Kinetic and thermodynamic studies of 9-aminocamptothecin hydrolysis at physiological pH in the presence of human serum albumin

Targeted internalization and activation of glycosidic switch liposomes by a biological macromolecule mPEG×EphA2 increases therapeutic efficacy against lung cancer

Glycosidic switch liposome (GSL) technology efficiently encapsulates and stabilizes potent anticancer drugs in liposomes using a reversible glucuronide ester. Enzymatic hydrolysis of the glucuronide switch in target cell lysosomes produces parental drug. Our study examined the potential of a bispecific macromolecule, a polyethylene glycol (PEG) engager (mPEG×EphA2), generated by fusing a humanized anti-methoxy PEG (mPEG) Fab with an anti-EphA2 single-chain antibody, to increase GSL uptake into cancer cells and boost the anticancer activity by targeting PEG on GSL and an internalizing tumor antigen. Combining GSL with the PEG engager creates αEphA2/GSL, targeting cancer cells to generate topoisomerase I poison 9-aminocamptothecin (9 AC) for cell killing. Targeted liposomes can bind CL1-5 human lung adenocarcinoma cells and increase GSL internalization from 0 % to 62.4 % in 60 min. αEphA2/GSL showed slightly higher cellular cytotoxicity than non-targeted GSL, but targeted GSL increased 9 AC intratumoral concentrations by 8.4 fold at 24 h. The 9 AC tumor/blood ratio of αEphA2/GSL was nearly 6-fold higher than αDNS/GSL (control engager GSL). Using targeted GSL, five of seven mice with solid CL1-5 tumors were cured. The mPEG×EphA2 engager can enhance GSL drug uptake and generation, boosting lung cancer treatment efficacy, suggesting that αEphA2/GSL is a promising treatment for tumors overexpressing EphA2.

Silicon-containing analogs of camptothecin as anticancer agents

The plant pentacyclic alkaloid camptothecin and its structural analogs were extensively studied. These compounds are interesting due to the antitumor activity associated with their ability to inhibit topoisomerase I in tumor cells. During the last decades of the 20th century, a large number of the silicon-containing camptothecins (silatecans) were synthesized. 7-tert-Butyldimethylsilyl-10-hydroxy-camptothecin (DB-67 or AR-67) has enhanced lipophilicity and demonstrates a antitumor activity superior to its carbon analog. To date, certain silatecans are under clinical trials and their ultimate role in cancer therapy appears promising. In this review, we present chemical methodologies for the synthesis of silicon-containing camptothecins, their chemical properties, biological activity, and results of clinical trials.

Effect of ultrasonic pretreatment on kinetics of gelatin hydrolysis by collagenase and its mechanism

Gelatin is a mixture of soluble proteins prepared by partial hydrolysis of native collagen. Gelatin can be enzymatically hydrolyzed to produce bioactive hydrolysates. However, the preparation of gelatin peptide with expected activity is usually a time-consuming process. The production efficiency of gelatin hydrolysates needs to be improved. In present work, effect of ultrasonic pretreatment on kinetic parameters of gelatin hydrolysis by collagenase was investigated based on an established kinetic model. With ultrasonic pretreatment, reaction rate constant and enzyme inactivation constant were increased by 27.5% and 27.8%, respectively. Meanwhile, hydrolysis activation energy and enzyme inactivation energy were reduced by 36.3% and 43.0%, respectively. In order to explore its possible mechanism, influence of sonication on structural properties of gelatin was determined using atomic force microscopy, particle size analyzer, fluorescence spectroscopy, protein solubility test and Fourier transform infrared spectroscopy. Moreover, hydrogen peroxide was used as a positive control for potential sonochemical effect. It was found that reduction of gelatin particle size was mainly caused by physical effect of ultrasound. Increased solubility and variation in β-sheet and random coil elements of gelatin were due to sonochemical effect. Both physical and chemical effects of sonication contributed to the change in α-helix and β-turn structures. The current results suggest that ultrasound can be potentially applied to stimulate the production efficiency of gelatin peptides, mainly due to its effects on modification of protein structures.

Serum albumin binding analysis and toxicological screening of novel chroman-2,4-diones as oral anticoagulants

Two chroman-2,4-dione derivatives, namely 2a and 2f, were tested as in vivo anticoagulants by seven days of continuous per os application to adult male Wistar rats in a concentration of 20 mg/kg of body weight. Derivatives were selected from a group of six previously intraperitoneally applied compounds on the basis of presenting remarkable activity in a concentration of 2 mg/kg of body weight. The derivatives 2a and 2f are VKORC1 inhibitors, and comparison of the absorption spectra, association, and dissociation constants suggested that the compounds will be bound to serum albumin in the same manner as warfarin is, leading to transfer towards the molecular target VKORC1. After oral administration, the compounds proved to be anticoagulants comparable with warfarin, inasmuch as the measured prothrombin times for 2a and 2f were 56.63 and 60.08 s, respectively. The INR values of 2a and 2f ranged from 2.6 to 2.8, recommending them as useful therapeutics in the treatment of patients suffering from thromboembolic events and atrial fibrillation. The high percentage of binding and high binding affinity of 2a and 2f towards serum albumin reduced the risk of induced internal bleeding. Several kinds of toxicity studies were performed to investigate whether or not 2a and 2f can cause pathological changes in the liver, kidneys, and DNA. The catalytic activity of serum enzymes, concentration and catalytic activity of liver and kidney oxidative stress markers and enzymes, respectively, as well as the observed hepatic and renal morphological changes indicated that the compounds in relation to warfarin induced irrelevant hepatic toxicity, no increment of necrosis, and inconsiderable oxidative damage in the liver and kidneys. Estimation of DNA damage using the comet assay confirmed that 2a and 2f caused no clinically significant genotoxicity. The higher activity and lower toxicity of 2f recommended this compound as a better drug candidate than 2a.