Carfilzomib.

Carfilzomib (CFZ) is a potent, second-generation proteasome inhibitor (PI), with significant activity as a single agent and in combination with other antimyeloma agents in patients with relapsed or refractory multiple myeloma (RRMM). CFZ binds selectively and irreversibly to its target and leads to antiproliferative and proapoptotic effects on cancer cells. This irreversible inhibition is dose- and time-dependent in vitro and in vivo. CFZ as monotherapy and in combination with other antimyeloma agents (e.g., as CFZ and dexamethasone [Kd]) achieved very good responses, progression-free survival (PFS) and overall survival (OS). In several ongoing studies, CFZ is being investigated in triplet and quadruplet schedules of CFZ, lenalidomide and dexamethasone (KRd), CFZ, cyclophosphamide, dexamethasone (KCd) and with antibodies, like elotuzumab or daratumumab. The multitude of completed and ongoing studies confirmed a tolerable safety profile of CFZ, a significantly lower incidence of neuropathy compared to bortezomib (BTZ) and a slightly higher incidence of cardiotoxicity, which is closely observed and precautions taken to avoid them as best as possible. In July 2012, the US Food and Drug Administration (FDA) approved CFZ as a single agent for RRMM patients with disease progression after two prior therapies, including BTZ and immunomodulatory drugs (IMiDs). The combination of KRd and Kd followed, being approved by both FDA and European Medicines Agency (EMA) in 2015 and 2016, respectively. Moreover, CFZ is being evaluated in patients with newly diagnosed MM (NDMM), in high-risk smoldering MM and for maintenance approaches.

Determination of real-time efflux phenotypes in Escherichia coli AcrB binding pocket phenylalanine mutants using a 1,2'-dinaphthylamine efflux assay.

To evaluate the importance of phenylalanine residues for substrate transport in the Escherichia coli efflux pump protein AcrB, we subjected Phe-to-Ala binding pocket mutants to a real-time efflux assay with the novel near-infrared lipophilic membrane probe 1,2'-dinaphthylamine (1,2'-DNA). All mutations, with the exception of F617A, led to considerable retardation of efflux. F610A was the point mutation with the most pronounced impact, followed by F628A, F615A, F136A, and F178A. This is the first study to demonstrate the importance of single phenylalanine residues within the AcrB binding pocket for real-time substrate transport.

Efflux inhibition by selective serotonin reuptake inhibitors in Escherichia coli.

OBJECTIVES: To evaluate the antimicrobial and synergistic (hypothetically due to the inhibition of efflux pumps) effects of selective serotonin reuptake inhibitors (SSRIs) in Escherichia coli strains overproducing various resistance-nodulation-division (RND) efflux pumps. METHODS: MICs of various SSRIs and of clinically relevant antibiotics in the presence and absence of sertraline were determined for E. coli strains overproducing the RND efflux pumps AcrAB, AcrEF, MdtEF and MexAB. The effect of sertraline on Nile red efflux was evaluated in a real-time efflux assay. Expression of marA and acrB was monitored using quantitative RT-PCR. RESULTS: In MIC assays there was limited synergy of sertraline with tetracycline, oxacillin, linezolid and clarithromycin, depending on the individual pump overexpressed and on whether rich or minimal medium was used. Sertraline, as the most potent SSRI with regard to bacterial growth inhibition, led to rapid dose-dependent Nile red efflux inhibition, and was also found to increase the expression of marA and acrB. CONCLUSIONS: A possible explanation for the discrepancy between the MIC and real-time efflux assays was that sertraline is a weak inducer of marA and acrB, thereby reducing its initial antibacterial and sensitizing effects over time. The results indicate that sertraline may be useful as a model efflux pump inhibitor for in vitro short-term experiments in E. coli, but is unlikely to be clinically useful as a co-drug against Gram-negative bacteria.

Susceptibility of clinical Staphylococcus aureus isolates to innate defense antimicrobial peptides.

Antimicrobial peptides (AMPs) are effector molecules of innate immunity. To determine whether AMP susceptibility of S. aureus varies according to different types of infection, 102 isolates from patients with S. aureus bacteremia or recurrent skin and soft tissue infection, and colonizing isolates were investigated. Using microbroth dilution assays we found a narrow range of MICs of human ß-defensin-3, cathelicidin LL-37 and bovine indolicidin without significant differences between the groups. Colony-forming unit (CFU) assays revealed minor differences in bactericidal activity with slightly but not significantly higher CFU reduction in colonizing isolates. These data do not support a role for differential AMP susceptibility in vitro as a major determinant of S. aureus invasive infection.