Drug-induced liver injury (DILI) has been the most frequent cause of post-marketing drug withdrawals in the last 50years. The multifactorial nature of events that precede severe liver injury in human ...patients is difficult to model in rodents due to a variety of confounding or contributing factors that include disease state, concurrent medications, and translational species differences. In retrospective analyses, a consistent risk factor for DILI has been the inhibition of the Bile Salt Export Pump (BSEP). One compound known for potent BSEP inhibition and severe DILI is troglitazone. The purpose of the current study is to determine if serum profiling of 19 individual bile acids by liquid chromatography-mass spectrometry (LC/MS) can detect perturbations in bile acid homeostasis in rats after acute intravenous (IV) administration of vehicle or 5, 25, or 50mg/kg troglitazone. Minimal serum transaminase elevations (approximately two-fold) were observed with no evidence of microscopic liver injury. However, marked changes in individual serum bile acids occurred, with dose-dependent increases in the majority of the bile acids profiled. When compared to predose baseline values, tauromuricholic acid and taurocholic acid had the most robust increase in serum levels and dynamic range, with a maximum fold increase from baseline of 34-fold and 29-fold, respectively. Peak bile acid increases occurred within 2hours (h) after dosing and returned to baseline values before 24h. In conclusion, serum bile acid profiling can potentially identify a mechanistic risk of clinical DILI that could be poorly detected by traditional toxicity endpoints.
•Troglitazone is a potent BSEP inhibitor and perturbs bile acid homeostasis in rats.•Taurine-conjugated bile acids had the best dynamic range of profiled bile acids.•Serum bile acids identify mechanistic DILI that cannot be detected with routine toxicity testing.•The study design captures transient changes in bile acids in context with in vivo exposures.
Hydrotropy is a phenomenon where the presence of a large quantity of one solute enhances the solubility of another solute. The mechanism of this phenomenon remains elusive and a topic of debate. This ...study employed molecular dynamics simulation to investigate the hydrotropic mechanism of a model system consisting of a hydrotropic agent, nicotinamide (NA), a poorly water-soluble solute, PG-300995 (PG), and water. Our study demonstrates that NA and PG undergo significant aggregation in the aqueous solution, a result correlating closely to the self-aggregation of NA under the same conditions. The correlations are found both structurally and dynamically, suggesting that the self-aggregation of NA may be a prerequisite, or at least a major contributor, to its hydrotropic effects. The self-aggregation of NA allows the segregation of the hydrophobic solute from water, a key step to ease the energy increase to the system. Energetic evidences directly show that the hydrotropic solubilization is favored in the presence of NA aggregation. These results are in strong support of the molecular aggregation hypothesis for hydrotropic solubilization. Additionally, it is found that the restoration of water-water HBs from the interference of the NA and PG molecules plays an important role for the aggregation. The HBs between the solute and the hydrotrope may contribute, but is not vital, to the aggregation and hence the hydrotropic effects. The dynamic data confirm that the aggregates, while remain in liquid state, are much more active dynamically than a pure NA amorphous/liquid phase under the same temperature and pressure. By equilibrating an NA amorphous agglomerate with water, it is found that the aggregation state, rather than an NA-water two phase system, is the equilibrium state of the NA+water system.
Heat shock protein 90 (Hsp90) is a molecular chaperone protein implicated in stabilizing the conformation and maintaining the function of many cell-signaling proteins. Many oncogenic proteins are ...more dependent on Hsp90 in maintaining their conformation, stability, and maturation than their normal counterparts. Furthermore, recent data show that Hsp90 exists in an activated form in malignant cells but in a latent inactive form in normal tissues, suggesting that inhibitors selective for the activated form could provide a high therapeutic index. Hence, Hsp90 is emerging as an exciting new target for the treatment of cancer. We now report on a novel series of 2-amino-6-halopurine Hsp90 inhibitors exemplified by 2-amino-6-chloro-9-(4-iodo-3,5-dimethylpyridin-2-ylmethyl)purine (30). These highly potent inhibitors (IC50 of 30 = 0.009 μM in a HER-2 degradation assay) also display excellent antiproliferative activity against various tumor cell lines (IC50 of 30 = 0.03 μM in MCF7 cells). Moreover, this class of inhibitors shows higher affinity for the activated form of Hsp90 compared to our earlier 8-sulfanylpurine Hsp90 inhibitor series. When administered orally to mice, these compounds exhibited potent tumor growth inhibition (>80%) in an N87 xenograft model, similar to that observed with 17-allylamino-17-desmethoxygeldanamycin (17-AAG), which is a compound currently in phase I/II clinical trials.
It is well recognized that poor dissolution rate and solubility of drug candidates are key limiting factors for oral bioavailability. While numerous technologies have been developed to enhance ...solubility of the drug candidates, poor water solubility continuously remains a challenge for drug delivery. Among those technologies, amorphous solid dispersions (SD) have been successfully employed to enhance both dissolution rate and solubility of poorly water-soluble drugs. This research reports a high-throughput screening technology developed by utilizing a 96-well plate system to identify optimal drug load and polymer using a solvent casting approach. A minimal amount of drug was required to evaluate optimal drug load in three different polymers with respect to solubility improvement and solid-state stability of the amorphous drug–polymer system. Validation of this method was demonstrated with three marketed drugs as well as with one internal compound. Scale up of the internal compound SD by spray drying further confirmed the validity of this method, and its quality was comparable to a larger scale process. Here, we demonstrate that our system is highly efficient, cost-effective, and robust to evaluate the feasibility of spray drying technology to produce amorphous solid dispersions.
We report on the discovery of benzo- and pyridino- thiazolothiopurines as potent heat shock protein 90 inhibitors. The benzothiazole moiety is exceptionally sensitive to substitutions on the aromatic ...ring with a 7‘-substituent essential for activity. Some of these compounds exhibit low nanomolar inhibition activity in a Her-2 degradation assay (28−150 nM), good aqueous solubility, and oral bioavailability profiles in mice. In vivo efficacy experiments demonstrate that compounds of this class inhibit tumor growth in an N87 human colon cancer xenograft model via oral administration as shown with compound 37 (8-(7-chlorobenzothiazol-2-ylsulfanyl)-9-(2-cyclopropylamino-ethyl)-9H- purin-6-ylamine).
Aurora kinase inhibitors have attracted a great deal of interest as a new class of antimitotic agents. We report a novel class of Aurora inhibitors based on a pentacyclic scaffold. A prototype ...pentacyclic inhibitor 32 (AKI-001) derived from two early lead structures improves upon the best properties of each parent and compares favorably to a previously reported Aurora inhibitor, 39 (VX-680). The inhibitor exhibits low nanomolar potency against both Aurora A and Aurora B enzymes, excellent cellular potency (IC50 < 100 nM), and good oral bioavailability. Phenotypic cellular assays show that both Aurora A and Aurora B are inhibited at inhibitor concentrations sufficient to block proliferation. Importantly, the cellular activity translates to potent inhibition of tumor growth in vivo. An oral dose of 5 mg/kg QD is well tolerated and results in near stasis (92% TGI) in an HCT116 mouse xenograft model.
1,3-Dicyclohexylurea (DCU), a potent soluble epoxide hydrolase (sEH) inhibitor has been reported to lower systemic blood pressure in spontaneously hypertensive rats. One limitation of continual ...administration of DCU for
in vivo
studies is the compound's poor oral bioavailability. This phenomenon is mainly attributed to its poor dissolution rate and low aqueous solubility. Previously, wet-milled DCU nanosuspension has been reported to enhance the bioavailability of DCU. However, the prosperities and limitations of wet-milled nanosuspension have not been fully evaluated. Furthermore, the oral pharmacokinetics of DCU in rodent are such that the use of DCU to understand PK/PD relationships of sEH inhibitors in preclinical efficacy model is less than ideal. In this study, the limitation of orally delivered DCU nanosuspension was assessed by a surface area sensitive absorption model and pharmacokinetic modeling. It was found that dosing DCU nanosuspension did not provide the desired plasma profile needed for PK/PD investigation. Based on the model and
in vivo
data, a subcutaneous route of delivery of nanosuspension of DCU was evaluated and demonstrated to be appropriate for future PK/PD studies.
Paclitaxel is a common chemotherapeutic agent that is effective against various cancers. The poor aqueous solubility of paclitaxel necessitates a large percentage of Cremophor EL:ethanol (USP) in its ...commercial formulation which leads to hypersensitivity reactions in patients. We evaluate the use of a crystalline nanosuspension versus the USP formulation to deliver paclitaxel to tumor-bearing xenograft mice. Anti-tumor efficacy was assessed following intravenous administration of three 20 mg/kg doses of paclitaxel. Paclitaxel pharmacokinetics and tissue distribution were evaluated, and differences were observed between the two formulations. Plasma clearance and tissue to plasma ratio of mice that were dosed with the nanosuspension are approximately 33- and 11-fold higher compared to those of mice that were given the USP formulation. Despite a higher tumor to plasma ratio for the nanosuspension treatment group, absolute paclitaxel tumor exposure was higher for the USP group. Accordingly, a higher anti-tumor effect was observed in the xenograft mice that were dosed with the USP formulation (90% versus 42% tumor growth inhibition). This reduction in activity of nanoparticle formulation appeared to result from a slower than anticipated dissolution
in vivo
. This study illustrates a need for careful consideration of both dose and systemic solubility prior utilizing nanosuspension as a mode of intravenous delivery.
The general solubility equation (GSE) proposed by Jain and Yalkowsky was used to estimate aqueous solubility of 1026 non-electrolytes. The only parameters used in the GSE are melting points (MP) and ...octanol–water partition coefficients (
K
ow). No fitted parameters and no training set are employed in the GSE. The experimental solubility values were taken from the AQUASOL dATAbASE. The average absolute error and the root-mean-square error in the solubility estimates are 0.38 and 0.53log units, respectively. Thus, with an observed MP and calculated
K
ow; the users can obtain a reasonable estimation of the aqueous solubility of any organic non-electrolyte.
The oral bioavailability of a drug candidate is influenced by its permeability, metabolism, and physicochemical properties. Among the physicochemical properties, solubility and dissolution rate often ...are the most critical factors affecting the oral bioavailability of a compound. The increasing challenge for the pharmaceutical industry is to achieve reasonable oral bioavailability of poorly water-soluble drug candidates. G-F is a potent and selective B-Raf (rapidly accelerated fibrosarcoma) inhibitor with poor water solubility and moderate permeability, which resulted in an absorption-limited exposure in preclinical safety studies. The intrinsic solubility of G-F is 8 μg/mL (i.e., 0.0188 nM). In this study, pH adjustment combined with cosolvency, micellization, or complexation was applied as a technique to enhance the solubility of G-F. pH 9.5 and 4 buffers were selected to combine with the solubilization agents based on G-F's acidic pKa of 7.47. The solubilization power of each solubilization agent was determined based on the experimental data. The solubility G-F can be increased up to 4000-fold in a selected combination. The advantage of combination over individual solubilization agent was demonstrated. In this study, the understanding of the solubilization power of each solubilization agent played an important role in the formulation development of this development candidate.
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