The emerging discipline of Quantitative Systems Pharmacology (QSP) enables the integration of quantitative experimental data describing the interactions between the various biological processes within the system using mathematical modeling to gain better insights into the factors that drive disease pathogenicity and influence antibiotic pharmacokinetics (PKs)/pharmacodynamics (PDs). Through our perspective we consider the evolution from PK/PD models to mechanism-based and systems-based models and then finally QSP. We further emphasize the need to invest in ambitious research that takes into consideration: (i) the antibiotic PK/PD activity, (ii) the time course of the host immune response to understand the progression of the infection, (iii) and a growing appreciation of the cellular and molecular networks using multi-omics analysis to understand the modulation of antimicrobial therapy at a true systems level.
Mounting antimicrobial resistance to carbapenemase-producing Klebsiella pneumoniae (CPKP) highlights the need to optimize currently available treatment options. The objective of this study was to explore alternative dosing strategies that limit the emergence of resistance to preserve the utility of last-line antibiotics by: (i) evaluating the pharmacodynamic (PD) killing activity of simulated humanized exposures to monotherapy and two-drug and three-drug combinations against CPKP bacterial isolates with different resistance mechanisms; and (ii) optimizing polymyxin B (PMB) exposure simulated in the three-drug combination regimens to maximize the killing activity. Two CPKP clinical isolates (BAA2146 (NDM-1) and BRKP76 (KPC-2)) were evaluated over 168 hours using a hollow-fiber infection model simulating clinically relevant PMB, fosfomycin, and meropenem dosing regimens. PMB-based three-drug combinations were further optimized by varying the initial exposure (0-24 hours) or maintenance dose received over the duration of treatment. The area under the bacterial load-versus-time curve (AUCFU) was used to determine PD activity. Overall reductions in PMB exposure ranged from 2 to 84%. BAA2146 and BRKP76 had median (range) AUCFUs of 11.0 (10.6-11.6) log 10 CFU hour/mL and 7.08 (7.04-11.9) log 10 CFU hour/mL, respectively. The PMB "front loaded" 2.5 mg/ kg/day + 0.5 mg/kg maintenance dose in combination with meropenem and fosfomycin was a promising regimen against BRKP76, with an overall reduction in PMB exposure of 56% while still eradicating the bacteria. Tailored triplecombination therapy allows for the optimization of dose and treatment duration of last-line agents like PMB to achieve adequate drug exposure and appropriate PD activity while minimizing the emergence of resistance.
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