Predicting Human Dermal Drug Concentrations Using PBPK Modeling and Simulation: Clobetasol Propionate Case Study

Quantitative in silico tools may be leveraged to mechanistically predict the dermato-pharmacokinetics of compounds delivered from topical and transdermal formulations by integrating systems of rate equations that describe permeation through the formulation and layers of skin and pilo-sebaceous unit, and exchange with systemic circulation via local blood flow. Delivery of clobetasol-17 propionate (CP) from DermovateTM cream was simulated using the Transdermal Compartmental Absorption & Transit (TCATTM) Model in GastroPlus®. The cream was treated as an oil-in-water emulsion, with model input parameters estimated from publicly available information and quantitative structure-permeation relationships. From the ranges of values available for model input parameters, a set of parameters was selected by comparing model outputs to CP dermis concentration-time profiles measured by dermal open-flow microperfusion (Bodenlenz et al. Pharm Res. 33(9):2229-38, 2016). Predictions of unbound dermis CP concentrations were reasonably accurate with respect to time and skin depth. Parameter sensitivity analyses revealed considerable dependence of dermis CP concentration profiles on drug solubility in the emulsion, relatively less dependence on dispersed phase volume fraction and CP effective diffusivity in the continuous phase of the emulsion, and negligible dependence on dispersed phase droplet size. Effects of evaporative water loss from the cream and corticosteroid-induced vasoconstriction were also assessed. This work illustrates the applicability of computational modeling to predict sensitivity of dermato-pharmacokinetics to changes in thermodynamic and transport properties of a compound in a topical formulation, particularly in relation to rate-limiting steps in skin permeation. Where these properties can be related to formulation composition and processing, such a computational approach may support the design of topically applied formulations.

Establishing the Bioequivalence Safe Space for Immediate-Release Oral Dosage Forms using Physiologically Based Biopharmaceutics Modeling (PBBM): Case Studies

For oral drug products, in vitro dissolution is the most used surrogate of in vivo dissolution and absorption. In the context of drug product quality, safe space is defined as the boundaries of in vitro dissolution, and relevant quality attributes, within which drug product variants are expected to be bioequivalent to each other. It would be highly desirable if the safe space could be established via a direct link between available in vitro data and in vivo pharmacokinetics. In response to the challenges with establishing in vitro-in vivo correlations (IVIVC) with traditional modeling approaches, physiologically based biopharmaceutics modeling (PBBM) has been gaining increased attention. In this manuscript we report five case studies on using PBBM to establish a safe space for BCS Class 2 and 4 across different companies, including applications in an industrial setting for both internal decision making or regulatory applications. The case studies provide an opportunity to reflect on practical vs. ideal datasets for safe space development, the methodologies for incorporating dissolution data in the model and the criteria used for model validation and application. PBBM and safe space, still represent an evolving field and more examples are needed to drive development of best practices.

Mechanistic Oral Absorption Modeling and Simulation for Formulation Development and Bioequivalence Evaluation: Report of an FDA Public Workshop

On May 19, 2016, the US Food and Drug Administration (FDA) hosted a public workshop, entitled “Mechanistic Oral Absorption Modeling and Simulation for Formulation Development and Bioequivalence Evaluation.”1 The topic of mechanistic oral absorption modeling, which is one of the major applications of physiologically based pharmacokinetic (PBPK) modeling and simulation, focuses on predicting oral absorption by mechanistically integrating gastrointestinal transit, dissolution, and permeation processes, incorporating systems, active pharmaceutical ingredient (API), and the drug product information, into a systemic mathematical whole‐body framework.2

Combination of decentralized waste drying and SSF techniques for household biowaste minimization and ethanol production

The results of the demonstration of an innovative household biowaste management and treatment scheme established in two Greek Municipalities for the production of lignocellulosic ethanol using dehydrated household biowaste as a substrate, are presented within this research. This is the first time that biowaste drying was tested at a decentralized level for the production of ethanol using the Simultaneous Saccharification and Fermentation (SSF) process, at a pilot scale in Greece. The decentralized biowaste drying method proved that the household biowaste mass and volume reduction may reach 80% through the dehydration process used. The chemical characteristics related to lignocellulosic ethanol production have proved to differ substantially between seasons thus; special attention should be given to the process applied for ethanol production mainly regarding the enzyme quality and quantity used during the pretreatment stage. The maximum ethanol production achieved was 29.12g/L, approximately 60% of the maximum theoretical yield based on the substrate's sugar content. The use of the decentralized waste drying as an alternative approach for household biowaste minimization and the production of second generation ethanol is considered to be a promising approach for efficient biowaste management and treatment in the future.

Alendronate sodium

This chapter is a review on physical and chemical properties, methods of preparation, analysis, as well as pharmacodynamics and pharmacokinetics of Alendronate sodium (4-amino-1-hydroxybutane-1,1-diphosphonic acid sodium salt), a bone metabolism regulator, indicated for the treatment of excessive bone resorption and osteoporosis.

Carvedilol

Carvedilol ((2RS)-1-(9H-carbazol-4-yloxy)-3-[[2-(2-methoxyphenoxy)ethyl]amino]propan-2-ol), a β1-, β2-, and α1-adrenoreceptor blocker drug with antioxidant and antiproliferative effects, is indicated for treatment of hypertension, stable angina pectoris, and congestive heart failure. A profile of this drug substance is provided in this chapter and includes physical characteristics of Carvedilol (e.g., UV-vis, IR, NMR, and mass spectra). Details regarding the stability of Carvedilol in the solid state and solution phase are presented and methods of analysis (compendial and literature) are summarized. Furthermore, an account of the pharmacokinetics (ADME) and synthesis of Carvedilol are presented.

Validated HPLC assay for iron determination in biological matrices based on ferrioxamine formation

A simple, robust and reproducible HPLC method has been developed and validated for iron determination in biological matrices. It is based on chelation with desferrioxamine (DFO) and the measurement of the chelate ferrioxamine (FO). The method was developed to permit monitoring of iron bio-kinetics and estimation of iron status in experimental animals. The chromatography was performed on a stainless steel XTerra MS C18 column (Waters; 250 mm x 4.6 mm i.d., 5 microm) using a gradient of Tris-HCl buffer (10mM, pH 5) and acetonitrile. The method was validated in terms of selectivity, linearity (0.3-80 nmol on-column), limit of detection (0.2 nmol on-column), low limit of quantification (0.3 nmol on-column), recovery (91-102%), intra- and inter-day reproducibility, stability, and robustness. The method's universal applicability was illustrated by monitoring plasma and heart iron kinetic profiles in rats after a single intraperitoneal (i.p.) injection of 200mg/kg iron dextran.

Pharmacokinetic studies of a novel 1,2,4-thiadiazole derivative, inhibitor of Factor XIIIa, in the rabbit by a validated HPLC method

Activated Factor XIII (FXIIIa) stabilizes fibrin clot by covalent cross-linking of fibrin strands in the fibrin, making it resistant to physiological and pharmacologically induced fibrinolysis. Inhibition of Factor XIIIa offers a novel approach to treatment of thrombosis. Selected derivatives of 1,2,4-thiadiazoles, presently in discovery and development, may offer new treatment strategies as inhibitors of Factor XIIIa. In order to evaluate its pharmacokinetic (PK) profile and to facilitate the selection of drug candidates for drug discovery and development process, we developed and validated a simple and selective reversed-phase high-performance liquid chromatographic method (RP-HPLC) with UV detection for the determination of N-[6-(imidazo[1,2-d][1,2,4]thiadiazol-3-ylamino)hexyl]-2-nitrobenzensulfonamide (5624) in rabbit plasma. The plasma protein precipitation and sample preparation was achieved by using acetonitrile, followed by organic phase evaporation to dryness and the residue reconstitution in the mobile phase. The 5624 recovery from the plasma was about 90%. Chromatography was performed on a C18 column using a gradient of acetonitrile in water as a mobile phase. A chemically related compound, N-[6-(imidazo[1,2-d][1,2,4]thiadiazol-3-ylamino)hexyl]naphthalene-1-sulfonamide (5422), was used as an internal standard. Limit of detection (LOD), based on signal to noise ratio>3, was 0.2 microM (on-column amount of about 7 ng), while limit of quantification (LOQ), based on signal to noise ratio>10, was 0.5 microM (on-column amount of about 20 ng). The plasma samples for the PK study were collected at defined time points during and after 5624 slow intravenous infusion (25 mg/kg) to male White New Zealand rabbits and analyzed by RP-HPLC method. The PK parameters, such as half-life, volume of distribution, total clearance, elimination rate constant etc., were determined. The PK profile of 5624 offered insights in the design and development of additional new compounds, derivatives of 1,2,4-thiadiazole, with desired PK properties.

Metabolic and pharmacokinetic evaluation of a Novel 3-hydroxypyridinone iron chelator, CP502, in the rat

A recently synthesized 3-hydroxypyridinone derivative with an amido function at the 2-position, CP502 (1,6-dimethyl-3-hydroxy-4-(1H)-pyridinone-2-carboxy-(N-methyl)-amide hydrochloride), exhibited high in vitro iron chelating potency (pFe3+ =21.7). It was targeted as a new iron-chelating candidate for further development in early pre-clinical testing. To evaluate its pharmacokinetics, including oral bioavailability, metabolic and disappearance profiles, studies were conducted in Sprague Dawley male rats. A single 150 mg/kg intravenous and oral dose was given to male Sprague Dawley rats (N=6, B.Wt. 250g). The rats were placed in metabolic cages and fasted overnight before the dosing. Venous blood samples (200 microL per withdrawal) were collected at defined time points before (blank) and up to 28 h post administration. Urine and feces were collected before dosing (blank) and in 24 h intervals up to 72 h post administration. Plasma CP502 concentration versus time profiles were consistent with two-compartment distribution, and the oral bioavailability approached 100%. Total clearance and mean residence time (i.v.) were 1.02 L/kg/h and 1.10 h, respectively. Simultaneous computer fitting yielded V1 and Vss estimates of 0.96 L/kg and 1.74 L/kg, respectively. CP502 was mainly excreted unchanged via urine (45.29+/-9.40 % of total dose) or as glucuronide (6.46+/-1.22% of total dose). High iron chelation potential and favorable pharmacokinetic and metabolic profiles indicate that CP502 is a promising candidate for further development.

Improved high-performance liquid chromatographic method for the pharmacokinetic studies of a novel iron chelator, CP502, in rats

An improved reverse-phase high-performance liquid chromatographic method (RP-HPLC) for the determination of a novel iron chelator CP502 (1,6-dimethyl-3-hydroxy-4-(1H)-pyridinone-2-carboxy-(N-methyl)-amide hydrochloride) in rat plasma, urine and feces was developed and validated. The separation was performed on a polymeric column using a mobile phase composed of 1mM ethylenediaminetetra-acetic acid disodium salt (EDTA), acetonitrile, methanol and methylene chloride. Separation of CP502 from plasma, urine or feces endogenous compounds was achieved by gradient elution. Retention times of CP502 and its major metabolite (glucuronide) were about 13 and 4 min, respectively. The method was validated in terms of limit of detection (LOD), limit of quantification (LOQ), selectivity (endogenous from plasma, urine or feces), linearity, extraction recovery, robustness (column selection, mobile phase composition, detection mode, internal standard (IS) selection, analyte stability), day-to-day reproducibility and system suitability (repeatability, peak symmetry and resolution). The method is applicable to bioavailability and pharmacokinetic studies of CP502 in rats.

An HPTLC method for the determination and the purity control of ciprofloxacin HCl in coated tablets

A high-performance thin-layer chromatographic method (HPTLC) has been developed for the determination and the purity control of a synthetic fluoroquinolone antibiotic ciprofloxacin hydrochloride in coated tablets when desfluoro compound, ethylene diamine compound, by-compound A and fluoroquinolonic acid are considered as impurities. Silica gel F254 was used as a stationary phase and a mixture of acetonitrile, ammonia 25%, methanol and methylene chloride (1:2:4:4, v/v/v/v) as a mobile phase. The method was validated in terms of linearity (range), selectivity (placebo and related compounds), precision, accuracy (Recovery), system suitability (repeatability, peak symmetry, resolution) and impurities limit of detection (LOD). The analysis of variance (ANOVA) and t-test were applied to correlate the results of ciprofloxacin hydrochloride determination in coated tablets by means of the HPTLC method and the official British Pharmacopoeia (BP 1999) high-performance liquid chromatographic (HPLC) method.

Capillary Gas-Chromatographic Retention Behavior and Physico-Chemical Properties of Underivatized Equine Estrogens

The capillary gas-chromatographic retention behavior of six underivatized equine estrogens (estrone, equilin, equilenin and their corresponding 17α-diols) on a mixed stationary phase (non-polar CP-Sil 5 CB and slightly polar CP-Sil 19 CB capillary columns coupled in series) was characterized by their Kovats retention indices and steroid numbers. In order to find whether a correlation exists between the chromatographic retention and some physico-chemical properties of the compounds, their octanol-water partition coefficients and dipole moments were measured. No straightforward correlation was observed between the physico-chemical properties and the retention behavior, which suggests that the GC separation of equine estrogens is governed by some specific electron donor-electron acceptor interactions of a chemical nature.