Pritam Thapa

Solid self-nanoemulsifying drug delivery system (S-SNEDDS) containing phosphatidylcholine for enhanced bioavailability of highly lipophilic bioactive carotenoid lutein

The objectives of this study was to prepare solid self-nanoemulsifying drug delivery system (S-SNEDDS) containing phosphatidylcholine (PC), an endogenous phospholipid with excellent in vivo solubilization capacity, as oil phase for the delivery of bioactive carotenoid lutein, by spray drying the SNEDDS (liquid system) containing PC using colloidal silica (Aerosil® 200 VV Pharma) as the inert solid carrier, and to evaluate the enhanced bioavailability (BA) of lutein from S-SNEDDS. The droplet size analyses revealed droplet size of less than 100 nm. The solid state characterization of S-SNEDDS by SEM, DSC, and XRPD revealed the absence of crystalline lutein in the S-SNEDDS. The bioavailability study performed in rabbits resulted in enhanced values of C(max) and AUC for S-SNEDDS. The enhancement of C(max) for S-SNEDDS was about 21-folds and 8-folds compared with lutein powder (LP) and commercial product (CP), respectively. The relative BA of S-SNEDDS compared with CP or LP was 2.74-folds or 11.79-folds, respectively. These results demonstrated excellent ability of S-SNEDDS containing PC as oil phase to enhance the BA of lutein in rabbits. Thus, S-SNEDDS containing PC as oil phase could be a useful lipid drug delivery system for enhancing the BA of lutein in vivo.

Retinoic acid signaling pathways in development and diseases.

Retinoids comprise a group of compounds each composed of three basic parts: a trimethylated cyclohexene ring that is a bulky hydrophobic group, a conjugated tetraene side chain that functions as a linker unit, and a polar carbon-oxygen functional group. Biochemical conversion of carotenoid or other retinoids to retinoic acid (RA) is essential for normal regulation of a wide range of biological processes including development, differentiation, proliferation, and apoptosis. Retinoids regulate various physiological outputs by binding to nuclear receptors called retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which themselves are DNA-binding transcriptional regulators. The functional response of RA and their receptors are modulated by a host of coactivators and corepressors. Retinoids are essential in the development and function of several organ systems; however, deregulated retinoid signaling can contribute to serious diseases. Several natural and synthetic retinoids are in clinical use or undergoing trials for treating specific diseases including cancer. In this review, we provide a broad overview on the importance of retinoids in development and various diseases, highlighting various retinoids in the drug discovery process, ranging all the way from retinoid chemistry to clinical uses and imaging.

Boron chemicals in diagnosis and therapeutics

Advances in the field of boron chemistry have expanded the application of boron from material use to medicine. Boron-based drugs represent a new class of molecules that possess several biomedical applications including use as imaging agents for both optical and nuclear imaging as well as therapeutic agents with anticancer, antiviral, antibacterial, antifungal and other disease-specific activities. For example, bortezomib (Velcade(®)), the only drug in clinical use with boron as an active element, was approved in 2003 as a proteasome inhibitor for the treatment of multiple myeloma and non-Hodgkins lymphoma. Several other boron-based compounds are in various phases of clinical trials, which illustrates the promise of this approach for medicinal chemists working in the area of boron chemistry. It is expected that in the near future, several boron-containing drugs should become available in the market with better efficacy and potency than existing drugs. This article discusses the current status of the development of boron-based compounds as diagnostic and therapeutic agents in humans.

NADPH oxidase inhibitors: a patent review.

Introduction: NADPH oxidases, a family of multi-subunit enzyme complexes, catalyze the production of reactive oxygen species (ROS), which may contribute to the pathogenesis of a variety of diseases. In addition to the first NADPH oxidase found in phagocytes, four non-phagocytic NADPH oxidase isoforms have been identified, which all differ in their catalytic subunit (Nox1-5) and tissue distribution. Areas covered: This paper provides a comprehensive review of the patent literature on NADPH oxidase inhibitors, small molecule Nox inhibitors, peptides and siRNAs. Expert opinion: Since each member of the NADPH oxidase family has great potential as a therapeutic target, several different compounds have been registered as NADPH oxidase inhibitors in the patent literature. As yet, none have gone through clinical trials, and some have not completed preclinical trials, including safety and specificity evaluation. Recently, small molecule pyrazolopyridine and triazolopyrimidine derivatives have been submitted as potent NADPH oxidase inhibitors and reported as first-in-class inhibitors for idiopathic pulmonary fibrosis and acute stroke, respectively. Further clinical efficacy and safety data are warranted to prove their actual clinical utility.

Novel self-nanoemulsifying drug delivery system for enhanced solubility and dissolution of lutein

Self-nanoemulsifying drug delivery system (SNEDDS) containing oil (Phosal 53 MCT), surfactant (Labrasol), and cosurfactant (Transcutol-HP or Lutrol-E400) was prepared to enhance solubility and dissolution of lutein. Ternary phase diagram of the SNEDDS was constructed to identify the self-emulsifying regions following which the percentage of oil, surfactant, and cosurfactant in the SNEDDS were optimized in terms of emulsification time and mean emulsion droplet size. The optimized SNEDDS consists of 25% oil, 60% surfactant, and 15% cosurfactant. When measured using USP XXIII dissolution apparatus II, the emulsification time of the SNEDDS prepared with Transcutol-HP as cosurfactant was less than 20 sec, and it was 20–30 sec in the SNEDDS prepared with Lutrol-E400. Mean emulsion droplet size was slightly smaller when Transcutol-HP was used as cosurfactant (80 ± 6 nm), compared to when Lutrol- E400 was used (93 ± 6 nm). Dissolution of lutein from the solid SNEDDS (physical mixture of the optimized SNEDDS and Aerosil 200) took place immediately (less than 5 min) in distilled water, and, once dissolved, no precipitation or aggregation of the drug were observed. In contrast, no drug was released from lutein powder or from the commercial product (Eyelac®) until 3 h of the study duration.

2-Thienyl-4-furyl-6-aryl pyridine derivatives: Synthesis, topoisomerase I and II inhibitory activity, cytotoxicity, and structure-activity relationship study

Designed and synthesized 60 2-thienyl-4-furyl-6-aryl pyridine derivatives were evaluated for their topoisomerase I and II inhibitory activities at 20 microM and 100 microM and cytotoxicity against several human cancer cell lines. Compounds 8, 9, 11-29 showed significant topoisomerase II inhibitory activity and compounds 10 and 11 showed significant topoisomerase I inhibitory activity. Most of the compounds (7-21) possessing 2-(5-chlorothiophen-2-yl)-4-(furan-3-yl) moiety showed higher or similar cytotoxicity against HCT15 cell line as compared to standards. Most of the selected compounds displayed moderate cytotoxicity against MCF-7, HeLa, DU145, and K562 cell lines. Structure-activity relationship study revealed that 2-(5-chlorothiophen-2-yl)-4-(furan-3-yl) moiety has an important role in displaying biological activities.

Dihydroxylated 2,4,6-triphenyl pyridines: Synthesis, topoisomerase I and II inhibitory activity, cytotoxicity, and structure—activity relationship study

Twelve dihydroxylated 2,4,6-triphenyl pyridines were designed and synthesized which contain hydroxyl groups at ortho, meta or para position of 2- and 6-phenyl, or 2- and 4-phenyl rings attached to the central pyridine. They were evaluated for topoisomerase I and II inhibitory activity, and cytotoxicity against several human cancer cell lines for the development of novel anticancer agents. Generally, dihydroxylated 2,4,6-triphenyl pyridines exhibited stronger topoisomerase II inhibitory activity, and cytotoxicity compared to those of monohydroxylated 2,4,6-triphenyl pyridines. The concrete structure-activity relationship was observed that dihydroxylated 2,4,6-triphenyl pyridines with hydroxyl group at meta or para position of 2-phenyl ring displayed significant topoisomerase II inhibitory activity as well as cytotoxicity. Positive correlation between topoisomerase II inhibitory activity and cytotoxicity was observed for compounds 10, 12, 13, 17-20 and 22.

2,6-Dithienyl-4-furyl pyridines: Synthesis, topoisomerase I and II inhibition, cytotoxicity, structure–activity relationship, and docking study

For the development of novel antitumor agents, 2,6-dithienyl-4-furyl pyridine derivatives were prepared and evaluated for their topoisomerase I and II inhibitory activity as well as cytotoxicity against several human cancer cell lines. Among the 21 prepared compounds, compound 24 exhibited strong topoisomerase I inhibitory activity. In addition, a docking study with topoisomerase I and compound 24 was performed.

A series of novel terpyridine-skeleton molecule derivants inhibit tumor growth and metastasis by targeting topoisomerases.

A series of novel terpyridine-skeleton molecules containing conformational rigidity, 14 containing benzo[4,5]furo[3,2-b]pyridine core and 15 comprising chromeno[4,3-b]pyridine core, were synthesized, and their biological activities were evaluated. 3-(4-Phenylbenzo[4,5]furo[3,2-b]pyridin-2-yl)phenol (8) was determined to be a nonintercalative topo I and II dual catalytic inhibitor and 3-(4-phenylchromeno[4,3-b]pyridine-2-yl)phenol (22) was determined to be a nonintercalative topo IIα specific catalytic inhibitor by various assays. These two catalytic inhibitors induced apoptosis in addition to G1 arrest in T47D human breast cancer cells with much less DNA toxicity than etoposide. Compounds 8 and 22 significantly inhibited tumor growth in HCT15 subcutaneously implanted xenografted mice. The modification of compounds 8 and 22 with the introduction of a methoxy instead of a hydroxy group enhanced endogenous topo inhibitory activity, metabolic stability in diverse types of liver microsomes and improved pharmacokinetic parameters in rat plasma such as augmentation of bioavailability (41.3% and 33.2% for 2-(3-methoxyphenyl)-4-phenylbenzofuro[3,2-b]pyridine (8-M) and 3-(4-phenylchromeno[4,3-b]pyridine-2-yl)methoxybenzene (22-M), respectively).

Synthesis of 2-(thienyl-2-yl or -3-yl)-4-furyl-6-aryl pyridine derivatives and evaluation of their topoisomerase I and II inhibitory activity, cytotoxicity, and structure–activity relationship

A series of 2-(thienyl-2-yl or -3-yl)-4-furyl-6-aryl pyridine derivatives were designed, synthesized, and evaluated for their topoisomerase I and II inhibition and cytotoxic activity against several human cancer cell lines. Compounds 10-19 showed moderate topoisomerase I and II inhibitory activity and 20-29 showed significant topoisomerase II inhibitory activity. Structure-activity relationship study revealed that 4-(5-chlorofuran-2-yl)-2-(thiophen-3-yl) moiety has an important role in displaying topoisomerase II inhibition.