Comparision of Mutant Selection

1
Comparision of Mutant Selection Window
Hypothesis with Traditional Pharmacodynamics
2
Pharmacodynamic Correlates with Cure
Time above MIC
AUC above MIC
Serum drug concentration
MIC
Time
Time post-administration
3
Dosing Strategies and Mutant Enrichment
gtMPC
Cmax/MIC and AUC/MIC
Serum or tissue drug concentration
MPC
Mutant Selection Window
MIC
Time post-administration
4
Comparison of MPC Approach and Traditional
Pharmacodynamics

• MPC
• Designed to block
• resistance
• Indexed to mutant
• growth
• Conceptual threshold
• Clinical correlates
• unknown

• Traditional PD
• Designed to cure
• patients
• Indexed to susceptible
• cell growth
• Empirical threshold
• Based on clinical data

5
Applications to Streptococcus neumoniae
6
Fluoroquinolone Structure
O
O
F
OH
N
N
N
O
CH3
H3C
levofloxacin
O
O
O
O
F
OH
OH
H
N
N
N
N
HN
O
O
F
H3C
H
H3C
F
Moxifloxacin
Garenoxacin
7
Pharmacodynamic Comparison with S. pneumoniae
levo
10
cipro
MPC
Plasma drug concentration (fold of MIC)
MIC
1
0.1
0
5
10
15
20
25
Time post-administration (hr)
8
Two Situations Producing Concentrations Inside
the Window
levo with S. pneumoniae
10
MPC
cipro with S. aureus
Plasma drug concentration (fold of MIC)
MIC
1
0.1
0
5
10
15
20
25
Time post-administration (hr)
9
Levofloxacin resistance among clinical isolates
of S. pneumoniae
Geographic region Dates of sample Number of isolates tested resistant
USA 1994-1995 1523 0.3
USA 1997-1998 1596 0.5
USA 1999-2000 1531 0.7
USA 1997-1998 2950 0.1
USA 1998-1999 4296 0.6
USA 1999-2000 9499 0.5
USA 2000-2001 6362 0.8
USA/Canada 1997-1998 3854 0.2-0.3
USA/Canada 1999 1201 0.9
Canada 1994-1998 7224 0.4
Canada 2000 2245 0.9
Japan 1997-1998 218 0.9
China 1997-1998 124 0.8
Germany 1997-1998 283 0.4
Hong Kong 2000 180 10
Brooklyn 1997,1999 138 1.4
10
Recovery of Fluoroquinolone-resistant S.
pneumoniae
Levo
1
Moxi
10-2
MIC99
MIC99
10-4
Fraction of cells recovered
10-6
10-8
10-10
?
0.1
1
Fluoroquinolone (µg/ml)
11
MPC and Fluoroquinolone Pharmacokinetics
10
Moxifloxacin
Levofloxacin
9
MPC90
8
7
750 mg
500 mg
6
Plasma drug concentration (mg/ml)
5
4
3
MPC90
2
MIC90
MIC90
1
0
0
10
20
30
40
50
0
10
20
30
40
50
Time post-administration (hr)
12
Comparison of Fluoroquinolones by MPC-based
Pharmacodynamics
t
MPC
Serum Concentration
MIC
Time
Fluoroquinolone MPC90 (mg/ml) Time above MPC90
(hr) Moxifloxacin 2
18 Gemifloxacin 1
4 Gatifloxacin 4
1-2 Levofloxacin
8
0
13
Recovery of Fluoroquinolone-resistant S.
pneumoniae
Levo
1
Moxi
MIC99
MIC99
10-2
10-4
Fraction of cells recovered
10-6
10-8
10-10
?
0.1
1
Fluoroquinolone (ug/ml)
14
Topoisomerase Mutants Selected by Levofloxacin
and Moxifloxacin
Fraction of Identity of mutants cells
recovered Selected by moxi
Selected by levo as mutants gyrA
gyrB parC parE gyrA gyrB parC parE 3.0 X
10-5 none none none none 4.4 X
10-6 none none none none none none n
one none none none none none 1.8 X
10-6 none none S79Y none 2.0 X
10-7 none none none none none none S79Y none
none none S79Y none none none D83H
none 1.3 X 10-7 none none none none 5.6
X 10-9 none none none none none none n
one none none none none none none non
e none none 1.2 X 10-9 none none none none
none none S79Y none S81Y none none none no
ne none S79Y none 2.9 X10-10 S81Y
none none none S81Y none none none 1.6
X10-10 S81Y none none none S81Y none none non
e   Changes in QRDR of the indicated genes
103
15
Effect of a parCr mutation on recovery of
resistant mutants
1
MIC99
parCr
MIC99
wt
10-2
Fraction of cfu recovered
10-4
10-6
10-8
10-10
MPC
MPC
0.1
1
10
Moxifloxacin (mg/ml)
S. pneumoniae
16
Fluoroquinolone Challenge Adds Topoisomerase
Mutations to S. pneumoniae
Strain Agent Changes in QRDR   ParC
ParE GyrA GyrB   70 D83G,
K137N none E85K
none 70 multiple D83G I460V
E85K none Gemi K137N, S79F
E474K S81Y 70 Moxi-1 D83G,
K137N none E85K, S81F
none 70 Moxi-2 D83G
none E85K, S81F none
K137N, S79F
17
Applications to Staphylococcus aureus
18
Mutant Selection Window and Fluoroquinolone
Pharmacokinetics S. aureus
Garenoxacin (BMS284756)
Ciprofloxacin
10
MPC90
30
MPC90
cipS
cipR
Drug (mg/ml)
1
MIC90
MPC90
MIC90
MIC90
0.03
0.2
0
5
10
15
20
25
0
5
10
15
20
25
Time post-administration (hr)
19
Dose above MPC
Serum or tissue drug con.
MPC-based Potencywith S. aureus
Time post-administration
Compound MPC (mg/ml) Cmax (mg/ml) half-life
(hr)  Norfloxacin 22
1.45 3.25 Tobramycin 20
52 1.8 Chloramphenicol 40
26 6.5 Rifampicin 480
9.5 2 Penicillin G
1 512 0.9 Vancomycin 40
39 6.5 Moxifloxacin 0.6
4.5 12
20
Mutant Selection Window with S. aureus
  Compound MPC (mg/ml) MIC99
(mg/ml) MPC/MIC99   Norfloxacin
22 0.85 26 Tobramycin
20 0.27 74 Chloramphenicol
40 1.9 21 Rifampicin
480 0.003 160,000 Penicillin G
1 0.015 67 Vancomycin
40 0.65
62 Moxifloxacin 0.6 0.05 12
21
Is the Mutant Selection Window Restricted to
Fluoroquinolones?
22
Mutant Selection with Erythromycin and Penicillin
M. smegmatis
S. aureus
10-1
Fraction of input cfu recovered
10-3
10-5
10-7
10-9
0.01
0.1
1
10
100
1000
0.1
1
10
100
1000
Erythromycin (mg/ml)
Penicillin (mg/ml)
23
Mutant Selection with Yeast (Canadia glabrata)
clinical resistant isolate
1
10-2
10-4
wild-ytpe
Fraction of input CFU recovered
10-6
10-8
0.001
0.01
0.1
1
10
100
Miconazole (mg/ml)
24
Why is the Selection Window Hypothesis Useful?
25
Gradual Increase of Resistance
breakpoint
Number of isolates
MIC
26
Problems for implementing direct attack of mutants

• No animal or clinical studies done
• Currently requires altruism (dosing higher than
  needed for cure)
• With S. pneumoniae time is running out
  (cross-resistance)

27
Literature Cited