Methods for drug discovery: development of potent, selective, orally effective cholecystokinin antagonists

3-(Acylamino)-5-phenyl-2H-1,4-benzodiazepines, antagonists of the peptide hormone cholecystokinin (CCK), are described. Developed by reasoned modification of the known anxiolytic benzodiazepines, these compounds provide highly potent, orally effective ligands selective for peripheral (CCK-A) receptors, with binding affinities approaching or equaling that of the natural ligand CCK-8. The distinction between CCK-A receptors on the one hand and CNS (CCK-B), gastrin, and central benzodiazepine receptors on the other is demonstrated by using the structure-activity profiles of the new compounds. Details of the binding of these agents to CCK-A receptors are examined, and the method of development of these compounds is discussed in terms of its relevance to the general problem of drug discovery.     

Determination of metabolite pharmacokinetics for orally administered prodrugs

The theoretical evaluation of a pharmacokinetic precursor/metabolite model was accomplished utilizing an integral approach based on clearance. Particular attention was paid to prodrugs where a single active intermediate results directly from the parent drug. This model, however, can be utilized for any drug in which a single first-pass metabolic adduct results. Complete elucidation of the first-pass and metabolic systemic pharmacokinetics is possible when plasma and urine concentration data are available after only oral drug administration. The generality of the model does not require prior knowledge of whether the metabolite was formed systemically or presystemically, and only limited metabolic pathway profiling. The model was applied to the evaluation of the angiotensin-converting enzyme inhibitor prodrug pentopril.     

口服拉贝洛尔母乳药动学的风险评估与哺乳期合理用药

目的：基于口服拉贝洛尔在妊娠期高血压产妇的乳汁药动学,评估哺乳期用药风险和干预哺乳时间,促进哺乳期合理用药。方法：选取2016年10月-2017年7月住院分娩的60例妊娠期高血压产妇泌乳后口服拉贝洛尔片的乳汁,采用超高效液相色谱串联质谱法（UPLC-MS/MS）测定乳汁药物浓度,并计算药动学相关参数和用药风险评估指标。结果：妊娠高血压产妇产后继续服用拉贝洛尔（100 mg,q8h,n=60）,乳汁中药动学参数：达峰时间（t_max）为（2.7±0.9）h、达峰浓度（C_max）为（268.0±71.9）ng·mL^-1、半衰期（t_1/2）为（4.1±1.7）h。母乳用药风险评估指标,TID （theoretical infant dose,理论婴儿剂量）为（0.026±0.012）（95% CI：0.025~0.027）mg·kg^-1·d^-1,RID （relative infant dose,相对婴儿剂量）为（0.53%±0.13%）（95% CI：0.49%~0.58%）。结论：妊娠期高血压产妇产后继续服用拉贝洛尔,受哺婴儿理论剂量和相对剂量均低于风险限,安全性较高,可在服药3~4 h后到下次服药周期前按需哺乳。     

肽结构改造——药物开发的理想途径*

肽类化合物正逐渐成为开发新型药物先导化合物的重要来源。由于经典肽的结构在体内容易受到备种蛋白酶的作用而分解失活,且直链肽分子的柔曲性强,与受体结合的优势构象不突出,从而影响到与受体结合的选择性及活性强度。因此以经典肽为活性先导化合物进行结构改造成为开发新药的理想途径之一。现系统地归纳了活性肽如N-甲基肽、伪肽、末端改均肽、环肽、位点变构肽、娄肽、非天然肽、肽核酸、糖肽、拟肽、缀合肽等结构改造的类型,同时对一些代表性改构及活性情况分别予以介绍。     

定量药理学与儿童药物研发和合理用药

1引言 儿童合理用药是摆在世界各国临床药理学工作者和儿科医生面前一个亟待解决而又悬而难决的课题。长期以来，儿童作为弱势群体和人类的未来是社会大众的保护对象，伦理上不接受儿童作为药物试验的受试者。即使是常用于儿童的药物，也很少在儿童中试验过。     

Synthesis and biological evaluation of orally active prodrugs of indomethacin

Synthesis and biological evaluation of orally active prodrugs (1a-d) of indomethacin are described. Prodrugs 1a-c showed a similar degree of anti-inflammatory activity, and prodrug 1d was found to be less potent than the parent drug indomethacin (1). Ulcer index (UI) data indicated that 1a (UI = 19), 1c (UI = 0), and 1d (UI = 0) were substantially less ulcerogenic and 1b (UI = 62) was more ulcerogenic than parent drug 1 (UI = 47). These prodrugs demonstrated good stability at acidic and basic pH and found to be more lipophilic than parent drug compound 1, indicated by partition coefficients measured in octanol-buffer system at pH 7.4 and 3.0. On the basis of in vivo studies, 1a and 1c compounds were selected for metabolic stability in rat liver microsome (RLM) and rat plasma (RP), and both were found to be enzymatically labile. Prodrugs 1a and 1c emerged as potent anti-inflammatory agents with a lesser potential for ulcer than the parent drug indomethacin.     

合理用药咨询系统的开发与应用

目的：建立合理用药咨询系统，为医院药师开展药学服务提供技术支持。方法：收集整理药物信息、疾病信息及药物治疗方案等相关资料，建立SQL数据库，运用Visual Basic（VB）语言实现前台咨询与后台数据库之间的互动，构建合理用药咨询系统。结果：建立了4710种药品（以通用名计）、3650种疾病的药物治疗方案的合理用药咨询系统，通过药物治疗方案的药物列表，将疾病治疗方案数据库与药品数据库有机地联系起来，建立多种检索方式，支持模糊查询，实现了数据资源的共享和充分利用。结论：合理用药咨询系统应用于医院及其他医疗单位，是医院药师参与临床疾病药物治疗，为病人提供药学服务，提高医疗质量，推进合理用药的有效工具。     

The development of orally administrable gemcitabine prodrugs with d-enantiomer amino acids: Enhanced membrane permeability and enzymatic stability

Gemcitabine prodrugs with d- and l-configuration amino acids were synthesized and their chemical stability in buffers, resistance to glycosidic bond metabolism, enzymatic activation, permeability in Caco-2 cells and mouse intestinal membrane, anti-proliferation activity in cancer cell were determined and compared to that of parent drug, gemcitabine. Prodrugs containing d-configuration amino acids were enzymatically more stable than ones with l-configuration amino acids. The activation of all gemcitabine prodrugs was 1.3–17.6-fold faster in cancer cell homogenate than their hydrolysis in buffer, suggesting enzymatic action. The enzymatic activation of amino acid monoester prodrugs containing d-configuration amino acids in cell homogenates was 2.2–10.9-fold slower than one of amino acid monoester prodrugs with l-configuration amino acids. All prodrugs exhibited enhanced resistance to glycosidic bond metabolism by thymidine phosphorylase compared to parent gemcitabine. Gemcitabine prodrugs showed superior the effective permeability in mouse jejunum to gemcitabine. More importantly, the high plasma concentration of d-amino acid gemcitabine prodrugs was observed more than one of l-amino acid gemcitabine prodrugs. In general, the 5′-mono-amino acid monoester gemcitabine prodrugs exhibited higher permeability and uptake than their parent drug, gemcitabine. Cell proliferation assays in AsPC-1 pancreatic ductal cell line indicated that gemcitabine prodrugs were more potent than their parent drug, gemcitabine. The transport and enzymatic profiles of 5′-d-valyl-gemcitabine and 5′-d-phenylalanyl-gemcitabine suggest their potential for increased oral uptake and delayed enzymatic bioconversion as well as enhanced uptake and cytotoxic activity in cancer cells, would facilitate the development of oral dosage form for anti-cancer agents and, hence, improve the quality of life for the cancer patients.     

Drug glycosides: potential prodrugs for colon-specific drug delivery

The influence of prodrug structure on specificity of glycoside/glycosidase based colon-specific drug delivery was studied by preparing nine steroid glycosides, measuring their relative lipophilicities, and hydrolyzing them with bacterial glycosidases from rat intestines. The 21-yl beta-D-glucosides and galactosides of dexamethasone, prednisolone, hydrocortisone, and fludrocortisone and the 21-yl beta-D-cellobioside of prednisolone were prepared by a modified Koenigs-Knorr reaction. The deacetylated glycoside prodrugs, along with the P-nitrophenyl derivatives of beta-D-glucoside, galactoside, and cellobioside, were subjected to hydrolysis by the contents of the rat stomach, proximal small intestine (PSI), distal small intestine (DSI), and cecum. All the prodrugs were hydrolyzed slowly by PSI and stomach contents, more rapidly by contents of the DSI, and most rapidly by cecal contents. This is the basis of the site-specific drug delivery reported earlier (Friend, D. R.; Chang, G. W. J. Med. Chem. 1984, 27, 261). Furthermore, the prodrugs themselves had very different susceptibilities to hydrolysis. Hydrolysis rates catalyzed by DSI contents decreased in the following order: prednisolon-21-yl beta-D-galactoside (10) greater than prednisolon-21-yl beta-D-glucoside (2) greater than prednisolon-21-yl beta-D-cellobioside (13) greater than dexamethason-21-yl beta-D-galactoside (9) greater than dexamethason-21-yl beta-D-glucoside (1). Hydrolysis of cellobioside 13 was only half that of glucoside 2 and one-fourth that of galactoside 10. Hydrolysis of all the prodrugs in cecal contents was rapid, with the exceptions of hydrocortison-21-yl beta-D-glucoside (5) and fludrocortison-21-yl beta-D-glucoside (7), which were hydrolyzed more slowly than the other glucoside prodrugs. Eadie-Hofstee plots for hydrolysis of the glucoside compounds suggested that bacterial beta-D-glucosidase activity in the colon may be more heterogeneous in nature than beta-D-galactosidase activity. Relative lipophilicities of the prodrugs and free steroids were compared by measuring their octanol-buffer partition coefficients (P). The logarithm of the P of cellobioside 13 (-0.56) was considerably lower than that of the other prodrugs, which ranged from 0.11 to 0.84. Log P of the free steroids ranged from 1.54 to 1.73. These relative rates of hydrolysis and relative lipophilicities, along with previously reported animal experiments, enable one to estimate the site specificity of glycoside prodrugs prior to extensive animal studies.     

The heart of drug discovery and development: rational target selection

Critical to the discovery and development of drugs and vaccines is the rational selection of biochemical, immunologic or molecular targets. To understand the rationale for target selection, we review strengths and weaknesses of the four main approaches: whole animal disease models; molecular targeting; epidemiology/observation studies, and genomics. After classifying diseases into those with a relatively stable pathophysiology (e.g., hypertension and gout) versus those with an unstable pathophysiology (e.g., AIDS and influenza) to aid in understanding target selection, we provide examples of successful and unsuccessful selection of drug and vaccine targets, focusing on the molecular and epidemiological/observational approaches. We discuss the reasons that molecular targeting has led to successful control of many diseases, whereas the epidemiological/observational approach has had a checkered history. We also assess the potential power of the genomic approach, specifically the curative versus controlling/preventive strategies. With combined genetic and molecular approaches and judicious use of whole animal models and properly performed epidemiology/observation studies to select the appropriate targets, the future for controlling, preventing and even curing many diseases is very bright indeed.     

Aqueous degradation of N-(hydroxymethyl)phthalimide in the presence of specific and general bases. Kinetic assessment of N-hydroxymethyl derivatives of nitrogen heterocycles as possible prodrugs

The conversion of N-(hydroxymethyl)phthalimide (NHPH) to phthalimide could not be detected within 300 s at pH 9.0, whereas in 0.18 M NaOH complete conversion of NHPH to phthalimide was observed within 50 s. In the presence of 0.2-0.4 M 1,4-diazabicyclo[2.2.2]octane buffer solutions (pH 9.30-9.54), 40-60% conversion of NHPH to phthalimide occurred within 90-120 s. The initial concentration of NHPH affected the extent of conversion of NHPH to phthalimide.     

Utility of physiologically based pharmacokinetic models to drug development and rational drug discovery candidate selection

The present paper proposes a modeling and simulation strategy for the prediction of pharmacokinetics (PK) of drug candidates by using currently available in silico and in vitro based prediction tools for absorption, distribution, metabolism and excretion (ADME). These methods can be used to estimate specific ADME parameters (such as rate and extent of absorption into portal vein, volume of distribution, metabolic clearance in the liver). They can also be part of a physiologically based pharmacokinetic (PBPK) model to simulate concentration-time profiles in tissues and plasma resulting from the overall PK after intravenous or oral administration. Since the ADME prediction tools are built only on commonly generated in silico and in vitro data, they can be applied already in early drug discovery, prior to any in vivo study. With the suggested methodology, the following advantages of the mechanistic PBPK modeling framework can now be utilized to explore potential clinical candidates already in drug discovery: (i) prediction of plasma (blood) and tissue PK of drug candidates prior to in vivo experiments, (ii) supporting a better mechanistic understanding of PK properties, as well as helping the development of more rationale PK-PD relationships from tissue kinetic data predicted, and hence facilitating a more rational decision during clinical candidate selection, and (iii) the extrapolation across species, routes of administration and dose levels.     

In vitro evaluation of dendrimer prodrugs for oral drug delivery

Dendrimer-based prodrugs were used to enhance the transepithelial permeability of naproxen, a low solubility model drug. The stability of the dendrimer-naproxen link was assessed. Naproxen was conjugated to G0 polyamidoamine (PAMAM) dendrimers either by an amide bond or an ester bond. The stability of G0 prodrugs was evaluated in 80% human plasma and 50% rat liver homogenate. The cytotoxicity of conjugates towards Caco-2 cells was determined and the transport of the conjugates across Caco-2 monolayers (37 degrees C) was reported. In addition, one lauroyl chain (L) was attached to the surface group of G0 PAMAM dendrimer of the diethylene glycol ester conjugate (G0-deg-NAP) to enhance permeability. The lactic ester conjugate, G0-lact-NAP, hydrolyzed slowly in 80% human plasma and in 50% rat liver homogenate (t(1/2)=180 min). G0-deg-NAP was hydrolyzed more rapidly in 80% human plasma (t(1/2)=51 min) and was rapidly cleaved in 50% liver homogenate (t(1/2)=4.7 min). The conjugates were non-toxic when exposed to Caco-2 cells for 3h. Permeability studies showed a significant enhancement in the transport of naproxen when conjugated to dendrimers; L-G0-deg-NAP yielding the highest permeability. Dendrimer-based prodrugs with appropriate linkers have potential as carriers for the oral delivery of low solubility drugs such as naproxen.     

Kinetic model for solid-state degradation of gabapentin

Gabapentin degrades directly to gabapentin-lactam (gaba-L) in the solid state. The objective of this study was to formulate a drug degradation model that accounted for the environmental storage conditions and mechanical stress (prior to storage) on lactamization kinetics. The effects of mechanical stress on drug degradation kinetics were determined by milling gabapentin in a FRITSCH Planetary Micro Mill for 0 and 60 min. The resultant gabapentin powder was stored at 40 °C-60 °C and 5%-30% relative humidity. The rate of gaba-L formation was measured by high-performance liquid chromatography. An irreversible two-step autocatalytic reaction scheme was fit using nonlinear regression methods. The resultant kinetic model was used to predict the time-dependent concentration of degradant of gabapentin tablets prepared under various exemplary manufacturing conditions, thereby demonstrating the ability of the model to link manufacturing variation and chemical stability in solid-state gabapentin formulations.