Monash Institute of Pharmaceutical Sciences Sheep as a clinically relevant model to assess the pharmacokinetics of colistin and colistin methanesulfonate

Monash Institute of Pharmaceutical Sciences

Sheep as a clinically relevant model to assess the pharmacokinetics of colistin and colistin methanesulfonate after pulmonary and intravenous administration

Dr Tri-Hung NguyenDrug Delivery to the Lung Conference Edinburgh, December 2012

2

• Increasing prevalence in hospital environments

• Product of antimicrobial misuse

• Sources of MDR lung infections

• Klebsiella pneumoniae

• Acinetobacter baumanii

• Pseudomonas aeruginosa

• Opportunistic infections

• Prevalent amongst immunocompromised patients

• Cystic fibrosis

• Critically ill

Multiple drug resistant Gram negative infections

Soon et al. Antimicrob Agents Chemother 2006

0 5 µm

3

Antimicrobial Development

Clatworthy et al., Nat Chem Biol 2007.

4

Antimicrobial Resistance

Clatworthy et al., Nat Chem Biol 2007.

5

Declining numbers of new antimicrobial agents

1983-87 1988-92 1993-97 1998-2002 2003-07 2008-12

To

tal n

um

be

r o

f n

ew

ag

ents

0

2

4

6

8

10

12

14

16

18

Adapted from Spellberg et al. Clin Infect Dis 2011 Antimicrobials with activity against Gram-negatives

EMEA 2009

6

Antimicrobial Resistance

7

Colistin (Polymyxin E)

O

OO

O

O

O

O

O

O

OHO

HO

O

NH

HN

HNH

N

HN

NH

HN

NH

HN

HN

NH

NH2

NH2

NH2

NH2

NH2 R6

R1

1 L-Dab

2 L-Thr

3 L-Dab

4 L-Dab

5 L-Dab

7 L-Leu

8 L-Dab

9 L-Dab

10 L-Thr

Colistin R6 = D-LeuPolymyxin B R6 = D-PheColistin A & polymyxin B1 R1 = 6-methyloctanoic acidColistin B & polymyxin B2 R1 = 6-methylheptanoic acid

• Cationic polypeptide antimicrobial

• First used in the 1950’s and 1960’s

8




• Amphiphilic molecule

• Hydrophilic peptide ring

O

OO

O

O

O

O

O

O

OHO

HO

O

NH

HN

HNH

N

HN

NH

HN

NH

HN

HN

NH

NH2

NH2

NH2

NH2

NH2 R6

R1

1 L-Dab

2 L-Thr

3 L-Dab

4 L-Dab

5 L-Dab

7 L-Leu

8 L-Dab

9 L-Dab

10 L-Thr


Peptide Ring

9






• Hydrophobic tail

O

OO

O

O

O

O

O

O

OHO

HO

O

NH

HN

HNH

N

HN

NH

HN

NH

HN

HN

NH

NH2

NH2

NH2

NH2

NH2 R6

R1

1 L-Dab

2 L-Thr

3 L-Dab

4 L-Dab

5 L-Dab

7 L-Leu

8 L-Dab

9 L-Dab

10 L-Thr


Hydrophobic tail

10






• Hydrophobic tail

• Mode of action

• Positively charged amino groups

• Interaction with bacterial cell membrane

O

OO

O

O

O

O

O

O

OHO

HO

O

NH

HN

HNH

N

HN

NH

HN

NH

HN

HN

NH

NH2

NH2

NH2

NH2

NH2 R6

R1

1 L-Dab

2 L-Thr

3 L-Dab

4 L-Dab

5 L-Dab

7 L-Leu

8 L-Dab

9 L-Dab

10 L-Thr


Positively charged

11

Colistin and colistin methanesulfonate (CMS)

• Colistin

• Nephrotoxicity and neurotoxicity on high systemic exposure

• Superseded by newly developed antibiotics

• Bronchoconstriction when inhaled

12

Colistin and colistin methansulfonate (CMS)

• Colistin

• Nephro- and neurotoxicity on high systemic exposure

• Superseded by newly developed antibiotics

• Bronchoconstriction on inhaled use

• Inactive prodrug

• Colistin methanesulfonate (CMS)

• Amines replaced with methylene sulfonic acid moieties

13

Clinical use of colistin and CMS

•Colistin currently used in clinical practice

•Inconsistencies with doses administered

•Need to refine dosing regimens

• Improve efficacy

• Prevent resistance

•Potential toxicity at high dose limits dose excursions

14

Clinical use of colistin and CMS

•Colistin currently used in clinical practice

•Inconsistencies with doses administered

•Need to refine dosing regimens

• Improve efficacy

• Prevent resistance

•Potential toxicity at high dose limits dose excursions

Can a pre-clinical model be used to assess targeted delivery of antibiotics and inform clinical practice?

15

In vivo lung models Mouse Rat Guinea-pig Dog Sheep Human

Body mass (kg) 0.02-0.04 0.25-0.35 0.4 10-15 45 70-80

Nose/mouth breathers

Nose Nose Nose Nose/mouth Nose/mouth Nose/mouth

Trachea-bronchial branching pattern

Monopodial Monopodial Monopodial Monopodial Dichotomous Irregularly

dichotomous

Lung mass (g) 0.12 1.5 - 100 250-1000 1000

Lung volume (mL) 0.74 8.6 13 736 2800 4341

Lung Lobation5 lobes

left lung (1) and right lung (4)

Left lung is not divided

-6 lobes

left lung (2) and right lung (4)

6 lobes left lung (2) and

right lung (4)

5 lobes left lung (2) and

right lung (3)

Alveoli diameter (μm)

47 70 65 126 150-300 200-400

Tidal volume (ml) 0.15-0.18 0.87-2.08 1.72 – 1.75

11.4 – 16.6

180 – 405 400 – 616

Respiratory rate (breaths/min)

163 85 90 23 15 – 40 12

16

Hypothesis

Sheep are a suitable preclinical model to assess the localised delivery of an antimicrobial to the lung

17

• 6 merino sheep

• Four way randomised crossover study

• Surgical cannulation

• Jugular vein: IV administration

• Carotid artery: Blood collection

• IV administration

• 2.5 mg/kg or equivalent

• Colistin (sulfate salt)

• CMS (sodium salt)

• IV infusion at 1 mL/min

• Blood and broncho-alveolar lavage (BAL) fluid sampled up to 24 hr after administration

In-vivo studies

18

Pulmonary administration of colistin and CMS

• Conducted in conscious sheep

• Endotracheal tube directed via nostril into the trachea

• Colistin and CMS solution nebulised over 25 min

• Blood sampled up to 24 hr after administration

• BAL fluid collected from lung sections

• 1, 4 and 24 hr after administration

• Colistin and CMS plasma analysed via HPLC

19

Data analysis

• Non-compartmental analysis

• Population modeling (S-ADAPT and SADAPT-TRAN software/MC-PEM algorithm)

• Takes into account the true biological variability between sheep

• Enables prediction of concentration vs. time profiles at other dosage regimens

• Supports translation from sheep into humans and allometric scaling

• The PK model can be combined with a pharmacodynamic model to predict antibacterial effects

20

IV colistin pharmacokinetics

• IV colistin sulfate

• Fits 3 compartment model

• Decrease in plasma concentrations over time

Time (h)

0 2 4 6 8 10

Dru

g plasma concentration (m

g/L)

0.1

1

10

100

1000Colistin sulfate

21

IV CMS pharmacokinetics

• IV CMS



• Similar elimination phase

• Colistin conversion from CMS

• Increased concentration over time

• No colistin/CMS concentrations were detected in epithelial lung fluid (ELF)

Time (h)

0 2 4 6 8 10

Dru


g/L)

0.1

1

10

100

1000CMSColistin from CMS

22

IV colistin and CMS pharmacokinetics

• IV colistin sulfate and CMS



• Similar elimination phase

• Colistin conversion from CMS

• Increased concentration over time

• No colistin/CMS concentrations were detected in epithelial lung fluid (ELF)

Time (h)

0 2 4 6 8 10

Dru


g/L)

0.1

1

10

100

1000Colistin sulfateCMSColistin from CMS

23

IV colistin from CMS pharmacokinetics

Pharmacokinetic Parameter

Colistin from CMS Sheep

Colistin from CMS Human

Colistin from CMS Rat

AUC (mg/L x h) 23.9 ± 7.5

t1/2 (h) 9.1 ± 6.1

Tmax (h) 3.1 ± 0.55

Cmax (mg/L) 2.6 ± 0.4

24




Colistin from CMS Humans

Colistin from CMS Rats

AUC (mg/L x h) 23.9 ± 7.5

t1/2 (h) 9.1 ± 6.1 *5.9-14.4

Tmax (h) 3.1 ± 0.55

Cmax (mg/L) 2.6 ± 0.4

٭ Imberti et al. Chest (2010) Garonzik et al. Antimicrob. Agents Chemother. (2011) Plachouras et al. Antimicrob. Agents Chemother. (2009)

25




Colistin from CMS Humans

Colistin from CMS Rats

AUC (mg/L x h) 23.9 ± 7.5

t1/2 (h) 9.1 ± 6.1 *5.9-14.4 #0.4-1.2

Tmax (h) 3.1 ± 0.55

Cmax (mg/L) 2.6 ± 0.4

٭ Imberti et al. Chest (2010) Garonzik et al. Antimicrob. Agents Chemother. (2011) Plachouras et al. Antimicrob. Agents Chemother. (2009)

# Marchand et al. J. Antimicrob. Chemother. (2010) Li et al. Antimicrob Agents Chemother (2003) Li et al. Antimicrob Agents Chemother (2004)

26

Population PK model: IV clearance


ColistinSheep

Colistin Humans

ColistinRats

Clearance (L/h) 1.3 *1.1 #0.1

* Reed et al. J. Clin Pharmacol. (2002) # Li et al. J. Antimicrob. Chemother. (2003)

27

Local delivery of colistin and CMS to the lung

• Epithelial lung fluid concentration

• Colistin and CMS concentration decreased over time

• Colistin from CMS increased then decreased

• Conversion from CMS

• No detectable colistin concentration measured in plasma

• Consistent with human data

• < 0.14mg/L*

• Colistin binding to tissues?Time (h)

1 4 24

Colistin/C

MS

Concentration (m

g/L)

10

100

1000

10000Colistin Sulfate CMSColistin from CMS

* Ratjen et al. J. Antimicrob. Chemother. (2006) Jensen et al. J. Antimicrob. Chemother. (1987)

28

Local delivery of colistin and CMS to the lung

• Epithelial lung fluid concentration

• Colistin and CMS concentration decreased over time

• Colistin from CMS increased then decreased

• Conversion from CMS

• No detectable colistin concentration measured in plasma

• Consistent with human data

• < 0.14 mg/L*

• Colistin binding to tissues?

* Ratjen et al. J. Antimicrob. Chemother. (2006) Jensen et al. J. Antimicrob. Chemother. (1987)

Marchand et al. Antimicrob. Agents Chemother (2010)

Systemic plasma concentrations measured in rats

29

Population PK model: Lung delivery

PUL colistin dose

Colistin in

ELFColistin in lung

tissues

Colistin clearance (4.6 mL/h)

distributionColistin in absorption

compartment

absorption

30

Population PK model: Lung delivery

PUL CMS dose

PUL colistin dose

CMS in ELF

Colistin in

ELF

CMS in lung tissues

Colistin in lung tissues

Metabolism to colistin

Colistin clearance (4.6 mL/h)

distribution


distribution

CMS in absorption compartment

Colistin in absorption

compartment

absorption

absorption

31

Summary• Sheep were examined as a clinically relevant model to assess the PK of the

antimicrobial colistin and CMS

• Decreases in CMS plasma concentrations after IV administration corresponded to an increase in formed colistin

• No colistin or CMS detected in ELF after IV administration

32

Summary• Sheep were examined as a clinically relevant model to assess the PK of the

antimicrobial colistin and CMS

• Decreases in CMS plasma concentrations after IV administration corresponded to an increase in formed colistin

• No colistin or CMS detected in ELF after IV administration

• CMS concentrations decreased in ELF over 24 h with increasing colistin concentrations after pulmonary administration

• No colistin or CMS detected in plasma

• Correlates to clinical data

• Population PK modeling indicated that CMS was distributed and metabolised in ELF and lung tissue after pulmonary administration

• Sheep have been demonstrated to be a clinically relevant model to evaluate the PK of antimicrobials administered to the lung.

33

Acknowledgments


Dr Michelle McIntosh

Linh Lieu

Biotechnology Research Laboratories (Monash University)

Prof Els Meeusen

Dr Robert Bishcof

Gary Nguyen

Centre for Medicine Use and Safety (Monash University)

Dr Cornelia Landersdorfer


Sheep as a clinically relevant model to assess the pharmacokinetics of colistin and colistin methansulfonate after pulmonary and intravenous administration

Dr Tri-Hung NguyenDrug Delivery to the Lung Conference Edinburgh, December 2012

35

Population PK model: IV administration

IV CMS dose

IV colistin dose

CMS in plasma

Colistin in

plasma

CMS in slowly equilibrating

tissues

Colistin in

slowly equilibrating

tissues


colistin elimination

distribution


distribution


CMS in rapidly equilibrating

tissues

Colistin in

rapidly equilibrating

tissues

CMS elimination

distribution

distribution

36

Population PK model: IV clearance

Parameter Colistin from CMS Colistin

Clearance (L/h) 1.32 0.784

Central volume of distribution (L) 0.50 0.32

Peripheral volume of distribution (Fast equilibrating, L)

7.45 3.25

Peripheral volume of distribution (Slow equilibrating, L)

92.9 59.1

Conversion of CMS to colistin in central and fast equilibrating peripheral compartment (h-1)

0.05

Documents

Monash Institute of Pharmaceutical Sciences Sheep as a clinically relevant model to assess the pharmacokinetics of colistin and colistin methanesulfonate