Characterization and In Vitro Methotrexate Release from Methotrexate/Gelatin Conjugates of Opposite Conjugate Bond Polarity

Purpose. Our laboratory has previously prepared gelatin/methotrexate (MTX) conjugates containing mixed conjugation sites and by-product crosslinking, both of which may alter conjugate effectiveness. In this study, we prepared and evaluated gelatin/MTX conjugates having specific conjugate bond sites and minimal by-product crosslinking. Methods. Opposite polarity conjugates were produced by coupling gelatin having blocked amino groups with MTX (G-MTX) and by coupling MTX having blocked amino groups with gelatin (M-GEL) using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide HCl. Amino groups were blocked using citraconic anhydride and deblocked under acidic conditions. Gelatin and MTX contents were determined spectrophotometrically. The stability of each conjugate was determined by evaluating their in vitro release of MTX in isotonic buffer at pH 7.4 and 37°C for 7 days. Results. The G-MTX and M-GEL conjugates contained 21 and 1.2 mole MTX/mole gelatin and released 12 and 17% MTX by 7 days resulting in pseudo-first order release rate constants of 0.76×10^–3 and 1.0×10^–3 hr^–1, respectively. Alternate MTX species ( 10%) were detected during the release study and were attributed to low molecular weight gelatin/MTX fragments and MTX polymers. Conclusions. Gelatin/MTX conjugates having opposite conjugate bond polarities and minimal by-product crosslinking have been produced and slowly released MTX by hydrolytic cleavage indicating good stability for future cell culture studies.     

Fabrication and Characterization of Surface Engineered Rifampicin Loaded Lipid Nanoparticulate Systems for the Potential Treatment of Tuberculosis: An In Vitro and In Vivo Evaluation

The main aim of the present investigation highlights the development of mannose appended rifampicin containing solid lipid nanoparticles (Mn-RIF-SLNs) for the management of pulmonary TB. The developed Mn-RIF-SLNs showed particle size of Mn-RIF-SLNs (479 ± 13 nm) which was found to be greater than that of unconjugated SLNs (456 ± 11 nm), with marginal reduction in percentage entrapment efficiency (79.41 ± 2.42%). The in vitro dissolution studies depicted an initial burst release followed by sustained release profile indicating biphasic release pattern, close-fitting Weibull model having least F-value. The cytotoxicity studies using J774A.1 cell line represented that the developed SLNs were non-toxic and safe as compared to free drug. Fluorescence imaging and flow cytometric (FACS) analysis depicted significant (1.79-folds) intracellular uptake of coumarin-6 (fluorescent marker) loaded Mn–C6-SLNs. The in vivo pharmacokinetic studies in sprague-dawley rats were performed and Mn-RIF-SLNs showed remarkable enhancement in terms of relative bioavailability (~17-folds) as compared to its drug solution via oral administration. The biodistribution studies revealed higher lung accumulation (1.8-folds) of Mn-RIF-SLNs as compared to the Un-RIF-SLNs. In conclusion, the developed Mn-RIF-SLNs could serve as a promising tool for delivering the drug cargo to the site of infection (lungs) in the treatment of TB.     

Characterization of Ring-Opening Reaction of Succinimide Linkers in ADCs

A new class of highly potent biopharmaceutical drugs, antibody-drug conjugates (ADCs), has been proven to be clinically effective to treat oncologic diseases. ADCs contain 3 major components: the monoclonal antibody, cytotoxic drug, and chemical linker. THIOMAB? drug conjugates and interchain-cysteine ADCs are common ADC platforms that apply thiol-maleimide chemistry via Michael addition to conjugate linker-drugs to cysteine residues. However, the resulting succinimide ring in the linker is susceptible to ring-opening reactions via hydrolysis, especially at high pH and elevated temperatures. Once the succinimide ring is opened, in vivo stability of the ADCs can be changed and the therapeutic activity will be altered. In this study, we investigated the impact of conjugation sites on succinimide ring opening for ADCs. A new methodology based on imaged capillary isoelectric focusing was developed to monitor the formation of succinimide ring-opened products. In addition, a reverse-phase high-performance liquid chromatography method was used to monitor site-specific ring-opening reactions. Our data confirmed that succinimide ring-opening rates in ADCs are conjugation-site dependent. With a good understanding of the conjugation site impact on final product’s stability, it is potentially feasible to modify ring-opening rates in vitro to achieve desirable in vivo stability and biological activity.     

小型化抗体偶联药物及类似物的研究进展

在癌症治疗中,实体瘤的治疗效果一直是医药界关注的热点。临床上用于治疗实体瘤的靶向药物——抗体和抗体偶联药物存在其相对分子质量较大,导致穿透性有限的问题,在实体瘤治疗中无法发挥预期疗效,且由于其在体内的循环时间长,易对肝和其他组织产生脱靶毒性,限制治疗窗。使用小型化的偶联物或类似药物,如抗体片段偶联药物、支架抗体偶联物或多肽偶联物,将有利于药物快速穿透肿瘤组织,使毒素在肿瘤组织内迅速聚集,且相比于传统抗体偶联药物,小型化偶联物通过肾脏代谢比率增加,从而降低药物因长时间体循环导致的不良反应。但是其过短的半衰期会造成进入肿瘤的实际药量减少,因此也衍生出不同半衰期延长方法,以调节药物半衰期,增加药物进入肿瘤组织的总量,提高治疗效果。通过对不同的小片段技术和代表性药物的临床前或临床进展情况进行介绍,以及对其发展方向进行讨论,以期为小型化抗体偶联药物及类似物的研发提供参考。     

Pharmacokinetics and Preventive Effects of Sulfo-Albumin as a Novel Macromolecular Hydrogen Sulfide Prodrug on Carbon Tetrachloride-Induced Hepatic Injury

Hydrogen sulfide (H₂S) has been recently recognized as a gaseous signaling molecule that controls various biological activities. In the present study, we developed sulfo-albumin as a macromolecular H₂S prodrug for therapeutic use, in which multisulfide groups (source of H₂S) were conjugated with bovine serum albumin through a covalent linkage. In an in vitro study on H₂S release in phosphate buffered saline solution, we found that H₂S was released from sulfo-albumin in the presence of 5-mM glutathione but not in its absence. Furthermore, sulfo-albumin was taken up by RAW 264.7 cells, and it released H₂S in cells but not in plasma. These results indicate that H₂S can be selectively released from sulfo-albumin in cells. ¹¹¹In-labeled sulfo-albumin predominantly accumulated in the liver, dependent upon the number of sulfide groups, after intravenous injection in mice. In a carbon tetrachloride-induced acute liver injury mouse model, sulfo-albumin significantly suppressed the increase in plasma aspartate aminotransferase and alanine aminotransferase activities, which are indicators of hepatocyte injury, after intravenous injection. These findings indicate that sulfo-albumin is a promising compound for the treatment of hepatic injuries.     

趋淋巴抗癌药丝裂霉素-右旋糖酐偶联物的合成及生物学性质的研究

利用右旋糖酐(T10 ～500) 局部注射后可选择性被网状上皮细胞或巨噬细胞通过胞饮作用摄取,而不会透过毛细血管壁进入血液,在体内很快被代谢,无毒无滞留的特性,将一定分子量的右旋糖酐(T77) 与抗肿瘤小分子药物丝裂霉素C(mitomycin C,MMC) 通过一个间隔基偶联成高分子靶向抗肿瘤药物:丝裂霉素右旋糖酐偶联物( MMCD) ,对偶联物的生物学性质进行研究,并将该偶联物用于口腔癌淋巴转移的实验性研究中,实验结果说明MMCD具有强的抗肿瘤活性,并具有明显的趋淋巴靶向性     

Design of Hollow Hyaluronic Acid Cylinders for Sustained Intravitreal Protein Delivery

A hollow cylinder intravitreal implant was developed to achieve sustained release of protein to the retina for the treatment of retinal diseases. Hollow cylinders were fabricated by molding and cross-linking hyaluronic acid, the major component of the vitreous humor. Hollow cylinders were filled with a concentrated protein solution, and the properties of the cylinder walls were tested. Cross-linked hyaluronic acid hydrogels with swelling degrees as low as 2.7 were achieved as a means to extend the release of protein. Hollow cylinders were capable of releasing an antigen-binding fragment for over 4 months at a maximum release rate of 4 μg per day. Protein release from hollow cylinders was modeled using COMSOL Multiphysics^® software, and diffusion coefficients between 1.0 × 10^?11 and 3.0 × 10^?11 cm²/s yielded therapeutically effective levels of protein. Cylinders with a 1 mm outer radius were capable of loading >1 mg of protein while releasing at least 2.5 μg a day for over 4.5 months. Although smaller cylinders facilitate intravitreal placement, decreasing the cylinder radius severely limited drug loading. Design of hollow cylinder intravitreal implants must balance high drug loading to reduce device size with control of the diffusion coefficient to sustain protein release.     

Biophysical Properties and Heating-Induced Aggregation of Lysine-Conjugated Antibody-Drug Conjugates

The commercially available antibody-drug conjugate (ADC) product, Kadcyla^® is synthesized using a 2-step reaction, wherein the linker is conjugated to native lysines on the mAb in step 1, followed by drug conjugation to the linker-modified antibody in step 2. In our study, we synthesized a lysine-conjugated ADC (Syn-ADC) on the same trastuzumab scaffold as Kadcyla^® using a 1-step reaction. Mass spectrometry of both products revealed a subpopulation of Kadcyla^® containing free linkers conjugated to the mAb, but not conjugated to the drug, which were absent in the 1-step reaction ADC product. Differential scanning calorimetry thermograms showed that the drug and linker conjugation significantly reduced the thermal stability and energies of activation for the denaturation of the C_H2 domain of the ADCs. The heating induced aggregation events started as early as ～57°C and ～45°C for Kadcyla^® and Syn-ADC, respectively, compared with 71°C for Herceptin^®. The colloidal stability measurements clearly showed that the hydrophobic drug payload on ADCs significantly reduced the repulsive interprotein interactions when compared to the unconjugated antibody under formulation buffer conditions (pH 6.0). Attaching hydrophobic drug and linker moieties onto the antibody lowered the thermal and colloidal stabilities and increased the aggregation propensity of the ADCs.     

寡核苷酸-DNA嵌入剂偶联物的合成

对寡核苷酸－ＤＮＡ嵌入剂偶联物的化学合成途径进行了归纳总结,并对腾的分离、纯化与鉴定方法作简单介绍。ＤＮＡ嵌入剂可先引入到用于寡核苷酸合成的核苷酸单体,然后再通过ＤＮＡ自动合成仪引入到寡核苷酸的预定位点,也可在寡核苷酸合成后解保护之前或之后,通过特异的化学反应直接共价偶联到寡核苷酸的预定位点,通过以上两种途径,可将ＤＮＡ嵌入剂共价偶联到寡核苷酸的３′末端、５′末端,两端或中间位点。     

Synthesis and in Vitro Degradation of Testosterone-Lipid Conjugates

Testosterone-lipid conjugates were obtained by covalent binding of the drug to 1,3-dipalmitoylglycerol via succinic acid to 4-(1,3-dipalmitoyl-2-glyceryl)butyric acid and to 3-palmitoyloxy-2-palmitoyloxymethylpropionic acid. In contrast to the corresponding bis-deacyl derivatives, the lipids were not significantly hydrolyzed in aqueous buffers and in plasma. Incubation with pancreatic lipase yielded primarily the bis-deacyl compounds, which are comparable to monoglycerides, and subsequently slowly liberated testosterone. It is concluded that the lipid conjugates are substrates for pancreatic lipase. However, the drug was released very slowly due to steric hindrance.     

Oxidation-Induced Destabilization of Model Antibody-Drug Conjugates

Oxidation of biopharmaceutics represents a major degradation pathway, which may impact bioactivity, serum half-life, and colloidal stability. This study focused on the quantification of oxidation and its effects on structure and colloidal stability for a model antibody and its lysine (ADC-L) and cysteine (ADC-C) conjugates. The effects of oxidation were evaluated by a forced degradation study using H₂O₂ and a shelf-life simulation, which used degrading polysorbate 80 as source for reactive oxygen species. Differential scanning fluorimetry revealed decreasing transition temperatures of the CH₂ domain with rising oxidation, resulting in a loss of colloidal stability as assessed by size-exclusion high pressure liquid chromatography. The conjugation technique influences structural changes of the monoclonal antibody (mAb) and subsequently alters the impact of oxidation. ADC-C was most effected by oxidation as the CH₂ domain showed the biggest destabilization on conjugation compared to the mAb and ADC-L. Quantification of Fc methionine oxidation by analytical protein A chromatography revealed 4-fold higher oxidation after 8 weeks for the ADC-C compared to the mAb. Payload degradation was observed independently of the conjugation technique used or if free in solution by ultraviolet-visible. In addition, adding antioxidants can be a suitable approach to prevent oxidation and achieve baseline stabilization of the proteins.     

Starlike vs. Classic Macromolecular Prodrugs: Two Different Antibody-Targeted HPMA Copolymers of Doxorubicin Studied in Vitro and in Vivo as Potential Anticancer Drugs

Purpose. Two different monoclonal antibody-targeted HPMA copolymer-doxorubicin conjugates, classic and starlike, were synthesized to be used for site-specific cancer therapy. The anti-mouse Thy-1.2 (IgG3) and two anti-human CD71/A (IgG1) and CD71/B (IgG2a) monoclonal antibodies were used as targeting structures. Methods. Their binding and cytotoxic activity in vitro, body distribution, and anticancer activity in vivo were evaluated. Results. The results of flow cytometric analysis showed comparable binding of classic and starlike conjugates to the target cells. The in vitro cytotoxic effect was 10-fold higher if cancer cells were exposed to the starlike conjugate compared to the classic one. Biodistribution studies showed that the starlike conjugate remained in a relatively high concentration in blood, whereas the classic conjugate was found in a 6.5-times lower amount. In contrast to the low antitumor activity of free doxorubicin and nontargeted HPMA copolymer-doxorubicin conjugate, both anti-Thy-1.2 targeted conjugates (classic and starlike) cured all mice bearing T-cell lymphoma EL4. On the other hand, starlike conjugates containing anti-CD71/A or anti-CD71/B monoclonals as targeting structures were more effective against human colorectal cancer SW 620 than the classic one. Conclusions. We have shown that the starlike conjugates are more effective systems for targeted drug delivery and cancer treatment than classic conjugates.     

Conjugates of Antisense Oligonucleotides with the Tat and Antennapedia Cell-Penetrating Peptides: Effects on Cellular Uptake,Binding to Target Sequences,and Biologic Actions

Purpose. The attainment of effective intracellular delivery remains an important issue for pharmacologic applications of antisense oligonucleotides. Here, we describe the synthesis, binding properties, and biologic properties of peptide-oligonucleotide conjugates comprised of the Tat and Ant cell-penetrating peptides with 2-O-methyl phosphorothioate oligonucleotides. Methods. The biologic assay used in this study measures the ability of the antisense molecule to correct splicing of an aberrant intron inserted into the Luciferase gene; thus, this assay clearly demonstrates the delivery of functional antisense molecules to the splicing machinery within the nucleus. The binding affinities of the conjugates to their target sequences were measured by surface plasmon resonance (BIAcor) techniques. Results. The peptide-oligonucleotide conjugates progressively entered cells over a period of hours and were detected in cytoplasmic vesicles and in the nucleus. Peptide-oligonucleotide conjugates targeted to the aberrant splice site, but not mismatched controls, caused an increase in Luciferase activity in a dose-responsive manner. The kinetics of Luciferase appearance were consistent with the course of the uptake process for the conjugates. The effects of peptide conjugation on the hybridization characteristics of the oligonucleotides were also examined using surface plasmon resonance. The peptide-oligonucleotide conjugates displayed binding affinities and selectivities similar to those of unconjugated oligonucleotides. Conclusions. Conjugation with cell-penetrating peptides enhances oligonucleotide delivery to the nucleus without interfering with the base-pairing function of antisense oligonucleotides.     

聚乙二醇-达沙替尼结合物的合成及初步药效研究

目的 合成2种聚乙二醇-达沙替尼结合物（JK120303和JK120304）,并评价结合物JK120303和JK120304在K562人慢性髓系白血病皮下瘤模型中的抗肿瘤作用。方法 将达沙替尼用缬氨酸衍生后分别和mPEG-二肽酸和4arm-PEG-乙酸反应得到聚乙二醇-达沙替尼结合物,于NOD/SCID小鼠右侧背部皮下接种K562细胞,建立人慢性髓系白血病异种移植动物皮下模型,根据相对肿瘤增殖率进行疗效评价。结果 合成得到2个聚乙二醇-达沙替尼结合物。结合物JK120303（2.5 mg·kg^-1和5 mg·kg^-1）的药效优于达沙替尼（5 mg·kg^-1）,结合物JK120304（2.5 mg·kg^-1和5 mg·kg^-1）的药效与达沙替尼（5 mg·kg^-1）相当。结论 聚乙二醇-达沙替尼结合物JK120303药效优于达沙替尼,值得进一步研究。     

Chitosan Nanoparticles as New Ocular Drug Delivery Systems: in Vitro Stability,in Vivo Fate,and Cellular Toxicity

PURPOSE: To assess the potential of chitosan (CS) nanoparticles for ocular drug delivery by investigating their interaction with the ocular mucosa in vivo and also their toxicity in conjunctival cell cultures. METHODS: Fluorescent (CS-fl) nanoparticles were prepared by ionotropic gelation. The stability of the particles in the presence of lysozyme was investigated by determining the size and their interaction with mucin, by measuring the viscosity of the mucin dispersion. The in vivo interaction of CS-fl nanoparticles with the rabbit cornea and conjunctiva was analyzed by spectrofluorimetry and confocal microscopy. Their potential toxicity was assessed in a human conjunctival cell line by determining cell survival and viability. RESULTS: CS-fl nanoparticles were stable upon incubation with lysozyme and did not affect the viscosity of a mucin dispersion. In vivo studies showed that the amounts of CS-fl in cornea and conjunctiva were significantly higher for CS-fl nanoparticles than for a control CS-fl solution, these amounts being fairly constant for up to 24 h. Confocal studies suggest that nanoparticles penetrate into the corneal and conjunctival epithelia. Cell survival at 24 h after incubation with CS nanoparticles was high and the viability of the recovered cells was near 100%. CONCLUSIONS: CS nanoparticles are promising vehicles for ocular drug delivery.     

Synthesis and In Vitro Evaluation of Chitosan-EDTA-Protease-Inhibitor Conjugates Which Might Be Useful in Oral Delivery of Peptides and Proteins

Purpose. To develop a novel mucoadhesive polymer that protects peptide drugs from degradation by secreted as well as membrane-bound proteases in the intestine, and to evaluate this polymer in vitro. Methods. The serine protease inhibitors antipain, chymostatin and elastatinal were covalently linked to chitosan (poly-[l 4]--D-glucosamine). Thereafter, the complexing agent ethylenediaminete-traacetic acid (EDTA) was bound to the remaining primary amino groups of the polymer. The inhibitory effect of the resulting polymer-conjugate towards trypsin (EC 3.4.21.4), chymotrypsin (EC 3.4.21.1), elastase (3.4.21.36), carboxypeptidase A (EC 3.4.17.1), carboxypeptidase B (EC 3.4.17.2) and aminopeptidase N (EC 3.4.11.2) as well as its mucoadhesive properties were evaluated in vitro. Results. Whereas the novel polymer-conjugate exhibited excellent swelling properties, its adhesive force was under our assay conditions 42% lower than that of unmodified chitosan. However, the polymer-conjugate showed a strong inhibitory activity towards all tested serine proteases. Due to its additional high binding affinity towards bivalent metal ions, it also inhibited the Zn²⁺-dependent exopeptidases carboxypeptidase A, B and aminopeptidase N. Conclusions. The novel mucoadhesive polymer-conjugate described in this study seems to be a useful tool in overcoming the enzymatic barrier to perorally administered therapeutic peptides and proteins.     

Synthesis,Characterization and In Vivo Efficacy of PEGylated Insulin for Oral Delivery with Complexation Hydrogels

Purpose  This work evaluated the feasibility of combining insulin PEGylation with pH responsive hydrogels for oral insulin delivery. Methods  A mono-substituted PEG–insulin conjugate was synthesized and purified. The site of conjugation was determined by MALDI-TOF MS. Uptake and release of PEGylated insulin was performed in complexation hydrogels to simulate oral dosing. The bioactivity of the conjugate and PK/PD profile was measured in vivo in rats. Results  PEGylation was confirmed to be specifically located at the amino terminus of the B-chain of insulin. Higher loading efficiency was achieved with PEGylated insulin than regular human insulin in pH responsive hydrogels. The release of PEGylated insulin was lower than that of human insulin at all pH levels considered. Full retention of bioactivity of the PEG–insulin conjugate was confirmed by intravenous dosing while subcutaneous dosing exhibited a relative hypoglycemic effect 127.8% that of human insulin. Conclusions  Polyethylene glycol conjugated specifically to the amino terminus of the B-chain of insulin maintained the bioactivity of the protein and significantly extended the duration of the hypoglycemic effect. Used in combination with pH responsive hydrogels, PEGylated insulin has significant potential for oral delivery.     

Development of Liposomal Systems of Finasteride for Topical Applications: Design,Characterization, and In Vitro Evaluation

Finasteride (FNS) is a “drug of choice” for benign prostate hypertrophy and prostate cancer. The drug has also been reported to be useful orally in the treatment of some difficult-to-treat androgen-dependent skin disorders, such as seborrhea, acne, hirsutism, and androgenetic alopecia. However, the ideal route for its administration (i.e., topical) remains unexplored. This has logically suggested the search for strategic formulation approaches to make the drug effective on topical applications, hitherto unexplored. The present study targets the encasement of drug molecules in the interiors of vesicular compartments (liposomes) made up of hydrogenated phospholipids, as an attempt toward the development of a trans-epidermal therapeutic system of FNS. Multilamellar drug-loaded liposomes were prepared by thin-film hydration with sonication method and optimized with respect to drug payload, entrapment efficiency, and size by formulating different vesicular compositions under different process conditions. The vesicular systems consisting of saturated phospholipid (100 mg), cholesterol (50 mg), and FNS (5 mg) showed highest drug payload (2.9 mg/100 mg of total lipids), and drug entrapment efficiency (88.6%). Mean (± SD) vesicle size of the prepared liposomes was found to be 3.66 ± 1.6 μm. Significantly higher skin permeation of FNS through excised abdominal mice skin of FNS was achieved from the liposomal formulations vis-à-vis corresponding solution and conventional gels. Liposomal FNS formulations also showed more than fivefold higher deposition of drug in skin than the corresponding plain drug solution and conventional gel. Stability studies indicated that the liposomal formulations were quite stable in the refrigerated conditions for 2 months with negligible drug leakage or vesicle size alteration during the storage period. Results of the current studies with FNS-loaded vesicular systems project the high plausibility of a topical liposomal formulation for effective localized delivery of Finasteride.     

Design of Virus-Mimicking Polyelectrolyte Complexes for Enhanced Oral Insulin Delivery

The viscous and elastic mucus layer is still an undesirable barrier for oral insulin delivery. To solve the problem, virus-mimicking nanosized polyelectrolyte complex (PEC) was designed and their capacity in enhancing peroral insulin absorption in combination with bifunctional material sodium dodecyl sulfate (SDS) coating was investigated. Inspired by nature, virus-mimicking chitosan (CS)-modified L-Phe derivatives were synthesized to simulate the components of viral envelopes and then PECs between CS-g-N-Phe copolymers and insulin were prepared to achieve both structure and composition simulation of virus envelope. Based on the results from both in vitro and in vivo studies, it was concluded that in vitro mucodiffusion and in vivo hypoglycemic effect were dependent on L-Phe graft ratio, with CS-g-N-Phe_20.2%/insulin PECs presenting 2.0- to 2.2-fold higher relative pharmacological bioavailability than nonmodified CS/insulin PECs. Thereafter, SDS solution was applied as outer layer coating on the surface of virus-mimicking PECs. The coated PECs showed improved enzymatic stability, enhanced transport across mucus layer as well as intestinal epithelium in an SDS concentration–dependent manner, with 0.6% SDS coating presenting the best effect, with further enhanced relative pharmacological bioavailability in healthy rats and prolonged therapeutic effect up to 9 h.