Impact of a CXCL12/CXCR4 Antagonist in Bleomycin (BLM) Induced Pulmonary Fibrosis and Carbon Tetrachloride (CCl4) Induced Hepatic Fibrosis in Mice.

Modulation of chemokine CXCL12 and its receptor CXCR4 has been implicated in attenuation of bleomycin (BLM)-induced pulmonary fibrosis and carbon tetrachloride (CCl4)-induced hepatic injury. In pulmonary fibrosis, published reports suggest that collagen production in the injured lung is derived from fibrocytes recruited from the circulation in response to release of pulmonary CXCL12. Conversely, in hepatic fibrosis, resident hepatic stellate cells (HSC), the key cell type in progression of fibrosis, upregulate CXCR4 expression in response to activation. Further, CXCL12 induces HSC proliferation and subsequent production of collagen I. In the current study, we evaluated AMD070, an orally bioavailable inhibitor of CXCL12/CXCR4 in alleviating BLM-induced pulmonary and CCl4-induced hepatic fibrosis in mice. Similar to other CXCR4 antagonists, treatment with AMD070 significantly increased leukocyte mobilization. However, in these two models of fibrosis, AMD070 had a negligible impact on extracellular matrix deposition. Interestingly, our results indicated that CXCL12/CXCR4 signaling has a role in improving mortality associated with BLM induced pulmonary injury, likely through dampening an early inflammatory response and/or vascular leakage. Together, these findings indicate that the CXCL12-CXCR4 signaling axis is not an effective target for reducing fibrosis.

Assessing the oral bioavailability of difluorosialic acid prodrugs, potent viral neuraminidase inhibitors, using a snapshot PK screening assay.

Difluorosialic acids (DFSAs) are potent inhibitors of viral neuraminidase that demonstrate activity against oseltamivir- and zanamivir-resistant strains of influenza. Unfortunately, low oral bioavailability precludes their development as second generation neuraminidase inhibitors for treating influenza as this leaves them unsuitable for use in an oral formulation. Herein is described the preparation of a series of DFSA prodrugs designed to increase oral bioavailability. These prodrugs were evaluated using a snapshot PK screen and stability tests, with successful candidates being further assessed with a full pharmacokinetic workup. These new prodrugs increased oral bioavailability by up to three times that seen for the parent DFSAs.

Irinophore C™, a lipid nanoparticle formulation of irinotecan, abrogates the gastrointestinal effects of irinotecan in a rat model of clinical toxicities.

Irinotecan is a water-soluble camptothecin derivative with clinical activity against colorectal and small cell lung cancers and is currently a standard of care therapeutic in the treatment of colorectal cancer in combination with 5-fluorouracil. One of the major clinical issues limiting the use of irinotecan is gastrointestinal toxicity manifested as life-threatening diarrhea which is reported in up to 45% of treated patients. The studies summarized here tested, in a rat model of irinotecan-associated gastro-intestinal toxicity, whether a lipid nanoparticle formulation of irinotecan, Irinophore C™, mitigated early-onset or late-onset diarrhea when given at doses equivalent to unformulated irinotecan that engenders both early- and late-onset diarrhea. Specifically, rats administered intravenously on two consecutive days with unformulated irinotecan at 170 mg/kg then 160 mg/kg experienced transient early-onset diarrhea after each administration and then experienced significant late-onset diarrhea peaking 4 days after treatment. Irinophore C™ given at the identical dose and schedule did not elicit either early- or late-onset diarrhea in any animals. When Irinophore C™ was combined with 5-fluorouracil there was also no early- or late-onset diarrhea observed. Histopathological analysis of the gastro-intestinal tract confirmed that the effects associated with irinotecan treatment were absent in rats given Irinophore C™ at the identical dose. Pharmacokinetic analysis demonstrated significantly higher systemic concentrations of irinotecan in rats given the nanoparticle formulation compared to those given unformulated irinotecan. These results demonstrate that the Irinophore C™ formulation is significantly less toxic than irinotecan, used either as a single agent or in combination with 5-fluorouracil, in a rat model of irinotecan-induced gastrointestinal toxicity.

Novel ligands balance estrogen receptor ß and α agonism for safe and effective suppression of the vasomotor response in the ovariectomized female rat model of menopause.

Vasomotor thermo-dysregulation (hot flashes) are an often debilitating symptom of menopause. Effective treatment is achieved primarily through activation of the estrogen receptor (ER)α with estrogens but is also associated with increased risk for breast and uterine cancer. In this study, we have tested novel compounds lacking the B ring of 17-hydroxy-ß-estradiol (E2) (A-CD compounds) with differing ratios of ERα:ERß binding affinities for the ability to reduce diurnal/nocturnal tail-skin temperatures (TSTs) in the ovariectomized female rat menopausal hot flash model. Normal mammary tissue expresses the predominantly antiproliferative ERß. Therefore, we hypothesized that a preferential ERß agonist with fractional ERα activity would safely reduce TSTs. The A-CD compound, L17, is a preferential ERß agonist that has a ratio of ERß:ERα binding affinity relative to E2 of 9.3 (where ERß:ERα for E2, 1.0). In the ovariectomized rat, daily administration of low doses (1 mg/kg) of the A-CD compound TD81 (ERα:ERß relative affinity, 15.2) was ineffective in temperature regulation, whereas L17 showed a trend toward TST reduction. Both E2 and the A-CD compound, TD3 (ERß:ERα relative affinity, 5.0), also reduced TSTs but had marked proliferative effects on mammary and uterine tissues. At 2 mg/kg, L17 strongly reduced TSTs even more effectively than E2 but, importantly, had only minimal effect on uterine weight and mammary tissues. Both E2- and L17-treated rats showed similar weight reduction over the treatment period. E2 is rapidly metabolized to highly reactive quinones, and we show that L17 has 2-fold greater metabolic stability than E2. Finally, L17 and E2 similarly mediated induction of c-fos expression in neurons within the rat thermoregulatory hypothalamic median preoptic nucleus. Thus, the A-CD compound, L17, may represent a safe and effective approach to the treatment of menopausal hot flashes.

The autophagy inhibitor verteporfin moderately enhances the antitumor activity of gemcitabine in a pancreatic ductal adenocarcinoma model.

Pancreatic ductal adenocarcinoma (PDAC) is highly resistant to chemotherapy. It has been described as requiring elevated autophagy for growth and inhibiting autophagy has been proposed as a treatment strategy. To date, all preclinical reports and clinical trials investigating pharmacological inhibition of autophagy have used chloroquine or hydroxychloroquine, which interfere with lysosomal function and block autophagy at a late stage. Verteporfin is a newly discovered autophagy inhibitor that blocks autophagy at an early stage by inhibiting autophagosome formation. Here we report that PDAC cell lines show variable sensitivity to verteporfin in vitro, suggesting cell-line specific autophagy dependence. Using image-based and molecular analyses, we show that verteporfin inhibits autophagy stimulated by gemcitabine, the current standard treatment for PDAC. Pharmacokinetic and efficacy studies in a BxPC-3 xenograft mouse model demonstrated that verteporfin accumulated in tumors at autophagy-inhibiting levels and inhibited autophagy in vivo, but did not reduce tumor volume or increase survival as a single agent. In combination with gemcitabine verteporfin moderately reduced tumor growth and enhanced survival compared to gemcitabine alone. While our results do not uphold the premise that autophagy inhibition might be widely effective against PDAC as a single-modality treatment, they do support autophagy inhibition as an approach to sensitize PDAC to gemcitabine.

Treatment of colorectal cancer using a combination of liposomal irinotecan (Irinophore C™) and 5-fluorouracil.

PURPOSE: To investigate the use of liposomal irinotecan (Irinophore C™) plus or minus 5-fluorouracil (5-FU) for the treatment of colorectal cancer. EXPERIMENTAL DESIGN: The effect of irinotecan (IRI) and/or 5-FU exposure times on cytotoxicity was assessed in vitro against HT-29 or LS174T human colon carcinoma cells. The pharmacokinetics and biodistribution of Irinophore C™ (IrC™) and 5-FU, administered alone or in combination, were compared in vivo. A subcutaneous model of HT-29 human colorectal cancer in Rag2-M mice was utilized to assess the efficacy of IrC™ alone, and in combination with 5-FU. RESULTS: The cytotoxicity of IRI and 5-FU were strongly dependent on exposure time. Synergistic interactions were observed following prolonged exposure to IRI/5-FU combinations. Pharmacokinetics/biodistribution studies demonstrated that the 5-FU elimination rate was decreased significantly when 5-FU was co-administered intravenously with IrC™, versus alone. Significant decreases in 5-FU elimination were also observed in plasma, with an associated increase of 5-FU in some tissues when 5-FU was given by intraperitoneal injection and IrC™ was given intravenously. The elimination of IrC™ was not significantly different when administered alone or in combination with 5-FU. Therapeutic studies demonstrated that single agent IrC™ was significantly more effective than the combination of IRI/5-FU; surprisingly, IrC™/5-FU combinations were no more effective than IrC™ alone. The administration of combinations of 5-FU (16 mg/kg) and IrC™ (60 mg IRI/kg) showed increased toxicity when compared to IrC™ alone. Treatment with IrC™ alone (60 mg IRI/kg) delayed the time required for a 5-fold increase in initial tumor volume to day 49, compared to day 23 for controls. When IrC™ (40 mg IRI/kg) was used in combination with 5-FU (16 mg/kg), the time to increase tumor volume 5-fold was 43 days, which was comparable to that achieved when using IrC™ alone (40 mg IRI/kg). CONCLUSIONS: Single agent IrC™ was well tolerated and has significant therapeutic potential. IrC™ may be a suitable replacement for IRI treatment, but its use with free 5-FU is complicated by IrC™-engendered changes in 5-FU pharmacokinetics/biodistribution which are associated with increased toxicity when using the combination.

Development of a weak-base docetaxel derivative that can be loaded into lipid nanoparticles.

Hydrophobic uncharged drugs such as docetaxel are difficult to encapsulate and retain in liposomal nanoparticles (LNP). In this work we show that a weak base derivative of docetaxel can be actively loaded into LNP using pH gradient loading techniques to achieve stable drug encapsulation and controlled release properties. Docetaxel was derivatized at the hydroxyl group in the C-2' position to form an N-methyl-piperazinyl butanoic acid ester. The free hydroxyl group in this position is essential for anticancer activity and the prodrug has, therefore, to be converted into the parent drug (docetaxel) to restore activity. Cytotoxicity testing against a panel of cancer cell lines (breast, prostate and ovarian cancer) demonstrated that the prodrug is readily converted into active drug; the derivative was found to be as active as the parent drug in vitro. The docetaxel derivative can be efficiently loaded at high drug-to-lipid ratios (up to 0.4 mg/mg) into LNP using pH loading techniques. Pharmacokinetic, tolerability and efficacy studies in mice demonstrate that the LNP-encapsulated prodrug has the long drug circulation half-life required for efficient tumor accumulation (50-100 times higher drug plasma levels compared with free derivative and Taxotere, the commercial docetaxel formulation), is active in a xenograft model of breast cancer (MDA-MB-435/LCC6), and is well tolerated at i.v. doses of 3 times higher than the maximum tolerated dose (MTD) of the parent drug. This is the first demonstration that a therapeutically active, remote-loaded, controlled-release LNP formulation of a taxane can be achieved. The approach reported here has broad applicability to other approved drugs as well as new chemical entities.

Irinophore C: a liposome formulation of irinotecan with substantially improved therapeutic efficacy against a panel of human xenograft tumors.

PURPOSE: To assess the pharmacokinetics, tumor drug accumulation, and therapeutic activity of Irinophore C, a novel liposomal formulation of irinotecan (CPT-11). EXPERIMENTAL DESIGN: The plasma lactone/carboxy levels of CPT-11 and SN-38 were determined in mice after a single i.v. dose of irinotecan (Camptosar), or Irinophore C, and the plasma t(1/2), plasma area under the curve, plasma C(max), and plasma clearance were calculated. Further, plasma and tumor drug levels were also measured in tumor-bearing mice following Irinophore C treatment. The efficacy of Irinophore C was compared with that of Camptosar in five s.c. human tumor xenografts using single-dose treatment (LS 180), a total of three doses administered at 4-day intervals (H460), or a total of three doses administered at 7-day intervals (Capan-1, PC-3, and HT-29). RESULTS: Compared with Camptosar, Irinophore C mediated an 8-fold increase in t(1/2), a 100-fold increase in C(max), a 1,000-fold increase in area under the curve, and a 1,000-fold decrease in clearance for the active lactone form of CPT-11. Further, the plasma and tumor SN-38 lactone levels were consistent for at least 48 h post-Irinophore C injection. Camptosar treatment (40 mg/kg) mediated a delay in the time required for tumors to increase to four times their pretreatment size compared with controls (T-C). T-Cs ranged from 2 days (LS 180 model) to 18 days (PC-3 model). Irinophore C (40 mg/kg) engendered T-Cs ranging from 14 days (LS 180 model) to 87 days (Capan-1 model). CONCLUSION: Irinophore C improved CPT-11/SN-38 pharmacokinetics, promoted tumor drug accumulation, and increased therapeutic efficacy in a panel of five distinct human tumor xenografts.

A novel liposomal irinotecan formulation with significant anti-tumour activity: use of the divalent cation ionophore A23187 and copper-containing liposomes to improve drug retention.

We determined whether the method used to encapsulate irinotecan into 1,2-distearoyl-sn-glycero-phosphocholine/cholesterol (DSPC/Chol; 55:45 mol%) liposomes influenced: (i) irinotecan release rate and (ii) therapeutic efficacy. DSPC/Chol (55:45 mol%) liposomes were prepared with: (i) unbuffered CuSO4; (ii) buffered (pH 7.5) CuSO4; (iii) unbuffered MnSO4 and the ionophore A23187 (exchanges internal metal2+ with external 2H+ to establish and maintain a transmembrane pH gradient); and (iv) unbuffered CuSO4 and ionophore A23187. All formulations exhibited >98% irinotecan encapsulation (0.2 drug-to-lipid molar ratio; 10 min incubation at 50 degrees C). Following a single intravenous injection (100mg/kg irinotecan) into Balb/c mice, the unbuffered CuSO4 plus A23187 formulation mediated a half-life of irinotecan release of 44.4h; a >or=4-fold increase compared to the other liposome formulations. This surprising observation demonstrated that the CuSO4 plus A23187 formulation enhanced irinotecan retention compared to the MnSO4 plus A23187 formulation, indicating the importance of the divalent metal. A single dose of the CuSO4 plus A23187 formulation (50mg/kg irinotecan) mediated an 18-fold increase in median T-C (the difference in days for treated and control subcutaneous human LS 180 adenocarcinoma xenografts to increase their initial volume by 400%) when compared to a comparable dose of Camptosar. Improved irinotecan retention was associated with increased therapeutic activity.

Influence of poly(ethylene glycol) grafting density and polymer length on liposomes: relating plasma circulation lifetimes to protein binding.

The incorporation of poly(ethylene glycol) (PEG)-conjugated lipids in lipid-based carriers substantially prolongs the circulation lifetime of liposomes. However, the mechanism(s) by which PEG-lipids achieve this have not been fully elucidated. It is believed that PEG-lipids mediate steric stabilization, ultimately reducing surface-surface interactions including the aggregation of liposomes and/or adsorption of plasma proteins. The purpose of the studies described here was to compare the effects of PEG-lipid incorporation in liposomes on protein binding, liposome-liposome aggregation and pharmacokinetics in mice. Cholesterol-free liposomes were chosen because of their increasing importance as liposomal delivery systems and their marked sensitivity to protein binding and aggregation. Specifically, liposomes containing various molecular weight PEG-lipids at a variety of molar proportions were analyzed for in vivo clearance, aggregation state (size exclusion chromatography, quasi-elastic light scattering, cryo-transmission and freeze fracture electron microscopy) as well as in vitro and in vivo protein binding. The results indicated that as little as 0.5 mol% of 1,2-distearoyl-sn-glycero-3-phosphatidylethanolamine (DSPE) modified with PEG having a mean molecular weight of 2000 (DSPE-PEG(2000)) substantially increased plasma circulation longevity of liposomes prepared of 1,2-distearoyl-sn-glycero-3-phosphatidylcholine (DSPC). Optimal plasma circulation lifetimes could be achieved with 2 mol% DSPE-PEG(2000). At this proportion of DSPE-PEG(2000), the aggregation of DSPC-based liposomes was completely precluded. However, the total protein adsorption and the protein profile was not influenced by the level of DSPE-PEG(2000) in the membrane. These studies suggest that PEG-lipids reduce the in vivo clearance of cholesterol-free liposomal formulations primarily by inhibition of surface interactions, particularly liposome-liposome aggregation.

Coencapsulation of irinotecan and floxuridine into low cholesterol-containing liposomes that coordinate drug release in vivo.

A liposomal delivery system that coordinates the release of irinotecan and floxuridine in vivo has been developed. The encapsulation of floxuridine was achieved through passive entrapment while irinotecan was actively loaded using a novel copper gluconate/triethanolamine based procedure. Coordinating the release rates of both drugs was achieved by altering the cholesterol content of distearoylphosphatidylcholine (DSPC)/distearoylphosphatidylglycerol (DSPG) based formulations. The liposomal retention of floxuridine in plasma after intravenous injection was dramatically improved by decreasing the cholesterol content of the formulation below 20 mol%. In the case of irinotecan, the opposite trend was observed where increasing cholesterol content enhanced drug retention. Liposomes composed of DSPC/DSPG/Chol (7:2:1, mole ratio) containing co-encapsulated irinotecan and floxuridine at a 1:1 molar ratio exhibited matched leakage rates for the two agents so that the 1:1 ratio was maintained after intravenous administration to mice. The encapsulation of irinotecan was optimal when copper gluconate/triethanolamine (pH 7.4) was used as the intraliposomal buffer. The efficiency of irinotecan loading was approximately 80% with a starting drug to lipid molar ratio of 0.1/1. Leakage of floxuridine from the liposomes during irinotecan loading at 50 degrees C complicated the ability to readily achieve the target 1:1 irinotecan/floxuridine ratio inside the formulation. As a result, a procedure for the simultaneous encapsulation of irinotecan and floxuridine was developed. This co-encapsulation method has the advantage over sequential loading in that extrusion can be performed in the absence of chemotherapeutic agents and the drug/drug ratios in the final formulation can be more precisely controlled.

In vitro and in vivo characterization of a combination chemotherapy formulation consisting of vinorelbine and phosphatidylserine.

The purpose of these studies was to design an intravenous drug formulation consisting of two active agents having synergistic in vitro activity. Specifically, we describe a novel drug combination consisting of a cytotoxic agent (vinorelbine) with an apoptosis-inducing lipid (phosphatidylserine, PS). In vitro cytotoxicity screening of PS and vinorelbine, alone and in combination, against human MDA435/LCC6 breast cancer and H460 lung cancer cells was used to identify the molar ratio of these two agents required for synergistic activity. PS and vinorelbine were co-formulated in a lipid-based system at the synergistic molar ratio and the pharmacokinetic and antitumor characteristics of the combination assessed in mice bearing H460 tumors. The cytotoxicity of the lipid, and the synergy between the lipid and vinorelbine, were specific to PS; these effects were not observed using control lipids. A novel formulation of PS, incorporated as a membrane component in liposomes, and encapsulating vinorelbine using a pH gradient based loading method was developed. The PS to vinorelbine ratio in this formulation was 1/1, a ratio that produced synergistic in vitro cytotoxicity over a broad concentration range. The vinorelbine and PS dual-agent treatment significantly delayed the growth of subcutaneous human H460 xenograft tumors in Rag2M mice compared to the same dose of free vinorelbine given alone or given as a cocktail of the free vinorelbine simultaneously with empty PS-containing liposomes. These studies demonstrate the potential to develop clinically relevant drug combinations identified using in vitro drug-drug interactions combined with lipid-based delivery systems to co-formulate drugs at their synergistic ratios.

Liposomal drug delivery: recent patents and emerging opportunities.

It is challenging to develop innovative, as well as commercially viable, lipid-based drug delivery systems for the treatment of cancer because of the breadth of existing intellectual property that limits freedom-to-operate. For example, novel compositions can be described in which a new chemical entity is associated with a lipid based carrier, but if the loading method or components of the lipid compositions are proprietary then the ability to develop novel compositions will require access to the appropriate intellectual property. We believe it is useful to present a review of the patent literature describing novel liposomal drug delivery systems given by parenteral administration to humans for the treatment of serious medical conditions such as cancer. This review is intended to: (i) identify and describe novel approaches that have recently been protected by US or international patents and patent applications, and; (ii) identify founding technology in the field which is recently off-patent, thus presenting emerging opportunities for the development of new therapeutic options for patients. Issued patents, and selected patent applications, having publication dates in 2005 or 2006 were retrieved from searches of the US, European, German, Japanese, INPADOC and WIPO PCT databases. Liposomal delivery systems patented for systemic administration in the treatment of human medical conditions were reviewed in detail.

Transition metal-mediated liposomal encapsulation of irinotecan (CPT-11) stabilizes the drug in the therapeutically active lactone conformation.

PURPOSE: To determine whether entrapped transition metals could mediate the active encapsulation of the anticancer drug irinotecan into preformed liposomes. Further, to establish that metal complexation could stabilize liposomal irinotecan in the therapeutically active lactone conformation. MATERIALS AND METHODS: Irinotecan was added to preformed 1,2-distearoyl-sn-glycero-phosphocholine/cholesterol (DSPC/chol) liposomes prepared in CuSO4, ZnSO4, MnSO4, or CoSO4 solutions, and drug encapsulation was determined over time. The roles of the transmembrane pH gradient and internal pH were evaluated. TLC and HPLC were used to monitor drug stability and liposome morphology was assessed by cryo-TEM. RESULTS: Irinotecan was rapidly and efficiently loaded into preformed liposomes prepared in unbuffered (approximately pH 3.5) 300 mM CuSO4 or ZnSO4. For Cu-containing liposomes, results suggested that irinotecan loading occurred when the interior pH and the exterior pH were matched; however, addition of nigericin to collapse any residual transmembrane pH gradient inhibited irinotecan loading. Greater than 90% of the encapsulated drug was in its active lactone form and cryo-TEM analysis indicated dark intravesicular electron-dense spots. CONCLUSION: Irinotecan is stably entrapped in the active lactone conformation within preformed copper-containing liposomes as a result of metal-drug complexation.

Gene silencing in the development of personalized cancer treatment: the targets, the agents and the delivery systems.

The advent of sophisticated experimental tools that can probe the molecular pathology of cancer has revealed a number of genes and gene families that could prove attractive targets for cancer therapy. Thus, gene silencing strategies have been envisioned to treat cancer by targeting the cancer cell's capacity to: (I) resist conventional treatment methods (chemotherapy and radiotherapy), (II) promote angiogenesis, and (III) metastasize and/or to survive microenvironments that normally would promote cell apoptosis/necrosis. The realization of such strategies is limited by the lack of pharmaceutically-viable technologies that enable the safe and effective delivery of gene-targeting agents to neoplastic cells following systemic administration. There are many reasons for this, including an incomplete understanding of how cancer cells respond when genes are silenced. Further the pharmacokinetic and pharmacodynamic attributes of gene therapy products are not well understood. This review will discuss gene therapy strategies that have been developed based on gene inhibition by the use of antisense oligonucleotides, ribozymes and RNA interference (RNAi). In this context, several particularly promising targets will be described, with a focus on strategies that have progressed to the stage where clinical trials have been initiated. The review highlights product development strategies that emphasize non-viral systemic formulations and the potential for delivery systems to become an enabling technology for development of effective gene therapy products.

Copper-topotecan complexation mediates drug accumulation into liposomes.

These studies describe the role of transition metal ions in the liposomal encapsulation of topotecan. Liposomes (1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol (CH) (55:45, mole ratio)) were prepared with manganese (Mn), copper (Cu), zinc (Zn) or cobalt (Co) ion gradients (metal inside). Subsequently, topotecan was added to the liposome exterior (final drug-to-lipid ratio (mol/mol) of 0.2) and drug encapsulation was measured as a function of time and temperature. No drug loading was achieved with liposomes containing Co or Zn. Topotecan could be encapsulated into Mn-containing liposomes only in the presence of the ionophore, A23187 suggesting that a transmembrane pH gradient was necessary. However, Cu-containing liposomes, in the presence or absence of an imposed pH gradient, efficiently encapsulated topotecan. It has been reported that Cu(II) can form transition metal complexes with camptothecin; therefore, the Cu-topotecan interaction was characterized in solution as a function of pH. These investigations demonstrated that topotecan inhibited formation of an insoluble Cu hydroxide precipitate. Cryo-TEM analysis of the topotecan-loaded Cu liposomes showed electron-dense intravesicular precipitates. Further studies demonstrated that only the active lactone form of the drug was encapsulated and this form predominated in Cu-containing liposomes. Copper complexation reactions define a viable methodology to prepare liposomal camptothecin formulations.

Preparation, characterization, and biological analysis of liposomal formulations of vincristine.

Vincristine is a dimeric Catharanthus alkaloid derived from the Madagascan periwinkle that acts by binding to tubulin and blocking metaphase in actively dividing cells. While vincristine is widely used in the treatment of a number of human carcinomas, its use is associated with dose-limiting neurotoxicity, manifested mainly as peripheral neuropathy. It is known that the therapeutic activity of vincristine can be significantly enhanced after its encapsulation in appropriately designed liposomal systems. Enhanced efficacy is also associated with a slight decrease in drug toxicity. Thus, the therapeutic index of vincristine can be enhanced significantly through the use of a liposomal delivery system. Vincristine may be encapsulated into liposomes of varying lipid composition by several techniques, including passive loading, pH gradient loading, and ionophore-assisted loading. However, most research has focused on the encapsulation of vincristine in response to a transbilayer pH gradient, which actively concentrates the drug within the aqueous interior of the liposome. This chapter details the preparation and evaluation of liposomal vincristine. Specifically, we elaborate on the components (choice of lipids, molar proportions, etc.), methods (preparation of liposomes, drug loading methods, etc.), critical design features (size, surface charge, etc.), and key biological endpoints (circulation lifetime, bioavailability, efficacy measurements) important to the development of a formulation of vincristine with enhanced therapeutic properties.

A literature review of single agent treatment of multiply relapsed aggressive non-Hodgkin's lymphoma.

To analyze the available literature describing the treatment of relapsed aggressive non-Hodgkin's lymphoma (NHL) with single-agent chemotherapies, several comprehensive electronic and manual inspections of the literature were performed for the period from 1966 to the present. Each paper was examined to capture the following data: study type; patient demographics and characteristics; study endpoints, including responses, and method used to evaluate response; toxicities, and the power of the study. A wide variety of single-agent protocols continue to be studied, indicating no currently accepted standard therapy in this patient population. Reported response rates varied between 0 and 67%. The majority of trials were small, uncontrolled studies that used widely varying inclusion/exclusion criteria and had limited reporting of histology, response, prior treatments, and other key parameters. We were able to find only four agents, etoposide, vincristine, vinorelbine and possibly rituximab, with sufficient reproducible evidence to suggest greater than 30% activity (CR + PR rate) when given to patients with second or greater relapse of aggressive NHL. Consequently, the usefulness of the agents in these reports remains to be established in larger trials with more detailed reporting. The advantages that would be brought by an active non-myelosuppressive agent for patients having this condition emerge clearly from this review.