C O N C L U S I O N S

A B S T R A C T Background: The emergence and spread of multidrug-resistant (MDR) Enterobacteriaceae is limiting available options to treat infections caused by these pathogens. SPR206 is a polymyxin analogue that exhibits potent in vitro activity against key Gram-negative pathogens like Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli (Ec) and Klebsiella pneumoniae, including MDR variants. Here, we describe the efficacy of SPR206 in an immunocompetent murine ascending urinary tract infection (UTI) model using Ec ATCC700928 (Ec700928) and Ec UTI89 (Ec89) as infecting organisms. Material/methods: The minimum inhibitory concentration (MIC) against Ec700928 and Ec89 were determined for SPR206 and polymyxin B (PMB) using CLSI methodology. Female C3H/HeN mice were maintained on 5% glucose drinking water for 5 days prior to infection. Mice were infected by inoculating the bladder intraurethrally (UT) via catheter. SPR206 and PMB were dosed at various concentrations by subcutaneous (SC) administration, every 8 hours (q8h) for 3 days. Treatment started 1-day post infection and mice were euthanized 4 days after the first treatment. Kidney tissues were homogenized, serially diluted, plated on permissive media with colony forming units (CFU) counted after overnight incubation. Results: The MIC of PMB and SPR206 for Ec700928 was determined to be 0.125 and 0.03 mg/L, respectively. The MIC for Ec89 were 0.06 mg/L and 0.125mg/L, respectively. In both studies, robust growth of the infecting organism in kidney tissue of 1.0 log10 CFU/g between day 1 and day 4 was observed. Administration of PMB and SPR206 at 4 mg/kg q8h SC for 3 days reduced the burden of Ec89by 2.9 and 3.0 log CFU/g compared to the day 1 control. Administration of PMB and SPR206 at 4 mg/kg q8h SC for 3 days reduced the burden of Ec700928 by 1.5 and 4.1 log CFU/g compared to the day 1 control, respectively. Conclusions: The in vivo pharmacology studies described here demonstrate that SPR206 exhibits similar, or superior, efficacy to PMB in immunocompetent murine ascending UTI infections. These data support the continued development of SPR206 for intravenous administration in the hospital setting for the treatment of serious Gram-negative infections.

1CLSI M07-A10: Methods for Dilution Antimicrobial Susceptibility Testing for Aerobic Bacteria 2Hung et al. 2009 PNAS 4(8): 1230 - 1243

•  The in vivo studies described herein demonstrated that SPR206 exhibits similar or superior burden reductions compared to PMB •  These data support the continued development of SPR206 for the treatment of serious Gram-negative infections.

R E F E R E N C E S A C K N O W L E D G M E N T S

Strain MIC (mg/L)

PMB SPR206 LEVO E. coli ATCC700928 0.125 0.03 0.06

E. coli UTI89 0.06 0.125 0.5

Treatment Log10 Group Geometric mean (CFU/g)

Log10 change from pre-treatment levels

Pre-treatment Control 7.19 NA Vehicle Control 8.24 +1.1

Levofloxacin 20 mg/kg QD x 3d 3.12 -4.1 PMB 0.25 mg/kg TID x 3d 6.20 -0.2

PMB 1 mg/kg TID x 3d 6.61 -0.2 PMB 4 mg/kg TID x 3d 5.36 -1.5

SPR206 0.25 mg/kg TID x 3d 8.29 +1.1 SPR206 1 mg/kg TID x 3d 7.08 +0.9 SPR206 4 mg/kg TID x 3d 3.11 -4.1

Treatment Log10 Geometric mean (CFU/g)

Log10 change from pre-treatment levels

Pre-treatment Control 6.05 NA Vehicle Control 7.0 +0.95

Levofloxacin 20 mg/kg QD x 3d 3.07 -2.98 PMB 0.25 mg/kg TID x 3d 6.83 +0.58

PMB 1 mg/kg TID x 3d 4.79 -1.26 PMB 4 mg/kg TID x 3d 3.15 -2.90

SPR206 0.25 mg/kg TID x 3d 5.37 -0.68 SPR206 1 mg/kg TID x 3d 3.75 -2.30 SPR206 4 mg/kg TID x 3d 3.05 -3.00

Ec ATCC700928 – PMB vs SPR206 Figure 2. Ec UTI89 – PMB vs SPR206 Figure 3.

Table 2. Burden reduction in Ec ATCC900728 with PMB or SPR206 administration Table 3. Burden reduction in Ec UTI89 with PMB or SPR206 administration

In Vivo Efficacy of SPR206 in an Immunocompetent Murine Ascending Urinary Tract Infection Model Caused by

Escherichia coli L. Grosser, K. Heang and A. Rubio

Spero Therapeutics, Cambridge, MA, USA

Troy Lister Spero Therapeutics

troy@sperotx.com

Poster-138 ASM ESCMID 2018 Lisbon, Portugal

This project has been funded in whole or in part with Federal funds from the National Institute of Allergy and Infectious Diseases, National Institutes of Health, Department of Health and Human Services, under Contract No. HHSN272201500014C

R E S U LT S

I N T R O D U C T I O N •  The emergence of multidrug-resistant (MDR) Enterobacteriaceae has resulted in fewer available treatment

options. •  SPR206 (Figure 1) is a polymyxin analogue that exhibits potent in vitro activity against key Gram-negative

pathogens Acinetobacter baumannii, Pseudomonas aeruginosa, Escherichia coli (Ec) and Klebsiella pneumoniae, including MDR variants

•  Here, we describe the efficacy of SPR206 in an immunocompetent murine ascending urinary tract infection (UTI) model using Ec ATCC700928 and Ec UTI89 as the infecting organisms.

•  The minimum inhibitory concentration (MIC) against Ec700928 and Ec89 were determined for SPR206 and polymyxin B (PMB) using CLSI methodology1.

•  The infection was established similar to that described in Hung et al.2 •  Female C3H/HeN mice were maintained on 5% glucose drinking water for 5 days prior to infection. •  Mice were infected by inoculating the bladder intraurethrally (UT) via catheter. •  SPR206 and PMB were dosed at various concentrations by subcutaneous (SC) administration, every 8 hours

(q8h) for 3 days. •  Treatment started 1 day post-infection and mice were euthanized 4 days after the first treatment. Kidney tissues

were homogenized, serially diluted, plated on permissive media with colony forming units (CFU) counted after overnight incubation.

M E T H O D S

Figure 1. Structure of SPR206

Table 1. MIC of strains used in the studies