Mechanism of action of fluoroquinolones: the basics...

Transcription

1 Mechanism of action of fluoroquinolones: the basics... PRI DA DA gyrase Topo isomerase Gram (-) Gram (+) 1

2 2 key enzymes in DA replication: DA gyrase topoisomerase IV bacterial DA is supercoiled 2

3 Ternary complex DA - enzyme - fluoroquinolone VALETLY LSED IRULAR DA DA GYRASE catalytic subunits DA GYRASE ATP binding subunits LURQUILES: 4 stacked molecules (Shen, in Quinolone Antimicrobial Agents, 1993) 3

4 Ternary complex DA - enzyme - fluoroquinolone VALETLY LSED IRULAR DA DA GYRASE catalytic subunits DA GYRASE ATP binding subunits LURQUILES: 4 stacked molecules abral et al., ature,

5 Resistance to fluoroquinolones: the basics decreased permeability efflux pump DA DA gyrase Topo isomerase mutation of the enzymes Gram (-) Gram (+) 5

6 luoroquinolones are the first entirely man-made antibiotics: do we understand our molecule? R 5 R 6 H R 7 X 8 R 1 Don t panic, we will travel together. 6

7 hemistry and Activity This is where all begins... 7

8 The pharmacophore common to all fluoroquinolones BIDIG T DA R 5 BIDIG T THE EZYME R 6 - BIDIG T THE EZYME R 7 X 8 R 1 AUT-ASSEMBLIG DMAI (for stacking) 8

9 rom chloroquine to nalidixic acid... nalidixic acid H H 3 H 3 - l chloroquine H H l 2 H 5 7-chloroquinoline (synthesis intermediate found to display antibacterial activity) 9

10 alidixic acid * a - - b typical chemical features of fluoroquinolones (a, b, c) BUT a naphthridone ( at position 8: ) H 3 c 2 H 5 limited usefulness as drug narrow antibacterial spectrum (Enterobacteriaceae only) short half-life (1.5h) high protein binding (90%) * Belg. pat. 612,258 to Sterling Drugs,

11 rom nalidixic acid to the 1st fluoroquinolone (1 of 4) nalidixic acid oxolinic acid * - 1. modify naphthyridone into quinolone - H 3 2 H 5 2 H 5 shows reduced protein binding... * Ger. pat. to Warner Lambert, 1967 * quinoleine 11

12 rom nalidixic acid to the 1st fluoroquinolone (1 of 4) nalidixic acid flumequine * - 2. discovery of flumequine * - H 3 2 H 5 H 3 shows weak but broad Gram(-) activity * Ger pat. to Rikker Labs, 1973 * benzo-quinolizine 12

13 rom nalidixic acid to the 1st fluoroquinolone (1 of 4) nalidixic acid pipemidic acid * - 3. introduce a piperazine * - H 3 2 H 5 H 2 H 5 shows longer half-life... * Ger. Pat. to Roger Bellon, 1974 * pyrido-2-3-pyrimidine 13

14 rom nalidixic acid to the 1st fluoroquinolone (1 of 4) norfloxacin * nalidixic acid combine all 3 features * H 3 - H 1 H 3 2 H broader Gram(-) activity less protein binding (50%) longer half-life (3-4h) * Belgian patent 863,429, 1978 to Kyorin * 6-fluoro-7-pyrimidino-quinoleine 14

15 rom norfloxacin to the other 1st generation fluoroquinolones: pefloxacin norfloxacin - H H 3 Add a methyl to still increase half-life - H 3 pefloxacin * 15 H 3 * Ger. pat. 2,840,910 to Roger Bellon/Dainippon,1979

16 rom norfloxacin to the other 1st generation fluoroquinolones: ofloxacin norfloxacin - tricyclic compound (as in flumequine but morpholine ring) H H 3 * Eur. pat. Appl. 47,005 to Daiichi, 1982 H 3 pefloxacin - H 3 H 3 - H 3 16 ofloxacin*

17 H rom norfloxacin to the other 1st generation fluoroquinolones: ciprofloxacin norfloxacin H 3 - cyclopropyl to increase potency H ciprofloxacin * - - H 3 H 3 H 3 H 3 - pefloxacin ofloxacin * Ger. pat. 3,142,854 to Bayer AG,

18 "1st generation" fluoroquinolones norfloxacin ciprofloxacin - - H piperazine H 3 H cyclo propyl - - methyl H 3 H 3 H 3 H 3 pefloxacin ofloxacin morpholine 18

19 The "first generation" of fluoroquinolones t 1/2 activity alidixic acid orfloxacin 3-4 h ++ xolinic acid Pefloxacin 11 h + inoxacin Pipemidic acid floxacin iprofloxacin leroxacin improved anti Gram (-) activity 6 h h +++ Rufloxacin 19

20 rom ofloxacin to levofloxacin... floxacin is a racemic mixture H 3 H 3 - H H 3 Levofloxacin is the pure (-) S isomer * The active form of ofloxacin is the (-) S isomer * Eur. pat. 206,283 to Daiichi,

21 The present "first generation" of fluoroquinolones t 1/2 activity alidixic acid orfloxacin 3-4 h ++ xolinic acid Pefloxacin 11 h + lumequine Pipemidic acid floxacin iprofloxacin leroxacin improved anti Gram (-) activity 6 h h +++ Rufloxacin Levofloxacin 6 h ++++ twice as active as ofloxacin per g 21

22 How to improve the chemotherapeutic usefulness of the "first generation" fluoroquinolones 1. Maintain broad Gram(-) activity 2. Improve Gram(+) activity 2d generation 3. Acquire activity against anaerobes 3d generation 22

23 The second generation fluoroquinolones Temafloxacin a Sparfloxacin b Grepafloxacin c Gatifloxacin d Gram (-); improved Gram (+) anti-anaerobe a: Toyama, 1988 (?) ; b: Dainippon, ; c: tskuda, 1989; d: Kyorin,

24 The third generation fluoroquinolones linafloxacin a Trovafloxacin b Moxifloxacin c Gemifloxacin d anti-gram (-) anti-gram (+) anti-anaerobe a:kyorin, 1987; b: Pfizer, 1993; c: Bayer, 1994; d: LG hemical Ltd., S. Korea,

25 Activity against S. pneumoniae I II H3 H2 - III - - H H 3 sparfloxacin H H 3 moxifloxacin YES H H ciprofloxacin H 3 H H 3 + H H 25 temafloxacin trovafloxacin

26 Resistance au fluoroquinolones : les mécanismes de base... perméabilité diminuée pompes à efflux DA DA gyrase Topo isomerase mutation des enzymes cibles Gram (-) Gram (+) 26

27 Resistance au fluoroquinolones : rôle des mutations au niveau de la cible Gram (-) Gram (+) DA DA gyrase Topo isomerase Élévation des MI de 3 à 5 dilutions ( 20 X) par mutation mutation des enzymes cibles 27

28 Is there a SAR for emergence of resistance? The "Mutant Prevention oncentration" * "When Mycobacterium bovis BG and Staphylococcus aureus were plated on agar containing increasing concentrations of fluoroquinolone, colony numbers exhibited a sharp drop, followed by a plateau and a second sharp drop. The plateau region correlated,vith the presence of first-step resistant mutants. Mutants were not recovered at concentrations above those required for the second sharp drop, thereby defining a mutant prevention concentration (MP). A 8-methoxy group lowered the MP for an -1-cyclopropyl fluoroquinolone" 28

29 Is there a SAR for emergence of resistance? Bactericidal activity of Qs against Mycobaterium bovis raction of survivors MI (99) 1 MP (10) H 3 - H 5 2 H R PD PD R = H 3 R = H MI MP MP/MI Q concentration Dong et al; AA 43:

30 luoroquinolones with a 8-methoxy I II III H H H 3 H H 3 H H 3 ciprofloxacin gatifloxacin moxifloxacin ot in Belgium Yes 30

31 Toxicity This is where all may fail... 31

32 requent side effects of fluoroquinolones: is there a SAR? MPLEXATI WITH METALLI IS (e, Al, Mg, a) PHTTXIITY DRUG ITERATIS: IHIBITI cyt P450 (1A2)??? S TXIITY (BIDIG T GABA REEPTR) GASTR-ITESTIAL DISMRT ARTILAGE and MUSULSQUELETAL TXIITY 32

33 SAR of frequent side effects R H R H R a ++, Al +++, e ++ complexation Binding to GABA receptor R Penetration in S R 5 - All Qs R 7 X 8 cipro, grepa... Inhibition of P450 R 1 sparflo, flero, lomeflo Phototoxicity Inhibition of P450 33

34 luoroquinolone with low or no drug interactions.. Moxifloxacin - Yes H H 3 34

35 Rare side effects of fluoroquinolones: REAL TXIITY crystalluria, hematuria, interstitial nephritis, acute renal failure ARDIA TXIITY (QT prolongation, Torsades de pointe)? HEPATTXIITY temafloxacin syndrome / trovafloxacin syndrome 35

36 Pharmacokinetics This is where people start sleeping.. 36

37 SAR of pharmacokinetic parameters Bulky substituant R 5 H cipro gati moxi t 1/2 R 7 X 8 R 1 peflo, oflo, gati, moxi V d 37

38 SAR of main pharmacokinetic parameters: how to get a long half life t 1/2 (h) no. of daily administrations H 3 oflo / lévo x* peflo 10 2 x* flero x H 3 H grepa x gati 13 1 x H 3 H 2 H 2 H gemi 8 1 x trova 10 1 x moxi 12 1 x H 3 + H H other Q x * higher MI... 38

39 Resistance: do not forget the correct dosing... Inadequate dosing of antibiotics is probably an important reason for misuse and subsequent risk of resistance. A recommendation on proper dosing regimens for different infections would be an important part of a comprehensive strategy. The possibility to produce such a dose recommendation based on pharmacokinetic and pharmacodynamic considerations will be further investigated in one of the PMP working parties European Agency of the Evaluation of Medicinal Products (London) EMEA discussion paper on Antimicrobial resistance 3 January 1999 EMEA/9880/99 39

40 Pharmacokinetic parameters in relation with efficacy Dose max MI for AU MI for (mg) (mg/l) pk/mi=10 (mg.h/l) AUI=125 norflo 400 (X2) peflo 400 (X2) cipro 500 (X2) oflo 200 (X2) levoflo moxi

41 ptimizing dosage for fluoroquinolones oncentration MI increase the amount administered, in order to optimize AU/MI Peak/MI AU/MI and peak/mi should be > 125 should be > 10 Get both a peak and a AU!! Time (h) 41

42 % of sensitive strains moxi levo How to apply this? Levofloxacin 500 mg 1X /day AU [(mg/l)xh] 47 peak [mg/l] 5 MI max < 0.5 2X /day 94 5 < MI Moxifloxacin 400 mg 1X/day AU [(mg/l)xh] 48 peak [mg/l] 4.5 MI max < 0.5 MI data: J. Verhaegen et al.,

43 Take home message Dosage is key to success Dosage should match bacterial sensitivity peak, AU/MI are keys to success use a single, appropriate dose for long-life fluoroquinolones (moxifloxacin), or repeat the dose for short-lived fluoroquinolones (all others so far ) for fluoroquinolones, the limit is an MI of 0.5 µg/ml 43