Impact of spore biology on the rate of kill and suppression of resistance in Bacillus anthracis.

Bacillus anthracis is complex because of its spore form. The spore is invulnerable to antibiotic action. It also has an impact on the emergence of resistance. We employed the hollow-fiber infection model to study the impacts of different doses and schedules of moxifloxacin on the total-organism population, the spore population, and the subpopulations of vegetative- and spore-phase organisms that were resistant to moxifloxacin. We then generated a mathematical model of the impact of moxifloxacin, administered by continuous infusion or once daily, on vegetative- and spore-phase organisms. The ratio of the rate constant for vegetative-phase cells going to spore phase (K(vs)) to the rate constant for spore-phase cells going to vegetative phase (K(sv)) determines the rate of organism clearance. The continuous-infusion drug profile is more easily sensed as a threat; the K(vs)/K(sv) ratio increases at lower drug exposures (possibly related to quorum sensing). This movement to spore phase protects the organism but makes the emergence of resistance less likely. Suppression of resistance requires a higher level of drug exposure with once-daily administration than with a continuous infusion, a difference that is related to vegetative-to-spore (and back) transitioning. Spore biology has a major impact on drug therapy and resistance suppression. These findings explain why all drugs of different classes have approximately the same rate of organism clearance for Bacillus anthracis.

Retrospective Analysis of Bioanalytical Method Validation Approaches in Biosimilar Biological Product Development.

Development and validation of a bioanalytical method for biosimilar biological product development (BPD) can be challenging. It requires the development of a bioanalytical method that reliably and accurately measures both proposed biosimilar and reference products in a biological matrix. This survey summarizes the current state of bioanalysis in BPD. Bioanalytical data from 28 biosimilar biologic license applications submitted to U.S. Food and Drug Administration (FDA) up to December 2018 were analyzed. The aim of the analysis was to provide (i) a summary of the bioanalytical landscape for BPD, (ii) a cumulative review of bioanalytical method validation approaches to aid in understanding how a specific method was selected, and (iii) a summary of data regarding bioanalytical bias differences between products. Results show diversity of the bioanalytical approaches used, as well as the observed differences in bioanalytical bias. Our findings highlight the need for understanding the critical aspects of BPD bioanalysis and clarifying BPD bioanalytical best practices, which could help ensure consistent method validation approaches in the BPD community.

Update on the pharmacokinetic aspects of antiretroviral agents: implications in therapeutic drug monitoring.

The observed inter-individual variation in antiretroviral pharmacokinetics (PK) that results in a wide range of drug exposures from fixed-dose regimens has led to increasing interest in the clinical use of therapeutic drug monitoring (TDM) to individualize dosing of antiretroviral therapy (ART). The focus of this review is to provide an overview of literature available to support therapeutic drug monitoring among the current classes of antiretrovirals, suggest patient populations that may benefit from TDM and bring forth some of the limitations that may exist for widespread use of TDM in a traditional clinical setting.