No abstract

Simocyclinone D8 is a potent inhibitor of bacterial gyrase, produced by Streptomyces antibioticus Tu 6040. It contains an aminocoumarin moiety, similar to that of novobiocin, which is linked by an amide bond to a structurally complex acyl moiety, consisting of an aromatic angucycline polyketide nucleus, the deoxysugar olivose and a tetraene dicarboxylic acid. We have now investigated the enzyme SimL, responsible for the formation of the amide bond of simocyclinone. The gene was cloned, expressed in S. lividans T7, and the protein was purified to near homogeneity, and characterized. The 60 kDa protein catalyzed both the ATP-dependent activation of the acyl component as well as its transfer to the amino group of the aminocoumarin ring, with no requirement for a 4'-phosphopantetheinyl cofactor. Besides its natural substrate, simocyclinone C4, SimL also accepted a range of cinnamic and benzoic acid derivatives and several other, structurally very diverse acids. These findings make SimL a possible tool for the creation of new aminocoumarin antibiotics.

Tepotinib (MSC2156119J) is an oral, potent, highly selective MET inhibitor. This open-label, phase I study in healthy volunteers (EudraCT 2013-003226-86) investigated its mass balance (part A) and absolute bioavailability (part B). In part A, six participants received tepotinib orally (498 mg spiked with 2.67 MBq [ 14 C]-tepotinib). Blood, plasma, urine, and feces were collected up to day 25 or until excretion of radioactivity was <1% of the administered dose. In part B, six participants received 500 mg tepotinib orally as a film-coated tablet, followed by an intravenous [ 14 C]-tepotinib tracer dose (53-54 kBq) 4 h later. Blood samples were collected until day 14. In part A, a median of 92.5% (range, 87.1-96.9%) of the [ 14 C]-tepotinib dose was recovered in excreta. Radioactivity was mainly excreted via feces (median, 78.7%; range, 69.4-82.5%). Urinary excretion was a minor route of elimination (median, 14.4% [8.8-17.7%]). Parent compound was the main constituent in excreta (45% [feces] and 7% [urine] of the radioactive dose). M506 was the only major metabolite. In part B, absolute bioavailability was 72% (range, 62-81%) after oral administration of 500 mg tablets (the dose and formulation used in phase II trials). In conclusion, tepotinib and its metabolites are mainly excreted via feces; parent drug is the major eliminated constituent. Oral bioavailability of tepotinib is high, supporting the use of the current tablet formulation in clinical trials. Tepotinib was well tolerated in this study with healthy volunteers.

Cilengitide (EMD 121974, manufactured by Merck KGaA, Darmstadt, Germany) is an αv-integrin receptor antagonist showing high affinity for αvβ3 and αvβ5.This study determined the mass balance of cilengitide in healthy volunteers receiving a single intravenous infusion of 2.1 MBq (14) C-cilengitide spiked into 250 mL of 2000 mg of cilengitide. Blood, urine, and feces were collected up to day 15 or until excretion of radioactivity was below 1% of the administered dose. Total radioactivity derived from the administration of (14) C-cilengitide and unlabeled cilengitide levels were determined and used for calculation of pharmacokinetic parameters.(14) C-cilengitide-related radioactivity was completely recovered (94.5%; 87.4%-100.6%) and was mainly excreted into urine (mean, 79.0%; range, 70.3%-88.2%) and to a lesser extent into feces (mean, 15.5%; range, 9.3%-20.3%). Of the administered dose, 77.5% was recovered as unchanged cilengitide in urine. The concentration profiles of cilengitide and total radioactivity in plasma were comparable. No circulating metabolites were identified in plasma and urine. Two metabolites,M606-1 and M606-2, were identified in feces considered to be formed by intestinal peptidases or by peptidases from fecal bacteria. In conclusion, the data show that following intravenous administration, (14) C-cilengitide was completely recovered, was excreted mainly via renal elimination, and was not metabolized systemically.

Keywords14 C, absolute bioavailability, elimination route, mass balance, pimasertib AIMThis trial (NCT: 01713036) investigated the absolute bioavailability, mass balance and metabolite profile of pimasertib in a new design combining these investigations in a single group of patients. METHODSSix male patients with pathologically confirmed, locally advanced or metastatic solid tumours were enrolled. Exclusion criteria included Eastern Cooperative Oncology Group performance status >1. In Part A of the trial, patients received a 60 mg oral dose of unlabelled pimasertib followed by an intravenous (i.v.) RESULTS Following i.v. administration, [14 C]pimasertib exhibited a geometric mean total body clearance of 45.7 l h À1 (geometric coefficient of variation [geometric CV]: 47.2%) and a volume of distribution of 229 l (geometric CV: 42.0%). Absolute bioavailability was 73%. The majority of the oral [ 14 C] dose (85.1%) was recovered in excreta. Total radioactivity was mainly excreted into urine (52.8%) and faeces (30.7%) with 78.9% of the [ 14 C] dose recovered as metabolites. Two major circulating metabolites were identified in plasma: a carboxylic acid (M445) and a phosphoethanolamine conjugate (M554). The safety profile was in line with the published pimasertib trials. CONCLUSIONPimasertib showed a favourable pharmacokinetic profile with high absolute bioavailability and a unique metabolic pathway (conjugation with phosphoethanolamine). British Journal of Clinical Pharmacology WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT• Pimasertib is a new selective, oral inhibitor of mitogen-activated protein kinases 1 and 2 (MEK1/2).• Comprehensive information about the pharmacokinetics, including absolute bioavailability, metabolism and elimination routes, of cancer drugs is often incomplete. WHAT THIS STUDY ADDS• Description of a trial design combining investigation of absolute bioavailability and mass balance/metabolite identification in a single group of six male cancer patients.• Identification of a new metabolic pathway for drugs, i.e. conjugation with phosphoethanolamine.• Information about key pharmacokinetic parameters and the drug disposition of pimasertib in cancer patients. Tables of Links