A Pharmacologic Approach to Prevent Daptomycin Resistance in VRE

 描述(由申请人提供)：由万古霉素耐药屎肠球菌(VREfm)引起的感染受到治疗选择有限的困扰，与万古霉素敏感菌株相比，与死亡率增加有关。达托霉素(DAP)是一种脂肽抗生素，其活性依赖于VREfm菌株最小抑菌浓度(MIC)以上的浓度曲线下的最佳面积(AUC)，具有很强的抗VREfm活性。然而，临床上会出现对DAP的耐药性，数据表明，为了防止DAP耐药性的出现，有必要将剂量超过目前批准的每天6 mg/kg。即使增加DAP剂量可能也不足以防止耐药性，因为VREfm具有两个不同调控基因系统(iliFSR和yycFG)的突变，表明有能力抵抗单独使用DAP治疗。这些突变在“易感”水平较高(3-4微克/毫升)的VREfm伴DAP MICs中很常见。因此，涉及联合治疗的新的治疗方案是必要的，值得研究。β-内酰胺类药物与DAP联合使用是有意义的；由于体外数据有限，已经证明了β-内酰胺类药物能够增强DAP对VREfm的活性。我们研究的总体目标是确定单独使用DAP方案对抗已知遗传变化的VREfm的DAP剂量暴露断点(药代动力学/药效学[PK/PD]断点)，使他们具有DAP耐药倾向，然后评估β-内酰胺类药物积极影响该断点的能力。这些数据将为预防DAP耐药性和提供杀菌活性的最佳DAP暴露(剂量方案)与β-内酰胺类药物联合使用提供重要信息。长期目标是优化VREfm感染患者的预后，并保留DAP作为对抗这些耐药病原体的活性制剂，同时确定当DAP MIC升高时用于预防DAP耐药性的最佳β-内酰胺类药物。中心假设是，β-内酰胺类药物将通过降低VREfm DAP MIC来增加DAP AUC0-24/MIC的比率，从而提供更好的耐药性预防和杀菌活性。这项拟议研究背后的理由是，关于DAP与VREfm的剂量关系以及β-内酰胺联合治疗如何影响它的数据将导致这些隐匿性感染患者的最佳治疗方案。中心假说将通过追求三个特定目标来验证：1)确定在临床剂量下是否可以达到AUC24/MIC断点，以在体外PK/PD模型中克服对DAP耐药的VREfm；2)在体外PK/PD模型中评估几种关键的β-内酰胺类药物以优化DAP AUC24/MIC暴露，并恢复对DAP耐药的VREfm的DAP活性；3)在已建立的动物心内膜炎模型中测试单独和联合应用对VRE粪便的体外DAP AUC24/MIC暴露以验证这些参数。在前两个目标下，将使用一个成熟的模拟心内膜赘生物(SEV)体外模型(先前针对兔心内膜炎模型进行验证)来确定断点(以及相应的DAP剂量)，使用不同临床剂量的DAP和β-内酰胺类药物。这项拟议的研究具有创新性，因为我们将使用体外和体内PK/PD模型来确定治疗VREfm的最佳β-内酰胺加DAP联合方案，这些方案尚未通过像这样的复杂建模进行深入研究。这项研究意义重大，因为它有望为理解最佳DAP剂量策略提供完整的知识，并为协同对抗具有DAP耐药倾向的VREfm提供最佳的β-内酰胺类药物。一旦掌握了这些知识，最终的结果将是改善患者的预后，并将DAP作为治疗VREfm感染的一种可行的治疗选择。

 DESCRIPTION (provided by applicant): Infections caused by vancomycin-resistant Enterococcus faecium (VREfm) are plagued by limited treatment options and are associated with increased mortality compared to vancomycin-susceptible strains. Daptomycin (DAP), a lipopeptide antibiotic with activity contingent upon an optimized area under the concentration curve (AUC) over the minimum inhibitory concentration (MIC) of the VREfm strain, possesses potent activity against VREfm. However, resistance to DAP occurs clinically, and data demonstrate that doses above the currently approved 6 mg/kg/day are necessary to prevent DAP resistance emergence. Even elevated DAP doses may not be sufficient to prevent resistance, as VREfm with mutations in two different regulatory gene systems (liaFSR and yycFG) demonstrate the ability to resist treatment with DAP alone. These mutations are frequent among VREfm with DAP MICs in the higher levels of "susceptible" (3-4 µg/ml). As such, novel therapeutic regimens involving combinations are necessary and warrant study. Beta-lactams are of interest in combination with DAP; as limited in vitro data have demonstrated the ability of beta-lactams to enhance DAP activity against VREfm. The overall objective of our study is to define the DAP dose exposure breakpoint (pharmacokinetic/pharmacodynamic [PK/PD] breakpoint) with DAP regimens alone against VREfm with known genetic changes giving them proclivity for DAP resistance and then evaluate the ability of beta-lactams to positively affect that breakpoint. These data will provide important information on the optimal DAP exposure (dosing regimens) in combination with beta-lactams to prevent DAP resistance and provide bactericidal activity. The long-term goal is to optimize VREfm infection patient outcomes and preserve DAP as a viable agent against these resistant pathogens while determining the optimal beta-lactam to use in combination for DAP resistance prevention when the DAP MIC is elevated. The central hypothesis is that beta-lactams will increase the DAP AUC0-24/MIC ratio by lowering the VREfm DAP MIC and thus provide improved resistance prevention and bactericidal activity. The rationale behind the proposed research is that data on the DAP dose relationship with VREfm and how it is affected by beta-lactam co-therapy will lead to optimal treatment regimens for patients with these insidious infections. The central hypothesis will be tested by pursuing three Specific Aims: 1) Determine if an AUC24h/MIC breakpoint is achievable at clinical dosages to overcome DAP resistance in VREfm with predisposition for DAP resistance in an in vitro PK/PD model, 2) Evaluate several key beta-lactams to optimize DAP AUC24h/MIC exposure and restore DAP activity against VREfm with predisposition for DAP resistance in an in vitro PK/PD model, and 3) test the in vitro derived DAP AUC24h/MIC exposures alone and in combination with a beta-lactam for VRE-faecium in a well-established animal endocarditis model to validate these parameters. Under the first two aims, a well-established in vitro model of simulated endocardial vegetations (SEVs) (previously validated against a rabbit endocarditis model) will be used to determine breakpoints (and corresponding DAP doses) using various clinical doses of DAP and beta-lactams. The proposed research is innovative because we will use both in vitro and in vivo PK/PD models to determine optimal beta-lactam plus DAP combination regimens against VREfm that have yet to be studied in-depth with complex modeling such as this. The research is significant because it is expected to provide knowledge integral to understanding optimal DAP dosing strategies and the best beta-lactam for synergy against VREfm with proclivity for DAP resistance. Once such knowledge is available, improved patient outcomes and the preservation of DAP as a viable therapeutic option in the treatment of VREfm infections will be the ultimate result.