Dose Ranging and Dose Fractionation of Tebipenem-Pivoxil (SPR994) in Neutropenic Murine Thigh Models of Gram-Negative Bacterial Infection Posted on June 11, 2018 at 2:34 pm.Written by Spero Therapeutics View Presentation Post navigation Frequency of Spontaneous Mutations Conferring Reduced Susceptibility to Tebipenem (SPR859) among Susceptible and Extended-Spectrum Beta-Lactamase Producing Escherichia coli and Klebsiella PneumoniaeIn Vivo Efficacy of Tebipenem-Pivoxil (SPR994) in Neutropenic Murine Lung Models of Gram-Negative Bacterial Infection