Synthesis and biological activity of a gemcitabine phosphoramidate prodrug

A gemcitabine (2',2'-difluorodeoxycytidine, dFdC) phosphoramidate prodrug designed for the intracellular delivery of gemcitabine 5'-monophosphate was synthesized. The prodrug was about an order of magnitude less active than gemcitabine against wild-type cells, and the nucleoside transport inhibitor dipyridamole reduced prodrug activity. The prodrug was more active than gemcitabine against two deoxycytidine kinase-deficient cell lines. The results suggest that the prodrug is a potent growth inhibitor that can bypass dCK deficiency at higher drug concentrations.     

Synthesis and biological evaluation of a cytarabine phosphoramidate prodrug

Recently, we reported a novel approach for the intracellular delivery of the anti-cancer nucleotide 5-fluoro-2'-deoxyuridine 5'-monophosphate (FdUMP) using phosphoramidate-based prodrugs. These phosphoramidate prodrugs contain an ester group that undergoes intracellular activation, liberating phosphoramidate anion, which in turn undergoes spontaneous cyclization and P-N bond cleavage to yield the nucleoside monophosphate quantitatively. This approach has now been extended to cytarabine [1-beta-D-arabinofuranosylcytosine (Ara-C)], an anti-cancer nucleoside that is limited in its utility because of poor intracellular transport characteristics and weak activity as a substrate for tumor cell kinases. The cytarabine phosphoramidate prodrug 1 has been synthesized and evaluated in comparison with cytarabine for growth inhibitory activity against wild-type, nucleoside transport-deficient, and nucleoside kinase-deficient CEM leukemia cell lines. The prodrug was comparable in growth inhibitory activity (IC50 = 32 nM) to cytarabine (IC50 = 16 nM) in wild-type CCRF-CEM cells following drug treatment for 72 h. The nucleoside transport-deficient CEM/AraC8C exhibited a high level of resistance (6400-fold) to cytarabine but was more sensitive (210-fold resistant vs CCRF-CEM cells) to prodrug 1. Similarly, the deoxycytidine kinase-deficient cell line (CEM/dCK-) was highly resistant to cytarabine (13900-fold) but more sensitive (106-fold resistant vs CCRF-CEM cells) to prodrug 1. These results indicate that prodrug 1 is significantly more potent than cytarabine against transport- and kinase-deficient cell lines and are consistent with a mechanism involving intracellular delivery of cytarabine 5'-monophosphate.     

Synthesis, physico-chemical and biological characterization of a paclitaxel macromolecular prodrug.

Paclitaxel was attached to poly(hydroxyethylaspartamide) via a succinic spacer arm by a two-step protocol: (1) synthesis of 2'-O-succinyl-paclitaxel; (2) synthesis of PHEA-2'-O-succinyl-paclitaxel. The 2'-O-succinyl-paclitaxel derivative and the macromolecular conjugate were characterized by UV, IR, NMR and mass spectrometry analysis. The reaction yields were over 95% and the purity of products over 98%. Paclitaxel release and degradation from 2'-O-succinyl-paclitaxel occurred at a faster rate at pH 5.5 than 7.4. After 30 h of incubation at pH 5.5 and 7.4 the released free paclitaxel was about 40 and 20%, respectively. In plasma both drug release and degradation were found to occur at a higher rate than in buffer at pH 7.4 suggesting that an enzymatic mechanism could be involved. The paclitaxel release and degradation from PHEA-2'-O-succinyl-paclitaxel were negligible at pH 5.5 and 7.4 and very slow in plasma. Investigation carried out using murine myeloid cell line showed that the polymeric prodrug maintains partial pharmacological activity of paclitaxel. The DL50 of the conjugate (over 40 ng/ml) as compared to free paclitaxel (about 1 ng/ml) was correlated to the slow drug release. Finally a pharmacokinetic study carried out by intravenous inoculation of the macromolecular prodrug to mice demonstrated that the polymer conjugation modify dramatically the in vivo fate of the drug. The conjugate disappeared from the bloodstream much more quickly as compared to both free drug and naked polymer. Massive accumulation of bioconjugate in the liver (80% of the dose) was found to persist throughout 1 week.     

醋氯芬酸的合成

目的合成醋氯芬酸.方法以氯乙酸为原料,和2,3-二氢吡喃酯化反应合成氯乙酸四氢吡喃酯,再经缩合、酸解反应制得目标化合物.结果及结论本工艺操作简单,适合工业化生产,总产率达87%,制备出产品纯度较高.     

醋氯芬酸的合成

目的确定一种新的醋氯芬酸合成工艺。方法以双氯芬酸钠、溴乙酸叔丁酯为原料,在丙酸液中以无水三氯化铝为催化剂制得醋氯芬酸粗品,粗品用丙酮重结晶制得醋氯芬酸。结果质量符合国家食品药品监督管理局标准YBH11202004。结论本工艺收率较高且稳定,产品质量符合法定标准,易工业化生产。     

Synthesis and biological properties of A-71497: a prodrug of tosufloxacin

Tosufloxacin (5, A-61827 tosylate or T-3262) is currently under product development by both Abbott Laboratories and Toyama Chemical Co. Its registration as antibacterial agent has been approved in Japan. It has been found to be extremely effective in treating several bacterial infections. However, due to its inherent low water solubility, the development of an intravenous formulation will be extremely difficult and may preclude its parenteral use. In search of a more water-soluble analog of tosufloxacin for parenteral use, the 3-formyl derivative of tosulfoxacin, A-71497 (13), was synthesized for evaluation. It was found to produce high plasma levels of tosufloxacin upon both oral and subcutaneous administration to mice. High plasma levels of tosufloxacin were also obtained when 13 was administered both orally and intravenously to dogs. It possesses increased water solubility and makes the development of intravenous formulation possible. The chemical synthesis as well as biological properties of A-71497 (13) are described.     

Synthesis and in vitro studies on a potential dopamine prodrug

Dopamine delivery to the central nervous system (CNS) undergoes the permeability limitations of blood-brain barrier (BBB) which is a selective interface that excludes most water-soluble molecules from entering the brain. Neutral amino acids permeate the BBB by specific transport systems. Condensation of dopamine with neutral amino acids could afford potential prodrugs able to interact with the BBB endogenous transporters and easily enter the brain. The synthesis and characterization of the dopamine derivative 2-amino-N-[2-(3,4-dihydroxy-phenyl)-ethyl]-3-phenyl-propionamide (7) is described. The chemical and enzymatic stability of 7 was evaluated. The molecular weight (300 Da) and Log Papp (0.76) indicated that the physico-chemical characteristics of compound 7 are adequate to cross biological membranes. Compound 7 was enzymatically cleaved to free dopamine in rat brain homogenate (t1/2 = 460 min). In human plasma, the t1/2 of 7 was estimated comparable to that reported for L-DOPA. In view of a possible oral administration of 7, studies of its chemical behavior under conditions simulating those of the gastrointestinal tract showed that no dopamine production occurred; furthermore, 7 is able to permeate through a simulated intestinal mucosal membrane. The collected data suggest that compound 7 could beconsidered a very valuable candidate for subsequent in vivo evaluation.     

Synthesis,biological activities and docking studies of novel 2,4-dihydroxybenzaldehyde based Schiff base

The present study describes the synthesis and characterization of a series of novel Schiff bases derived from 2,4-dihydroxybenzaldehyde. The biological activities of the newly synthesized compounds were examined by investigating their antioxidant, antibacterial, antifungal, enzyme inhibition and DNA interaction potential. The potential of these compounds as an antioxidant was determined by 2,2-diphenylpicrylhydrazyl radical scavenging method. The antibacterial and antifungal activities of these compounds were assayed by the disk diffusion method, while the enzyme inhibition studies were carried out against acetylcholinesterase and butyrylcholinesterase. The aforementioned studies revealed that the newly synthesized Schiff bases can be used as potential inhibitors for cholinesterase. In addition, the molecular docking studies also agreed well with the experimental results with better interaction patterns in the cases of acetylcholinesterase and butyrylcholinesterase. The DNA binding interactions in these synthesized compounds was studied by the UV–Vis absorption titration method and the results of calculated thermodynamic parameters such as binding constant (K) and free energy change (ΔG) were calculated accordingly. Most of these Schiff bases displayed relatively higher positive values for K and larger negative values for ΔG, indicating efficient binding of these Schiff bases with the DNA. During the course of this study, we also carried out the computational analysis for the determination of the mode of binding of these compounds with the DNA structure.     

醋氯芬酸安全性药理研究

目的:观察醋氯芬酸对神经系统、心血管系统、呼吸系统和消化系统的影响.方法:观察ig给予醋氯芬酸(5,15和45mg·kg-1)对小鼠的大体行为、自主活动和睡眠诱导的影响.观察ig给予醋氯芬酸(6,12和30mg·kg-1)对大鼠的呼吸频率和幅度的变化,收缩压和舒张压,心率及心律,心电图的QRS波、ST段、T波、PR间期的影响.观察ig给予醋氯芬酸(9,15和25mg·kg-1)对大鼠的致胃溃疡作用.结果:小鼠ig醋氯芬酸(45mg·kg-1)有协同戊巴比妥钠睡眠诱导作用外,其余指标均无明显影响.空腹大鼠ig醋氯芬酸半数致胃溃疡剂量(UD50)为19.9mg·kg-1.结论:醋氯芬酸在产生药效剂量下,或更高剂量下对神经系统、心血管系统和呼吸系统均无影响.大鼠UD50为19.9mg·kg-1.     

Diacerein mutual prodrug for osteoarthritis: synthesis,in vitro kinetic studies and preliminary pharmacological screening

A gastro-sparing diacerein mutual prodrug was designed and synthesized by linking it to D-glucosamine as a promoiety with an objective of increasing the potential of its anti-inflammatory activity and improving its hydrophilic characteristics so as to make its parenteral administration feasible. Diacerein was linked with D-glucosamine through amide linkage and was subjected to in vitro release studies in aqueous buffers of varied pH range. 97% release of diacerein was achieved in phosphate buffer (pH 7.4) with a half-life of 48 min, following first order kinetics. Preliminary screening was carried in a one-month study in experimental osteoarthritis in rats induced by mono-iodoacetate and therapeutic efficacy of the conjugate was evaluated for changes in knee-diameter, spontaneous locomotor activity, alkaline phosphatase and glucosaminoglycan levels. The prodrug was also tested for anti-inflammatory activity in Freund’s adjuvant arthritis and local irritant effect on rat stomach by Rainsford’s cold stress method. The prodrug exhibited quicker onset of action than diacerein with respect to reduction in knee diameter, improved locomotor activity, better anti-inflammatory and gastro-sparing activity. The preliminary results are promising. In vivo kinetic studies and evaluation in mono-iodoacetate induced osteoarthritis over a period of three months is in progress to establish its effectiveness in the management of osteoarthritis.     

Synthesis, pharmacokinetics, and pharmacodynamics studies of valsartan peptide derivatives

In order to increase the intestinal permeability of valsartan, 14 esters and peptide derivatives of valsartan were chemically synthesized and their absorption characteristics were described. All derivatives were stable and could be better absorbed into the small intestine than valsartan. There are two barriers for the absorption of valsartan derivatives. The elongated half-life (t(1/2)) and stable blood concentrations for compound 4 due to the hydrolysis of the ester group in the second barrier were demonstrated in pharmacokinetic experiments. Furthermore, compound 4 also displayed modest anti-hypertension activity in vivo, which makes structural modification of valsartan, especially for the purpose of improvement of its intestinal permeability, valuable for further studies.     

Pharmacodynamics and pharmacokinetics of YM128, a GPIIb/IIIa antagonist prodrug

We examined the biochemical properties of YM‐57029 ({4‐[4‐(4‐Carbamimidoylphenyl)‐3‐oxopiperazin‐1‐yl]piperidino}acetic acid monohydrochloride trihydrate) and the pharmacodynamics and pharmacokinetics of its prodrug, YM128 (Ethyl (Z)‐(4‐{4‐[4‐(N²‐hydroxycarbamimidoyl)phenyl]‐3‐oxopiperazin‐1‐yl}piperidino)acetate), an orally‐active glycoprotein IIb/IIIa (GPIIb/IIIa) antagonist. YM‐57029 strongly inhibited aggregation of human platelets induced by various agonists, with IC50 values ranging from 3.6 to 51 nM. YM‐57029 specifically inhibited fibrinogen binding to purified GPIIb/IIIa about 1,000‐fold more potently than Arg‐Gly‐Asp‐Ser (RGDS). Moreover, YM‐57029 effectively inhibited an Arg‐Gly‐Asp (RGD) peptide binding to platelets, suggesting that YM‐57029 competed with the RGD sequence of ligand. YM‐57029 or YM128 dose‐dependently inhibited ex vivo platelet aggregation after iv bolus injection or oral administration to beagle dogs and cynomolgus monkeys. However, YM128 exerted more potent and prolonged inhibitory effects on platelet aggregation than YM‐57029 after oral administration to cynomolgus monkeys. Furthermore, YM‐57029 prolonged template bleeding time at a dose that inhibited ex vivo platelet aggregation during cumulative iv infusion to cynomolgus monkeys. Metabolic and pharmacokinetic studies showed that YM128 effectively converted into YM‐57029 in liver microsomes from humans as well as dogs and monkeys, and that bioavailabilities of YM128 in dogs and monkeys were 32.3 and 22.2%, respectively. These results suggest that YM128, a prodrug of YM‐57029, may be a valuable GPIIb/IIIa antagonist with good bioavailability in humans. Drug Dev. Res. 55:149–161, 2002. © 2002 Wiley‐Liss, Inc.     

Clinical pharmacokinetics of XP13512, a novel transported prodrug of gabapentin

Gabapentin absorption occurs in only a limited region of the small intestine and saturates at doses used clinically, resulting in dose-dependent pharmacokinetics, high interpatient variability, and potentially ineffective drug exposure. XP13512/GSK1838262 is a novel transported prodrug of gabapentin that is absorbed throughout the entire length of the intestine by high-capacity nutrient transporters. In 4 studies of healthy volunteers (136 subjects total), the pharmacokinetics of XP13512 immediate- and extended-release formulations were compared with those of oral gabapentin. XP13512 immediate-release (up to 2800 mg single dose and 2100 mg twice daily) was well absorbed (>68%, based on urinary recovery of gabapentin), converted rapidly to gabapentin, and provided dose-proportional exposure, whereas absorption of oral gabapentin declined with increasing doses to <27% at 1200 mg. Compared with 600 mg gabapentin, an equimolar XP13512 extended-release dose provided extended gabapentin exposure (time to maximum concentration, 8.4 vs 2.7 hours) and superior bioavailability (74.5% vs 36.6%). XP13512 may therefore provide more predictable gabapentin exposure and decreased dosing frequency.     

Estimation of paracetamol and aceclofenac in tablet formulation by ratio spectra derivative spectroscopy

A new sensitive, simple, rapid and precise method for simultaneous estimation of paracetamol and aceclofenac in combined tablet dosage form has been developed. The method is based on ratio derivative spectrophotometry. The amplitude in first derivative of the ratio spectra at 256 nm and 268 nm (minima) were selected to determine paracetamol and aceclofenac in combined formulation. The method showed good linearity, accuracy and reproducibility. Results of analysis were validated statistically and by recovery studies.     

Biological and metabolic study of naproxen-propyphenazone mutual prodrug.

Naproxen-propyphenazone (NAP-PP) esters were synthesized as prodrugs with the aim of improving the therapeutic index through prevention of gastrointestinal irritation and bleeding. The structures of the synthesized NAP-PP hybrid esters were confirmed by IR and 1H NMR spectroscopy and their purity was established by elemental analysis, HPLC and TLC. The release of NAP as well as PP derivatives, from the ester prodrugs was studied. A validated analytical HPLC method for the estimation of the NAP, and the prodrugs was developed. Also the enzymatic hydrolysis products of the ester were identified by GC-MS and in conjugation with HPLC. The kinetics of ester hydrolysis was studied in two different non-enzymatic buffer solutions, at pH 1.2, and 7.4 as well as in liver homogenates. Study of analgesic and anti-inflammatory properties in comparison with the reference compounds has shown that both analgesic and anti-inflammatory activities were present at the same doses of the investigated compounds. The ester III was found to be less irritating to gastric mucosal membrane than the parent drugs. These results suggest that the synthesized prodrugs are characterized by better therapeutic index than the parent drugs.     

奥丙嗪衍生物的合成及其生物活性研究

目的 设计合成一系列NO供体型奥丙嗪，并考察它们的体外NO释放活性与抗炎活性。方法 以奥丙嗪为原料，利用其羧基将奥丙嗪与呋咱环结构或硝酸酯结构偶联起来，得到NO供体型奥丙嗪。结果与结论 合成11个NO供体型奥丙嗪衍生物，其中化合物Ⅰa、Ⅰg和Ⅱa～Ⅱd6个化合物为新化合物，目标化合物的结构经MS和^1H-NMR确认。呋咱环型化合物在体外能有效地释放出NO，大多数化合物仍保持抗炎活性。     

Synthesis and biological activities of 8-arylflavones

A number of 8-arylflavones have been synthesized as congeners of wogonin and evaluated for their inhibitory activities of PGE2 production. 8-Arylflavones were obtained from commercially available chrysin via two different synthetic pathways. Most 8-arylflavones exhibited much reduced inhibitory activities against COX-2 catalyzed PGE2 production compared to that of wogonin. Functional group replacement at the 8-position of wogonin from methoxy to aryl group caused loss of inhibitory activity. Our present results imply that the functional group at the 8-position of flavones seems to play very important roles for bioactivity.     

Nonclinical pharmacokinetics of BMS-292655, a water-soluble prodrug of the antifungal ravuconazole

The phosphate ester, BMS-292655, was developed as a water-soluble prodrug of the antifungal agent, ravuconazole (BMS-207147). BMS-292655 was comparatively stable in rat, beagle dog, cynomolgus monkey and human plasma, but was hydrolysed upon incubation with liver S9 preparations from all species. The major product in rat, monkey and human S9 was BMS-207147, while in dog S9, the intermediate ester, BMS-300043, predominated. BMS-300043 itself was more stable in dog S9 than in S9 preparations from the other species. Intravenous administration of BMS-292655 to rats, beagle dogs and cynomolgus monkeys indicated species differences in the extent of formation of BMS-207147 (monkeys>rats>dogs). The lower overall generation of BMS-207147 in dogs was consistent with the presence of circulating plasma levels of BMS-300043. BMS-300043 was present in monkey plasma but not detectable in rat plasma. The conversion of BMS-292655 to BMS-207147 in the presence of human S9 indicated the potential for BMS-292655 to function as a BMS-207147 prodrug in humans. The similarity in the hydrolysis of BMS-292655 when incubated with human and monkey S9 in vitro, coupled with the effective release of BMS-207147 from BMS-292655 upon i.v. administration to monkeys, is consistent with this conclusion.     

Synthesis,characterization, and biological studies of diosgenyl analogs

A series of diosgenyl analogs were prepared from diosgenin to evaluate their anticancer activity and antithrombotic property. Analog 4, which had a spiroketal structure with a 6-aminohexanoic acid residue, exhibited the highest potency against all five tumor cell lines. It significantly blocked tumor growth, induced cell apoptosis and autophagy, and regulated cellular calcium concentration, mitochondrial membrane potential, adenosine triphosphate, and cell cycle. In addition, fluorescence-tagged compounds indicated that the analogs could rapidly accumulate in the cytoplasm, but no specific localization in the nucleus of cancer cells was observed. Furthermore, preliminary structure–activity relationship studies demonstrated that spiroketal analogs exhibit better antithrombotic activity than furostanic analogs, which exhibit the opposite effect by promoting thrombosis. Our study indicates that compound 4 may be a promising anticancer drug candidate for cancer patients with thromboembolism.