Discovery and Optimization of DNA Gyrase and Topoisomerase IV Inhibitors with Potent Activity against Fluoroquinolone-Resistant Gram-Positive Bacteria.

Herein, we describe the discovery and optimization of a novel series that inhibits bacterial DNA gyrase and topoisomerase IV via binding to, and stabilization of, DNA cleavage complexes. Optimization of this series led to the identification of compound 25, which has potent activity against Gram-positive bacteria, a favorable in vitro safety profile, and excellent in vivo pharmacokinetic properties. Compound 25 was found to be efficacious against fluoroquinolone-sensitive Staphylococcus aureus infection in a mouse thigh model at lower doses than moxifloxacin. An X-ray crystal structure of the ternary complex formed by topoisomerase IV from Klebsiella pneumoniae, compound 25, and cleaved DNA indicates that this compound does not engage in a water-metal ion bridge interaction and forms no direct contacts with residues in the quinolone resistance determining region (QRDR). This suggests a structural basis for the reduced impact of QRDR mutations on antibacterial activity of 25 compared to fluoroquinolones.

Opportunities and Challenges in Developing a Cryptosporidium Controlled Human Infection Model for Testing Antiparasitic Agents.

Cryptosporidiosis is a leading cause of moderate-to-severe diarrhea in low- and middle-income countries, responsible for high mortality in children younger than two years of age, and it is also strongly associated with childhood malnutrition and growth stunting. There is no vaccine for cryptosporidiosis and existing therapeutic options are suboptimal to prevent morbidity and mortality in young children. Recently, novel therapeutic agents have been discovered through high-throughput phenotypic and target-based screening strategies, repurposing malaria hits, etc., and these agents have a promising preclinical in vitro and in vivo anti-Cryptosporidium efficacy. One key step in bringing safe and effective new therapies to young vulnerable children is the establishment of some prospect of direct benefit before initiating pediatric clinical studies. A Cryptosporidium controlled human infection model (CHIM) in healthy adult volunteers can be a robust clinical proof of concept model for evaluating novel therapeutics. CHIM could potentially accelerate the development path to pediatric studies by establishing the safety of a proposed pediatric dosing regimen and documenting preliminary efficacy in adults. We present, here, perspectives regarding the opportunities and perceived challenges with the Cryptosporidium human challenge model.

The Safety and Antiviral Activity of BZF961 with or without Ritonavir in Patients Infected with Hepatitis C Virus: A Randomized, Multicenter Trial.

PURPOSE: Infection with hepatitis C virus is the leading cause of infectious disease mortality in the United States. BZF961 is a novel small molecule inhibitor of the hepatitis C virus NS3-4A protease. Here we present the results of a randomized, double-blinded, placebo-controlled, multicentered study in treatment-naïve patients with chronic hepatitis C virus genotype-1 infection. METHODS: Patients were enrolled sequentially in 2 parts and treated for 3days. BZF961 was administered as monotherapy (500mg BID for 3 days) or in combination with the cytochrome P450 3A4 inhibitor ritonavir to boost its exposure (BZF961 10, 20, or 50mg QD or BID). FINDINGS: BZF961 was safe and well tolerated in the patients studied with no serious adverse events. There were no appreciable differences in adverse events among patients who received BZF961, BZF961 with ritonavir, or placebo. There was a significant, clinically meaningful reduction in viral load from baseline in patients treated either with BZF961 500mg every 12hours alone or BZF961 50mg every 12hours in combination with ritonavir. Activity against the hepatitis C virus of the lower-dose regimens was apparent but more modest. There were no relevant changes from baseline viral loads in placebo-treated patients. IMPLICATIONS: Coadministration of ritonavir with BZF961 boosted BZF961 exposure (including Cmin, which is the clinically relevant parameter associated with antiviral activity) in a therapeutic range with less variability compared with BZF961 alone. For strategic reasons, BZF961 is no longer under development.

Application of melt granulation technology using twin-screw extruder in development of high-dose modified-release tablet formulation.

Development of modified-release oral tablets of drug products usually requires release-modifying polymers at the level of above 50% of the total weight. This makes the development of high-dose products, especially with doses in the range of 750-1000 mg, difficult because the tablet size becomes unacceptably high. This report presents the development of high-dose modified-release formulation of an active pharmaceutical ingredient (API), imatinib mesylate, with a drug load of approximately 90%, by melt granulation using a twin-screw extruder. For an 800 mg dose, 956 mg of drug substance (salt) was needed and the final weight of tablet was approximately 1074 mg. By carefully selecting polymers based on their physicochemical properties, the release rate could be modified between desired times of 4 to >10 h for the total drug release. Mixtures of API and polymer were melt granulated at 185 °C, which is below the melting point of API (212 °C) but above the glass transition temperatures of polymers used. The confocal Raman microscopic imaging revealed that the API remained as unmelted, crystalline particles, and polymers were finely distributed on the surface and in between API particles. The formulations were found to be robust as no change in tableting and drug release properties was observed when manufacturing parameters were altered to challenge the process. The in vivo modified-release properties of formulations were demonstrated in human pharmacokinetic studies.

Application of melt granulation technology to enhance tabletting properties of poorly compactible high-dose drugs.

Using metformin HCl as the model drug and hydroxypropylcellulose (HPC) as the polymeric excipient, a melt granulation (MG) process that employs a twin-screw extruder has been developed to enhance compactibility of poorly compactible high-dose drug substances. A high (90%) drug-load tablet formulation, containing 1025 mg of active pharmaceutical ingredients and 109 mg of excipients, was produced. Drug-polymer-powder mixtures were melt granulated at a temperature above glass transition of HPC (130°C) but below melting point of metformin HCl (224°C). MG was compared with modified wet granulation (WG) and solvent granulation (SG) processes. Under identical compression force, the hardness of tablets produced was MG>SG>WG and the friability was MG

Investigation of Metformin HCl lot-to-lot variation on flowability differences exhibited during drug product processing.

The purpose of this study was to determine the cause for flowability difference observed during drug product processing when different Metformin HCl drug substance batches of varying age were used. It was found that the lead time (age) between the final step (milling) in the manufacturing process of the Metformin HCl drug substance could be a factor. The lead time had an impact on flowability of Metformin/excipient blends during drug product processing even though these batches had no apparent differences in their release specifications. To study and understand the aging effect, two batches of Metformin HCl manufactured at different periods of time were selected. The surface energy values obtained by the density functional theory (DFT) method together with X-ray diffraction patterns, thermally stimulated current measurements, and dynamic vapor sorption isotherms indicated that the freshly manufactured Metformin HCl material contains detectable amounts of surface crystal defects, but are absent in aged sample, which could be the cause of flowability differences of Metformin/excipient blends observed during the drug product processing. Having identified the cause for different flow behavior, a method to destroy these defects was designed and the issue was resolved by rapid aging of Metformin HCl under humidity at room temperature.

Application of melt extrusion in the development of a physically and chemically stable high-energy amorphous solid dispersion of a poorly water-soluble drug.

Formulation of active pharmaceutical ingredients (API) in high-energy amorphous forms is a common strategy to enhance solubility, dissolution rate and, consequently, oral bioavailability of poorly water-soluble drugs. Amorphous APIs are, however, susceptible to recrystallization and, therefore, there is a need to physically stabilize them as solid dispersions in polymeric carriers. Hot melt extrusion has in recent years gained wide acceptance as a method of choice for the preparation of solid dispersions. There is a potential that the API, the polymer or both may degrade if excessively high temperature is needed in the melt extrusion process, especially when the melting point of the API is high. This report details a novel method where the API was first converted to an amorphous form by solvent evaporation and then melt-extruded with a suitable polymer at a drug load of at least 20% w/w. By this means, melt extrusion could be performed much below the melting temperature of the drug substance. Since the glass transition temperature of the amorphous drug was lower than that of the polymer used, the drug substance itself served as the plasticizer for the polymer. The addition of surfactants in the matrix enhanced dispersion and subsequent dissolution of the drug in aqueous media. The amorphous melt extrusion formulations showed higher bioavailability than formulations containing the crystalline API. There was no conversion of amorphous solid to its crystalline form during accelerated stability testing of dosage forms.