晶体药物专利申请的技巧及注意事项

近几年来药物研发单位申请多晶体药物专利的数量在整个药品专利申请中所占比例不断上升.作为药物研发单位和生产企业的决策者和有关人员,特别是从事晶体药物研发的工作者非常有必要了解与晶体药物专利文件的撰写、药物专利的申请、审查和保护相关的知识.从新颖性、创造性、单一性方面介绍晶体药物专利申请的要求和注意事项,以及权利要求书、说明书的撰写技巧,供药物研发单位的相关人员参考.     

Comparison of the mechanical properties of the crystalline and amorphous forms of a drug substance

PURPOSE: To better understand the influence of long-range molecular order on the processing characteristics of an active pharmaceutical ingredient (API). METHODS: Crystalline and amorphous samples of a model drug substance were isolated and their "true" density, crystallinity, melting point, glass transition temperature, particle size distribution, and powder flow characteristics determined. Compacts of a standard porosity were manufactured from each form and their dynamic indentation hardness, quasi-static indentation hardness, tensile strength and "compromised tensile strength" determined. X-ray powder diffraction was used to confirm that no changes were induced by compact formation or testing. RESULTS: The crystalline and amorphous forms of the drug substance had relatively high melting and glass transition temperatures (approximately 271 and 142 degrees C, respectively) and were physically and chemically stable under the conditions of the testing laboratory. Consistent with this there was no evidence of crystallinity in the amorphous samples or vice versa before, during or after testing. The two API lots were effectively equivalent in their particulate properties (e.g. particle size distribution), although differences in their particle morphologies were observed which influenced powder flow behavior. The compacts of the bulk drug samples exhibited moderate ductility, elasticity, and strength, and high brittleness, in keeping with many other drug substance samples. A significantly greater compression stress was required to form the compacts of the crystalline material, and these sample materials were more ductile, less brittle and less elastic than those made from the amorphous API. There were no major differences in the tensile strength or the viscoelasticity of the compacts made from the crystalline and amorphous samples. CONCLUSIONS: The mechanical properties of compacted amorphous and crystalline samples of a drug substance have been measured and the contributions due to the molecular ordering of the crystalline form proposed. Small but significant differences in the mechanical properties were noted which could potentially affect the processing performance of API.     

A comparative assessment of solubility advantage from glassy and crystalline forms of a water-insoluble drug.

The objective of the present study was to generate and characterize the glassy state of Irbesartan (IBS), with a view to exploit the solubility advantage from disordered high energy system. The major reason for limited solubility benefit from amorphous systems is their devitrification, on exposure to primarily aqueous dissolution medium. IBS is a lipophilic molecule and exhibits poor aqueous solubility and incomplete dissolution. IBS was found to be a good glass former (with glass transition/melting temperature >0.7), non-hygroscopic in nature and showed reasonable solid-state stability. The present work places particular emphasis on studying the influence of various dissolution environments on the devitrification of amorphous system. It was noted that IBS forms a relatively 'stable' glassy system with a 2.5-fold increase in aqueous solubility and a higher intrinsic dissolution rate (IDR). The dissolution behavior showed pH dependency and about eight-fold solubility advantage was obtained from amorphous system at pH 3. Both the crystalline and amorphous forms exhibited appreciably high solubility in HCl and HCl strength was found to significantly influence the solubility of crystalline form. Amorphous IBS showed reduced devitrification in HCl, as against water, thus highlighting the effect of dissolution environment on devitrification kinetics. Statistical and mathematical analyses were performed to compare the solubility advantage obtained using amorphous IBS vis-à-vis the crystalline counterpart.     

Nanoencapsulation I. Methods for preparation of drug-loaded polymeric nanoparticles

Polymeric nanoparticles have been extensively studied as particulate carriers in the pharmaceutical and medical fields, because they show promise as drug delivery systems as a result of their controlled- and sustained-release properties, subcellular size, and biocompatibility with tissue and cells. Several methods to prepare nanoparticles have been developed during the last two decades, classified according to whether the particle formation involves a polymerization reaction or arises from a macromolecule or preformed polymer. In this review the most important preparation methods are described, especially those that make use of natural polymers. Advantages and disadvantages will be presented so as to facilitate selection of an appropriate nanoencapsulation method according to a particular application.     

The detection of amorphous material in a nominally crystalline drug using modulated temperature DSC--a case study

Two batches (1 and 2) of an experimental drug (L7) which have shown marked differences in their chemical stability profiles were examined with a view to identifying the presence of small quantities of amorphous material using modulated temperature DSC (MTDSC). The external morphological characteristics of the two batches were similar although marked differences were seen in the moisture uptake profiles. MTDSC studies indicated that while no evidence for a glass transition could be seen for Batch 1, a T(g) and accompanying relaxation endotherm were observed for Batch 2. Comparison with a glassy form of the drug indicated that the amorphous content was in the region of 5-6% w/w in Batch 2. Dynamic moisture sorption studies indicated that while Batch 2 showed a higher uptake profile than Batch 1, addition of 5% w/w amorphous material to Batch 1 led to the establishment of a very similar profile to that seen for Batch 2. It was concluded that Batch 2 contains amorphous material which is responsible for the greater moisture uptake (and by implication poor chemical stability) of this sample and that the glass transition of this fraction may be characterised using MTDSC.     

用混合粉碎法制备晶体药物与β-环糊精包合物

目的制备晶体药物与β-环糊精的包合物;分析包合物中药物的分散状态;考察最佳粉碎时间及形成包合物的适宜贮存湿度。方法采用混合粉碎法制备包合物;根据红外图谱、粉末X-射线衍射验证包合物的形成及最佳粉碎时间;通过升华失重确定包合物中药物分子的分散状态;变换贮存湿度考察包合物的聚结稳定性。结果制成的包合物为无定形结构,药物分子进入β-环糊精空穴中通过分子间氢键结合;包合物的分散度和粉碎时间有关,本系统的最佳粉碎时间为10 min;包合物中药物分子的状态受贮存时相对湿度的影响,在相对湿度低于75%下贮存时,包合物的分散状态未发生明显变化。结论采用混合粉碎法制备包合物,具有较好的稳定性;将晶体难溶性药物与β-环糊精混合粉碎可得到非晶质包合物,能有效地提高难溶性药物的溶解度。     

Nanostructured liquid crystalline formulation as a remarkable new drug delivery system of anti-epileptic drugs for treating children patients

Purpose

Development of a new dosage-form of antiepileptic-drugs appropriated for children.

Using Terahertz pulse spectroscopy to study the crystalline structure of a drug: a case study of the polymorphs of ranitidine hydrochloride

We describe the application of Terahertz pulse spectroscopy to polymorph identification. The particular compounds investigated were the different crystalline Forms 1 and 2 of ranitidine hydrochloride, both in the pure form and also obtained as a marketed pharmaceutical product. Identification was clear. The technique has advantages that excitation is not via a powerful laser source, as used in Raman spectroscopy, so phase changes or photochemical reactions in polymorphs do not occur. Terahertz absorption spectral interpretation and instrumentation are similar to basic Fourier transform infrared (FTIR) spectroscopy and therefore easy to understand. The sample preparation techniques used are the same as those used in FTIR and Raman spectroscopies. The data obtained is complementary to Raman Spectroscopy. As the selection rules are different between the two techniques, we are able to obtain new data set directly related to crystalline structure adding to that obtained by Raman spectroscopy. Terahertz pulse spectroscopy provides information on low-frequency intermolecular vibrational modes; these are difficult to assess in Raman spectroscopy due to the proximity of the laser exciting line. It is concluded that the method has a wide range of applications in pharmaceutical science including formulation, high throughput screening, and inspection in storage.     

Drying of crystalline drug nanosuspensions-The importance of surface hydrophobicity on dissolution behavior upon redispersion

d-alpha-Tocopherol polyethylene glycol 1000 succinate (TPGS)-stabilized nanosuspensions (25wt%, relative to the drug weight) were produced by media milling for 9 model drug compounds [cinnarizine, griseofulvin, indomethacin, itraconazole, loviride, mebendazole, naproxen, phenylbutazone and phenytoin]. After 3 months of storage at room temperature, Ostwald ripening occurred in all of the samples, except for indomethacin. Whereas lowering the temperature could slow down the ripening, it markedly increased upon storage at 40 degrees C. As for ripening, settling generally became more pronounced at 40 degrees C compared to 4 degrees C. As the nanosuspensions were afflicted by Ostwald ripening and settling, we explored nanosuspension drying as a strategy to circumvent these stability issues. Spray-drying and freeze-drying were evaluated for nanosuspensions and coarse reference suspensions of the compounds. Nanoparticle agglomeration could be visually observed in all of the powders. To evaluate the effect of agglomeration on the key characteristic of drug nanocrystals (i.e. rapid dissolution), dissolution experiments were performed under poor sink conditions. It was found that the compounds could be categorized into 3 groups: (i) compounds for which it was impossible to differentiate between coarse and nanosized products (griseofulvin, mebendazole, naproxen), (ii) compounds that gave clear differences in dissolution profiles between the nanosized and the coarse products, but for which drying of the nanosuspensions did not decrease the dissolution performance of the product (indomethacin, loviride, phenytoin) and (iii) compounds that showed differences between coarse and nanosized products, but for which drying of the nanosuspensions resulted in a significant decrease of the dissolution rate (cinnarizine, itraconazole, phenylbutazone). To gain insight on the influence of the drug compound characteristics on the dissolution of the dried products, the dissolution behavior of the compounds of the second and the third group was linked to the compound's characteristics. It was found that compounds with a more hydrophobic surface resulted in agglomerates which were harder to disintegrate, for which dissolution was compromised upon drying. The same was found for compounds having higher logP values.     

脂质立方液晶纳米粒作为药物载体的研究进展

由两亲性脂质分散在水性环境中自发形成各种几何形态构成的药物输送载体正成为制剂载药系统研究的热点之一。脂质立方液晶纳米粒是一定浓度的两亲性脂质分散在水溶液中自组装成含双连续水区和脂质区的闭合脂质双层“蜂窝状(海绵状)”结构,该独特的内部双水道结构和巨大膜表面积使其能够包封各种不同极性和剂量的药物,具有多样化的药物包裹性。作为药物载体,脂质立方液晶纳米粒还具有载药量大、保护多肽蛋白类药物和制备工艺简单等优点;可口服、局部黏膜和注射等多种途径给药,在多种剂型中有广泛的应用。本文对脂质立方液晶纳米给药系统的研究进行归纳和总结,并展望了脂质立方液晶纳米粒新型药物载体的应用前景。     

Gelatine enhances drug dispersion in alginate bilayer film via the formation of crystalline microaggregates

In our previous study, a novel alginate-based bilayer film for slow-release wound dressings was successfully developed. We found that alginate alone yielded poor films; however, the addition of gelatine had significantly enhanced the drug dispersion as well as the physical properties. Here, an investigation of the drug–polymer interactions in the bilayer films was carried out. Drug content uniformity test and microscopy observation revealed that the addition of gelatine generated bilayer films with a homogenous drug distribution within the matrix. The FTIR and XRD data showed an increase in film crystallinity which might infer the presence of drug–polymer crystalline microaggregates in the films. DSC confirmed the drug–polymer interaction and indicated that the gelatine has no effect on the thermal behaviour of the microaggregates, suggesting the compatibility of the drug and excipients in the bilayer films. In conclusion, the addition of gelatine can promote homogenous dispersion of hydrophobic drugs in alginate films possibly through the formation of crystalline microaggregates.     

Crystallography of drug polymorphism: emergence of new resolution methods and prediction of crystalline structures

For the pharmaceutical and agrochemical industries, reducing development time is currently a primary objective to accelerate the marketing of new products. In-depth solid-state characterization is an essential element in achieving this performance. For this purpose, it is now recognized that, in a department of solid-state physical characterization, theoretical approaches have to be integrated with experimental tools. Benefiting from the constant improvement in computer hardware and software in terms of computing powers and algorithm development, these approaches appear to be a complementary method that can help explain and rationalize experimental data. In recent years, with the help of both molecular modeling tools and crystallographic databases, original methods have been developed and successfully applied to systems of variable complexity. The X-ray diffraction crystal structure determination makes it possible to calibrate the force field and to adapt it more precisely to the compound studied, thereby reducing one of the sources of uncertainty. Although crystal structures are preferentially determined from single crystal data, it has been recently shown that powder diffraction data can also be used when single crystals are missing. Therefore, the different benefits of such an approach are the following: ab initio predictive study of crystalline polymorphism, molecular packing analysis and detection of cleavage planes, prediction of morphology in vacuum. In conjunction with crystallite preferred orientation observed in powder patterns, grinding effects on the crystal habit and solvent effects in modifying growth can be clearly understood. Selected industrial cases exemplify the operational application of this methodology.     

Examination of liquid crystalline gel systems containing chlorhexidine on the structure and the drug release

The aim of the thesis was to examine liquid crystalline gel systems as novel, locally applied drug delivery systems. For developing liquid crystalline vehicle, different ratio of Synperonic A7--water mixtures was prepared. Chlorhexidine, chlorhexidine acetate and chlorhexidine gluconate were used as model drugs. Liquid crystalline structure, drug release and drug release kinetic of the samples were studied at increasing surfactant concentration and the effect of the different drugs on the physicochemical properties of the samples and on the membrane transport was examined. For the analysis of the prepared liquid crystalline systems polarising microscopy, rheology test, differential scanning calorimetry, small-angle neutron scattering and transmission electron microscopy were carried out. The drug release and membrane transport experiments were performed by Franz type vertical diffusion cell and Sartorius Resorptionsmodell apparatus. According to our results liquid crystalline vehicles of lamellar and hexagonal structure formed by increasing the surfactant concentration. The drug release studies indicated, that the kinetic of the release strongly depend on the liquid crystalline structure, zero order release occurs from hexagonal structures and anomalous transport occurs from lamellar structures. The addition of chlorhexidine species to the systems modified the structure of the liquid crystalline system. As a results of liquid crystal-drug interaction the solubility of chlorhexidine base and its diffusion through lipophilic membranes increased in comparison with those of the chlorhexidine salts.     

Lyotropic liquid crystalline phases formed from glycerate surfactants as sustained release drug delivery systems

A new class of surfactants with glycerate headgroups, that form viscous lyotropic liquid crystalline phases in excess water, have been investigated for their potential to provide sustained release matrices for depot drug delivery. Oleyl glycerate and phytanyl glycerate were used as representative surfactants of this new class, and their behaviour compared with that of glyceryl monooleate (GMO). The surfactants were found to form reverse hexagonal phase (H(II)) in excess water, and the matrices were loaded with a series of model hydrophobic and hydrophilic drugs, (paclitaxel, irinotecan, glucose, histidine and octreotide), and the release kinetics determined. In all cases, the release behaviour obeyed Higuchi kinetics, with linear drug release versus square root of time. The H(II) phases released model drugs slower than the GMO cubic phase matrix. The oleyl glycerate matrix was found to consistently release drug faster than the phytanyl glycerate matrix, despite both matrices being based on H(II) phase. To further demonstrate the potential utility of these materials as drug depot delivery systems, an injectable precursor formulation for octreotide was also prepared and demonstrated to provide controlled release for the peptide. The stability of the H(II) phase to likely in vivo breakdown products was also assessed.     

X-ray powder diffractometric method for quantitation of crystalline drug in microparticulate systems. I. Microspheres

Ethylcellulose microspheres containing tolnaftate (I) were prepared by the emulsion-solvent evaporation technique. An X-ray powder diffractometric method was developed to quantify the content of crystalline I in these microspheres. X-ray lines of I with d-spacings of 5.5 and 4.2 A were chosen for the quantitative analyses. Physical mixtures containing various weight fractions of I and blank (empty) microspheres were prepared and lithium fluoride (20% w/w) was added as the internal standard. The 5.5 and 4.3 A lines of I and the 2.3 A line of lithium fluoride were used for the quantitative analysis. A plot of the intensity ratio (intensity of the 5.5 A line of I/intensity of 2.3 A line of lithium fluoride) as a function of the weight percent of I in the mixture, resulted in a straight line. The crystalline content of I in the tolnaftate-loaded microspheres was determined using this standard curve. A second independent determination of the content of I was possible from the intensities of the 4.3 A line. The enthalpy of fusion of I, determined by differential scanning calorimetry (DSC), was also used as a measure of the crystalline content of I in the microspheres. The X-ray and DSC methods measure the content of crystalline I in the microspheres at room temperature ( approximately 25 degrees C) and at the melting point of I (111 degrees C), respectively. The total content of I in the microspheres was determined by HPLC. The DSC and X-ray results indicated that a substantial fraction of the incorporated I was dissolved in the ethylcellulose matrix.     

Nanoencapsulation of usnic acid: An attempt to improve antitumour activity and reduce hepatotoxicity.

Despite the recognised antiproliferative and antitumour properties of usnic acid, its therapeutic application has yet to be introduced. In fact, the high hepatotoxicity and low water solubility of usnic acid have somewhat restricted its practical use in anticancer therapy. The aim of this study was therefore to investigate the antitumour activity of usnic acid encapsulated into nanocapsules prepared with lactic co-glycolic acid polymer. Usnic acid-loaded nanocapsules were obtained using the interfacial deposition of a preformed polymer. The antitumour activity was confirmed on an ascitic tumour (Sarcoma-180) implanted in Swiss mice and estimated by means of the tumour inhibition. The results of antitumour activity confirmed that the encapsulation of usnic acid into PLGA-nanocapsules produced a 26.4% increase in tumour inhibition as compared with the standard free usnic acid treatment. Vacuolization of hepatocytes and a mild lymphocytic infiltration in portal spaces were observed in animals treated with free usnic acid. However, this hepatotoxicity was substantially reduced when animals were treated with usnic acid-loaded nanocapsules. No histological changes were noticed in the kidneys or spleen of animals treated either with usnic acid or usnic acid-loaded nanocapsules. These results suggest that nanoencapsulation may be a way of enabling usnic acid to be used in chemotherapy.