1. Evaluation of Tissue Distribution of TR-700 in Healthy Volunteers Using Microdialysis
Martina Sahre1,
Sreedharan Sabarinath1, PhD
Maria Grant2, MD,
Christoph Seubert3, MD, PhD,
Carisa deAnda4, PharmD
Hartmut Derendorf1, PhD
University of Florida,
College of Pharmacy, Departments of Pharmaceutics1, Therapeutics and Pharmacology2, Anesthesiology3,
Trius Therapeutics4, San Diego, California

2. Overview Introduction Study Design Results Conclusion TR-700 / TR-701
Rationale
Microdialysis
Study Design
Results
Conclusion

3. TR-700 Oxazolidinone class Phosphate ester prodrug (TR-701)
Limited water solubility
Phosphate ester prodrug (TR-701)
Rapid conversion to active drug

4. TR-700 Oxazolidinone class
Indication complicated skin and skin structure infections (cSSSI)
In vitro activity against:
S. aureus (MS and MR),
Linezolid-resistant MRSA carrying binding-site mutations, cfr gene
S. pneumoniae (PS, PR), S. pyogenes, S. agalactiae, Enterococci (inc.. VRE)
Rennie et al. (2003), Im et al. (2007), Jones et al. (2009), Shaw et al. (2007), Schaadt et al. (2009)

5. Rationale Plasma concentrations linked to PK/PD indices
Free drug in tissue more relevant
Drug molecules need to reach tissue
Factors: pH of tissues, pKa of drug, density of tissue, blood-tissue barrier, lipophilicity.
FDA and EMEA suggest to measure target tissue drug levels for dose-response studies

6. Mean Ceftobiprole Concentrations After Single 500 mg i.v. Dose
Mean Linezolid Concentrations After Single 600 mg i.v. Dose
C(tissue) < fc(plasma)
C(tissue) > fc(plasma)
Total Plasma,  Muscle Tissue,
 Adipose Tissue, --- Free Plasma
Barbour et al. (2009), Deghanyar et al. (2005)

7. Rationale Biopsy, skin blisters, imaging techniques
AUC of Moxifloxacin after 400 mg p.o single dose:
Measure unbound PK parameter in tissue using microdialysis
Plasma
Muscle Tissue
Subcutaneous Tissue
Saliva
Capillary Blood
Blister
AUC [µg*h/mL]
19.8
8.5
8.0
17.6
18.7
12.3
Factors: pH of tissues, pKa of drug, density of tissue, blood-tissue barrier, lipophilicity.
FDA and EMEA suggest to measure target tissue drug levels for dose-response studies
Mueller et al. (1999)

8. Microdialysis Principle
Diffusion through a
semipermeable membrane
“Mimics” blood vessel
Sampling tool
Assess free drug directly
No volume added or taken from tissue.
Only analyte taken or delivered.
Courtesy of CMA

9. Recovery Probe calibration → recovery factor
Probe is continuously perfused → no equilibrium
cdialysate < cmedium
Recovery defined as ratio cdialysate/cmedium
Dialysate: liquid recovered from probe
Medium: tissue or solution containing compound of interest
Factors influencing recovery:
Temperature, Membrane length, Flow-rate, Molecular size, Membrane properties, Tissue properties
Probe calibration → recovery factor

10. Retrodialysis Perfusate contains known concentration of compound
Dialysate concentration measured
Calculated recovery used to
adjust drug concentrations from
experiment
Courtesy of CMA

11. Study Design
TR-700 measured in plasma, s. c. adipose and muscle tissue
15 healthy volunteers
Pilot (n = 3) and Main Study (n = 12)
Two microdialysis probes implanted
Retrodialysis to calibrate probe
Washout period
Main Study
Single dose of study drug, 600 mg p.o.
Dialysate samples every 20 minutes for 12 h,
blood samples for 24 h after dosing
Protein binding samples 0, 2, 12h post dose
CMA 60 probe, Courtesy of CMA, Sweden)

12. Pilot Study Results
Recovery > 90%
Washout period 4 h

13. Main Study: Results Protein Binding 87 % (1.3%)
PB samples taken from each subject at 0, 2 and 12 h post dose and analysed using ultrafiltration.
Each individuals plasma c(total) were adj. with their respective protein binding.

14. Mean PK Parameters (SD)
Unit
Plasma
fPlasma
Adipose Tissue
Muscle Tissue
Cmax
(µg/mL)
5.37 (1.51)
0.70 (0.27)
0.66 (0.16)
0.74 (0.15)
Tmax§
(hr)
2 (1-4)
3.33 ( )
3.67 (1.67-7)
AUC0-12
(µg*h/mL)
38.8 (7.55)
4.96 (1.09)
5.27 (1.28)
5.95 (1.11)
AUC0-24
57.1 (14.7)
7.28 (1.91) -
AUC∞
70.0 (24.8)
8.89 (3.06)
16.6 (15.8)
14.6 (10.5)
t½§
8.13 ( )
9.22 ( )
9.59 ( )
CL/F
(L/hr)
9.46 (2.91) *
Vz/F
(L)
113 (19.3)
fAUC0-12, tissue/
fAUC0-12, plasma 
1.08 (0.22)
1.22 (0.18)
Protein Binding %
87.2 (1.3)
* Not applicable; § Median (Range); λz: terminal elimination rate constant
Cmax similar, T max 1 to 1.5 h later, AUC0-12 similar, t1/2 about 1 h longer in tissue, and free AUC0-12 ratios 1.1 and 1.2 show that free drug has no major barriers to distributing into tissues (observed only).

15. Conclusion
TR-700 conc. in observed tissues similar to unbound plasma concentrations
No significant difference between AUC0-12 for unbound plasma, adipose and muscle tissues
Drug and microdialysis well tolerated
Degree of tissue distribution corresponds with free drug available in plasma which is corroborated by the AUC0-12 being not stat. sign. Diff.

16. Acknowledgements Prof. Hartmut Derendorf
Maria Grant, MD and Christoph Seubert, MD, PhD
Sreedharan Sabarinath, PhD
General Clinical Research Center at the University of Florida
Philippe Prokocimer, MD
Trius Therapeutics, Inc.