Yohei Doi, MD, PhD Division of Infectious Diseases University of Pittsburgh School of Medicine  Background on

 Resistance mechanisms

 New aminoglycosides

, produced by a species of , was the first discovered  All subsequent aminoglycosides were derived from Streptomyces spp. (-mycin) or from spp. (-micin)  Active against various groups of . Not active against anaerobes

Mandell: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 7th ed.  Amino-glycoside

amino-containing or non- amino-containing sugars

six-membered ring with amino group substituents = kanamycin Generic Name Source Year Reported Streptomycin Streptomyces griseus 1944 Streptomyces fradiae 1949 Kanamycin Streptomyces kanamyceticus 1957 Streptomyces fradiae 1959

Gentamicin Micromonospora purpurea and Micromonospora echinospora 1963

Tobramycin Streptomyces tenebrarius 1967 Streptomyces kanamyceticus 1972 Micromonospora inyoensis 1975 Streptomyces spectabilis 1961 Micromonospora inyoensis 1970 Streptomyces kanamyceticus 1971 Isepamicin Micromonospora purpurea 1978

Mandell: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 7th ed.  Aminoglycosides are used for treatment of various conditions: . Streptomycin – tuberculosis . Paromomycin – cryptosporidiosis, amoebiasis, leishmaniasis . Spectinomycin – gonorrhea . /streptomycin – synergy with β-lactams for Enterococcus spp. . Gram-negative bacilli (GNB), including Pseudomonas aeruginosa  Toxicity: nephrotoxicity, ototoxicity  Safer alternatives for GNB infections (β-lactams, fluoroquinolones) have limited the use of aminoglycosides  Nonetheless, aminoglycosides continue to play an important role in the management of serious infections caused by GNBs: . In combination with broad-spectrum β-lactams for “empiric” therapy . For organisms resistant to all other antimicrobial agents  Three aminoglycosides are used systemically worldwide: . Gentamicin . . Amikacin  They are all “4,6-disubstituted deoxystreptamines” 4 6

4,6-disubstituted deoxystreptamines  On the other hand, the use of “4,5-disubstituted deoxystreptamines” is limited due to higher toxicity . Neomycin . Paromomycin

4,5-disubstituted deoxystreptamines  Aminoglycosides bind specifically to the aminoacyl site (A- site) of 16S ribosomal RNA within the prokaryotic 30S ribosomal subunits  Interfere with protein synthesis by inducing mistranslation

Yusupov MM, et al. Science 2001;292:883-96  Mutation of the 16S rRNA or ribosomal proteins  Reduced permeability  Export by efflux pumps  Enzymatic inactivation . The most common  Post-transcriptional methylation of 16S rRNA . The most broad-spectrum

Ramirez MS, et al. Drug Resist Updat 2010;13:151-71  Enzymatic inactivation is mediated by 3 classes of aminoglycoside-modifying enzymes (AMEs): . Acetyltransferases (AACs) . Nucleotidyltransferases (ANTs or AADs) . Phosphotransferases (APHs)

Ramirez MS, et al. Drug Resist Updat 2010;13:151-71  AMEs catalyze modification at −OH or −NH2 groups:

Ramirez MS, et al. Drug Resist Updat 2010;13:151-71  Resistance phenotypes of AMEs are substrate-specific:

Gm Siso Tob Amk Dbk Ntl Neo Sm

Phospho- APH(3’)-Ia R S S S S S R S transferases (APHs) APH(3’)-VIa S S S S S S R S

AAC(3)-Ia R R S S S S S S

Acetyltransferases AAC(3)-IIa R R R S R R S S (AACs)

AAC(6’)-Ib S R R R R R S S

Nucleotidyl- ANT(2”)-Ia R R R S R S S S transferases (ANTs/AADs) ANT(3”)-Ia S S S S S S S R

Shaw KJ, et al. Microbiol Rev 1993; 57:138–63  However, production of multiple AMEs may lead to resistance to all aminoglycosides  Further modifications have been made to generate aminoglycosides resistant to the effect of multiple AMEs . .  A derivative of dibekacin, first synthesized in 1973

 Demonstrates a broad spectrum of activity against Gram- positives and Gram-negatives, including those resistant to existing aminoglycosides

 Approved for treatment of MRSA infection in Japan and several other countries

 Arbekacin is a derivative of dibekacin, which is a derivative of kanamycin B

APH(3’)

APH(2”) AAC(6’)  Arbekacin has good activity against P. aeruginosa

Fujimura S, et al. Japanese Journal of Chemotherapy, 2009  And A. baumannii

Zapor MJ, et al. Antimicrob Agents Chemother 2010;54:3015-7  Adverse effects:

. Nephrotoxicity

. Ototoxicity

 Comparable to other intravenous aminoglycosides  Currently in clinical trial at Walter Reed National Military Medical Center (NCT01659515) . Bacterial infection of the respiratory tract, bloodstream, skin, soft tissue, bone, or genitourinary tract . Caused by MDR, ESBL-producing, carbapenemase-producing, cephalosporin-resistant Gram-negative bacteria, or . Caused by MRSA, VRE, VISA/VRSA . Arbekacin MIC of ≤4 mg/L

 Also, a nebulized formulation is moving to Phase I for ventilator-associated and hospital-acquired bacterial pneumonia

 A derivative of sisomicin  Demonstrates a broad spectrum of activity against Gram- positives and Gram-negatives Hydroxylethyl substituent

Hydroxyl-aminobutyric acid substituent

Armstrong ES and Miller GH. Curr Opin Microbiol 2010;13:565-73 Armstrong ES and Miller GH. Curr Opin Microbiol 2010;13:565-73 Armstrong ES and Miller GH. Curr Opin Microbiol 2010;13:565-73 Tobramycin Amikacin

Plazomicin Gentamicin

Endimiani A, et al. Antimicrob Agents Chemother 2009;53:4504--7  Phase I . Randomized, double-blind, placebo-controlled trials in healthy subjects . Pharmacokinetics, safety, tolerability . Linear and dose-proportional PK

. AUC0-24 = 239 ± 45h*mg/L, Cmax = 113 ± 17 mg/L, t1/2 = 3 ± 0.3 h, Vss = 0.24 ± 0.04 L/kg at 15 mg/kg, day 5 dose . No evidence of nephrotoxicity or ototoxicity

Cass RT, et al. Antimicrob Agents Chemothr 2011;55:5874-80  Phase I – lung penetration . Randomized, double-blind, placebo-controlled trial in healthy subjects . Once daily for 5 days; 10.7 mg/kg or 15 mg/kg . Lung penetration of plazomicin (the ratio of ELF to plasma AUC) was approximately 13%

ECCMID 2013; abstract P1637  Phase II . Randomized, double-blind, comparator (levofloxacin)-controlled trial in complicated UTI and acute pyelonephritis patients . Safety, efficacy . Comparable clinical and microbiological efficacy . One plazomicin patient had mild unilateral permanent tinnitus; another plazomicin patient had prolonged elevation of serum creatinine

ICAAC 2012; abstract L2-2118a  Phase III . A multicenter, international, randomized, assessor-blinded, active comparator-controlled study . Bloodstream infections (BSI) and nosocomial pneumonia due to CRE . Superiority of a plazomicin-based regimen compared with a colistin- based regimen in all-cause 28-day mortality  The activity of both arbekacin and plazomicin is lost when a strain produces an 16S ribosomal RNA methyltransferase (16S-RMTase)

Wachino J, et al. Drug Resist Updat 2012;15:133-48  An example of disk testing result for E. coli producing RmtD . amikacin, tobramycin, gentamicin and arbekacin

amikacin tobramycin

arbekacin gentamicin  16S-RMTases now have global distribution:

Wachino J, et al. Drug Resist Updat 2012;15:133-48  The combination of carbapenemase and 16S-RMTase is increasingly encountered  Combinations that have been reported: . NDM-1 MBL + ArmA/RmtB/RmtC

. OXA-23 carbapenemase + ArmA

. VIM-1/2 MBL+ ArmA/RmtB

. IMP-1 MBL + ArmA

. KPC + ArmA/RmtD

. SPM-1 MBL + RmtD  Still rare among KPC-producing K. pneumoniae  The use of aminoglycosides have been limited by resistance due to production of aminoglycoside modifying enzymes

 The new generation of aminoglycosides, designed to resist AMEs, hold promise as treatment options against highly-resistant Gram-negative infections

. In combination with another agent . Bloodstream infections (BSI) and nosocomial pneumonia due to carbapenem-resistant Enterobacteriaceae  University of Pittsburgh  Funding agencies . Lee Harrison . National Institutes of Health . Jessica O’Hara . Agency for Healthcare Research . Jesabel Rivera and Quality . Pennsylvania Department of  Instituto Adolfo Lutz Health . Doroti Oliveira de Garcia . Maria Fernanda Bueno . Gabriela Francisco

 Nagoya University . Yoshichika Arakawa . Jun-ichi Wachino