title: Assessment of the mass balance recovery and metabolite profile of avibactam in humans and in vitro drug-drug interaction potential.
abstract: Avibactam, a novel non-β-lactam β-lactamase inhibitor with activity against Ambler class A, class C, and some class D enzymes is being evaluated in combination with various β-lactam antibiotics to treat serious bacterial infections. The in vivo mass balance recovery and metabolite profile of [(14)C] avibactam (500 mg/1-h infusion) was assessed in six healthy male subjects, and a series of in vitro experiments evaluated the metabolism and drug-drug interaction potential of avibactam. In the mass balance study, measurement of plasma avibactam (using a validated liquid chromatography-tandem mass spectrometry method) and total radioactivity in plasma, whole blood, urine, and feces (using liquid scintillation counting) indicated that most of the avibactam was excreted unchanged in urine within 12 hours, with recovery complete (>97% of the administered dose) within 96 hours. Geometric mean avibactam renal clearance (158 ml/min) was greater than the product of unbound fraction of drug and glomerular filtration rate (109.5 ml/min), suggesting that active tubular secretion accounted for some renal elimination. There was no evidence of metabolism in plasma and urine, with unchanged avibactam the major component in both matrices. Avibactam demonstrated in vitro substrate potential for organic anion transporters 1 and 3 (OAT1 and OAT3) proteins expressed in human embryonic kidney 293 cells (Km > 1000 μM; >10-fold the Cmax of a therapeutic dose), which could account for the active tubular secretion observed in vivo. Avibactam uptake by OAT1 and OAT3 was inhibited by probenecid, a potent OAT1/OAT3 inhibitor. Avibactam did not interact with various other membrane transport proteins or cytochrome P450 enzymes in vitro, suggesting it has limited propensity for drug-drug interactions involving cytochrome P450 enzymes.
authors.affiliation: Quantitative Clinical Pharmacology, AstraZeneca R&D, Waltham, Massachusetts (K.V.); Drug Metabolism and Pharmacokinetics, Infection Innovative Medicines Unit, AstraZeneca R&D, Waltham, Massachusetts (A.G., J.A.); Quotient Clinical Ltd, Nottingham, United Kingdom (S.M.); Global Medicines Development, AstraZeneca, Wilmington, Delaware (T.E.); and AstraZeneca, Macclesfield, United Kingdom (J.C.-J., S.D.).
authors.forename: Karthick
authors.initials: K
authors.lastname: Vishwanathan
authors.forename: Stuart
authors.initials: S
authors.lastname: Mair
authors.forename: Anshul
authors.initials: A
authors.lastname: Gupta
authors.forename: James
authors.initials: J
authors.lastname: Atherton
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Clarkson-Jones
authors.forename: Timi
authors.initials: T
authors.lastname: Edeki
authors.forename: Shampa
authors.initials: S
authors.lastname: Das
mesh_terms: D000328:Adult; D000818:Animals; D000900:Anti-Bacterial Agents / Q000097:blood / Q000378:metabolism* / Q000652:urine; D053961:Azabicyclo Compounds / Q000097:blood / Q000378:metabolism* / Q000652:urine; D001692:Biological Transport; D002250:Carbon Radioisotopes; D002462:Cell Membrane / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D004285:Dogs; D004347:Drug Interactions; D005243:Feces / Q000737:chemistry; D057809:HEK293 Cells; D006801:Humans; D061985:Madin Darby Canine Kidney Cells; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008657:Metabolic Clearance Rate; D008861:Microsomes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D008875:Middle Aged; D011817:Rabbits; D013379:Substrate Specificity; D065093:beta-Lactamase Inhibitors
chemical_list: D000900:Anti-Bacterial Agents; D053961:Azabicyclo Compounds; D002250:Carbon Radioisotopes; D026901:Membrane Transport Proteins; D065093:beta-Lactamase Inhibitors; C543519:avibactam; D003577:Cytochrome P-450 Enzyme System