Lyophilized mixed micelles of exemestane: A novel paradigm to improve its absorption and anticancer activity.

The objective of the present investigation was to prepare and optimize lyophilized mixed micelles (Lyp-EXE-MMs) of exemestane (EXE) with improved solubility, bioavailability, in vivo anticancer activity, and physical stability, by using various cryoprotectants. The prepared lyophilized mixed micelles were characterized by various techniques, including dynamic light scattering, zeta potential, powdered X-ray diffraction, differential scanning calorimetry (DSC), nuclear magnetic resonance (1 H NMR), transmission electron microscopy (TEM), and so on. Thereafter, the lyophilized micelles were evaluated for ex vivo permeation, in vitro drug release and gene/protein expression (RT-PCR and Western blot analysis) in MCF-7 breast cancer cells. The developed formulation was also investigated for its in vivo anticancer study in BALB/c mice with induced breast cancer. The use of trehalose (10% w/w) was proven to be a suitable cryoprotectant for these micelles. Lyp-EXE-MMs were spherical, with a particle size of 42.9 ± 3.8 nm and a polydispersity index of 0.307 ± 0.122. Furthermore, % drug loading and % entrapment efficiency were found to be 5.8 ± 1.4 and 89.1 ± 1.1, respectively. Lyp-EXE-MMs showed sustained release behavior as compared to EXE-suspensions in SGF/SIF (pH 1.2 and 6.8) and phosphate buffer saline (pH 7.4). The micelles induced apoptosis through the regulation of BAX, BCL2, Caspase-3, p53, and CYP19A1 in MCF-7 cells, which was correlated to enhanced ex vivo drug permeation. Animals receiving EXE micelle formulations showed reduced tumor volume and improved survivability and pharmacokinetic parameters as compared to pure EXE. Lyp-EXE-MMs were found to withstand simulated harsh conditions of SGF/SIF during stability studies. The fabricated EXE micellar preparations hold a promising approach for breast cancer treatment.

Influence of Drug-Polymer Interactions on Dissolution of Thermodynamically Highly Unstable Cocrystal.

Solubility advantage of thermodynamically highly unstable cocrystals, which undergo solution-mediated phase transformation (SMPT) in less than 1 min, does not translate to enhanced dissolution. The present study was aimed to understand the impact of polymeric additives on dissolution of thermodynamically highly unstable cocrystal with specific emphasis on influence of drug-polymer interactions. Exemestane-maleic acid was selected as a model cocrystal with SMPT time of <30 s and eutectic constant ( Keu) of 75475. Hydroxypropylcellulose (HPC), hydroxypropyl methylcellulose acetate succinate (HPMCAS), and polyvinylpyrrolidone (PVP) were selected as polymers for a dissolution study based on measurement of induction time using precipitation study. In the presence of 0.2% w/v of HPC, the cocrystal showed significantly higher drug release (∼3-fold) as compared with the cocrystal in the absence of predissolved polymers. Differential dissolution profiles of the cocrystal were observed with each polymer and the order of increasing dissolution rate was found to be HPC ≈ HPMCAS > PVP. The molecular basis of the differential dissolution performance was investigated using infrared spectroscopy, solution-state nuclear magnetic resonance spectroscopy, and nuclear Overhauser effect spectroscopy (NOESY). The polymers with stronger interactions with drug in the cocrystal (HPMCAS and HPC) displayed higher dissolution rate as compared with that of no intermolecular interaction (PVP). The study also highlighted that, despite no influence of the polymers on the cocrystal SMPT, dissolution enhancement was achieved. This was attributed to small-sized drug crystals (1-3 µm) generated from the supersaturation-mediated crystallization and improved solvation due to drug-polymer interactions. These findings have implications on development of drug products using thermodynamically unstable cocrystals.

Identification of steroid C27 monooxygenase isoenzymes involved in sterol catabolism and stepwise pathway engineering of Mycobacterium neoaurum for improved androst-1,4-diene-3,17-dione production.

Cholesterol oxidase, steroid C27 monooxygenase and 3-ketosteroid-Δ1-dehydrogenase are key enzymes involved in microbial catabolism of sterols. Here, three isoenzymes of steroid C27 monooxygenase were firstly characterized from Mycobacterium neoaurum as the key enzyme in sterol C27-hydroxylation. Among these three isoenzymes, steroid C27 monooxygenase 2 exhibits the strongest function in sterol catabolism. To improve androst-1,4-diene-3,17-dione production, cholesterol oxidase, steroid C27 monooxygenase 2 and 3-ketosteroid-Δ1-dehydrogenase were coexpressed to strengthen the metabolic flux to androst-1,4-diene-3,17-dione, and 3-ketosteroid 9α-hydroxylase, which catalyzes the androst-1,4-diene-3,17-dione catabolism, was disrupted to block the androst-1,4-diene-3,17-dione degradation pathway in M. neoaurum JC-12. Finally, the recombinant strain JC-12S2-choM-ksdd/ΔkshA produced 20.1 g/L androst-1,4-diene-3,17-dione, which is the highest reported production with sterols as substrate. Therefore, this work is hopes to pave the way for efficient androst-1,4-diene-3,17-dione production through metabolic engineering.

Intracellular Environment Improvement of Mycobacterium neoaurum for Enhancing Androst-1,4-Diene-3,17-Dione Production by Manipulating NADH and Reactive Oxygen Species Levels.

As one of the most significant steroid hormone precursors, androst-1,4-diene-3,17-dione (ADD) could be used to synthesize many valuable hormone drugs. The microbial transformation of sterols to ADD has received extensive attention in recent years. In a previous study, Mycobacterium neoaurum JC-12 was isolated and converted sterols to the major product, ADD. In this work, we enhanced ADD yield by improving the cell intracellular environment. First, we introduced a nicotinamide adenine dinucleotide (NADH) oxidase from Bacillus subtilis to balance the intracellular NAD+ availability in order to strengthen the ADD yield. Then, the catalase gene from M. neoaurum was also over-expressed to simultaneously scavenge the generated H2O2 and eliminate its toxic effects on cell growth and sterol transformation. Finally, using a 5 L fermentor, the recombinant strain JC-12yodC-katA produced 9.66 g/L ADD, which increased by 80% when compared with the parent strain. This work shows a promising way to increase the sterol transformation efficiency by regulating the intracellular environment.

Structures of cytochrome P450 17A1 with prostate cancer drugs abiraterone and TOK-001.

Cytochrome P450 17A1 (also known as CYP17A1 and cytochrome P450c17) catalyses the biosynthesis of androgens in humans. As prostate cancer cells proliferate in response to androgen steroids, CYP17A1 inhibition is a new strategy to prevent androgen synthesis and treat lethal metastatic castration-resistant prostate cancer, but drug development has been hampered by lack of information regarding the structure of CYP17A1. Here we report X-ray crystal structures of CYP17A1, which were obtained in the presence of either abiraterone, a first-in-class steroidal inhibitor recently approved by the US Food and Drug Administration for late-stage prostate cancer, or TOK-001, an inhibitor that is currently undergoing clinical trials. Both of these inhibitors bind the haem iron, forming a 60° angle above the haem plane and packing against the central I helix with the 3ß-OH interacting with aspargine 202 in the F helix. Notably, this binding mode differs substantially from those that are predicted by homology models and from steroids in other cytochrome P450 enzymes with known structures, and some features of this binding mode are more similar to steroid receptors. Whereas the overall structure of CYP17A1 provides a rationale for understanding many mutations that are found in patients with steroidogenic diseases, the active site reveals multiple steric and hydrogen bonding features that will facilitate a better understanding of the enzyme's dual hydroxylase and lyase catalytic capabilities and assist in rational drug design. Specifically, structure-based design is expected to aid development of inhibitors that bind only CYP17A1 and solely inhibit its androgen-generating lyase activity to improve treatment of prostate and other hormone-responsive cancers.

Extraction and determination of trace amounts of three anticancer pharmaceuticals in urine by three-phase hollow fiber liquid-phase microextraction based on two immiscible organic solvents followed by high-performance liquid chromatography.

An automated three-phase hollow fiber liquid-phase microextraction based on two immiscible organic solvents followed by high-performance liquid chromatography with UV-Vis detection method was applied for the extraction and determination of exemestane, letrozole, and paclitaxel in water and urine samples. n-Dodecane was selected as the supported liquid membrane and its polarity was justified by trioctylphosphine oxide. Acetonitrile was used as an organic acceptor phase with desirable immiscibility having n-dodecane. All the effective parameters of the microextraction procedure such as type of the organic acceptor phase, the supported liquid membrane composition, extraction time, pH of the donor phase, hollow fiber length, stirring rate, and ionic strength were evaluated and optimized separately by a one variable at-a-time method. Under the optimal conditions, the linear dynamic ranges were 1.8-200 (R2  = 0.9991), 0.9-200 (R2  = 0.9987) and 1.2-200 µg/L (R2  = 0.9983), and the limits of detection were 0.6, 0.3, and 0.4 µg/L for exemestane, letrozole, and paclitaxel, respectively. To evaluate the capability of the proposed method in the analysis of biological samples, three different urinary samples were analyzed under the optimal conditions. The relative recoveries of the three pharmaceuticals were in the range of 91-107.3% for these three analytes.

Overexpression of cytochrome p450 125 in Mycobacterium: a rational strategy in the promotion of phytosterol biotransformation.

Androst-4-ene-3, 17-dione (AD) and androst-1, 4-diene-3, 17-dione (ADD) are generally produced by the biotransformation of phytosterols in Mycobacterium. The AD (D) production increases when the strain has high NAD+/NADH ratio. To enhance the AD (D) production in Mycobacterium neoaurum TCCC 11978 (MNR M3), a rational strategy was developed through overexpression of a gene involved in the phytosterol degradation pathway; NAD+ was generated as well. Proteomic analysis of MNR cultured with and without phytosterols showed that the steroid C27-monooxygenase (Cyp125-3), which performs sequential oxidations of the sterol side chain at the C27 position and has the oxidative cofactor of NAD+ generated, played an important role in the phytosterol biotransformation process of MNR M3. To improve the productivity of AD (D), the cyp125-3 gene was overexpressed in MNR M3. The specific activity of Cyp125-3 in the recombinant strain MNR M3C3 was improved by 22% than that in MNR M3. The NAD+/NADH ratio in MNR M3C3 was 131% higher than that in the parent strain. During phytosterol biotransformation, the conversion of sterols increased from 84 to 96%, and the yield of AD (D) by MNR M3C3 was increased by approximately 18% for 96 h fermentation. This rational strain modification strategy may also be applied to develop strains with important application values for efficient production of cofactor-dependent metabolites.

Synthesis and PI3 Kinase Inhibition Activity of a Wortmannin-Leucine Derivative.

Wortmannin is a potent covalent inhibitor of PI3K that shows substantial in vivo toxicity and thus is unsuitable for systemic therapeutic applications. One possible approach to minimize systemic toxicity is to generate a latent wortmannin pro-drug that will be selectively activated in target tissues. To test this approach, a wortmannin derivative with a leucine linker attached to C20 has been synthesized and tested for inhibition of PI3K activity in prostate cancer cells. Analysis of PI3K pathway inhibition by Wormannin-Leu (Wn-L) and intact Wortmannin (Wn) showed that attachment of Leu at C-20 decreased potency of PI3K pathway inhibition 10-fold compared to intact wortmannin, yet exceeded the potency of a competitive PI3K inhibitor LY294002.

Enantioselective Total Synthesis of (+)-Wortmannin.

A concise and enantioselective total synthesis of the potent PI3K inhibitor (+)-wortmannin is described. A Pd-catalyzed cascade reaction was first developed to connect a synthon derived from Hajos-Parrish ketone to a furan moiety. The subsequent Friedel-Crafts alkylation of the ß-position of a furan ring to an epoxide was optimized to establish the C10 quaternary center. (+)-Wortmannin was eventually accomplished by transformations following a late-stage oxidation of the furan allylic position. Kinome profiling and in vitro enzymatic assays were performed on 17-ß-hydroxy-wortmannin and an epoxide analogue.

Structural and Functional Evaluation of Clinically Relevant Inhibitors of Steroidogenic Cytochrome P450 17A1.

Human steroidogenic cytochrome P450 17A1 (CYP17A1) is a bifunctional enzyme that performs both hydroxylation and lyase reactions, with the latter required to generate androgens that fuel prostate cancer proliferation. The steroid abiraterone, the active form of the only CYP17A1 inhibitor approved by the Food and Drug Administration, binds the catalytic heme iron, nonselectively impeding both reactions and ultimately causing undesirable corticosteroid imbalance. Some nonsteroidal inhibitors reportedly inhibit the lyase reaction more than the preceding hydroxylase reaction, which would be clinically advantageous, but the mechanism is not understood. Thus, the nonsteroidal inhibitors seviteronel and orteronel and the steroidal inhibitors abiraterone and galeterone were compared with respect to their binding modes and hydroxylase versus lyase inhibition. Binding studies and X-ray structures of CYP17A1 with nonsteroidal inhibitors reveal coordination to the heme iron like the steroidal inhibitors. (S)-seviteronel binds similarly to both observed CYP17A1 conformations. However, (S)-orteronel and (R)-orteronel bind to distinct CYP17A1 conformations that differ in a region implicated in ligand entry/exit and the presence of a peripheral ligand. To reconcile these binding modes with enzyme function, side-by-side enzymatic analysis was undertaken and revealed that neither the nonsteroidal seviteronel nor the (S)-orteronel inhibitors demonstrated significant lyase selectivity, but the less potent (R)-orteronel was 8- to 11-fold selective for lyase inhibition. While active-site iron coordination is consistent with competitive inhibition, conformational selection for binding of some inhibitors and the differential presence of a peripheral ligand molecule suggest the possibility of CYP17A1 functional modulation by features outside the active site.

Cofactor engineering to regulate NAD+/NADH ratio with its application to phytosterols biotransformation.

BACKGROUND: Cofactor engineering is involved in the modification of enzymes related to nicotinamide adenine dinucleotides (NADH and NAD+) metabolism, which results in a significantly altered spectrum of metabolic products. Cofactor engineering plays an important role in metabolic engineering but is rarely reported in the sterols biotransformation process owing to its use of multi-catabolic enzymes, which promote multiple consecutive reactions. Androst-4-ene-3, 17-dione (AD) and androst-1, 4-diene-3, 17-dione (ADD) are important steroid medicine intermediates that are obtained via the nucleus oxidation and the side chain degradation of phytosterols by Mycobacterium. Given that the biotransformation from phytosterols to AD (D) is supposed to be a NAD+-dependent process, this work utilized cofactor engineering in Mycobacterium neoaurum and investigated the effect on cofactor and phytosterols metabolism. RESULTS: Through the addition of the coenzyme precursor of nicotinic acid in the phytosterols fermentation system, the intracellular NAD+/NADH ratio and the AD (D) production of M. neoaurum TCCC 11978 (MNR M3) were higher than in the control. Moreover, the NADH: flavin oxidoreductase was identified and was supposed to exert a positive effect on cofactor regulation and phytosterols metabolism pathways via comparative proteomic profiling of MNR cultured with and without phytosterols. In addition, the NADH: flavin oxidoreductase and a water-forming NADH oxidase from Lactobacillus brevis, were successfully overexpressed and heterologously expressed in MNR M3 to improve the intracellular ratio of NAD+/NADH. After 96 h of cultivation, the expression of these two enzymes in MNR M3 resulted in the decrease in intracellular NADH level (by 51 and 67%, respectively) and the increase in NAD+/NADH ratio (by 113 and 192%, respectively). Phytosterols bioconversion revealed that the conversion ratio of engineered stains was ultimately improved by 58 and 147%, respectively. The highest AD (D) conversion ratio by MNR M3N2 was 94% in the conversion system with soybean oil as reaction media to promote the solubility of phytosterols. CONCLUSIONS: The ratio of NAD+/NADH is an important factor for the transformation of phytosterols. Expression of NADH: flavin oxidoreductase and water-forming NADH oxidase in MNR improved AD (D) production. Besides the manipulation of key enzyme activities, which included in phytosterols degradation pathways, maintenance the balance of redox also played an important role in promoting steroid biotransformation. The recombinant MNR strain may be useful in industrial production.

Inhibition of phosphatidylinositol-3-kinase by the furanosesquiterpenoid hibiscone C.

The phosphatidylinositol-3-kinase (PI3K) pathway regulates cellular metabolism and is upregulated in many cancers, making it an attractive chemotherapeutic target. Wortmannin is a potent inhibitor of PI3K; however, its potential as a chemotherapeutic is limited due to its instability, lack of selectivity, and lengthy chemical synthesis. In contrast, hibiscone C, a structurally simpler and less studied member of the furanosteroid family, has been expediently prepared by total synthesis. We demonstrate that hibiscone C competitively inhibits PI3K activity in intact cells, slows proliferation, and induces cell death. Hibiscone C may therefore serve as a productive scaffold for the development of therapeutically relevant PI3K inhibitors.

Structural, biochemical, and biophysical characterization of idelalisib binding to phosphoinositide 3-kinase δ.

Idelalisib (also known as GS-1101, CAL-101, IC489666, and Zydelig) is a PI3Kδ inhibitor that has recently been approved for the treatment of several hematological malignancies. Given its use in human diseases, we needed a clear picture of how idelalisib binds to and inhibits PI3Kδ. Our data show that idelalisib is a potent and selective inhibitor of the kinase activity of PI3Kδ. A kinetic characterization clearly demonstrated ATP-competitive inhibition, and several additional biochemical and biophysical assays showed that the compound binds reversibly and noncovalently to the kinase. A crystal structure of idelalisib bound to the p110δ subunit of PI3Kδ furthers our understanding of the binding interactions that confer the potency and selectivity of idelalisib.

A ligand-specific kinetic switch regulates glucocorticoid receptor trafficking and function.

The ubiquitously expressed glucocorticoid receptor (GR) is a major drug target for inflammatory disease, but issues of specificity and target tissue sensitivity remain. We now identify high potency, non-steroidal GR ligands, GSK47867A and GSK47869A, which induce a novel conformation of the GR ligand-binding domain (LBD) and augment the efficacy of cellular action. Despite their high potency, GSK47867A and GSK47869A both induce surprisingly slow GR nuclear translocation, followed by prolonged nuclear GR retention, and transcriptional activity following washout. We reveal that GSK47867A and GSK47869A specifically alter the GR LBD structure at the HSP90-binding site. The alteration in the HSP90-binding site was accompanied by resistance to HSP90 antagonism, with persisting transactivation seen after geldanamycin treatment. Taken together, our studies reveal a new mechanism governing GR intracellular trafficking regulated by ligand binding that relies on a specific surface charge patch within the LBD. This conformational change permits extended GR action, probably because of altered GR-HSP90 interaction. This chemical series may offer anti-inflammatory drugs with prolonged duration of action due to altered pharmacodynamics rather than altered pharmacokinetics.

Arabidopsis dynamin-related proteins, DRP2A and DRP2B, function coordinately in post-Golgi trafficking.

Dynamin-related proteins (DRPs) are large GTPases involved in a wide range of cellular membrane remodeling processes. In Arabidopsis thaliana, two paralogous land plant-specific type DRPs, DRP2A and DRP2B, are thought to participate in the regulation of post-Golgi trafficking. Here, we examined their molecular properties and functional relationships. qRT-PCR and GUS assays showed that DRP2A and DRP2B were expressed ubiquitously, although their expressions were strongest around root apical meristems and vascular bundles. Yeast two-hybrid, bi-molecular fluorescent complementation, and co-immunoprecipitation mass spectrometry analyses revealed that DRP2A and DRP2B interacted with each other. In observations with confocal laser scanning microscopy and variable incidence angle fluorescent microscopy, fluorescent fusions of DRP2A and DRP2B almost completely co-localized and were mainly localized to endocytic vesicle formation sites of the plasma membrane, clathrin-enriched trans-Golgi network and the cell plate in root epidermal cells. Treatments with wortmannin, an inhibitor of phosphatidylinositol 3-/4-kinases, latrunculin B, an inhibitor of actin polymerization, and oryzalin, an inhibitor of microtubule polymerization, increased the resident time of DRP2A and DRP2B on the plasma membrane. These results show that DRP2A and DRP2B function coordinately in multiple pathways of post-Golgi trafficking in phosphatidylinositol 3- or 4-kinase and cytoskeleton polymerization-dependent manners.

Formulation pre-screening of inhalation powders using computational atom-atom systematic search method.

The synthonic modeling approach provides a molecule-centered understanding of the surface properties of crystals. It has been applied extensively to understand crystallization processes. This study aimed to investigate the functional relevance of synthonic modeling to the formulation of inhalation powders by assessing cohesivity of three active pharmaceutical ingredients (APIs, fluticasone propionate (FP), budesonide (Bud), and salbutamol base (SB)) and the commonly used excipient, α-lactose monohydrate (LMH). It is found that FP (-11.5 kcal/mol) has a higher cohesive strength than Bud (-9.9 kcal/mol) or SB (-7.8 kcal/mol). The prediction correlated directly to cohesive strength measurements using laser diffraction, where the airflow pressure required for complete dispersion (CPP) was 3.5, 2.0, and 1.0 bar for FP, Bud, and SB, respectively. The highest cohesive strength was predicted for LMH (-15.9 kcal/mol), which did not correlate with the CPP value of 2.0 bar (i.e., ranking lower than FP). High FP-LMH adhesive forces (-11.7 kcal/mol) were predicted. However, aerosolization studies revealed that the FP-LMH blends consisted of agglomerated FP particles with a large median diameter (∼4-5 µm) that were not disrupted by LMH. Modeling of the crystal and surface chemistry of LMH identified high electrostatic and H-bond components of its cohesive energy due to the presence of water and hydroxyl groups in lactose, unlike the APIs. A direct comparison of the predicted and measured cohesive balance of LMH with APIs will require a more in-depth understanding of highly hydrogen-bonded systems with respect to the synthonic engineering modeling tool, as well as the influence of agglomerate structure on surface-surface contact geometry. Overall, this research has demonstrated the possible application and relevance of synthonic engineering tools for rapid pre-screening in drug formulation and design.

Improvement on solubility of fluticasone propionate with cyclodextrins by mechanochemical activation.

To enhance the solubility and in vitro dissolution of fluticasone propionate (FP), a novel approach was developed with mechanochemical treatment. The order of solubilizing effect of ß-CD derivatives was observed as HP-ß-CD-SBE-ß-CD-ß-CD-HE-ß-CD, consequently, HP-ß-CD showed the highest stability constant. To further improve FP solubility, FP and HP-ß-CD were grinded using a roll mill, the optimal conditions, determined through single factor experiments, were as follows: rotation frequency of 60 Hz; milling time of 6h. mass ratio of 1: 7. In comparison with pure FP, a 280-fold increase in solubility and a 2.15-fold higher dissolution rate of ground mixture was obtained. The characterization of FP and HP-ß-CD complexes had been analyzed by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), powder X-ray diffractometry (PXRD) and fourier transform infrared spectroscopy (FT-IR). The results suggested that the interaction between FP and HP-ß-CD was strengthened and an amorphous ground mixture was gained. After stored for 60 days, the ground mixtures were stable both chemically and physically.

Transgenic silkworms expressing human insulin receptors for evaluation of therapeutically active insulin receptor agonists.

We established a transgenic silkworm strain expressing the human insulin receptor (hIR) using the GAL4/UAS system. Administration of human insulin to transgenic silkworms expressing hIR decreased hemolymph sugar levels and facilitated Akt phosphorylation in the fat body. The decrease in hemolymph sugar levels induced by injection of human insulin in the transgenic silkworms expressing hIR was blocked by co-injection of wortmannin, a phosphoinositide 3-kinase inhibitor. Administration of bovine insulin, an hIR ligand, also effectively decreased sugar levels in the transgenic silkworms. These findings indicate that functional hIRs that respond to human insulin were successfully induced in the transgenic silkworms. We propose that the humanized silkworm expressing hIR is useful for in vivo evaluation of the therapeutic activities of insulin receptor agonists.

Deletion of the gene encoding the reductase component of 3-ketosteroid 9α-hydroxylase in Rhodococcus equi USA-18 disrupts sterol catabolism, leading to the accumulation of 3-oxo-23,24-bisnorchola-1,4-dien-22-oic acid and 1,4-androstadiene-3,17-dione.

The gene encoding the putative reductase component (KshB) of 3-ketosteroid 9α-hydroxylase was cloned from Rhodococcus equi USA-18, a cholesterol oxidase-producing strain formerly named Arthrobacter simplex USA-18, by PCR according to consensus amino acid motifs of several bacterial KshB subunits. Deletion of the gene in R. equi USA-18 by a PCR-targeted gene disruption method resulted in a mutant strain that could accumulate up to 0.58 mg/ml 1,4-androstadiene-3,17-dione (ADD) in the culture medium when 0.2% cholesterol was used as the carbon source, indicating the involvement of the deleted enzyme in 9α-hydroxylation of steroids. In addition, this mutant also accumulated 3-oxo-23,24-bisnorchola-1,4-dien-22-oic acid (Δ1,4-BNC). Because both ADD and Δ1,4-BNC are important intermediates for the synthesis of steroid drugs, this mutant derived from R. equi USA-18 may deserve further investigation for its application potential.

Evidence for the existence of powder sub-populations in micronized materials: aerodynamic size-fractions of aerosolized powders possess distinct physicochemical properties.

PURPOSE: To investigate the agglomeration behaviour of the fine (<5.0 µm) and coarse (>12.8 µm) particle fractions of salmeterol xinafoate (SX) and fluticasone propionate (FP) by isolating aerodynamic size fractions and characterising their physicochemical and re-dispersal properties. METHODS: Aerodynamic fractionation was conducted using the Next Generation Impactor (NGI). Re-crystallized control particles, unfractionated and fractionated materials were characterized for particle size, morphology, crystallinity and surface energy. Re-dispersal of the particles was assessed using dry dispersion laser diffraction and NGI analysis. RESULTS: Aerosolized SX and FP particles deposited in the NGI as agglomerates of consistent particle/agglomerate morphology. SX particles depositing on Stages 3 and 5 had higher total surface energy than unfractionated SX, with Stage 5 particles showing the greatest surface energy heterogeneity. FP fractions had comparable surface energy distributions and bulk crystallinity but differences in surface chemistry. SX fractions demonstrated higher bulk disorder than unfractionated and re-crystallized particles. Upon aerosolization, the fractions differed in their intrinsic emission and dispersion into a fine particle fraction (<5.0 µm). CONCLUSIONS: Micronized powders consisted of sub-populations of particles displaying distinct physicochemical and powder dispersal properties compared to the unfractionated bulk material. This may have implications for the efficiency of inhaled drug delivery.