pharmacokinetics modeling also showed that profiling indicated that cobimetinib had been extensively metabo- intestinal clearance had to be included to adequately describe the at ASPET Journals on September 27, 2021 lized with only 1.6% and 6.6% of the dose remaining as unchanged oral profile. These collective data suggested that cobimetinib was drug in urine and feces, respectively. In vitro phenotyping exper- well absorbed following oral administration and extensively me- iments indicated that CYP3A4 was predominantly responsible for tabolized with intestinal first-pass metabolism contributing to its metabolizing cobimetinib. From this study, we concluded that disposition. Introduction phase III coBRIM study, cobimetinib plus vemurafenib reduced the risk Cobimetinib [GDC-0973/XL518, chemically identified as (S)- of disease worsening or death by half in patients with BRAF V600- (3,4-difluoro-2-(2-fluoro-4-iodophenylamino)phenyl)(3-hydroxy- mutated metastatic melanoma (hazard ratio = 0.51; 95% confidence – , 3-(piperidin-2-yl)azetidin-1-yl)methanone] (Fig. 1) is a novel interval = 0.39 0.68; P 0.0001). The median progression-free therapeutic small molecule being developed by F. Hoffman-La Roche, survival was 9.9 months for cobimetinib plus vemurafenib compared Ltd. (Basel, Switzerland) and Genentech. The molecule is a potent and with 6.2 months with vemurafenib alone (Larkin et al., 2014). In 2015, highly selective inhibitor of MEK1/2, a kinase that activates ERK1/2 in the U.S. Food and Drug Administration granted Priority Review (http:// the mitogen-activated protein kinase signaling cascade. The mitogen- www.fda.gov/ForPatients/Approvals/Fast/default.htm) for a New Drug activated protein kinase signaling cascade transduces multiple pro- Application for cobimetinib in combination with vemurafenib for the – liferative and differentiating signals within tumor cells and includes treatment of patients with BRAF V600 mutation positive advanced four major mammalian mitogen-activated protein kinase pathway melanoma. modules: ERK1 and ERK2, c-Jun NH2-terminal kinase, p38 kinase, Human radiolabeled studies are the accepted standard for providing a and ERK5 (Johnson and Lapadat, 2002; Roberts and Der, 2007). In the definitive understanding of the absorption, distribution, metabolism, and excretion properties of a drug since the radiolabel assures that all of the drug-related material can be accounted for. From the radiolabel 1Current affiliation: Anacor Pharmaceuticals, Inc., Palo Alto, CA. study, in addition to obtaining pharmacokinetics (PK) for the drug, the 2Current affiliation: Denali Therapeutics, Inc., South San Francisco, CA. identity and concentrations of circulating metabolites and the pathways dx.doi.org/10.1124/dmd.115.066282. of elimination (metabolism or excretion) are revealed (Beumer et al., s This article has supplemental material available at dmd.aspetjournals.org. 2006; Penner et al., 2009). Prior to the human mass balance study, ABBREVIATIONS: ACN, acetonitrile; AE, adverse event; AUC, area under the curve; CL, clearance; DDI, drug-drug interaction; F, bioavailability; Fa, fraction absorbed; Fg, fraction escaping gut wall elimination; Fh, fraction escaping hepatic elimination; HLM, human liver microsome; LC, liquid chromatography; MS, mass spectrometry; PBPK, physiologically based pharmacokinetics; PK, pharmacokinetics; SRM, selected reaction monitoring; t1/2, half-life; UDPGA, UDP glucuronic acid; UGT, UDP-glucuronosyltransferase. 28 Absorption, Metabolism, and Excretion of Cobimetinib In Humans 29 Materials and Methods Radiolabeled Drug and Reference Compounds. Cobimetinib and [14C] cobimetinib (radiochemical purity .98%) were synthesized by F. Hoffman-La Roche. For [14C]cobimetinib, the radiolabel was evenly distributed in the fluoro- iodoaniline ring (55 mCi/mmol specific activity) (Fig. 1). Synthetic standards for metabolites M12, M16, and M19 were synthesized at Genentech and Roche 13 (Basel, Switzerland). C6-cobimetinib (used as an internal standard for bioanalysis) was synthesized at Ricerca Biosciences (Concord, OH). Materials. 1-Aminobenzotriazole was purchased from Spectrum Chemical Corporation (Gardena, CA); CYP3cide was purchased from Toronto Research Chemicals (Toronto, Canada); and other chemical inhibitors (furafylline, tranylcypromine, ticlopidine, quercetin, sulfaphenazole, quinidine, ketocona- zole, troleandomycin, fluconazole), reduced b-nicotinamide adenine dinucleo- tide phosphate tetrasodium salt (NADPH), UDP glucuronic acid (UDPGA) Fig. 1. Chemical structure of [14C]cobimetinib. The asterisk denotes the location of trisodium salt, and alamethicin were purchased from Sigma-Aldrich (St. Louis, the 14C radiolabel, which was uniformly distributed throughout the fluoro- MO). All other chemicals and solvents were of analytic grade and were obtained iodoaniline ring. from commercial sources. Human liver microsomes [(HLMs), pool of 150 donors, mixed sex)], CYP Supersomes (CYP1A2, 2A6, 2B6, 2C8, 2C9, 2C18, 14 2C19, 2D6, 2E1, 3A4, and 3A5), and UDP-glucuronosyltransferase (UGT) Downloaded from cobimetinib was characterized in the preclinical species with C- Supersomes (UGT1A1, 1A3, 1A4, 1A6, 1A7, 1A8, 1A9, 1A10, 2B4, 2B7, radiolabeled mass balance studies (Choo et al., 2012). In rats and 2B15, and 2B17) were purchased from BD Biosciences (San Jose, CA). dogs, the administered dose was well absorbed, with 70%–80% of the CYP3A5 genotyped single donor HLMs were purchased from Xenotech radioactivity recovered in urine and bile. Metabolism was extensive (Lenexa, KS) and Corning Discovery Labware (Tewksbury, MA). with biliary excretion of metabolites as the primary pathway for Study Design. This was a single-center, open-label, nonrandomized study elimination. The major metabolic pathways were oxidative, although with the oral administration of radiolabeled cobimetinib (20 mg with approxi- some species differences in metabolism existed with rats primarily mately 200 mCi of radioactivity) to six healthy male subjects to determine the PK dmd.aspetjournals.org hydroxylating the aromatic core and dogs sequentially oxidizing the of the parent drug and to characterize metabolites in circulation and excreta. The piperidine-azetidine moieties (Takahashi, RH et al., manuscript in study was conducted at the Covance Clinical Research Unit (Madison, WI). The study followed the guidelines of the World Medical Association Declaration of preparation). Helsinki in its revised edition (http://www.wma.net/en/30publications/10policies/ The PK of cobimetinib following oral administration in patients with b3/), the current guidelines for Good Clinical Practice (http://www.fda.gov/ solid tumors have also been previously described (Musib et al., 2011). ScienceResearch/SpecialTopics/RunningClinicalTrials/), and other applicable Cobimetinib exhibited dose-proportional kinetics (;3.5–100 mg) with the regulatory requirements. All subjects provided written informed consent. coefficient of variability in exposure [area under the curve (AUC)] ranging Subjects. Volunteers that were eligible for inclusion in this study were male at ASPET Journals on September 27, 2021 from 21% to 120%. It has a low apparent clearance (CL) with a terminal (18–55 years of
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