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Objective: There is considerable uncertainty regarding the optimal use of rifampicin for the treatment of tuberculous (TB) meningitis. A pharmacokinetic modeling and simulation study of rifampicin concentrations in cerebrospinal fluid (CSF) during TB meningitis treatment was performed in this study. Methods: Parameters for rifampicin pharmacokinetics in CSF were estimated using individual-level rifampicin pharmacokinetic data, and the model was externally validated in three separate patient cohorts. Monte Carlo simulations of rifampicin serum and CSF concentrations were performed. The area under the rifampicin CSF concentration-versus-time curve during 24 h (AUC0–24) relative to the minimum inhibitory concentration (MIC) served as the pharmacodynamic target. Results: Across all simulated patients on the first treatment day, 85% attained the target AUC0–24/MIC ratio of 30 under a weight-based dosing scheme approximating 10 mg/kg. At the rifampicin MIC of 0.5 mg/l, the probability of AUC0–24/MIC target attainment was 26%. With an intensified dosing strategy corresponding to 20 mg/kg, target attainment increased to 99%, including 93% with a MIC of 0.5 mg/l. Conclusions: Under standard dosing guidelines, few TB meningitis patients would be expected to attain therapeutic rifampicin exposures in CSF when the MIC is ≥0.5 mg/l. Either downward adjustment of the rifampicin MIC breakpoint in the context of TB meningitis, or intensified rifampicin dosing upwards of 20 mg/kg/day, would reflect the likelihood of pharmacodynamic target attainment in CSF. Keywords: Tuberculosis, Meningitis, Tuberculous meningitis, Pharmacokinetics, Pharmacodynamics

Background. Rifampin malabsorption is frequently observed in tuberculosis patients coinfected with human immunodeficiency virus (HIV) but cannot be predicted by patient factors such as CD4+ T cell count or HIV viral load. Methods. We sought to describe the relationship between HIV-associated immune activation, measures of gut absorptive capacity and permeability, and rifampin pharmacokinetic parameters in a pilot study of 6 HIV-infected, tuberculosis-uninfected patients who were naïve to antiretroviral therapy. Results. The median rifampin area under the concentration-versus-time curve during the 8-hour observation period was 42.8 mg·hr/L (range: 21.2 to 57.6), with a median peak concentration of 10.1 mg/L (range: 5.3 to 12.5). We observed delayed rifampin absorption, with a time to maximum concentration greater than 2 hours, in 2 of 6 participants. There was a trend towards increased plasma concentrations of sCD14, a marker of monocyte activation in response to bacterial translocation, among participants with delayed rifampin absorption compared to participants with rapid absorption (p=0.06). Conclusions. Delayed rifampin absorption may be associated with elevated markers of bacterial translocation among HIV-infected individuals naïve to antiretroviral therapy. This trial is registered with NCT01845298.

Indian rhesus macaques (Macaca mulatta) are routinely used in preclinical studies to evaluate therapeutic Abs and candidate vaccines. The efficacy of these interventions in many cases is known to rely heavily on the ability of Abs to interact with a set of Ab FcγR expressed on innate immune cells. Yet, despite their presumed functional importance, M. mulatta Ab receptors are largely uncharacterized, posing a fundamental limit to ensuring accurate interpretation and translation of results from studies in this model. In this article, we describe the binding characteristics of the most prevalent allotypic variants of M. mulatta FcγR for binding to both human and M. mulatta IgG of varying subclasses. The resulting determination of the affinity, specificity, and glycan sensitivity of these receptors promises to be useful in designing and evaluating studies of candidate vaccines and therapeutic Abs in this key animal model and exposes significant evolutionary divergence between humans and macaques.

The development of drug resistance remains a critical problem for current HIV-1 antiviral therapies, creating a need for new inhibitors of HIV-1 replication. We previously reported on a novel anti-HIV-1 compound, N(2)-(phenoxyacetyl)-N-[4-(1-piperidinyl-carbonyl)benzyl]glycinamide (14), that binds to the highly conserved phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P(2))binding pocket of the HIV-1 matrix (MA) protein. In this study, we re-evaluate the hits from the virtual screen used to identify compound 14 and test them directly in an HIV-1 replication assay using primary human peripheral blood mononuclear cells. This study resulted in the identification of three new compounds with antiviral activity; 2-(4-{[3-(4-fluorophenyl)-1,2,4-oxadiazol-5-yl]methyl})-1-piperazinyl)-N-(4-methylphenyl)-acetamide (7), 3-(2-ethoxyphenyl)-5-[[4-(4-nitrophenyl)piperazin-1-yl]methyl]-1,2,4-oxadiazole (17), and N-[4-ethoxy-3-(1-piperidinylsulfonyl)phenyl]-2-(imidazo[2,1-b][1,3]thiazol-6-yl)acetamide (18), with compound 7 being the most potent of these hits. Mechanistic studies on 7 demonstrated that it directly interacts with and functions through HIV-1 MA. In accordance with our drug target, compound 7 competes with PI(4,5)P(2) for MA binding and, as a result, diminishes the production of new virus. Mutation of residues within the PI(4,5)P(2) binding site of MA decreased the antiviral effect of compound 7. Additionally, compound 7 displays a broadly neutralizing anti-HIV activity, with IC(50) values of 7.5–15.6 μm for the group M isolates tested. Taken together, these results point towards a novel chemical probe that can be used to more closely study the biological role of MA and could, through further optimization, lead to a new class of anti-HIV-1 therapeutics.

In an effort to identify broadly active inhibitors of HIV-1 entry into host cells, we had previously reported a family of dodecamer triazole-peptide conjugates with nanomolar affinity for viral surface protein gp120. This class of peptides exhibits potent antiviral activity and the capacity to simultaneously inhibit interaction of viral envelope protein with both CD4 and co-receptor. In the current investigation, we used minimization of structural complexity of the lead triazole inhibitor HNG-156 (peptide 1) in order to explore the limits of the pharmacophore that enables dual antagonism and to improve opportunities for peptidomimetic design. Truncations of both carboxyl- and amino-terminal residues of the initial 12 amino acid residues of peptide 1 were found to have minimal effect on both affinity and antiviral activity. In contrast, the central triazole Pro-Trp cluster at residues 6 and 7 with ferrocenyl-triazole-Pro (Ftp) was found to be critical for bioactivity. Amino terminal residues distal to the central triazole Pro-Trp sequence tolerated decreasing degrees of side chain variation upon approaching the central cluster. A peptide fragment containing residues 3-7 (Asn-Asn-Ile-Ftp-Trp) exhibited substantial direct binding affinity, antiviral potency, dual receptor site antagonism and induction of gp120 structuring, all properties defining the functional signature of the parent compound 1. This active core contains a stereochemically specific hydrophobic triazole-Pro-Trp cluster, with a short N-terminal peptide extension providing groups for potential main chain and side chain hydrogen binding. The results of this work argue that the pharmacophore for dual antagonism is structurally limited, enhancing the potential to develop minimized peptidomimetic HIV-1 entry inhibitors that simultaneously suppress binding of envelope protein to both of its host cell receptors. The results also argue that the target epitope on gp120 is relatively small, pointing to a localized allosteric inhibition site in the HIV-1 envelope that could be targeted for small-molecule inhibitor discovery.

Background The cost and complexity of current approaches to therapeutic drug monitoring during tuberculosis (TB) therapy limits widespread use in areas of greatest need. We sought to determine whether urine colorimetry could have a novel application as a form of therapeutic drug monitoring during anti-TB therapy. Methods Among healthy volunteers, we evaluated 3 dose sizes of rifampin (150 mg, 300 mg, and 600 mg), performed intensive pharmacokinetic sampling, and collected a timed urine void at 4 h post-dosing. The absorbance peak at 475 nm was measured after rifamycin extraction. The optimal cutoff was evaluated in a study of 39 HIV/TB patients undergoing TB treatment in Botswana. Results In the derivation study, a urine colorimetric assay value of 4.0 × 10−2 Abs, using a timed void 4 h after dosing, demonstrated a sensitivity of 92 % and specificity of 60 % to detect a peak rifampin concentration (Cmax) under 8 mg/L, with an area under the ROC curve of 0.92. In the validation study, this cutoff was specific (100 %) but insensitive (28 %). We observed similar test characteristics for a target Cmax target of 6.6 mg/L, and a target area under the drug concentration-versus-time curve (AUC0–8) target of 24.1 mg•hour/L. Conclusions The urine colorimetric assay was specific but insensitive to detect low rifampin serum concentrations among HIV/TB patients. In future work we will attempt to optimize sampling times and assay performance, with the goal of delivering a method that can translate into a point-of-care assessment of rifampin exposure during anti-TB therapy.