Dynamic time-kill curve characterization of spectinamide antibiotics 1445 and 1599 for the treatment of tuberculosis.

Spectinamides are a novel class of antibiotics under development for the treatment of MDR- and XDR-tuberculosis, with 1599 and 1445 as early lead candidates within this group. In order to evaluate and differentiate the pharmacological properties of these compounds and assist in candidate selection and design of optimal dosing regimens in animal models of Mtb infection, time kill curve assessments were performed in a previously established in vitro PK/PD model system. The performed studies and subsequent pharmacometric analysis indicate that the anti-mycobacterial activity of 1599 exhibits concentration-dependent killing whereas 1445 shows time-dependent killing. These findings are supported by the fact that the PKPD index that best describes bacterial killing is T > MIC for 1445, but fCmax/AUC for 1599. The differential killing behavior among the lead candidates can be rationalized by the differences in post-antibiotic effect: 15.7 h for 1445 compared the 133 h for 1599. Overall, the PK/PD based analysis of the in vitro pharmacologic killing profile of spectinamides 1599 and 1445 on mycobacteria provided valuable insights that contributed to lead candidate selection and preclinical development of these compounds.

Spectinamides: a new class of semisynthetic antituberculosis agents that overcome native drug efflux.

Although the classical antibiotic spectinomycin is a potent bacterial protein synthesis inhibitor, poor antimycobacterial activity limits its clinical application for treating tuberculosis. Using structure-based design, we generated a new semisynthetic series of spectinomycin analogs with selective ribosomal inhibition and excellent narrow-spectrum antitubercular activity. In multiple murine infection models, these spectinamides were well tolerated, significantly reduced lung mycobacterial burden and increased survival. In vitro studies demonstrated a lack of cross resistance with existing tuberculosis therapeutics, activity against multidrug-resistant (MDR) and extensively drug-resistant tuberculosis and an excellent pharmacological profile. Key to their potent antitubercular properties was their structural modification to evade the Rv1258c efflux pump, which is upregulated in MDR strains and is implicated in macrophage-induced drug tolerance. The antitubercular efficacy of spectinamides demonstrates that synthetic modifications to classical antibiotics can overcome the challenge of intrinsic efflux pump-mediated resistance and expands opportunities for target-based tuberculosis drug discovery.

Pharmacokinetics of a combination of Δ9-tetrahydro-cannabinol and celecoxib in a porcine model of hemorrhagic shock.

Hemorrhagic shock involves loss of a substantial portion of circulating blood volume leading to diminished cardiac output and oxygen delivery to peripheral tissues. In situations where an immediate resuscitation cannot be provided, pharmacotherapy with a novel combination of Δ9-tetrahydro-cannabinol (THC) and celecoxib (CEL) is currently investigated as an alternative strategy to prevent organ damage. In the present study, 28 Yorkshire×Landrace pigs were used to study the pharmacokinetics of THC and CEL in an established porcine model of hemorrhagic shock. Pigs in hemorrhagic shock received 0.5, 1 or 4 mg/kg THC and 2 mg/kg CEL, while normotensive pigs received 1 mg/kg THC and 2 mg/kg CEL by intravenous injection. THC and CEL plasma concentrations were simultaneously determined by LC-MS/MS. Pharmacokinetic parameters and their between animal variability were obtained using standard non-compartmental analysis as well as a compartmental analysis using nonlinear mixed effects modeling. The concentration-time profiles of THC and CEL followed a multi-exponential decline and their pharmacokinetics were similar in hemorrhagic shock and normotensive conditions, despite the substantial change in hemodynamics in the animals with shock. This interesting finding might be due to the pharmacologic effect of the THC/CEL combination, which is intended to maintain adequate perfusion of vital organs in shock. Overall, this study established THC and CEL pharmacokinetics in a porcine shock model and provides the basis for dose selection in further studies of THC and CEL in this indication.

Discovery of novel 2-aryl-4-benzoyl-imidazoles targeting the colchicines binding site in tubulin as potential anticancer agents.

A series of 2-aryl-4-benzoyl-imidazoles (ABI) was synthesized as a result of structural modifications based on the previous set of 2-aryl-imidazole-4-carboxylic amide (AICA) derivatives and 4-substituted methoxylbenzoyl-aryl-thiazoles (SMART). The average IC(50) of the most active compound (5da) was 15.7 nM. ABI analogues have substantially improved aqueous solubility (48.9 µg/mL for 5ga vs 0.909 µg/mL for SMART-1, 0.137 µg/mL for paclitaxel, and 1.04 µg/mL for combretastatin A4). Mechanism of action studies indicate that the anticancer activity of ABI analogues is through inhibition of tubulin polymerization by interacting with the colchicine binding site. Unlike paclitaxel and colchicine, the ABI compounds were equally potent against multidrug resistant cancer cells and the sensitive parental melanoma cancer cells. In vivo results indicated that 5cb was more effective than DTIC in inhibiting melanoma xenograph tumor growth. Our results suggest that the novel ABI compounds may be developed to effectively treat drug-resistant tumors.

In vitro pharmacokinetic/pharmacodynamic models in anti-infective drug development: focus on TB.

For rapid anti-tuberculosis (TB) drug development in vitro pharmacokinetic/pharmacodynamic (PK/PD) models are useful in evaluating the direct interaction between the drug and the bacteria, thereby guiding the selection of candidate compounds and the optimization of their dosing regimens. Utilizing in vivo drug-clearance profiles from animal and/or human studies and simulating them in an in vitro PK/PD model allows the in-depth characterization of antibiotic activity of new and existing antibacterials by generating time­kill data. These data capture the dynamic interplay between mycobacterial growth and changing drug concentration as encountered during prolonged drug therapy. This review focuses on important PK/PD parameters relevant to anti-TB drug development, provides an overview of in vitro PK/PD models used to evaluate the efficacy of agents against mycobacteria and discusses the related mathematical modeling approaches of time­kill data. Overall, it provides an introduction to in vitro PK/PD models and their application as critical tools in evaluating anti-TB drugs.