Reactive oxygen species assay-based risk assessment of drug-induced phototoxicity: classification criteria and application to drug candidates

Quantification of cellular phototoxicity of organelle stains by the dynamics of microtubule polymerization

Being able to quantify the phototoxicity of dyes and drugs in live cells allows biologists to better understand cell responses to exogenous stimuli during imaging. This capability further helps to design fluorescent labels with lower phototoxicity and drugs with better efficacy. Conventional ways to evaluate cellular phototoxicity rely on late-stage measurements of individual or different populations of cells. Here, we developed a quantitative method using intracellular microtubule polymerization as a rapid and sensitive marker to quantify early-stage phototoxicity. Implementing this method, we assessed the photosensitization induced by organelle dyes illuminated with different excitation wavelengths. Notably, fluorescent markers targeting mitochondria, nuclei, and endoplasmic reticulum exhibited diverse levels of phototoxicity. Furthermore, leveraging a real-time precision opto-control technology allowed us to evaluate the synergistic effect of light and dyes on specific organelles. Studies in hypoxia revealed enhanced phototoxicity of Mito-Tracker Red CMXRos that is not correlated with the generation of reactive oxygen species but a different deleterious pathway in low oxygen conditions.

Teaser

Microtubule dynamics in live cells allow quantification of cellular phototoxicity of fluorescent dyes in various conditions.

A cross-industry survey on photosafety evaluation of pharmaceuticals after implementation of ICH S10

A cross-industry survey was conducted by EFPIA/IQ DruSafe in 2018 to provide information on photosafety evaluation of pharmaceuticals after implementation of ICH S10. This survey focused on the strategy utilized for photosafety risk assessment, the design of nonclinical (in vitro and in vivo) and clinical evaluations, the use of exposure margins in risk assessment, and regulatory interactions. The survey results indicated that a staged approach for phototoxicity assessment has been widely accepted by regulatory authorities globally. The OECD-based 3T3 NRU Phototoxicity Test is the most frequently used in vitro approach. Modifications to this assay suggested by ICH S10 are commonly applied. For in-vitro-positives, substantial margins from in vitro IC₅₀ values under irradiation to C_max (clinical) have enabled further development without the need for additional photosafety data. In vivo phototoxicity studies typically involve dosing rodents and exposing skin and eyes to simulated sunlight, and subsequently evaluating at least the skin for erythema and edema. However, no formal guidelines exist and protocols are less standardized across companies. A margin-of-safety approach (based on C_max at NOAEL) has been successfully applied to support clinical development. Experience with dedicated clinical phototoxicity studies was limited, perhaps due to effective de-risking approaches employed based on ICH S10.

An approach to evaluate metabolite-related phototoxicity with combined use of photochemical properties and skin deposition

Some chemicals have been reported to cause metabolite-related phototoxicity, and this study aimed to verify the applicability of photosafety assessment based on photochemical and pharmacokinetic properties to evaluate the metabolite-related phototoxicity risk. The phototoxic risk of imipramine (IMI) and its metabolite, desipramine (DMI), was evaluated by photochemical and pharmacokinetic analyses. IMI and DMI were found to have similar photoreactivities based on the generation of reactive oxygen species. The skin concentrations of IMI and DMI reached maximal levels at approximately 1 and 4 h, respectively, after oral administration of IMI (10 mg/kg), and DMI showed high skin deposition compared with IMI. According to the results, DMI was identified as a contributor to phototoxicity induced by orally-taken IMI. In in vivo phototoxicity testing, ultraviolet A irradiation from 3 to 6 h after oral administration of IMI (100 mg/kg) caused more potent phototoxic reactions compared with that from 0 to 3 h, and DMI yielded by metabolism of IMI would be associated with phototoxic reactions caused by orally-administered IMI. In addition to the data on IMI, a parent chemical, photochemical and pharmacokinetic profiling of its metabolite, DMI, led to reliable phototoxicity prediction of orally-administered IMI. Thus, characterization of the photosafety of metabolites would generate reliable information on the phototoxicity risk of parent chemicals, and the proposed strategy may facilitate comprehensive photosafety assessment of drug candidates in pharmaceutical development.

[Current Issues in Photosafety Evaluation]

Phototoxicity is a toxic response elicited by topically applied or systemically administered photoreactive chemicals after exposure to light and can be broadly categorized into photoirritation, photoallergy, photogenotoxicity, and photocarcinogenicity. The need in the 21st century for accurate evaluation of photosafety has led to the publication of a number of guidelines from government agencies in Europe and the U.S.A. as well as the Organisation for Economic Co-operation and Development (OECD). In this review, we first discuss the mechanisms of phototoxicity and how they can be evaluated. We then discuss the state of the art and challenges now faced in photosafety evaluation of pharmaceuticals and cosmetics. Additionally, we describe the latest developments in OECD test guidelines (TG) for assessing photosafety, including revisions to the in vitro 3T3 neutral red uptake (NRU) phototoxicity test (TG 432) and the newly adopted reactive oxigen species (ROS) assay (TG 495). We will emphasize the importance of selecting the most appropriate means of evaluation with reference to the latest guidelines and other legal criteria for conducting photosafety evaluation.

Strategic photosafety screening system consisting of in chemico photoreactivity and in vitro skin exposure for quinolone derivatives

The main objective of this study was to verify the applicable domain of a proposed photosafety screening system, consisting of a reactive oxygen species (ROS) assay and in vitro skin permeation test, for dermally-applied chemicals. Quinolones (QNLs) were selected as test compounds, including enoxacin, flumequine, moxifloxacin, nalidixic acid, orbifloxacin, and oxolinic acid. The ROS assay and in vitro skin permeation test were employed to evaluate photoreactivity and skin deposition of QNLs, respectively. All QNLs exhibited significant ROS generation on exposure to simulated sunlight; in particular, enoxacin was indicative of potent photoreactivity compared with the other 5 QNLs. Steady-state concentration values of flumequine and nalidixic acid were calculated to be 5.0 and 8.2 μg/mL, respectively, and higher than those of the other QNLs. Based on the photoreactivity and skin exposure of QNLs, the phototoxic risk was ranked, and the predicted phototoxic risk by the proposed system was mostly in agreement with observed in vivo phototoxicity, suggesting the applicability of the proposed strategy to photosafety assessment of QNLs. The proposed screening would be efficacious to predict phototoxic risk of dermally-applied chemicals.

Comparative analysis of the phototoxicity induced by BRAF inhibitors and alleviation through antioxidants

BACKGROUND

Small molecules tackling mutated BRAF (BRAFi) are an important mainstay of targeted therapy in a variety of cancers including melanoma. Albeit commonly reported as side effect, the phototoxic potential of many BRAFi is poorly characterized. In this study, we evaluated the phototoxicity of 17 distinct agents and investigated whether BRAFi-induced phototoxicity can be alleviated by antioxidants.

METHODS

The ultraviolet (UV) light absorbance of 17 BRAFi was determined. Their phototoxic potential was investigated independently with a reactive oxygen species (ROS) and the 3T3 neutral red uptake (NRU) assay in vitro. To test for a possible phototoxicity alleviation by antioxidants, vitamin C, vitamin E phosphate, trolox, and glutathione (GSH) were added to the 3T3 assay of selected inhibitors.

RESULTS

The highest cumulative absorbance for both UVA and UVB was detected for vemurafenib. The formation of ROS was more pronounced for all compounds after irradiation with UVA than with UVB. In the 3T3 NRU assay, 8 agents were classified as phototoxic, including vemurafenib, dabrafenib, and encorafenib. There was a significant correlation between the formation of singlet oxygen (P = .026) and superoxide anion (P < .001) and the phototoxicity observed in the 3T3 NRU assay. The phototoxicity of vemurafenib was fully rescued in the 3T3 NRU assay after GSH was added at different concentrations.

CONCLUSION

Our study confirms that most of the BRAF inhibitors exhibited a considerable phototoxic potential, predominantly after exposure to UVA. GSH may help treat and prevent the phototoxicity induced by vemurafenib.

Photochemically stabilized formulation of dacarbazine with reduced production of algogenic photodegradants

The present study aimed to develop a photochemically stabilized formulation of dacarbazine [5-(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide; DTIC] for reducing the production of algogenic photodegradant (5-diazoimidazole-4-carboxamide; Diazo-IC). Photochemical properties of DTIC were characterized by UV-visible light spectral analysis, reactive oxygen species (ROS) assay, and photostability testing. A pharmacokinetic study was conducted after intravenous administration of DTIC formulations (1 mg-DTIC/kg) to rats. DTIC exhibited strong absorption in the UVA range, and photoirradiated DTIC exhibited marked ROS generation. Thus, DTIC had high photoreactive potential. After exposure of DTIC (1 mM) to simulated sunlight (250 W/m²) for 3 min, remaining DTIC and yielded Diazo-IC were estimated to be ca. 230 μM and 600 μM, respectively. The addition of radical scavenger (1 mM), including l-ascorbic acid, l-cysteine (Cys), l-histidine, D-mannitol, l-tryptophan, or l-tyrosine, to DTIC (1 mM) could attenuate DTIC photoreactions, and in particular, the addition of Cys to DTIC brought ca. 34% and 86% inhibition of DTIC photodegradation and Diazo-IC photogeneration, respectively. There were no significant differences in the calculated pharmacokinetic parameters of DTIC between DTIC and DTIC with Cys (0.67 mg/kg). From these findings, the supplementary use of Cys would be an effective approach to improve the photostability of DTIC with less production of Diazo-IC.

Exploration of alternative test methods to evaluate phototoxicity of ophthalmic agents by using Statens Seruminstitut Rabbit Cornea cell lines and 3D human reconstituted cornea models

Many chemicals have been reported to induce phototoxicity. The absorbance of light energy within the sunlight range is a common characteristic of phototoxicity. The 3T3 NRU phototoxicity test (PT) in 3T3 mouse skin fibroblasts has been used to identify the phototoxic potential induced by excited chemicals after exposure to ultra violet (UV). However, as phototoxicity may occur in ocular cells, it is necessary to develop a more suitable test for cornea-derived cells. In this study, we attempted to establish a new in vitro PT method in rabbit corneal cell lines (SIRC). We evaluated five ophthalmic agents, ciprofloxacin, levofloxacin, lomefloxacin, norfloxacin, and tetracycline, for their cytotoxic potential and in vitro phototoxicity. The results obtained using 3D human corneal models revealed that the UV-induced eye tissue toxicity by the test substances showed good correlation with those obtained using the in vitro phototoxicity test. However, the results from the 3D PT for ciprofloxacin, norfloxacin, and tetracycline in the 3D human cornea model were only partially comparable. Therefore, we suggest the SIRC cell line as a new phototoxicity test model; however, a sequential testing strategy, such as 3D PT, was also proposed to obtain relevant information for topical eye agents.

Implications of melanin binding in ocular drug delivery

Pigmented ocular tissues contain melanin within the intracellular melanosomes. Drugs bind to melanin at varying extent that ranges from no binding to extensive binding. Binding may lead to drug accumulation to the pigmented tissues and prolonged drug retention in the melanin containing cells. Therefore, melanin binding is an important feature that affects ocular drug delivery and biodistribution, but this topic has not been reviewed since 1998. In this review, we present current knowledge on ocular melanin, melanosomes and binding of drugs to pigmented cells and tissues. In vitro, in vivo and in silico methods in the field were critically evaluated, because the literature in this field can be confusing if the reader does not properly understand the methodological aspects. Literature analysis includes a comprehensive table of literature data on melanin binding of drugs. Furthermore, we aimed to give some insights beyond the current literature by making a chemical structure based classification model for melanin binding of drugs and kinetic simulations that revealed significant interplay between melanin binding and drug permeability across the melanosomal and plasma membranes. Overall, more mechanistic and systematic research is needed before the impact of melanin binding on ocular drug delivery can be properly understood and predicted.

Amorphous Solid Dispersion of Meloxicam Enhanced Oral Absorption in Rats With Impaired Gastric Motility

Meloxicam (MEL) shows a slow onset of action in severe pain patients on account of delayed gastric motility. This study aimed to develop an amorphous solid dispersion (ASD) of MEL to achieve rapid oral absorption in severe pain patients. ASD formulations of MEL with hydroxypropylmethylcellulose (ASD-MEL/HPMC) and polyacrylates and polymethacrylates (ASD-MEL/EUD) were prepared and physicochemically characterized. Oral absorption behavior of MEL samples was also clarified in both normal and propantheline (PPT)-pretreated rats with impaired gastric motility. MEL in the formulations was amorphous, and ASD formulations of MEL exhibited high dissolution behavior in acidic solution. After oral administration of crystalline MEL (1 mg-MEL/kg), a 69% reduction in AUC_0-4 was observed between normal and PPT-pretreated rats. For orally dosed ASD-MEL/HPMC (1 mg-MEL/kg), there were approximately 9- and 12-fold increases of AUC_0-4 in normal and PPT-pretreated rats, respectively, in comparison with crystalline MEL (1 mg-MEL/kg). However, the oral absorption behavior of ASD-MEL/EUD (1 mg-MEL/kg) was low and similar to that of crystalline MEL. The infrared spectroscopic study revealed potent interactions between MEL and EUD, possibly leading to marked attenuation of MEL absorption. This ASD approach might provide rapid oral absorption of MEL in severe pain patients, possibly leading to better clinical outcomes.

Photodynamic Treatment of Oral Squamous Cell Carcinoma Cells with Low Curcumin Concentrations

Objective: Curcumin is known for its anti-oxidative, anti-inflammatory and anti-tumorigenic qualities at concentrations ranging from 3.7µg/ml to 55µg/ml. Therefore it is pre-destined for tumour therapy. Due to high oral doses that have to be administered and the low bioavailability of curcumin new therapy concepts have to be developed. One of these therapy concepts is the combination of low curcumin concentrations and UVA or visible light. Aim of our study was to investigate the influence of this treatment regime on oral squamous cell carcinoma cells. Materials and Methods: A human oral squamous cell carcinoma cell line (HN) was pre-incubated with low curcumin concentrations (0.01µg/ml to 1µg/ml). Thereafter cell cultures were either left un-irradiated or were irradiated either with 1J/cm² UVA or for 5min with visible light. Quantitative analysis of proliferation, membrane integrity, oxidative potential and DNA fragmentation were done. Results: It could be shown that low curcumin concentrations neither influenced proliferation, nor cell morphology, nor cell integrity nor apoptosis. When combining these curcumin concentrations with UVA or visible light irradiation cell proliferation as well as development of reactive oxygen species was reduced whereas DNA fragmentation was increased. Concentration as well as light entity specific effects could be observed. Conclusions: The present findings substantiate the potential of the combination of low curcumin concentrations and light as a new therapeutic concept to increase the efficacy of curcumin in the treatment of cancer of the oral mucosa.

Biological fate of food nanoemulsions and the nutrients they carry – internalisation, transport and cytotoxicity of edible nanoemulsions in Caco-2 intestinal cells

Internalisation of edible food nanoemulsions by CaCo-2 intestinal cells. The structure of edible nanoemulsions increases five times upon incorporation of reactive/ROS producing nutrients/APIs.

Phototoxicity: Its Mechanism and Animal Alternative Test Methods

The skin exposure to solar irradiation and photoreactive xenobiotics may produce abnormal skin reaction, phototoxicity. Phototoxicity is an acute light-induced response, which occurs when photoreacive chemicals are activated by solar lights and transformed into products cytotoxic against the skin cells. Multifarious symptoms of phototoxicity are identified, skin irritation, erythema, pruritis, and edema that are similar to those of the exaggerated sunburn. Diverse organic chemicals, especially drugs, are known to induce phototoxicity, which is probably from the common possession of UV-absorbing benzene or heterocyclic rings in their molecular structures. Both UVB (290~320 nm) and UVA (320~400 nm) are responsible for the manifestation of phototoxicity. Absorption of photons and absorbed energy (hv) by photoactive chemicals results in molecular changes or generates reactive oxygen species and depending on the way how endogenous molecules are affected by phototoxicants, mechanisms of phototoxcity is categorized into two modes of action: Direct when unstable species from excited state directly react with the endogenous molecules, and indirect when endogeneous molecules react with secondary photoproducts. In order to identify phototoxic potential of a chemical, various test methods have been introduced. Focus is given to animal alternative test methods, i.e., in vitro, and in chemico assays as well as in vivo. 3T3 neutral red uptake assay, erythrocyte photohemolysis test, and phototoxicity test using human 3-dimensional (3D) epidermis model are examples of in vitro assays. In chemico methods evaluate the generation of reactive oxygen species or DNA strand break activity employing plasmid for chemicals, or drugs with phototoxic potential.

Nonclinical Safety and Toxicology

Nonclinical safety pharmacology and toxicology testing of drug candidates assess the potential adverse effects caused by the drug in relation to its intended use in humans. Hazards related to a drug have to be identified and the potential risks at the intended exposure have to be evaluated in comparison to the potential benefit of the drug. Preclinical safety is thus an integral part of drug discovery and drug development. It still causes significant attrition during drug development.Therefore, there is a need for smart selection of drug candidates in drug discovery including screening of important safety endpoints. In the recent years,there was significant progress in computational and in vitro technology allowing in silico assessment as well as high-throughput screening of some endpoints at very early stages of discovery. Despite all this progress, in vivo evaluation of drug candidates is still an important part to safety testing. The chapter provides an overview on the most important areas of nonclinical safety screening during drug discovery of small molecules.

Intra-/inter-laboratory validation study on reactive oxygen species assay for chemical photosafety evaluation using two different solar simulators

A previous multi-center validation study demonstrated high transferability and reliability of reactive oxygen species (ROS) assay for photosafety evaluation. The present validation study was undertaken to verify further the applicability of different solar simulators and assay performance. In 7 participating laboratories, 2 standards and 42 coded chemicals, including 23 phototoxins and 19 non-phototoxic drugs/chemicals, were assessed by the ROS assay using two different solar simulators (Atlas Suntest CPS series, 3 labs; and Seric SXL-2500V2, 4 labs). Irradiation conditions could be optimized using quinine and sulisobenzone as positive and negative standards to offer consistent assay outcomes. In both solar simulators, the intra- and inter-day precisions (coefficient of variation; CV) for quinine were found to be below 10%. The inter-laboratory CV for quinine averaged 15.4% (Atlas Suntest CPS) and 13.2% (Seric SXL-2500V2) for singlet oxygen and 17.0% (Atlas Suntest CPS) and 7.1% (Seric SXL-2500V2) for superoxide, suggesting high inter-laboratory reproducibility even though different solar simulators were employed for the ROS assay. In the ROS assay on 42 coded chemicals, some chemicals (ca. 19-29%) were unevaluable because of limited solubility and spectral interference. Although several false positives appeared with positive predictivity of ca. 76-92% (Atlas Suntest CPS) and ca. 75-84% (Seric SXL-2500V2), there were no false negative predictions in both solar simulators. A multi-center validation study on the ROS assay demonstrated satisfactory transferability, accuracy, precision, and predictivity, as well as the availability of other solar simulators.

Exposure to phototoxic NSAIDs and quinolones is associated with an increased risk of melanoma

PURPOSE

Ultraviolet radiation exposure is the most important exogenous risk factor for cutaneous malignancies. It is possible that phototoxic drugs promote the development of cutaneous melanoma (CM) by intensifying the effect of ultraviolet light on the skin. We investigated the association between the use of common systemic phototoxic drugs and development of CM.

METHODS

This study was a case-control study in a Dutch population-based cohort. The drug dispensing data was obtained from PHARMO, a Dutch drug dispensing and hospital admissions registry, and linked to PALGA, the nationwide pathology network of the Netherlands. The cases were patients diagnosed with pathologically confirmed primary CM between 1991 and 2004. Controls were sampled from the PHARMO population. Exposure to systemic phototoxic drugs was measured and included antimicrobial agents, diuretics, antipsychotic drugs, antidiabetic drugs, cardiac drugs, antimalarials and nonsteroidal anti-inflammatory drugs (NSAIDs). A multivariate conditional logistic regression analysis was performed to study the association between exposure to phototoxic drugs and CM.

RESULTS

The study population included 1,318 cases and 6,786 controls. Any phototoxic drug during the study period was dispensed for 46 % of the cases and 43 % of the controls (p = 0.012). The use of quinolones [odds ratio (OR) 1.33, 95 % confidence interval (CI) 1.01-1.76] and propionic acid derivative NSAIDs (OR 1.33, 95 % CI 1.14-1.54) had a positive association with CM.

CONCLUSIONS

Our study shows that the use of phototoxic drugs is associated with an increased risk of developing CM. Even a short-term use of phototoxic quinolones and propionic acid derivative NSAIDs may increase the risk for CM. Patient education to promote sun-protective behaviour is essential to avoid immediate adverse effects and possible long-term effects of phototoxic drugs.

Inhalable powder formulation of pirfenidone with reduced phototoxic risk for treatment of pulmonary fibrosis

PURPOSE

Orally-taken pirfenidone (PFD), an idiopathic pulmonary fibrosis drug, often causes severe phototoxicity. Present study aimed to develop a respirable powder formulation for PFD (PFD-RP) to minimize phototoxic risk.

METHODS

Photochemical properties of PFD were examined using a reactive oxygen species (ROS) assay and photostability testing. PFD-RP was characterized with a focus on photostability, in vitro inhalation performance, and the efficacy in antigen-sensitized rats. Pharmacokinetic studies were conducted after oral and intratracheal administration of PFD formulations.

RESULTS

Although PFD solution exhibited photodegradation under simulated sunlight (250 W/m²), both PFD powder and PFD-RP were photochemically stable. Laser diffraction and cascade impactor analyses on PFD-RP suggested its high dispersion and fine in vitro inhalation performance. Inhaled PFD-RP (300 μg-PFD/rat) could suppress antigen-evoked pulmonary inflammation in rats as evidenced by decreases in recruited inflammatory cells and neutrophilia-related biomarkers in the lung. Exposure of PFD to light-exposed tissues (skin and eye) after intratracheal administration of PFD-RP at a pharmacologically effective dose (300 μg-PFD/rat) was 90-130-fold less than that of the oral PFD dosage form at a phototoxic dose (160 mg/kg).

CONCLUSIONS

PFD-RP might be an attractive alternative to the current oral PFD therapy with a better safety margin.

Drug-induced oxidative stress and toxicity

Reactive oxygen species (ROS) are a byproduct of normal metabolism and have roles in cell signaling and homeostasis. Species include oxygen radicals and reactive nonradicals. Mechanisms exist that regulate cellular levels of ROS, as their reactive nature may otherwise cause damage to key cellular components including DNA, protein, and lipid. When the cellular antioxidant capacity is exceeded, oxidative stress can result. Pleiotropic deleterious effects of oxidative stress are observed in numerous disease states and are also implicated in a variety of drug-induced toxicities. In this paper, we examine the nature of ROS-induced damage on key cellular targets of oxidative stress. We also review evidence implicating ROS in clinically relevant, drug-related side effects including doxorubicin-induced cardiac damage, azidothymidine-induced myopathy, and cisplatin-induced ototoxicity.

Establishment and intra-/inter-laboratory validation of a standard protocol of reactive oxygen species assay for chemical photosafety evaluation

A reactive oxygen species (ROS) assay was previously developed for photosafety evaluation of pharmaceuticals, and the present multi-center study aimed to establish and validate a standard protocol for ROS assay. In three participating laboratories, two standards and 42 coded chemicals, including 23 phototoxins and 19 nonphototoxic drugs/chemicals, were assessed by the ROS assay according to the standardized protocol. Most phototoxins tended to generate singlet oxygen and/or superoxide under UV-vis exposure, but nonphototoxic chemicals were less photoreactive. In the ROS assay on quinine (200 µm), a typical phototoxic drug, the intra- and inter-day precisions (coefficient of variation; CV) were found to be 1.5-7.4% and 1.7-9.3%, respectively. The inter-laboratory CV for quinine averaged 15.4% for singlet oxygen and 17.0% for superoxide. The ROS assay on 42 coded chemicals (200 µm) provided no false negative predictions upon previously defined criteria as compared with the in vitro/in vivo phototoxicity, although several false positives appeared. Outcomes from the validation study were indicative of satisfactory transferability, intra- and inter-laboratory variability, and predictive capacity of the ROS assay.

Novel solid self-emulsifying drug delivery system of coenzyme Q₁₀ with improved photochemical and pharmacokinetic behaviors

The present study was undertaken to develop a solid self-emulsifying drug delivery system of coenzyme Q(10) (CoQ(10)/s-SEDDS) with high photostability and oral bioavailability. The CoQ(10)/s-SEDDS was prepared by spray-drying an emulsion preconcentrate containing CoQ(10), medium-chain triglyceride, sucrose ester of fatty acid, and hydroxypropyl cellulose, and its physicochemical, photochemical, and pharmacokinetic properties were evaluated. The CoQ(10)/s-SEDDS powder with a diameter of ca. 15 μm was obtained by spray-drying, in which the CoQ(10) was mostly amorphized. The CoQ(10)/s-SEDDS exhibited immediate self-emulsification when introduced to aqueous media under gentle agitation, forming uniform fine droplets with a mean diameter of ca. 280 nm. There was marked generation of reactive oxygen species, in particular superoxide, from CoQ(10) exposed to simulated sunlight (250W/m(2)), suggesting potent photoreactivity. Nano-emulsified solution of CoQ(10) under light exposure underwent photodegradation with 22-fold higher degradation kinetics than crystalline CoQ(10), although the CoQ(10)/s-SEDDS was less photoreactive. After the oral administration of CoQ(10)/s-SEDDS (100 mg-CoQ(10)/kg) in rats, enhanced exposure of CoQ(10) was observed with increases in both C(max) and AUC of ca. 5-fold in comparison with those of orally administered crystalline CoQ(10). From the improved physicochemical and pharmacokinetic data, the s-SEDDS approach upon spray-drying might be a suitable dosage option for enhancing nutraceutical and pharmaceutical values of CoQ(10).

A multidisciplinary approach to characterise exposure risk and toxicological effects of PM₁₀ and PM₂.₅ samples in urban environments

Urban aerosol samples collected in Barcelona between 2008 and 2009 were toxicologically characterised by means of two complementary methodologies allowing evaluation of their Reactive Oxidative Stress (ROS)-generating capacity: the plasmid scission assay (PSA) and the dichlorodihydrofluorescin assay (DCFH). The PSA determined the PM dose able to damage 50% of a plasmid DNA molecule (TD(50) values), an indication of the ability of the sample to exert potential oxidative stress, most likely by formation of ·OH. This toxicity indicator did not show dependency on different air mass origins (African dust, Atlantic advection), indicating that local pollutant sources within or near the city are most likely to be mainly responsible for PM health effect variations. The average TD(50) values show PM(2.5-0.1) samples to be more toxic than the PM(10-2.5) fraction, with doses similar to those reported in previous studies in polluted urban areas. In addition, the samples were also evaluated using the oxidant-sensitive probe DCFH confirming the positive association between the amount of DNA damage and the generation of reactive oxidant species capable of inducing DNA strand break. Results provided by the PSA were compared with those from two other different methodologies to evaluate human health risk: (1) the toxicity of particulate PAHs expressed as the calculated toxicity equivalent of benzo[a]pyrene (BaPteq) after application of the EPA toxicity factors, and (2) the cancer risk assessment of the different PM sources detected in Barcelona with the receptor model Positive Matrix Factorisation (PMF) and the computer programme Multilinear Engine 2 (ME-2) using the organic and inorganic chemical compositions of particles. No positive associations were found between PSA and the toxicity of PAHs, probably due to the inefficiency of water in extracting organic compounds. On the other hand, the sum of cancer risk estimates calculated for each of the selected days for the PSA was found to correlate with TD(50) values in the fine fraction, with fuel oil combustion and industrial emissions therefore being most implicated in negative health effects. Further studies are necessary to determine whether toxicity is related to PM chemical composition and sources, or rather to its size distribution.

Formulation design and photochemical studies on nanocrystal solid dispersion of curcumin with improved oral bioavailability

Considerable interest has been focused on curcumin due to its use to treat a wide variety of disorders, however, the therapeutic potential of curcumin could often be limited by its poor solubility, bioavailability, and photostability. To overcome these drawbacks, efficacious formulations of curcumin, including nanocrystal solid dispersion (CSD-Cur), amorphous solid dispersion (ASD-Cur), and nanoemulsion (NE-Cur), were designed with the aim of improving physicochemical and pharmacokinetic properties. Physicochemical properties of the prepared formulations were characterized by scanning/transmission electron microscope for morphological analysis, laser diffraction, and dynamic light scattering for particle size analysis, and polarized light microscope, powder X-ray diffraction and differential scanning calorimetry for crystallinity assessment. In dissolution tests, all curcumin formulations exhibited marked improvement in the dissolution behavior when compared with crystalline curcumin. Significant improvement in pharmacokinetic behavior was observed in the newly developed formulations, as evidenced by 12- (ASD-Cur), 16- (CSD-Cur), and 9-fold (NE-Cur) increase of oral bioavailability. Upon photochemical characterization, curcumin was found to be photoreactive and photodegradable in the solution state, possibly via type 2 photochemical reaction, whereas high photochemical stability was seen in the solid formulations, especially CSD-Cur. On the basis of these observations, taken together with dissolution and pharmacokinetic behaviors, CSD strategy would be efficacious to enhance bioavailability of curcumin with high photochemical stability.

A current practice for predicting ocular toxicity of systemically delivered drugs

The ability to predict ocular side effects of systemically delivered drugs is an important issue for pharmaceutical companies. Although animal models involving standard clinical ophthalmic examinations and postmortem microscopic examinations of eyes are still used to identify ocular issues, these methods are being supplemented with additional in silico, in vitro, and in vivo techniques to identify potential safety issues and assess risk. The addition of these tests to a development plan for a potential new drug provides the opportunity to save time and money by detecting ocular issues earlier in the program. This review summarizes a current practice for minimizing the potential for systemically administered, new medicines to cause adverse effects in the eye.

In vitro and in vivo pharmacological characterization of PF-01354082, a novel partial agonist selective for the 5-HT(4) receptor

The pharmacological profile of PF-01354082, a selective 5-HT(4) receptor partial agonist, was investigated. PF-01354082 displayed high affinity for human 5-HT(4d) and dog 5-HT(4h) receptors in binding studies, having Ki values of 2.0 nM and 4.2 nM, respectively. By contrast, PF-01354082 did not show significant affinity for several other 5-HT receptors (5-HT(1A), 5-HT(1B), 5-HT(1D), 5-HT(2A), 5-HT(2B), 5-HT(2C), 5-HT(3A), and 5-HT(7)) or the dopamine D(2long) receptor. Functional assays using either cells expressing human recombinant 5-HT(4d) receptors or rat tunica muscularis mucosae demonstrated that PF-01354082 exhibited partial agonist activity at the 5-HT(4) receptor. The effects of PF-01354082 on in vitro receptor binding, ion channel activity, and sites of uptake were further investigated. PF-01354082 did not show biologically relevant binding activity at concentrations up to 10 microM except for binding to the 5-HT(4e) receptor. Furthermore, PF-01354082 decreased I(HERG) current by only 11% at a concentration of 300 microM, indicating that the compound had greater than 150,000-fold selectivity for the human 5-HT(4d) receptor over hERG channels. An in vivo study using a gastric motility model in conscious dogs demonstrated that oral administration of PF-01354082 resulted in marked and sustained stimulation of gastric motility in a dose-dependent manner. These results indicate that PF-01354082 is an orally active, highly selective, partial agonist of the human 5-HT(4) receptor that is expected to exert a favorable effect on gastrointestinal motor disorders with reduced adverse effects mediated by other related receptors.