Optimization of TopoIV Potency, ADMET Properties, and hERG Inhibition of 5-Amino-1,3-dioxane-Linked Novel Bacterial Topoisomerase Inhibitors: Identification of a Lead with In Vivo Efficacy against MRSA

Novel bacterial topoisomerase inhibitors (NBTIs) are among the most promising new antibiotics in preclinical/clinical development. We previously reported dioxane-linked NBTIs with potent antistaphylococcal activity and reduced hERG inhibition, a key safety liability. Herein, polarity-focused optimization enabled the delineation of clear structure-property relationships for both microsomal metabolic stability and hERG inhibition, resulting in the identification of lead compound 79. This molecule demonstrates potent antibacterial activity against diverse Gram-positive pathogens, inhibition of both DNA gyrase and topoisomerase IV, a low frequency of resistance, a favorable in vitro cardiovascular safety profile, and in vivo efficacy in a murine model of methicillin-resistant Staphylococcus aureus infection.

A systematic strategy for estimating hERG block potency and its implications in a new cardiac safety paradigm

Introduction

hERG block potency is widely used to calculate a drug's safety margin against its torsadogenic potential. Previous studies are confounded by use of different patch clamp electrophysiology protocols and a lack of statistical quantification of experimental variability. Since the new cardiac safety paradigm being discussed by the International Council for Harmonisation promotes a tighter integration of nonclinical and clinical data for torsadogenic risk assessment, a more systematic approach to estimate the hERG block potency and safety margin is needed.

Methods

A cross-industry study was performed to collect hERG data on 28 drugs with known torsadogenic risk using a standardized experimental protocol. A Bayesian hierarchical modeling (BHM) approach was used to assess the hERG block potency of these drugs by quantifying both the inter-site and intra-site variability. A modeling and simulation study was also done to evaluate protocol-dependent changes in hERG potency estimates.

Results

A systematic approach to estimate hERG block potency is established. The impact of choosing a safety margin threshold on torsadogenic risk evaluation is explored based on the posterior distributions of hERG potency estimated by this method. The modeling and simulation results suggest any potency estimate is specific to the protocol used.

Discussion

This methodology can estimate hERG block potency specific to a given voltage protocol. The relationship between safety margin thresholds and torsadogenic risk predictivity suggests the threshold should be tailored to each specific context of use, and safety margin evaluation may need to be integrated with other information to form a more comprehensive risk assessment.

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hERG potency/safety margin is a widely used nonclinical cardiac safety strategy.

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A new regulatory paradigm promotes the integration of nonclinical and clinical data.

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Lack of uncertainty quantification hindered using hERG potency in the new paradigm.

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A systematic method was established to address this limitation.

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Analysis supports using different safety margin thresholds in different context.

Post-war Kosovo: Part 3. Development and rehabilitation of emergency services

The recent crisis in Kosovo led to nearly complete destruction of a healthcare system serving the needs of approximately 2 million people. Even prior to the crisis, the pre-existing healthcare system had inadequate provisions for the delivery of Emergency Medical Services. More than 440 diverse governmental and non-governmental organizations (NGOs) arrived to assist (and often compete) in the rehabilitation of Kosovo's healthcare needs. Each brought with them individual biases and strategies for how this rehabilitation should occur, and each faced numerous unforeseen barriers to the implementation of its programs. The authors used a four-step, multi-modal, needs assessment to gather information on the needs and potential barriers to the implementation of a program to rehabilitate emergency services as discussed in Part II. This paper chronicles the phases of the Emergency Medicine program development and the process of responding to barriers and changing needs. The program's successes and failures are noted, and the actual barriers encountered are reviewed. Overall, the needs assessment tool employed in this program was useful in the implementation of a program to restore and rehabilitate Emergency Services in Kosovo. The authors recommend the use of combined quantitative and qualitative methods for developing priorities for interventions in post-conflict settings following complex emergencies.

Observation of high-energy neutrinos using Cerenkov detectors embedded deep in Antarctic ice

Neutrinos are elementary particles that carry no electric charge and have little mass. As they interact only weakly with other particles, they can penetrate enormous amounts of matter, and therefore have the potential to directly convey astrophysical information from the edge of the Universe and from deep inside the most cataclysmic high-energy regions. The neutrino's great penetrating power, however, also makes this particle difficult to detect. Underground detectors have observed low-energy neutrinos from the Sun and a nearby supernova, as well as neutrinos generated in the Earth's atmosphere. But the very low fluxes of high-energy neutrinos from cosmic sources can be observed only by much larger, expandable detectors in, for example, deep water or ice. Here we report the detection of upwardly propagating atmospheric neutrinos by the ice-based Antarctic muon and neutrino detector array (AMANDA). These results establish a technology with which to build a kilometre-scale neutrino observatory necessary for astrophysical observations.

Regulation of immunomodulatory functions by granulocyte-macrophage colony-stimulating factor and granulocyte colony-stimulating factor in vivo

The present study was designed to investigate in vivo immunomodulatory properties of hematopoietic growth factors. The influence on the activation of cytokine synthesis and on the expression of surface antigens associated with cellular activation of G-CSF or GM-CSF was investigated in cancer patients receiving these factors. One single dose of growth factor was administered to patients with bladder cancer (G-CSF group) or small cell lung cancer (GM-CSF group) before chemotherapy. After cytoreductive chemotherapy patients received supportive therapy with G-CSF or GM-CSF. Peripheral blood mononuclear cells and plasma samples were obtained for flow cytometry, Northern blot analysis, and assessment of cytokine protein levels after single-dose as well as after continuous cytokine administration. Our results demonstrate differences in the induction of biological activities by GM-CSF and G-CSF in vivo which correlate well with in vitro findings. Among mature hematopoietic cells the effect of G-CSF is restricted to the granulocyte lineage. With GM-CSF moderate but unequivocal modulation of monocyte function was observed. On peripheral blood monocytes expression of MHC class-II molecules and CD44 was markedly stimulated. After one single dose of GM-CSF, plasma levels of sCD25 and IL-1RA were significantly induced (p < 0.0001, p = 0.032, respectively) and a trend to increased IL-8 levels was observed. The changes in plasma proteins were not correlated with shifts of mRNA expression for IL-8 and IL-1RA. T-cell activation was not observed with either cytokine. These results suggest that immunomodulatory features are differentially regulated by G-CSF and GM-CSF. The clinical relevance of a selective use of both hematopoietic growth factors in various disease settings remains to be determined.

Long-term safety of treatment with recombinant human granulocyte colony-stimulating factor (r-metHuG-CSF) in patients with severe congenital neutropenias

Congenital neutropenias include a heterogenous group of diseases characterized by a decrease in circulating neutrophils. In phase I/II/III studies in patients with severe congenital and cyclic neutropenia, treatment with recombinant human granulocyte colony-stimulating factor (r-metHuG-CSF) resulted in a rise in the absolute neutrophil counts (ANC) and a reduction in infections. We report the effects of long-term safety of subcutaneous r-metHuG-CSF administration in 54 patients (congenital n = 44. cyclic n = 10) treated for 4-6 years. A sustained ANC response was seen in 40/44 severe congenital neutropenia patients and 10/10 cyclic neutropenia patients. Two patients required an increase of > 25% in dose to maintain a clinical response; one patient became refractory to therapy. A significant decrease in the incidence of severe infections and the need for intravenous antibiotics was noted. Significant adverse events noted which may or may not be related to therapy included: osteopenia (n = 15), splenomegaly (n = 12), hypersplenism (n = 1), vasculitis (n = 2), glomerulonephritis (n = 1), BM fibrosis (n = 2), MDS/leukaemia (n = 3), and transient inverted chromosome 5q with excess blasts (n = 1). R-metHuG-CSF has been well tolerated in the majority of patients and resulted in a long-term improvement in their clinical status.

[Long-term treatment with recombinant human granulocyte colony stimulating factor in patients with severe congenital neutropenia]

Severe congenital neutropenia is a disorder of myelopoiesis characterized by severe neutropenia secondary to either a maturational arrest of myelopoiesis at the level of promyelocytes (Kostmann-Syndrome; SCN) or regular cyclic fluctuations in the number of blood neutrophils with a median ANC below 500/microliter (cyclic neutropenia). We have treated 32 patients with SCN and 4 patients with cyclic neutropenia. Thirty of 32 patients with SCN and all 4 patients with SCN responded to r-met HuG-CSF treatment with an increase of the median ANC to above 1000/microliter. The doses needed to achieve and maintain the response varied between 0.8 and 120 micrograms/kg/d. Long-term treatment did not exhaust the myelopoiesis: The mean ANC remained stable up to 5 years of treatment. The increase in ANC was associated with dramatic clinical responses: significant reduction of severe bacterial infections, reduction of intravenous antibiotic treatment episodes, and reduction of hospitalizations. No severe bacterial infections occurred in any of the r-met HuG-CSF responders during long-term treatment. Severe adverse event, most likely associated with the underlying disease, included the development of MDS/Leukemia in two patients, and osteopenia/osteoporosis in 12 patients. These results demonstrate the beneficial effects of r-met HuG-CSF treatment in severe congenital neutropenia patients.

Sulfate and Nitrate Concentrations from a South Greenland Ice Core

An ice core in south Greenland covering the period 1869 to 1984 was analyzed for oxygen isotopes and chloride, nitrate, and sulfate concentrations. The data show that the "excess" (nonsea-salt) sulfate concentration has tripled since approximately 1900 to 1910 and the nitrate concentration has doubled since approximately 1955. The increases may be attributable to the deposition of these chemical specis from air masses carrying North American and Eurasian anthropogenic emissions.