Abstract

Pharmacokinetics and Tissue Distribution of Eravacycline following Intravenous Administration in Rabbits

V. PETRAITIS1, R. PETRAITIENE1, B. W. MAUNG1, F. KHAN1, J. NEWMAN2, A. MUTLIB3, X. NIU3, M. SATLIN1, T.J. WALSH1 1Weill Cornell Medicine of Cornell University, New York, NY, 2Tetraphase Pharmaceuticals, Watertown, MA, USA, 3Frontage, Exton, PA, USA

Correspondence: Vidmantas Petraitis, MD, Weill Cornell Medicine, 1300 York Ave., Rm. A-421, New York, NY 10065, tel: 212-746-7806, fax: 212-746-8675, Email: vip2007@med.cornell.edu

Background. Eravacycline (7-fluoro-9-pyrrolidinoacetamido-6-demethyl-6-deoxytetracycline or TP-434) is a novel, fully-synthetic fluorocycline of the tetracycline class that is designed through an innovative platform to retain activity against the two main acquired tetracycline-specific resistance mechanisms: drug efflux pumps and ribosomal protection. Eravacycline is particularly active against several life-threatening multidrug-resistant pathogens that are rapidly emerging worldwide, including Acinetobacter baumannii and carbapenem-resistant Enterobacteriaceae (CRE). A firm foundation in the PK/PD of experimental infections, including proper selection of dosage, plasma exposure, and duration, particularly of pneumonia and of vascular catheter-related bacteremia, is critical for successful clinical outcomes. We therefore characterized the plasma pharmacokinetics of eravacycline in rabbits in order to establish a dose-AUC relationship and to bridge that relationship to human dosing as a foundation for potential investigation in treatment of experimental pneumonias and vascular catheter-related bacteremia.Methods. Eravacycline was administered to NZW rabbits at 1, 2, 4, 8 & 10 mg/kg IV QD with a 5-10 min infusion (n = 20 (4/dosage group)). Plasma PK was analyzed as total and free exposures. The fraction unbound was calculated based upon a previous study based on concentrations between 0.1 to 100 mcg/mL. Infusion time was assumed to be 10 min for all rabbits. Results.

Introduction

Conclusions/Summary•  Within the single dose eravacycline PK study, the mean AUCs ranged from 5,375 ng•h/mL to 176,025

ng•h/mL across dosages 1 to 10 mg/kg/d. AUCs correlated well within the dosage range (r=0.97; p-0.0001).

•  Within the multidose eravacycline PK study, the mean AUCs ranged from 2,529 ng•h/mL to 29,888 ng•h/mL across the range of dosages from 0.5 mg/kg to 4 mg/kg/d.

•  Assuming an MIC of 1 µg/mL, for any one of MDR Enterobacteriaciae, these data would suggest fAUC/MIC ratios at 1 or 2 mg/kg Q12 of 3.3. to 6.7 that would predict potent activity in plasma and in most tissue sites.

•  For physicians treating patients in infections caused by susceptible bacteria in sites not yet currently studied in clinical trials, these data provide key information about the distribution of eravacycline that would inform probability of success or possibly the need for dose escalation to each target tissue exposures.

Eravacycline (7-fluoro-9-pyrrolidinoacetamido-6-demethyl-6-deoxytetracycline or TP-434) is a novel, synthetic tetracycline molecule that is available in parenteral and oral formulations. Eravacycline is designed through an innovative platform to be active against the two main acquired tetracycline-specific resistance mechanisms: drug efflux pumps and ribosomal protection. Eravacycline is two- to fourfold more potent than tigecycline versus Gram-positive cocci and two- to eightfold more potent than tigecycline versus Gram-negative bacilli.Eravacycline is particularly active in vitro against some of the most life-threatening multidrug resistant pathogens that are rapidly emerging worldwide. These include Acinetobacter baumannii, carbapenemase-producing Klebsiella pneumoniae (KPC), and Stenotrophomonas maltophilia. Prior to initiating clinical trials against these pathogens, a firm foundation in the PK/PD of experimental infections, particularly of pneumonia, intra-abdominal infections, and vascular catheter-related bacteremia, is necessary. As little is known about the penetration of eravacycline into key infection sites, we studied its plasma pharmacokinetics and tissue distribution in rabbits.

Results

Materials and Methods

Eravacycline Plasma Mean Concentrations after Single Dose

0 4 8 12 16 20 24 96 120 144 1680

15000

30000

45000

60000

Time (h)

ng/m

L

1 mg/kg2 mg/kg4 mg/kg8 mg/kg10 mg/kg

Eravacycline Plasma Mean Concentrations after Multiple Dosing

0 4 8 12 16 20 240

2500

5000

7500

10000

Time (h)

ng/m

L

0.5 mg/kg1 mg/kg2 mg/kg4 mg/kg

0 2 4 6 8 100

50000

100000

150000

200000

Dose (mg/kg)

AU

C(h

r.ng

/mL)

AUC vs Dose Single

r = 0.9749 (p = 0.0001)

A

0 1 2 3 40

10000

20000

30000

40000

Dose (mg/kg)

AU

C(h

r.ng

/mL)

AUC vs Dose Multiple

r = 0.9701 (p = 0.0001)

B

Eravacyline Plasma AUC vs Dose Correlation

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

5000

10000

15000

ng/g

Liver

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

2000

4000

6000

8000

10000

ng/g

Kidney (Medulla)

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

1000

2000

3000

4000

5000

ng/g

Spleen

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

5000

10000

15000

20000

ng/g

Kidney (Cortex)

Eravacyline Rabbit Tissue Mean Concentrations

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

50

100

150

200

ng/g

Cerebrum

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

1000

2000

3000

ng/g

Lung

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

500

1000

1500

ng/g

Heart

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

100

200

300

ng/g

Anterior Vena Cava

Eravacyline Rabbit Tissue Mean Concentrations

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

2000

4000

6000

8000

10000

ng/g

Gall Bladder

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

1000

2000

3000

ng/g

Psoas Muscle

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

500

1000

1500

2000

2500

ng/g

Pancreas

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

500

1000

1500

2000

2500

ng/g

Bone Marrow

Eravacyline Rabbit Tissue Mean Concentrations

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

50

100

150

200

ng/m

L

Aqueous humor

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

50

100

150

ng/g

Choroid

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

10

20

30

40

ng/m

L

Vitreous humor

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

50

100

150

200

250

ng/m

L

CSF

Eravacyline Rabbit Tissue/Fluid Mean Concentrations

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

20

40

60

80

100

ng/m

L

BAL Fluid

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

5000

10000

15000

20000

ng/m

L

Bile

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

50

100

150

ng/m

L

PAMS

0.5 m

g/kg

1 mg/kg

2 mg/kg

4 mg/kg

0

10000

20000

30000

ng/m

L

Urine

Eravacyline Rabbit Fluid Mean Concentrations

Semina

l Glan

d

Vesic

ular G

land

Bulbou

reth

ral G

land

Prosta

te

Teste

s0

500

1000

1500

2000

2500

ng/g

Eravacyline Mean Concentrations in Rabbit Male Organs

Dose MIC(mg/kg) (ug/mL) Cl fAUC fAUC/MIC0.5 0.5 0.6 833 1.671 0.5 0.6 1,667 3.332 0.5 0.6 3,333 6.674 0.5 0.6 6,667 13.330.5 1 0.6 833 0.831 1 0.6 1,667 1.672 1 0.6 3,333 3.334 1 0.6 6,667 6.67

Rabbit

AnimalsRabbits - Female New Zealand White rabbits weighing 2.6 to 3.5 kg were used in the study. Vascular access was established in each rabbit by the surgical placement of a Silastic tunneled central venous catheter.PharmacokineticsSingle-dose plasma pharmacokinetics - Eravacycline was administered to NZW rabbits at 1, 2, 4, 8, and 10 mg/kg IV QD with a 10 minute infusion. Plasma samples (1.0 mL of blood) were drawn before administration of eravacycline as baseline, drug infused over 10 min, and then blood drawn after the end of the IV infusion sequentially at 0.5, 1, 4, 8, 12, 24, 36, 48, 60, 72, 96, 120, 144, and 168 hours. Multi-dose plasma pharmacokinetics - Five groups of four animals received eravacycline daily QD at 0.5, 1-female, 1-male, 2, and 4 mg/kg as an IV infusion over 6 days with serial plasma sampling on day 6 and tissue sampling in 5 groups on day 7. Plasma samples (1.0 mL of blood) on day 7 were drawn immediately before administration and then sequentially after the end of the IV infusion at 0.5, 1, 2, 4, 6, 8, 12, and 24 hours. Tissue distribution studies - For the assessment of tissue concentrations of eravacycline, animals were euthanized on day 7, 1 h after last infusion. All rabbits were euthanized by IV pentobarbital and the following tissues were obtained at necropsy for analysis of drug concentrations: cerebrum, cerebrospinal fluid (CSF), choroid, vitreous humor, aqueous humor, heart, anterior vena cava, lung, BAL fluid, PAMS, liver, spleen, kidney (medulla), kidney (cortex), gall bladder, pancreas, bile, bone marrow, perirenal adipose tissue, and psoas muscle. Four male rabbits receiving 1 mg/kg dose, were studied for eravacycline concentrations in seminal gland, vesicular gland, bulbourethral gland, prostate, and testes.

Plasma Pharmacokinetics of Eravacycline after Intravenous Single Dose Administration at 1, 2, 4, 8, 10 mg/kg and Multiple Dosing at 0.5, 1, 2, 4 mg/kg to Healthy New Zealand White Rabbits

Results

Materials and Methods

Assuming an MIC=0.5 mcg/mL, dosages of 0.5 to 4.0 mg/kg will span the humanized target AUC/MIC ratios of 1.67 to 13.33 mcg/mL. Conclusion. The plasma pharmacokinetic profile of 0.5 to 4 mg/kg in NZW rabbits yields comparable exposure to that of humans and provides a platform for further study of eravacycline against MDR bacterial pathogens.

Tissue/Fluid Distribution of Eravacycline after Intravenous Multiple Dosing at 0.5, 1, 2, 4 mg/kg to Healthy New Zealand White Rabbits

0 10000 20000 30000 400000

5000

10000

15000

20000

AUC(hr.ng/mL)

Live

r (n

g/m

g)

AUC vs Liver correlations

r = 0.8146 (p = 0.0001)

0 10000 20000 30000 400000

5000

10000

AUC(hr.ng/mL)

Kid

ney

(Med

) (ng

/mg)

AUC vs Kidney (Medulla) correlations

r = 0.8800 (p = 0.0001)

0 10000 20000 30000 400000

1000

2000

3000

4000

AUC(hr.ng/mL)

Lung

(ng/

mg)

AUC vs Lung correlations

r = 0.8590 (p = 0.0001)

0 10000 20000 30000 400000

50

100

150

AUC(hr.ng/mL)

BA

L Fl

uid

(ng/

mg)

AUC vs BAL Fluid correlations

r = 0.7630 (p = 0.0001)

0 10000 20000 30000 400000

2000

4000

6000

AUC(hr.ng/mL)

Spl

een

(ng/

mg)

AUC vs Spleen correlations

r = 0.7838 (p = 0.0001)

0 10000 20000 30000 400000

5000

10000

15000

20000

25000

AUC(hr.ng/mL)

Kid

ney

(Cor

t) (n

g/m

g)

AUC vs Kidney (Cortex) correlations

r = 0.8876 (p = 0.0001)

0 10000 20000 30000 400000

1000

2000

3000

AUC(hr.ng/mL)

Bon

e M

arro

w (n

g/m

g)

AUC vs Bone Marrow correlations

r = 0.7747 (p = 0.0001)

0 10000 20000 30000 400000

50

100

150

AUC(hr.ng/mL)

PA

M (n

g/m

g)

AUC vs PAM correlations

r = 0.8593 (p = 0.0001)

0 2000 4000 60000

5000

10000

15000

20000

Plasma (ng/mL)

Live

r (n

g/m

g)

Plasma vs Liver correlations

r = 0.8003 (p = 0.0001)

0 2000 4000 60000

5000

10000

15000

Plasma (ng/mL)

Kid

ney

(Med

) (ng

/mg)

Plasma vs Kidney (Medulla) correlations

r = 0.9244 (p = 0.0001)

0 2000 4000 60000

1000

2000

3000

4000

Plasma (ng/mL)

Lung

(ng/

mg)

Plasma vs Lung correlations

r = 0.8650 (p = 0.0001)

0 2000 4000 60000

50

100

150

Plasma (ng/mL)

BA

L Fl

uid

(ng/

mg)

Plasma vs BAL Fluid correlations

r = 0.7611 (p = 0.0001)

0 2000 4000 60000

2000

4000

6000

Plasma (ng/mL)

Spl

een

(ng/

mg)

Plasma vs Spleen correlations

r = 0.7251 (p = 0.0001)

0 2000 4000 60000

5000

10000

15000

20000

Plasma (ng/mL)

Kid

ney

(Cor

t) (n

g/m

g)

Plasma vs Kidney (Cortex) correlations

r = 0.8853 (p = 0.0001)

0 2000 4000 60000

1000

2000

3000

4000

Plasma (ng/mL)

Bon

e M

arro

w (n

g/m

g)

Plasma vs Bone Marrow correlations

r = 0.7770 (p = 0.0001)

0 2000 4000 60000

50

100

150

Plasma (ng/mL)

PA

M (n

g/m

g)

Plasma vs PAM correlations

r = 0.8269 (p = 0.0001)

Dose (mg/kg) AUC(o-168) (hr·ng/mL) Cmax CL (L/hr/kg) Vd (L/kg) 1 5,375 ± 549 2,077 ± 496 0.18 ± 0.019 1.31 ± 0.172 12,563 ± 1,790 6,118 ± 1,789 0.16 ± 0.025 1.12 ± 0.324 36,146 ± 11,487 17,798 ± 5,393 0.12 ± 0.039 0.94 ± 0.278 121,905 ± 15,491 45,614 ± 7,887 0.066 ± 0.008 0.79 ± 0.13

10 176,025 ± 16,369 7,6325 ± 11,788 0.057 ± 0.005 0.84 ± 0.46

Processing of blood and tissues - Blood samples were collected in heparinized syringes, and plasma was separated by centrifugation. All plasma, body fluid and tissue samples were stored at -80°C until assay.Pharmacokinetic analysis - The pharmacokinetic profiles for eravacycline were computed from the drug concentration-time data using noncompartmental methods. The peak drug concentration (Cmax) and time of peak drug concentration were obtained directly from the observed data. The terminal elimination rate constant (kel) was obtained from a log-linear regression of the plasma concentration compared to time data in the terminal postdistribution phase. The area under the plasma drug concentration-versus-time curve (AUC0-24) was calculated by the log-linear trapezoidal rule. The total body clearance (CL) for was obtained from the equation dose/AUC0-24. The volume of distribution (Vd) for was calculated as Vd = CL/kel.

190