Oncogenic Herpesvirus Utilizes Stress-Induced Cell Cycle Checkpoints for Efficient Lytic Replication.

Kaposi's sarcoma herpesvirus (KSHV) causes Kaposi's sarcoma and certain lymphoproliferative malignancies. Latent infection is established in the majority of tumor cells, whereas lytic replication is reactivated in a small fraction of cells, which is important for both virus spread and disease progression. A siRNA screen for novel regulators of KSHV reactivation identified the E3 ubiquitin ligase MDM2 as a negative regulator of viral reactivation. Depletion of MDM2, a repressor of p53, favored efficient activation of the viral lytic transcription program and viral reactivation. During lytic replication cells activated a p53 response, accumulated DNA damage and arrested at G2-phase. Depletion of p21, a p53 target gene, restored cell cycle progression and thereby impaired the virus reactivation cascade delaying the onset of virus replication induced cytopathic effect. Herpesviruses are known to reactivate in response to different kinds of stress, and our study now highlights the molecular events in the stressed host cell that KSHV has evolved to utilize to ensure efficient viral lytic replication.

Validation of Dissolution Testing with Biorelevant Media: An OrBiTo Study.

Dissolution testing with biorelevant media has become widespread in the pharmaceutical industry as a means of better understanding how drugs and formulations behave in the gastrointestinal tract. Until now, however, there have been few attempts to gauge the reproducibility of results obtained with these methods. The aim of this study was to determine the interlaboratory reproducibility of biorelevant dissolution testing, using the paddle apparatus (USP 2). Thirteen industrial and three academic laboratories participated in this study. All laboratories were provided with standard protocols for running the tests: dissolution in FaSSGF to simulate release in the stomach, dissolution in a single intestinal medium, FaSSIF, to simulate release in the small intestine, and a "transfer" (two-stage) protocol to simulate the concentration profile when conditions are changed from the gastric to the intestinal environment. The test products chosen were commercially available ibuprofen tablets and zafirlukast tablets. The biorelevant dissolution tests showed a high degree of reproducibility among the participating laboratories, even though several different batches of the commercially available medium preparation powder were used. Likewise, results were almost identicalbetween the commercial biorelevant media and those produced in-house. Comparing results to previous ring studies, including those performed with USP calibrator tablets or commercially available pharmaceutical products in a single medium, the results for the biorelevant studies were highly reproducible on an interlaboratory basis. Interlaboratory reproducibility with the two-stage test was also acceptable, although the variability was somewhat greater than with the single medium tests. Biorelevant dissolution testing is highly reproducible among laboratories and can be relied upon for cross-laboratory comparisons.

Investigation of the Intra- and Interlaboratory Reproducibility of a Small Scale Standardized Supersaturation and Precipitation Method.

The high number of poorly water-soluble compounds in drug development has increased the need for enabling formulations to improve oral bioavailability. One frequently applied approach is to induce supersaturation at the absorptive site, e.g., the small intestine, increasing the amount of dissolved compound available for absorption. However, due to the stochastic nature of nucleation, supersaturating drug delivery systems may lead to inter- and intrapersonal variability. The ability to define a feasible range with respect to the supersaturation level is a crucial factor for a successful formulation. Therefore, an in vitro method is needed, from where the ability of a compound to supersaturate can be defined in a reproducible way. Hence, this study investigates the reproducibility of an in vitro small scale standardized supersaturation and precipitation method (SSPM). First an intralaboratory reproducibility study of felodipine was conducted, after which seven partners contributed with data for three model compounds; aprepitant, felodipine, and fenofibrate, to determine the interlaboratory reproducibility of the SSPM. The first part of the SSPM determines the apparent degrees of supersaturation (aDS) to investigate for each compound. Each partner independently determined the maximum possible aDS and induced 100, 87.5, 75, and 50% of their determined maximum possible aDS in the SSPM. The concentration-time profile of the supersaturation and following precipitation was obtained in order to determine the induction time (tind) for detectable precipitation. The data showed that the absolute values of tind and aDS were not directly comparable between partners, however, upon linearization of the data a reproducible rank ordering of the three model compounds was obtained based on the ß-value, which was defined as the slope of the ln(tind) versus ln(aDS)-2 plot. Linear regression of this plot showed that aprepitant had the highest ß-value, 15.1, while felodipine and fenofibrate had comparable ß-values, 4.0 and 4.3, respectively. Of the five partners contributing with full data sets, 80% could obtain the same rank order for the three model compounds using the SSPM (aprepitant > felodipine ≈ fenofibrate). The α-value is dependent on the experimental setup and can be used as a parameter to evaluate the uniformity of the data set. This study indicated that the SSPM was able to obtain the same rank order of the ß-value between partners and, thus, that the SSPM may be used to classify compounds depending on their supersaturation propensity.

Nanoparticle-based oral formulation can surprise you with inferior in vivo absorption in humans.

Particle size reduction leads to an increase in the drug dissolution rate, which in turn can lead to a substantial increase in the bioavailability of a poorly soluble compound. To improve bioavailability, a practically insoluble investigational drug, ODM-106, was nanomilled and capsule formulations with three different drug amounts were prepared for the first-in-man study. Fast in vitro dissolution was achieved from all the capsules containing different amounts of drug nanoparticles but in the clinical study, surprisingly, low bioavailability was observed from the highest capsule strength (100 mg) in comparison to a lower strength (10 mg). In order to study further the discrepant in vitro-in vivo correlation (IVIVC), a discriminative dissolution method was developed. It was noticed that the degree of supersaturation increased significantly as the stabilizers' concentration within the dried nanoformulations was increased. Hypromellose provided a physical barrier between nanoparticles to prevent aggregation during drying. SLS on the other hand improved wettability and provided supersaturation. The drug load, nanoparticle/polymer/surfactant/filler ratios and selected drying step were discovered to be critical to the nanoformulations' performance. Aggregation of nanoparticles, in the absence of optimal stabilizer concentration, compromised dissolution due to decreased surface area. In conclusion, the early development of a discriminative dissolution method and cautious selection of the nanoparticle/polymer ratio before manufacturing clinical batches is recommended.

How to stop disproportionation of a hydrochloride salt of a very weakly basic compound in a non-clinical suspension formulation.

Our objectives were to stabilize a non-clinical suspension for use in toxicological studies and to develop methods to investigate the stability of the formulation in terms of salt disproportionation. The compound under research was a hydrochloride salt of a practically insoluble discovery compound ODM-203. The first of the three formulation approaches was a suspension prepared and stored at room temperature. The second formulation was stabilized by pH adjustment. In the third approach cooling was used to prevent salt disproportionation. 5 mg/mL aqueous suspension consisting of 20 mg/mL PVP/VA and 5 mg/mL Tween 80 was prepared for each of the approaches. The polymer was used as precipitation inhibitor to provide prolonged supersaturation while Tween 80 was used to enhance dissolution and homogeneity of the suspension. The consequences of salt disproportionation were studied by a small-scale in vitro dissolution method and by an in vivo pharmacokinetic study in rats. Our results show that disproportionation was successfully suppressed by applying cooling of the suspension in an ice bath at 2-8 °C. This procedure enabled us to proceed to the toxicological studies in rats. The in vivo study results obtained for the practically insoluble compound showed adequate exposures with acceptable variation at each dose level.

Prediction of drug dissolution from Toremifene 80 mg tablets by NIR spectroscopy.

The aim of our study was to justify substitution of dissolution analysis for NIR measurement of Toremifene 80 mg tablets. We studied implementation of a NIRS method by integrating the method development to discrimination power of the dissolution method. Hence, we analyzed 20 DoE tablet batches and studied which of the critical formulation factors affecting dissolution were statistically significant. To study if these factors can be detected by NIRS, PLS calibration models were developed. Finally, PLS model was built to correlate NIR data with the actual dissolution results to predict the released amount of toremifene in 30 min. To obtain the data the tablet batches were measured by NIR using diffuse reflectance technique and multivariate analysis tool was used to calibrate the NIRS models. Correlations between the critical formulation factors and the NIR spectra of Toremifene 80 mg tablet were shown and it was thus justified to develop a NIRS prediction model for dissolution. Variance (R2), standard error of estimate (SEE) and standard error of prediction (SEP) of the model were 90.0%, 4.3% and 5.9%, respectively. It was thus shown that multi-phased and time consuming dissolution procedure could be substituted for fast non-invasive NIRS method.

Predicting the effect of prandial stage and particle size on absorption of ODM-204.

The prediction of absorption properties plays a key role in formulation development when the compound under development shows poor solubility and its absorption is therefore presumed to be solubility limited. In our work, we combined and compared data obtained from in vitro dissolution tests, transit intestinal model studies (TIM-1) and physiologically based pharmacokinetic modelling. Our aim was to determine the ability of these methods to predict performance of poorly soluble lipophilic weak base in vivo. The validity of the predictive methods was evaluated against the in vivo clinical pharmacokinetic (PK) data obtained after administration of the first test formulation, T1. The aim of our study was to utilize the models in evaluating absorption properties of the second test formulation, T2, which has not yet been clinically administered. The compound in the studies was ODM-204, which is a novel, orally administered, investigational, nonsteroidal dual inhibitor of CYP17A1 and androgen receptor. Owing to its physicochemical properties ODM-204 is prone to low or variable bioavailability. The models examined provided congruent data on dose dependent absorption, food effect at a dose of 200 mg and on the effect of API (active pharmaceutical ingredient) particle size on absorption. Our study shows that the predictive tools of in vitro dissolution, TIM-1 system and the PBPK (physiologically based pharmacokinetic) simulation, showed predictive power of different mechanisms of bioavailability and together provided valuable information for decision making.

Biorelevant dissolution testing of a weak base: Interlaboratory reproducibility and investigation of parameters controlling in vitro precipitation.

Following a previous study which aimed to determine the interlaboratory reproducibility of biorelevant dissolution testing in the USP 2 apparatus for commercial formulations of two weak acids (ibuprofen and zafirlukast), this study attempts to determine the interlaboratory reproducibility using a similar protocol for a commercially available formulation of a weak base, indinavir. Fourteen partners including twelve industrial and two academic partners participated in this study. To ensure uniformity, all partners were provided with a standardized protocol to perform (i) a single medium dissolution test in fasted state simulated gastric and intestinal fluids (FaSSGF and FaSSIF, respectively) and (ii) a two-stage dissolution experiment simulating gastrointestinal transfer. Optionally, partners could run a single-stage dissolution test in fed state simulated intestinal fluid (FeSSIF). For each dissolution test, one Crixivan® capsule (containing 400 mg indinavir as its sulfate salt) was added as dose of interest. For the single medium dissolution test in FaSSIF, all partners observed rapid release of indinavir resulting in supersaturated concentrations, followed by precipitation to equilibrium solubility. The degree and period of supersaturation varied among the participating laboratories. Average dissolution profiles in FeSSIF appeared to be highly reproducible with dissolved concentrations remaining lower than the thermodynamic solubility of indinavir in FeSSIF. For the two-stage dissolution test, most partners observed supersaturated concentrations in the intestinal compartment; two partners observed no supersaturation due to immediate precipitation. Given the fact that a high interlaboratory but low intralaboratory variability was observed when supersaturation/precipitation occurred, an undefined factor was hypothesized as a potential cause of the variability in precipitation. Hence, the impact of several experimental factors on the supersaturation and precipitation behavior of indinavir was investigated in a next step. The investigation indicated that variability is likely attributable to a combination of factors, especially, the time elapsed between sampling and dilution of the sample with the mobile phase. Therefore, when designing a test in which supersaturation and precipitation is anticipated, stringent control of the test methodology, especially regarding sampling and dilution, is needed.

Interlaboratory Validation of Small-Scale Solubility and Dissolution Measurements of Poorly Water-Soluble Drugs.

The purpose of this study was to investigate the interlaboratory variability in determination of apparent solubility (Sapp) and intrinsic dissolution rate (IDR) using a miniaturized dissolution instrument. Three poorly water-soluble compounds were selected as reference compounds and measured at multiple laboratories using the same experimental protocol. Dissolution was studied in fasted-state simulated intestinal fluid and phosphate buffer (pH 6.5). An additional 6 compounds were used for the development of an IDR measurement guide, which was then validated with 5 compounds. The results clearly showed a need for a standardized protocol including both the experimental assay and the data analysis. Standardization at both these levels decreased the interlaboratory variability. The results also illustrated the difficulties in performing disc IDR on poorly water-soluble drugs because the concentrations reached are typically below the limit of detection. The following guidelines were established: for compounds with Sapp >1 mg/mL, the disc method is recommended. For compounds with Sapp <100 µg/mL, IDR is recommended to be performed using powder dissolution. Compounds in the interval 100 µg/mL to 1 mg/mL can be analyzed with either of these methods.

Use of conventional surfactant media as surrogates for FaSSIF in simulating in vivo dissolution of BCS class II drugs.

The usefulness of selected conventional surfactant media to enhance dissolution of BCS class II drugs similarly to fasted state simulated intestinal fluid (FaSSIF) and to predict the absorption of drugs in vivo was evaluated. Dissolution behavior of danazol (Danol), spironolactone (Spiridon) and N74 (phase I compound) was compared between FaSSIF, containing physiological levels of sodium taurocholate (STC) and lecithin, and dissolution media containing various concentrations of anionic surfactant, sodium lauryl sulfate (SLS) or non-ionic surfactant, polysorbate (Tween) 80. Although these media differed largely in their solubilization ability, micelle size, diffusivity and surface tension, similar dissolution enhancing levels were achieved between FaSSIF and drug-specific concentrations of conventional surfactants. The dissolution enhancement was shown, however, to be important only for danazol and N74, molecules that are characterized by high hydrophobicity. An in vivo pharmacokinetic dog study was carried out with N74. Comparison of observed plasma profiles with simulated profiles obtained using compartmental absorption and transit model (CAT) indicated that 0.1% SLS medium was the best to predict in vivo plasma profiles and pharmacokinetic parameters (C(max) and AUC). This study demonstrates the potential of substituting FaSSIF with more simple and cost-effective conventional surfactant media. Use of in vivo prognostic amounts of synthetic surfactants in dissolution testing could largely assist in industrial drug development as well as in quality control purposes.

Equilibrium drug solubility measurements in 96-well plates reveal similar drug solubilities in phosphate buffer pH 6.8 and human intestinal fluid.

This study was conducted to develop a high throughput screening (HTS) method for the assessment of equilibrium solubility of drugs. Solid-state compounds were precipitated from methanol in 96-well plates, in order to eliminate the effect of co-solvent. Solubility of twenty model drugs was analyzed in water and aqueous solutions (pH 1.2 and 6.8) in 96-well plates and in shake-flasks (UV detection). The results obtained with the 96-well plate method correlated well (R(2)=0.93) between the shake-flask and 96-well plates over the wide concentration scale of 0.002-169.2mg/ml. Thereafter, the solubility tests in 96-well plates were performed using fasted state human intestinal fluid (HIF) from duodenum of healthy volunteers. The values of solubility were similar in phosphate buffer solution (pH 6.8) and HIF over the solubility range of 10(2)-10(5)µg/ml. The new 96-well plate method is useful for the screening of equilibrium drug solubility during the drug discovery process and it also allows the use of human intestinal fluid in solubility screening.