Xinghai Chen

Regiospecific substitution of N-acyl-2,3-dihydro-4-pyridones at C-5 via halogenation and cross-coupling

Abstract The C-5 position of N-Acyl-2-alkyl-2,3-dihydro-4-pyridones can be substituted by halogenation followed by a cross-coupling or carbonylation reaction.

Mechanistic study of BNP7787-mediated cisplatin nephroprotection: modulation of gamma-glutamyl transpeptidase

PurposeThe mechanisms for cisplatin-induced renal cell injury have been the focus of intense investigation for many years with a view to provide a more effective and convenient form of nephroprotection. BNP7787 (disodium 2,2′-dithio-bis ethane sulfonate; dimesna, Tavocept™), is a water-soluble disulfide investigational new drug that is undergoing clinical development for the prevention and mitigation of clinically important chemotherapy-induced toxicities associated with platinum-type chemotherapeutic agents. We hypothesized that part of BNP7787’s mechanism of action (MOA) pertaining to the potential prevention of cisplatin-induced nephrotoxicity involves the inhibition of gamma-glutamyl transpeptidase (GGT) activity, mediated by BNP7787-derived mesna–disulfide heteroconjugates that contain a terminal gamma-glutamate moiety [e.g., mesna–glutathione (MSSGlutathione) and mesna–cysteinyl-glutamate (MSSCE)].MethodsInhibition studies were conducted on human and porcine GGT to determine the effect of mesna–disulfide heteroconjugates on the enzyme’s activity in vitro. These studies utilized a fluorimetric assay that monitored the hydrolysis of l-gamma-glutamyl-7-amino-4-trifluoromethylcoumarin (GG-AFC) to AFC.ResultsMesna–disulfide heteroconjugates that contained gamma-glutamyl moieties were potent inhibitors of human and porcine GGT. An in situ-generated mesna–cisplatin conjugate was not a substrate for GGT.ConclusionsThe GGT xenobiotic metabolism pathway is postulated to be a major toxification pathway for cisplatin nephrotoxicity, and BNP7787 may play a novel and critical therapeutic role in the modulation of GGT activity. We further postulate that there are two general mechanisms for BNP7787-mediated nephroprotection against cisplatin-induced nephrotoxicity involving this pathway. First, the active BNP7787 pharmacophore, mesna, produces an inactive mesna–cisplatin conjugate that is not a substrate for the GGT toxification pathway (GGT xenobiotic metabolism pathway) and, second, BNP7787-derived mesna–disulfide heteroconjugates may serve as selective, potent inhibitors of GGT, possibly resulting in nephroprotection by a novel means.

SYNTHESIS OF 2,4-DISUBSTITUTED N-ACYL-5,6-DIHYDRO-2-PYRIDONES

Abstract A simple two-step procedure converts 2-substituted N-acyl-2,3-dihydro-4-pyridones to 2,4-disubstituted N-acyl-5,6-dihydro-2-pyridones.

Stabilization of the Karenitecin® lactone by alpha-1 acid glycoprotein.

PurposeCamptothecins contain a lactone ring that is necessary for antitumor activity, and hydrolysis of the lactone ring yields an inactive carboxylate species. Human serum albumin (HSA) and alpha-1 acid glycoprotein (AGP) are clinically significant plasma proteins thought to have important roles in camptothecin lactone stability. Herein, we examined the effect(s) of HSA and AGP on the lactone stability of Karenitecin, a novel, highly lipophilic camptothecin analog, currently at the phase 3 clinical testing stage.MethodsAn AGP-immobilized protein column was used to develop HPLC methods to evaluate the effect(s) of physiologically relevant HSA and AGP concentrations on the lactone/carboxylate ratio and hydrolysis kinetics of Karenitecin, camptothecin (CPT), and topotecan (TPT).ResultsPhysiologically relevant concentrations of HSA and AGP substantially slowed Karenitecin lactone hydrolysis. AGP was notably more effective at protecting the Karenitecin lactone from hydrolysis than HSA was in promoting hydrolysis. Additionally, AGP reversed the hydrolysis of partially hydrolyzed Karenitecin lactone. In contrast, HSA and AGP had minimal effects on hydrolysis of the TPT lactone, while the AGP/HSA solutions dramatically accelerated hydrolysis of the CPT lactone.ConclusionAGP strongly enhances the lactone stability of Karenitecin. Since Karenitecin is highly protein-bound in human plasma and exhibits greater lactone stability, relative to other camptothecins, in patient plasma samples, this newly identified role of AGP in promoting lactone stability may have important implications for the design of more effective anticancer agents within the Karentecin™ and camptothecin classes.

Accumulation of BNP7787 in Human Renal Proximal Tubule Cells

BNP7787, an investigational drug undergoing global Phase III development, appears to have potential advantages over other cytoprotective compounds that have been evaluated for preventing and mitigating cisplatin-induced nephrotoxicity. Herein, we characterized the in vitro accumulation of BNP7787 in human renal proximal tubule cells (HK-2) in which cisplatin is known to be taken up and accumulate. HK-2 cells were incubated with pharmacological concentrations of BNP7787 for varying times. Temperature-dependent accumulation of BNP7787 in cells was observed and the BNP7787-derived metabolite, mesna, formed intracellularly was directly monitored. The peak level of BNP7787-derived mesna measured in HK-2 cells was approximately 0.6 nmol/10(6) cells; this is pharmacologically similar to reported platinum concentrations in kidney cells and may be sufficient to afford nephroprotection. Therefore, in addition to previously suggested glomerular filtration, the cellular accumulation of BNP7787 by HK-2 cells is a plausible newly identified mechanism by which BNP7787 may accumulate in renal tubular cells, where it can exert its pharmacological effects to protect against cisplatin-induced nephrotoxicity by direct covalent conjugation of mesna with cisplatin, or by the formation of BNP7787-derived mesna-disulfide heteroconjugates that exert nephroprotective effects by inhibition of the key toxification enzyme targets γ-glutamyltranspeptidase and aminopeptidase N.

Comprehensive Comparative Study Using Ab Initio Computational Approaches on the Structures of Cisplatin, Oxaliplatin and BNP3029 (A Novel Substituted Cyano Ligand-based Platinum Analogue) and Activation Energy Barriers for the Attack of Nucleophiles on Cisplatin and BNP3029 and their Monoaquated Derivatives#

Cisplatin is an important anti-cancer agent widely used in the clinic; however, it has several notable limitations. To develop novel platinum analogues, key characteristics were considered that may result in more effective platinum analogues. Herein results based on ab initio geometry optimizations (gas- and solution-phase) on cisplatin (1), oxaliplatin_1R_2R (2) and BNP3029 (3, a novel substituted cyano ligand-based platinum analogue, PtCl2[N≡C(CH2)3(C6H5)]2) using the recently published potentials and basis sets for platinum are presented. Optimized quantum mechanical derived geometries of the 3 platinum agents were in good agreement with available experimental geometries. The reactivity of BNP3029 was compared to cisplatin by computing the activation free energy barriers for the attack of various nucleophiles on both 1 and 3 and their monoaquated derivatives. Based on the activation energy barriers, it was determined that: (i) the reaction rate may be similar for the attack of water on cisplatin and BNP3029; (ii) the reaction rate for the attack of DNA bases was slower for monoaquated BNP3029 compared to monoaquated cisplatin; and (iii) the reaction rates for a thiol/thiolate attack on monoaquated cisplatin or monoaquated BN3029 were similar. BNP3029 demonstrated potent cytotoxic activity in a variety of human cancer cell lines in comparison to cisplatin and oxaliplatin and also had potent cytotoxic activity in several platinum resistant cell lines.

Comprehensive Comparative Analysis of the Morphological Changes in a 12-mer DNA Oligonucleotide upon Platination by Cisplatin, Oxaliplatin and BNP3029 (a Substituted Cyano ligand-based Platinum analogue) using Molecular Dynamics Simulation Studies #

Cisplatin is an important anti-cancer agent widely used in the clinic; however, it has several notable limitations. To develop novel platinum analogues, key characteristics were considered that may result in more effective platinum analogues. In this study, we present comprehensive molecular dynamics simulation studies using a 12-mer DNA (5’-CCTCTggTCTCC-3’, gg= the site of platination) oligonucleotide which was platinated with cisplatin (1), oxaliplatin_1R_2R (2), and BNP3029 (3, a novel substituted cyano platinum analogue, PtCl2[N≡C(CH2)3(C6H5)]2), and analyzed the large data output using the Kolmogorov-Smirnov statistical analyses. In summary, data indicated that BNP3029-DNA had less A-like DNA morphology in comparison to cisplatin-DNA and oxaliplatin-DNA thus maintaining a more B-like DNA form. BNP3029 demonstrated more potent cytotoxic activity, relative to cisplatin and oxaliplatin, in a variety of human cancer cell lines, including several platinum-resistant cell lines.