PRESENTED BY –

NAVEEN KADIANDEPT. OF PHARMACEUTICAL CHEMISTRY

KLES’S COLLEGE OF PHARMACY, BELGAUM

Clavulanic Acid & Analogs

Contents

Introduction.β- lactamase Inhibitors.Clavulanic Acid.Clavulanic Acid Analogs.Reference.

Introduction

The discovery of the naturally occurring mechanism based inhibitor clavulanic acid, which causes potent & progressive inactivation of β- lactamases has created renewed interest in β- lactam combination therapy.

This interest has led to the design & synthesis of additional mechanism based β- lactamase Inhibitors, such as sulbactum & tazobactam, & isolation of naturally occurring β- lactams such as thienamycins, which both inhibit β- lactamases & interact with PBP’s.

β- lactam Antibiotics

β-lactam antibiotics are a broad class of antibiotics that include penicillin derivatives, cephalosporins, monobactams, carbapenems, and β-lactamase inhibitors that is, any antibiotic agent that contains a β-lactam nucleus in its molecular structure.

Common β-lactam antibiotics:

NO

S

Penicillins

NO

S

Cephalosporins

NO

Carbapenems

Development of Resistance

Widespread use of β- lactams, the largest family of antibiotics in current clinical use, has inevitably led to the emergence of resistant bacteria.

The commonly encountered mechanism of resistance is that attributable to production of β- lactamases, a group of enzymes capable of catalyzing the hydrolysis of the β- lactam ring.

The existence of these enzymes was recognized as earlier as 1940 soon after the isolation of penicillin, & fears relating to their plasmid-mediated spread through out the bacterial population have been fully realized.

FAILURE OF ANTIBIOTICS DUE TOBETA-LACTAMASE

Current Rate of Resistance

% increase in Resistance

Vancomycin/enterococci

25.9% 47%

Methicillin/S. aureus 54.5% 43%

Methicillin/Coagulase-negative staphylococci

86.7% 2%

3rd generation Cephalosporin Enterobacter spp

36.4% 3%

Imipenem/P. aeruginosa

18.5% 35%

Quinolone/P. aeruginosa

23.0% 49%

β- lactamases Classification

These enzymes are divided as:1) Class A contains enzymes from Gram-positive bacteria. The

majority of them are transmissible, plasmid-mediated enzymes, often referred to as penicillinases because their preferred substrates are penicillins.

2) Class B contains broad-spectrum metallo-enzymes which mainly hydrolyzing carbepenams.

3) Class C contains predominately chromosomally mediated enzymes from Gram-negative bacteria whose preferred substrates are cephalosporins are thus referred to as cephalosporinases.

4) Class D includes enzymes capable of hydrolyzing the more β- lactamase stable isoxazolyl penicillins.

Two strategies have evolved to combat β-

lactamases-mediated resistance.i. Development of classes of β- lactam antibiotics with

improved stability.ii. Identification of β- lactamase inhibitors for co-

administration with the other antibiotics.

β- lactamase Inhibitors

Although they exhibit negligible antimicrobial activity, they contain the beta-lactam ring.

Their sole purpose is to prevent the inactivation of beta-lactam antibiotics by binding the beta-lactamases, and, as such, they are co-administered with beta-lactam antibiotics.

1. clavulanic acid 2. tazobactam 3. sulbactam

Clavulanic Acid

Systematic (IUPAC) name: (2R,5R,Z)-3-(2-hydroxyethylidene)-7-oxo-4-oxa-1-aza-bicyclo[3.2.0] heptane-2-carboxylic acid

Clavulanic acid can be considered as the most important & representive among the inhibitors of β- lactamases.

It is first clinically useful β- lactamase inhibitor was identified as a natural product from a strain of Streptomyces clavuligerus.

Structurally it is a 1-oxopenam lacking the 6-acyl amino side chain of penicillins but possessing a 2-hydroxy ethylidene moiety at C-2

Clavulanic AcidClavulanate Potassium

Continue….

Clavulanic acid was invented around 1974/75 by British scientists working at the drug company Beecham.

Clavulanic acid exhibits very weak antibacterial activity, comparable with that of 6- amino penicillanic acid therefore is not useful as an antibiotic.

It is however, a potent inhibitor of S. aureus β- lactamase & plasmid-mediated β- lactamases elaborated by Gram negative bacilli.

Mechanism of action

Clavulanic acid has negligible intrinsic antimicrobial activity, despite sharing the β-lactam ring that is characteristic of beta-lactam antibiotics.

However, the similarity in chemical structure allows the molecule to act as a competitive inhibitor of beta-lactamases secreted by certain bacteria to confer resistance to beta-lactam antibiotics.

This inhibition restores the antimicrobial activity of beta-lactam antibiotics against a lactamase-secreting resistant bacteria.

Despite this, some bacterial strains have emerged that are even resistant to such combinations.

Marketed Combinations

Most commonly, the potassium salt potassium clavulanate is combined with amoxicillin (co-amoxiclav) [brand name Augmentin]

Timetin (potassium clavulanate plus ticarcillin)

Clavulanic acid has also been isolated from S. jumonjinensis the P-hydroxypropionyl Derivative of clavulanicacid was obtained (though only isolated as its benzyl ester) from Streptomyces clavuligerus

Clavulanic Acid Analogs

clavaminic acid

Sulbactam

Diazotization/bromination of 6-APA followed by oxidation, gave the 6,6-dibromopenicillanic acid sulfone which on catalytic hydrogenation provided sulbactam.

It is irreversible inhibitor of several β- lactamases. compared with clavulanic acid sulbactum is modest inhibitor the class-A enzymes. Also shows improved potency against class-C, although at level considered to be a little clinical use

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Sulbatam is penicillanic acid sulfone or 1,1 dioxopenicillanic acid

Fixed-dose combination of ampicillin sodium & sulbatam sodium, marketed under trade name Unasyn have been approved for use in U.S.

Tazobactam

Tazobactam is a penicillanic acid sulfone that is similar in structure to sulbactam.

It is more potent β- lactamase inhibitor than sulbatam & have slightly broder spectrum of activity than clavulanic acid.it has very weak antibacterial activity.

Tazobatam is available in injectable combination with piperacillin trade name Zosyn.

Interaction of sulbactam, clavulanic acid and tazobactam with penicillin-binding proteins of imipenem-resistant and -susceptible acinetobacter baumannii

Carl Urban a b Eddie Go a Noriel Mariano a James J. Rahal a c a Infectious Disease Section, Department of Medicine, The New York Hospital Medical Center of Queens, 56-45 Main Street, Flushing, New York 11355-5095, USA b Department of Microbiology, Cornell University Medical College, New York, USA c Department of Medicine, Cornell University Medical College, New York, USA *Corresponding author. Tel: (718) 670-1525; Fax: (718) 3539819.

ABSTRACT AbstractWe have encountered clinical isolates of Acinetobacter

baumannii which are resistant to all available antibiotics used in hospitals except for polymyxin B and the beta-lactamase inhibitor, sulbactam. To investigate the mechanisms of this unique activity, affinities of sulbactam and other beta-lactamase inhibitors for penicillin binding proteins were compared using imipenem-resistant and imipenem-sensitive isolates. The results of competition binding experiments indicate that all three beta-lactamase inhibitors bound to imipenem-susceptible Acinetobacter. Binding of sulbactam was greater than that of tazobactam and not detected with clavulanic acid to penicillin binding proteins of the imipenem-resistant strain of Acinetobacter.

Effect of clavulanic acid, sulbactam and tazobactam on three different ß-lactamases

from Bacteroides uniformis, Clostridium butyricwn and Fusobacterium nucleatum

M. Hedberg, L. Lindqvist, K. Tunér and C.E. Nord* Department of Microbiology, Huddinge University Hospital. Karolinska Institute S-141 86 Huddinge, Sweden and National Bacteriological Laboratory S-105 21 Stockholm, Sweden

The effect of three ß-lactamase inhibitors clavulanic acid, sulbactam

and tazobactam used in clinical practice were compared for their activity against purified ß-lactamases from Bacreroides uniformis, Clostridium butyricum and Fusobacterium nucleatum. The enzymes from B. uniformis and C. butyricum were produced in fermenters under controlled growth conditions and the enzyme from F. nucleatum was produced in batch cultures. Purification of the ß-lactamases was achieved by anion-exchange chromatography, gel filtration and FPLC-technique. The degree of inactivation of ß-lactamase activity was determined spectrophotometrically with nitrocefin as the substrate. The inhibitors in various concentrations were preincubated at 30°C together with the enzyme for different time periods (0·5–120 min) before determination of the remaining ß-lactamase activity. The inhibitors all decreased the activity of the ß-lactamases investigated. Clavulanic acid and sulbactam were capable of reducing the enzyme activity of the B. uniformis ß-lactamases more effectively than the C. butyricum and F. nucleatum ß-lactamases. All ß-lactamases tested were more susceptible to tazobactam than to clavulanic acid and sulbactam.

References

A.G. Brown ‘Discovery and development of new β -lactam antibiotics’ Beecham Pharmaceuticals Research Division, England. Pure & App!. Chem., Vol. 59, No. 3, pp. 475—484, 1987. Printed in Great Britain.© 1987.

Keith H. Baggaley, Allan G. Brownb and Christopher J. Schofield ‘Chemistry and biosynthesis of clavulanic acid and other clavams’.

Principles of Medicinal Chemistry by William O. Foye 3rd edition.

Medicinal Chemistry by Burger, 2nd edition. Organic Medical & P’ceutical Chemistry By Wilson

& Gisvold’s Textbook.www.sciencedirect.com