Discovery of Cycloalkyl[c]thiophenes as Novel Scaffolds for Hypoxia-Inducible Factor-2α Inhibitors.

Hypoxia-inducible factors (HIFs) are heterodimeric transcription factors induced in diverse pathophysiological settings. Inhibition of HIF-2α has become a strategy for cancer treatment since the discovery that small molecules, upon binding into a small cavity of the HIF-2α PAS B domain, can alter its conformation and disturb the activity of the HIF dimer complex. Herein, the design, synthesis, and systematic SAR exploration of cycloalkyl[c]thiophenes as novel HIF-2α inhibitors are described, providing the first chemotype featuring an alkoxy-aryl scaffold. X-ray data confirmed the ability of these inhibitors to induce perturbation of key amino acids by appropriately presenting key pharmacophoric elements in the hydrophobic cavity. Selected compounds showed inhibition of VEGF-A secretion in cancer cells and prevention of Arg1 expression and activity in IL4-stimulated macrophages. Moreover, in vivo target gene modulation was demonstrated with compound 35r. Thus, the disclosed HIF-2α inhibitors represent valuable tools for investigating selective HIF-2α inhibition and its effect on tumor biology.

Identification of solubility-limited absorption of oral anticancer drugs using PBPK modeling based on rat PK and its relevance to human.

Solubility is one of the key parameters that is optimized during drug discovery to ensure sufficient drug concentration in systemic circulation and to achieve the desired pharmacological response. We recently reported the application of PBPK analysis of early clinical pharmacokinetic data to identify drugs whose absorption are truly limited by solubility. In this work, we selected ten anticancer drugs that exhibit poor in vitro solubility to explore the utility of this approach to identify solubility-limited absorption based on rat pharmacokinetic data and compare the findings to human data. Oral rat pharmacokinetic studies were performed at the body weight-scaled doses of the model drugs' human food effect studies, and analyzed using a top-down PBPK modeling approach. A good correlation of solubility-limited absorption in rat and human was observed. These results allow an early identification of drugs with truly solubility-limited absorption, with the potential to guide decisions and save valuable resources in drug development.

Prediction of volume of distribution in humans: analysis of eight methods and their application in drug discovery.

The performance of eight different methods to predict human volume of distribution (VDss) using a large data set (N > 100) was evaluated.The accuracy was assessed by the end points % within two-fold and absolute average fold error (AAFE). The ability to rank order was accessed by the σ and bias was examined using average fold error. Significance of observed differences was established using statistical permutation testing.The Rodgers-Lukova equation, a tissue composition model, for acids and single species scaling based on rat for other ion classes showed the best results in absence of non-rodent data.The semimechanistic Øie-Tozer model based on all thee preclinical species showed the best performance overall (81% within two-fold, AAFE 1.55, σ 0.62). This was not statistically significantly better at the 95% confidence level than the same model based on two preclinical species or single species scaling from monkey. Thus, the use of primates appears difficult to justify when the sole goal is to extrapolate human volume of distribution.

Improved Prediction of in Vivo Supersaturation and Precipitation of Poorly Soluble Weakly Basic Drugs Using a Biorelevant Bicarbonate Buffer in a Gastrointestinal Transfer Model.

The characterization of intestinal dissolution of poorly soluble drugs represents a key task during the development of both new drug candidates and drug products. The bicarbonate buffer is considered as the most biorelevant buffer for simulating intestinal conditions. However, because of its complex nature, being the volatility of CO2, it has only been rarely used in the past. The aim of this study was to investigate the effect of a biorelevant bicarbonate buffer on intestinal supersaturation and precipitation of poorly soluble drugs using a gastrointestinal (GI) transfer model. Therefore, the results of ketoconazole, pazopanib, and lapatinib transfer model experiments using FaSSIFbicarbonate were compared with the results obtained using standard FaSSIFphosphate. Additionally, the effect of hydroxypropyl methylcellulose acetate succinate (HPMCAS) as a precipitation inhibitor was investigated in both buffer systems and compared to rat pharmacokinetic (PK) studies with and without coadministration of HPMCAS as a precipitation inhibitor. While HPMCAS was found to be an effective precipitation inhibitor for all drugs in FaSSIFphosphate, the effect in FaSSIFbicarbonate was much less pronounced. The PK studies revealed that HPMCAS did not increase the exposure of any of the model compounds significantly, indicating that the transfer model employing bicarbonate-buffered FaSSIF has a better predictive power compared to the model using phosphate-buffered FaSSIF. Hence, the application of a bicarbonate buffer in a transfer model set-up represents a promising approach to increase the predictive power of this in vitrotool and to contribute to the development of drug substances and drug products in a more biorelevant way.

Structure-based design of 7-azaindole-pyrrolidine amides as inhibitors of 11ß-hydroxysteroid dehydrogenase type I.

Indole-pyrrolidines were identified as inhibitors of 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1) by high-throughput screening. Optimisation of the initial hit through structure-based design led to 7-azaindole-derivatives, with the best analogues displaying single digit nanomolar IC(50) potency. The modeling hypotheses were confirmed by solving the X-ray co-crystal structure of one of the lead compounds. These compounds were selective against 11ß-hydroxysteroid dehydrogenase type 2 (selectivity ratio >200) and exhibited good inhibition of 11ß-HSD1 (IC(50)<1µM) in a cellular model (3T3L1 adipocytes).

Discovery and structure-guided drug design of inhibitors of 11beta-hydroxysteroid-dehydrogenase type I based on a spiro-carboxamide scaffold.

Spiro-carboxamides were identified as inhibitors of 11beta-hydroxysteroid-dehydrogenase type 1 by high-throughput screening. Structure-based drug design was used to optimise the initial hit yielding a sub-nanomolar IC(50) inhibitor (0.5nM) on human 11beta-HSD1 with a high binding efficiency index (BEI of 32.7) which was selective against human 11beta-HSD2 (selectivity ratio>200000).

Discovery and structure-activity relationships of pentanedioic acid diamides as potent inhibitors of 11beta-hydroxysteroid dehydrogenase type I.

Benzylamides of pentanedioic acid were identified as inhibitors of 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) by high-throughput screening. Optimisation to 2-adamantyl amides yielded inhibitors with single digit nanomolar IC(50)s on the 11beta-HSD1 human isoform. The hydroxy adamantyl amide lead compound was selective against 11beta-hydroxysteroid dehydrogenase type 2 (selectivity ratio >1000) and displayed good inhibition of 11beta-HSD1 (IC(50)<0.1microM) in a cellular model (3T3L1 adipocytes).

Involvement of caspase-10 in advanced glycation end-product-induced apoptosis of bovine retinal pericytes in culture.

Apoptosis appears to be the death mechanism of pericyte loss observed in diabetic retinopathy. We have previously shown that advanced glycation end-products (AGE-MGX) induce apoptosis of retinal pericytes in culture associated with diacylglycerol (DAG)/ceramide production. In the present study, we investigated possible caspase involvement in this process. Bovine retinal pericytes (BRP) were cultured with AGE-MGX and apoptosis examined after annexin V staining. Effects of peptidic inhibitors of caspases were determined on DAG/ceramide production and apoptosis. Pan-caspase inhibitor z-VAD-fmk (50 microM) was able to inhibit both DAG/ceramide production and apoptosis, whereas caspase-3-like inhibitor z-DEVD-fmk (50 microM) or caspase-9 inhibitor z-LEHD-fmk (50 microM) was only active on apoptosis. This differential effect strongly suggests involvement of initiator caspase(s) upstream and effector caspase(s) downstream DAG/ceramide production in AGE-mediated apoptosis. Pericyte treatment with caspase-8 inhibitor z-IETD-fmk (50 microM) did not protect cells against AGE-induced apoptosis and we failed to detect caspase-8 in pericytes by immunoblotting assay. Interestingly, one inhibitor of caspase-10 and related caspases z-AEVD-fmk (50 microM) inhibited both AGE-MGX-induced apoptosis and DAG/ceramide formation in pericytes. Cleavage of caspase-10 precursor into its active subunits was demonstrated by immunoblotting assay in pericytes incubated with AGE-MGX. These results strongly suggest that caspase-10, but not caspase-8, might be involved in the early phase of AGE-induced pericyte apoptosis, in contrast to caspase-9 and -3-like enzymes involved after DAG/ceramide production. This finding may provide new therapeutic perspectives for early treatment in diabetic retinopathy.

Advanced glycation end-products induce apoptosis of bovine retinal pericytes in culture: involvement of diacylglycerol/ceramide production and oxidative stress induction.

One of the earliest changes observed in retinal microvessels in diabetic retinopathy is the selective loss of intramural pericytes. We tested the hypothesis that AGE might be involved in the disappearance of retinal pericytes by apoptosis and further investigated the signaling pathway leading to cell death. Chronic exposure of pericytes to methylglyoxal-modified bovine serum albumin (AGE-BSA) (3 microM) leads to a 3-fold increase of apoptosis (8.9 +/- 1.1%), associated with an increase in cellular ceramide (185 +/- 12%) and diacylglycerol (194 +/- 9%) levels. Ceramide formation was almost inhibited (95%) by an acidic sphingomyelinase inhibitor, desipramine (0.3 microM). Dual inhibition of ceramide (95%) and diacylglycerol (80%) production was observed with a phosphatidylcholine-phospholipase C inhibitor, D609 (9.4 microM). Taken together, these results suggest activation of phosphatidylcholine-phospholipase C coupled to acidic sphingomyelinase. However, both inhibitors only partially protected pericytes against apoptosis, suggesting another apoptotic pathway independent of diacylglycerol/ceramide production. Treatments with various antioxidants completely inhibited pericyte apoptosis, suggesting oxidative stress induction during this apoptotic process. Inhibition of diacylglycerol/ceramide production by N-acetyl-L-cysteine suggests that oxidative stress acts upstream of the two metabolic pathways. AGE treated with metal chelators were also able to induce pericyte apoptosis, suggesting a specific effect of AGE on intracellular oxidative stress independent of redox-active metal ions bound to AGE. In conclusion, these results identify new biochemical targets involved in pericyte loss, which can provide new therapeutic perspectives in diabetic retinopathy.