1. 5/20/2015ISAP - 20091 Is the cellular accumulation of antibiotics a predictive factor for intracellular efficacy ? Sandrine Lemaire Université catholique de Louvain & Louvain Drug Research Institute Brussels, Belgium

2. 5/20/2015ISAP - 20092 Persistence and recurrence: the case of Staphylococcus aureus … Intracellular Staphylococcus aureus. A mechanism for the indolence of osteomyelitis Ellington et al, J Bone Joint Surg (2003), 85:918-921. Intracellular persistence of Staphylococcus aureus Small Colony Variants within keratinocytes: a cause for antibiotic treatment failure in a patient with Darier’s disease. von Eiff et al, Clin Infect Dis (2001), 32:1643-1647. Phagocytosis of Staphylococcus aureus by macrophages exerts cytoprotective effects manifested by the up-regulation of antiapoptotic factors. Koziel et al, PLoS One (2009), 4:e5210. Staphylococcus aureus an intracellular pathogen: the role of Small Colony Variants. Sendi and Proctor, Trends Microbiol (2009), 17:54-58 …

3. 5/20/2015ISAP - 20093 A simple scheme ? Cellular accumulation Antibiotic Antibacterial effect Phagolysosomial infection phagolysosomes

4. 5/20/2015ISAP - 20094 1st exemple: Torezolid (TR-700), a novel oxazolidinone Comparative cellular accumulation Torezolid accumulates quickly within cells, reaching an apparent cell. to extracell. concentration ratio of 12.5 – 15.

5. 5/20/2015ISAP - 20095 Torezolid vs. linezolid Lemaire et al, JAC, 2009 Torezolid is more active than linezolid against the intracellular forms of S. aureus (ATCC 25923) On a weight concentration basis, torezolid is 4-fold more potent than linezolid against intracellular forms of S. aureus. * Cs, Static concentration

6. 5/20/2015ISAP - 20096 Torezolid vs. linezolid Lemaire et al, JAC, 2009 When data are plotted against equipotent concentration (MIC multiples), torezolid and linezolid show undistinguishable concentration-dependent activities against intracellular forms of S. aureus This indicates that the main driver of torezolid intracell. activity is not the marked cell. accum, but its higher intrinsic activity Torezolid is more active than linezolid … Is it still true when comparing equipotent concentrations ?

7. Torezolid vs. Linezolid against others intracell. bacteria 5/20/2015ISAP - 20097 Cytosolic modelPhagosomal model MICs: L.M., TR-700, 0.125 mg/L vs LZD, 1 mg/L; L.P., TR-700, 0.25 mg/L vs LZD, 8 mg/L

8. 5/20/2015ISAP - 20098 2nd exemple: CEM-101, a novel fluoroketolide Comparative cellular accumulation CEM-101 accumulates to a larger extent than clarithromycin (CLR) and telithromycin (TEL)

9. 5/20/2015ISAP - 20099 CEM-101 vs. comparators CEM-101 is more active than CLR and TEL against intracellular forms of S. aureus (strain ATCC 25923) On a weight concentration basis, CEM-101 expresses consistently greater potency (decreases values of EC 50 and C s ) and slightly higher efficacy (E max ) than comparators. Lemaire et al, AAC (2009), 53:3734-3743

10. 5/20/2015ISAP - 200910 CEM-101 vs. comparators If we consider equipotent concentrations of antibiotics … When data are plotted against equipotent concentration (MIC multiples), the differences in EC 50 and static concentrations between drugs were minimized. This indicates that the main driver of CEM-101 intracell. activity is not the marked cell. accum, but its higher intrinsic activity * MICs at pH 7.4: CLR, 0.5 mg/L; TEL, 0.25 mg/L; CEM-101, 0.06 mg/L * Lemaire et al, AAC (2009), 53:3734-3743

11. 5/20/2015ISAP - 200911 Is it still a simple scheme ??? Cellular accumulation Antibiotic These studies demonstrate the critical role of intrinsic drug activity (MIC) in eliciting the antibacterial intracellular effects of TR-700 and CEM-101 whereas their increased cellular accumulation per se play only a minimal role. Antibacterial effect

12. 5/20/2015ISAP - 200912 Other factors ??? Cellular penetration Antibiotic Metabolism Binding Cooperation with host defences Physical or biochemical Conditions prevailing in the infected site Influx vs. efflux Bacterial stress response

13. Thank you for your attention 5/20/2015ISAP - 200913