Aqueous versus non-aqueous salt delivery strategies to enhance oral bioavailability of a mitogen-activated protein kinase-activated protein kinase (MK-2) inhibitor in rats

Evaluating Utilization of Tiny-TIM to Assess the Effect of Food on the Absorptions of Oral Drugs and Its Application on Biopharmaceutical Modeling

Safety and efficacy are the most critical factors for the development of modern medications. For oral drugs, evaluating drug exposure under various conditions is one of the most important outcomes for clinical trials. These data will help to better understand the safety and efficacy of new drugs. Studies involving potential drug-drug interactions, proton pump inhibitors, and intake of food are often conducted to assess the above. Among the above, the influence of food on exposure to the drug is one of the key data sets for regulatory submission. Since food may have either a positive or negative effect on drug exposure, it is important to obtain an early assessment of the food effect. To better forecast and plan for clinical studies, substantial efforts have been made in the industry to develop modeling and in-vitro and in-vivo assays. Despite the efforts, predicting the effect of food on exposure without integrating the dynamic of the gastrointestinal tract in the assessment remains challenging. In this study, we evaluated the utilization of the dynamic Gastro-Intestinal Model (Tiny-TIM) for the food effect of over 20 drugs/formulations in development or on the market that covers all BCS classes. In general, the Tiny-TIM predicted food effects were in good agreement with the reported data in humans. This suggests that Tiny-TIM can successfully capture the impact of physicochemical properties on absorption under the influence of food.

Small molecule targeting of the p38/Mk2 stress signaling pathways to improve cancer treatment

PURPOSE

Although a long-term goal of cancer therapy always has been the development of agents that selectively destroy cancer cells, more recent trends have been to seek secondary agents that sensitize cancer cells to existing treatment regimens. In this regard, the present study explored the possibility of using small molecule inhibitors of p38MAPK/MK2 stress signaling pathways as potential agents to enhance the sensitivity of cancer cells with abrogated G1 checkpoint to the DNA damaging agent etoposide by specifically targeting the DNA damage-induced G2 cell cycle checkpoint.

METHODS

We have applied CCK8 and FACS-based viability assays and cell cycle analysis to investigate the effect of small molecules SB203580 and MK2.III on the sensitivity of small cell lung cancer cells (SCLC) that lack the G1 checkpoint to the DNA damaging agent Etoposide when used in combination. We have also assessed the effectiveness of combination chemotherapy on tumor xenograft suppression with etoposide and MK2.III in immunosuppressed mice. In addition, additional CCK8 cell viability analysis of the MDA-MB-231 breast cancer cell line, and SW620, and SW480 colorectal cancer cell lines was performed.

RESULTS

Results suggest that etoposide produces a profound effect on the cell cycle profile of cells in a manner that is consistent with the degree of cell viability that is seen using the viable cell assay. Results of the co-treatment experiments revealed that the p38/MK2 kinase inhibitors SB203580 and MK2.III both enhanced the DNA-damaging effects of etoposide on NCI-H69 cell viability in vitro. Results revealed that in vivo MK2.III was able to act as a chemosensitizer when used in combination with etoposide making NCI-H69 lung cancer cells sensitive to chemotherapeutic drug by 45% compared to single usage of the drug. We also report that MK2.III sensitizes metastatic cell lines SW-620 and MDA-MB-231 to etoposide but does not increase the sensitivity of non-metastasizing SW-480 colorectal cells to DNA damaging agent in vitro.

CONCLUSION

Findings reported in this study provide evidence that specific inhibitors of MK2 may indeed improve overall cancer therapy; however, their effectiveness depends on cell types.

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.

Utilizing Tiny-TIM to Assess the Effect of Acid-Reducing Agents on the Absorption of Orally Administered Drugs

Acid-reducing agents (ARAs) are the most commonly used medicines to treat patients with gastric acid-related disorders. ARA administration results in an elevation of intragastric pH and eases symptoms such as acid reflux. However, this effect could also lead to a reduction in the absorption of some co-administered oral medications (i.e. weakly basic drugs) by decreasing their gastric solubility. This in turn can result in a significant reduction of the efficacy of the co-administered oral medications. In order to address this problem, substantial efforts in translational modeling and the development of predictive in-vitro assays to better forecast the effect of ARA on oral absorption are conducted in the pharmaceutical industry. Despite these efforts, it remains challenging to predict the impact of ARAs on co-administered drugs. In this study, we evaluated the utility of Triskelion's Gastro-Intestinal Model (Tiny-TIM) in predicting ARA effect on twelve model drugs whose in-vivo data are available. The Tiny-TIM prediction of the ARA effect matched the observed effect of ARA co-administration in humans for the 12 model compounds. In summary, Tiny-TIM is a very reliable and promising GI model to successfully predict the nature of DDI when ARAs are co-administered with the drug of interest.

Investigation of Dose-Dependent Factors Limiting Oral Bioavailability: Case Study With the PI3K-δ Inhibitor

It is understood that a potential issue for drugs with poor aqueous solubility is low oral absorption. If oral exposure issues arise when working with a low solubility drug candidate, the common action is to rely on enabling formulations to solve the issue. However, this approach becomes troublesome in the pre-clinical setting where compound absorption, distribution, metabolism, excretion properties are suboptimal and more factors limiting bioavailability may be at play. A narrow focus on solubility enhancement without a full understanding of compound absorption, distribution, metabolism, excretion properties can produce data that cloak the actual phenomena driving exposure. Compound 1 is a potent and selective PI3Kdelta inhibitor with poor aqueous solubility. In a pharmacokinetic study on dogs, exposure was found to be less than dose-linear. Besides the solubility, further investigations were conducted to identify other factors limiting oral exposure. It was observed that these limiting factors are dose dependent. Results from modeling pharmacokinetic under low-dose conditions suggest that exposure is significantly limited by metabolism and no exposure improvements should be expected from enabled formulations. Furthermore, enabling formulations are expected to exert a beneficial influence at higher doses. An in vivo test was conducted in dogs to verify this phenomenon.

An Investigation of Oral Exposure Variability and Formulation Strategy: A Case Study of PI3Kδ Inhibitor and Physiologically Based Pharmacokinetic Modeling in Beagle Dogs

It is well acknowledged that drugs with poor aqueous solubility are often associated with poor oral absorption. Fortunately, drugs with a basic pKa can take advantage of solubilization in the stomach under the acidic environment to improve exposure. Consequently, high in vivo variability is often observed when stomach pH is altered. When issue encountered, enabling formulations are often used to solve the problem. However, each enabling formulation has its limitations and the situation can be further complicated by other absorption distribution metabolism elimination parameters. Therefore, formulation strategies need to consider various scenarios in order to be effective. Compound 1 is a potent phosphoinositide 3-kinase delta inhibitor with poor intrinsic solubility and 2 basic pKas. It was dosed as a suspension in dogs and found to have mediocre oral bioavailability with high variability. It was hypothesized that this variability was caused by their stomach pH variability. Pharmacokinetic modeling suggested that the issue could be improved with particle size reduction. Meanwhile, it was found that although the Madin-Darby canine kidney permeability was reasonable, Madin-Darby canine kidney transfected with human MDR1 gene (MDCK-MDR1) suggested that Compound 1 is an efflux transporter substrate. Findings were integrated into the design for in vivo studies in dogs. Data obtained from those studies allowed us to quickly narrow down the formulation approaches.

Targeting Mitogen-Activated Protein Kinase-Activated Protein Kinase 2 (MAPKAPK2, MK2): Medicinal Chemistry Efforts To Lead Small Molecule Inhibitors to Clinical Trials

The p38/MAPK-activated kinase 2 (MK2) pathway is involved in a series of pathological conditions (inflammation diseases and metastasis) and in the resistance mechanism to antitumor agents. None of the p38 inhibitors entered advanced clinical trials because of their unwanted systemic side effects. For this reason, MK2 was identified as an alternative target to block the pathway but avoiding the side effects of p38 inhibition. However, ATP-competitive MK2 inhibitors suffered from low solubility, poor cell permeability, and scarce kinase selectivity. Fortunately, non-ATP-competitive inhibitors of MK2 have been already discovered that allowed circumventing the selectivity issue. These compounds showed the additional advantage to be effective at lower concentrations in comparison to the ATP-competitive inhibitors. Therefore, although the significant difficulties encountered during the development of these inhibitors, MK2 is still considered as an attractive target to treat inflammation and related diseases to prevent tumor metastasis and to increase tumor sensitivity to chemotherapeutics.

Incorporation of physiologically based pharmacokinetic modeling in the evaluation of solubility requirements for the salt selection process: a case study using phenytoin

In the pharmaceutical industry, salt is commonly used to improve the oral bioavailability of poorly soluble compounds. Currently, there is a limited understanding on the solubility requirement for salts that will translate to improvement in oral exposure. Despite the obvious need, there is very little research reported in this area mainly due to the complexity of such a system. To our knowledge, no report has been published to guide this important process and salt solubility requirement still remains unanswered. Physiologically based pharmacokinetic (PBPK) modeling offers a means to dynamically integrate the complex interplay of the processes determining oral absorption. A sensitivity analysis was performed using a PBPK model describing phenytoin to determine a solubility requirement for phenytoin salts needed to achieve optimal oral bioavailability for a given dose. Based on the analysis, it is predicted that phenytoin salts with solubility greater than 0.3 mg/mL would show no further increases in oral bioavailability. A salt screen was performed using a variety of phenytoin salts. The piperazine and sodium salts showed the lowest and highest aqueous solubility and were tested in vivo. Consistent with our analysis, we observed no significant differences in oral bioavailability for these two salts despite an approximate 60 fold difference in solubility. Our study illustrates that higher solubility salts sometimes provide no additional improvements in oral bioavailability and PBPK modeling can be utilized as an important tool to provide guidance to the salt selection and define a salt solubility requirement.

Evaluation of a nanoemulsion formulation strategy for oral bioavailability enhancement of danazol in rats and dogs

The objective of this study was to determine whether nanoemulsion formulations constitute a viable strategy to improve the oral bioavailability of danazol, a compound whose poor aqueous solubility limits its oral bioavailability. Danazol-containing oil-in-water nanoemulsions (NE) with and without cosurfactants stearylamine (SA) and deoxycholic acid (DCA) were prepared and characterized. Nanoemulsion droplets size ranging from 238 to 344 nm and with surface charges of -24.8 mV (NE), -26.5 mV (NE-DCA), and +27.8 mV (NE-SA) were reproducibly obtained. Oral bioavailability of danazol in nanoemulsions was compared with other vehicles such as PEG400, 1% methylcellulose (MC) in water (1% MC), Labrafil, and a Labrafil/Tween 80 (9:1) mixture, after intragastric administration to rats and after oral administration of NE-SA, a Labrafil solution, or a Danocrine® tablet to dogs. The absolute bioavailability of danazol was 0.6% (PEG400), 1.2% (1% MC), 6.0% (Labrafil), 7.5% (Labrafil/Tween80), 8.1% (NE-DCA), 14.8% (NE), and 17.4% (NE-SA) in rats, and 0.24% (Danocrine), 6.2% (Labrafil), and 58.7% (NE-SA) in dogs. Overall, danazol bioavailability in any nanoemulsion was higher than any other formulation. Danazol bioavailability from NE and NE-SA was 1.8- to 2.2-fold higher than NE-DCA nanoemulsion and could be due to significant difference in droplet size.

Strategies to address low drug solubility in discovery and development

Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.

In vitro and in vivo evaluation of amorphous solid dispersions generated by different bench-scale processes, using griseofulvin as a model compound

Drug polymer-based amorphous solid dispersions (ASD) are widely used in the pharmaceutical industry to improve bioavailability for poorly water-soluble compounds. Spray-drying is the most common process involved in the manufacturing of ASD material. However, spray-drying involves a high investment of material quantity and time. Lower investment manufacturing processes such as fast evaporation and freeze-drying (lyophilization) have been developed to manufacture ASD at the bench level. The general belief is that the overall performance of ASD material is thermodynamically driven and should be independent of the manufacturing process. However, no formal comparison has been made to assess the in vivo performance of material generated by different processes. This study compares the in vitro and in vivo properties of ASD material generated by fast evaporation, lyophilization, and spray-drying methods using griseofulvin as a model compound and hydroxypropyl methylcellulose acetate succinate as the polymer matrix. Our data suggest that despite minor differences in the formulation release properties and stability of the ASD materials, the overall exposure is comparable between the three manufacturing processes under the conditions examined. These results suggest that fast evaporation and lyophilization may be suitable to generate ASD material for oral evaluation. However, caution should be exercised since the general applicability of the present findings will need to be further evaluated.

Use of pharmaceutical salts and cocrystals to address the issue of poor solubility

Salt and cocrystal formation are the most commonly used method of increasing solubility and dissolution rate of pharmaceutical compounds, and are of particular interest for compounds with an intermediate to low aqueous solubility. However, selection of the most appropriate form does not necessarily equate to selection of the salt/cocrystal with the optimal aqueous solubility, but rather a balance between the best solubility and the best physicochemical properties. This review provides a presentation of salt and cocrystal selection, from a high throughput screening perspective and then an assessment of counter ion properties, common ion effects and the potential impact on the biopharmaceutical performance of the compound. In addition, there is a brief discussion of the impact on polymorphism, the potential use of salts and stoichiometric amorphous mixtures to stabilise amorphous forms and other potential issues for consideration from a pharmaceutical development perspective.

MAPKAP Kinase 2 (MK2) as a Target for Anti-inflammatory Drug Discovery

Despite the success of anti-TNFα biologicals, there remains a significant unmet need for novel oral anti-inflammatory drugs for the treatment of rheumatoid arthritis and related diseases. Vigorous exploration of many potential targets for inhibition of, for example, pro-inflammatory cytokine production has led to efforts to find inhibitor leads targeting many enzymes including the p38α substrate kinase MK2. MK2 has a key role in the production of several pro-inflammatory cytokines, and studies with knockout animals and inhibitor leads support the promise of MK2 as an anti-inflammatory target. However, MK2 has additional biological roles such as in cell cycle checkpoint control, suggesting caution in the use of MK2 inhibitors for chronic non-life-threatening clinical indications such as inflammation. MK2 inhibitor lead identification and optimization efforts in several labs have resulted in a variety of potent and specific lead molecules, some of which display in-vivo activity. However, potency loss from enzyme to cell, and cell to in vivo, is commonly significant. Further, poor enzyme to cell potency correlations are also common for MK2 lead chemical series, suggesting uncontrolled confounding factors in lead inhibitor properties, or that the biological roles of MK2 and related enzymes may still be poorly understood. While further efforts in identification of MK2 inhibitors may yet yield viable drug leads, efforts to date suggest caution with this target.