Encapsulation Of Doxorubicin Research Articles

Development of polymeric drug delivery system for recognizing vascular endothelial dysfunction

The vascular endothelium plays an important role in regulating vascular homeostasis. Damage to the endothelium can lead to cardiovascular diseases such as arteriosclerosis. Therefore, early-stage detection and evaluation of vascular endothelium dysfunction would be very important for effective diagnosis and therapy. We synthesized a polymeric drug carrier bearing an Evans blue analogue as a probing unit for endothelium injury. The polymeric carrier spontaneously formed stable nanoparticles with micelle-like structure in aqueous media and could encapsulate hydrophobic doxorubicin (DOX). The encapsulated DOX showed a sustainable release profile over a period of 10-60 h depending on the loaded DOX concentration. The polymeric carrier specifically adsorbed against the endothelium-injured site in extracted porcine aorta. These properties of the polymeric drug carrier will be suitable for specific drug delivery to endothelium dysfunctional region.

A Simple One-Step Protocol for Preparing Small-Sized Doxorubicin-Loaded Liposomes

A simple, single-step, extrusion-free protocol for preparing doxorubicin-loaded liposomes (100150 nm), based on the ethanol injection method (EIM), is described. Efficient encapsulation of doxorubicin (up to 98%) was obtained concomitantly with liposome preparation avoiding the need for an additional loading step. Parameters such as stock concentration of phospholipid, injection ratio, lipid composition, and drug-to-phospholipid ratio affected the resultant liposome size and magnitude of doxorubicin encapsulation. A lipid stock concentration (50 mM) and injection ratio (1:10) resulted in 96.0 +/- 2.92% encapsulation efficiency of doxorubicin (drug-to-lipid mole ratio: 0.192) and mean diameter of 135 +/- 2.32 nm for SCOL-2 formulation (DSPC/ cholesterol /oleic acid: 2/2/1; molar ratios). Replacement of phospholipid DSPC with DMPC or DPPC did not affect the mean liposome size and doxorubicin-encapsulation efficiency. These findings offer promise for scale-up and development on a large-scale production of doxorubicin-loaded liposomes for effective cancer therapy.

Non-Pegylated Lyposomal Doxorubicin, Cyclophosphamide, Vincristine, Prednisone and Rituximab (R-COMP) as Initial Treatment for Patients with Splenic Marginal Zone Lymphoma (SMZL). A GISL Study

Background: SMZL is an indolent lymphoma, presenting with massive splenomegaly generally associated with intrasinusoidal bone marrow infiltration. The encapsulation of doxorubicin into non-pegylated liposomes allows targeting of the drug to affected organs including spleen, lymphnodes and bone marrow.Methods: In 2005 the GISL started a phase II study for the treatment of patients with histologically confirmed SMZL, investigating safety and clinical profile of 6 courses of a modified R-CHOP regimen in which standard doxorubicin was substituted with non pegylated lyposomal doxorubicin (NPLD) used at the same doses (50mg/m2) (R-COMP). Main inclusion criteria were age > 18 yrs, normal cardiac function and active disease (at least one of the following; Hb <10g/dl; plt <100.000/mmc, symptomatic splenomegaly, elevated LDH, B symptoms, extrasplenic disease, LDT <12 months). Splenectomy was allowed prior to treatment start only in case of symptomatic spleen enlargement. The study was planned according to a two-stage Simon design using overall response rate as primary endpoint. We present the results of the analysis performed after the completion of study stage 1. The access to stage 2 is allowed if at least 12 responses are recorded among among the first 19 evaluable cases.Results: As of January 2007, 20 patient were enrolled with the following characteristics; median age 63 years (30–80), Hb <10g/dl in 20%, Lymphocytes > 5000/mmc in 65%, elevated LDH in 65%; 2 patients were splenectomized before treatment start. One patient was not available for response assessment. A clinical response was observed in all remaining 19 cases (ORR 100%); 12 (63%) cases obtained a CR. So far only one patient progressed at +1 month from treatment. Treatment was well tolerated with grade III/IV neutropenia in 8 patients (42%), grade III pulmonary toxicity in 1 patient and grade II peripheral neuropathy in 5 cases. In one case a reversible cardiac failure was reported after 1 month from the end of treatment.Conclusions: In conclusion 6 cycles of R-COMP combination represent a safe and promising treatment option for patients with clinically active SMZL.

Clinical and Pharmacokinetic Characteristics of Intracavitary Administration of Pegylated Liposomal Encapsulated Doxorubicin in Dogs with Splenic Hemangiosarcoma

Background: Canine splenic hemangiosarcoma (HSA) is a fatal malignancy, and most affected dogs die within a few months of diagnosis. Most dogs present with signs from tumor rupture, resulting in hemoabdomen and intra‐abdominal dissemination. The abdomen is also the main site of disease recurrence. Hypothesis: Intraperitoneal (IP) administration of doxorubicin will delay or prevent intra‐abdominal tumor recurrence and prolong survival in dogs with HSA. Animals: Fourteen dogs with splenic HSA. Methods: A prospective, unmasked, uncontrolled clinical trial. After staging of disease status and splenectomy, pegylated liposomal encapsulated doxorubicin was administered intraperitoneally (1 mg/kg body weight) every 3 weeks for 4 cycles. All dogs were monitored for recurrence of HSA. Samples of plasma and abdominal fluid were collected for measurement of doxorubicin concentration and pharmacokinetic analysis. Nonlinear mixed‐effect modeling was used to describe the pharmacokinetics of liposomal doxorubicin administered IP. Results: All 14 dogs died, 12 because of HSA and 2 from other causes. Postmortem examination was performed on 12 dogs. All 12 dogs died because of HSA‐related causes and had hepatic metastases and hemoabdomen. The IP‐treated dogs had fewer serosal, mesenteric, and omental metastases than historical controls treated with systemic doxorubicin. Results of the postmortem examination and pharmacokinetic analysis confirmed that IP delivery of doxorubicin resulted in an effective drug concentration with a clearance comparable with that after IV delivery. Conclusions and Clinical Importance: IP pegylated liposomal encapsulated doxorubicin administration did not prevent intra‐abdominal recurrence of HSA in dogs.

Improving Penetration in Tumors With Nanoassemblies of Phospholipids and Doxorubicin

Drug delivery and penetration into neoplastic cells distant from tumor vessels is critical for the effectiveness of solid tumor chemotherapy. We hypothesized that 10- to 20-nm nanoassemblies of phospholipids containing doxorubicin would improve the drug's penetration, accumulation, and antitumor activity. Doxorubicin was incorporated into polyethylene glycol-phosphatidylethanolamine (PEG-PE) block copolymer micelles by a self-assembly procedure to form nanoassemblies of doxorubicin and PEG-PE. In vitro cytotoxicity of micelle-encapsulated doxorubicin (M-Dox) against A549 human non-small-cell lung carcinoma cells was examined using the methylthiazoletetrazolium assay, and confocal microscopy, total internal reflection fluorescence microscopy, and flow cytometry were used to examine intracellular distribution and the cellular uptake mechanism. C57Bl/6 mice (n = 10-40 per group) bearing subcutaneous or pulmonary Lewis lung carcinoma (LLC) tumors were treated with M-Dox or free doxorubicin, and tumor growth, doxorubicin pharmacokinetics, and mortality were compared. Toxicity was analyzed in tumor-free mice. All statistical tests were two-sided. Encapsulation of doxorubicin in PEG-PE micelles increased its internalization by A549 cells into lysosomes and enhanced cytotoxicity. Drug-encapsulated doxorubicin was more effective in inhibiting tumor growth in the subcutaneous LLC tumor model (mean tumor volumes in mice treated with 5 mg/kg M-Dox = 1126 mm3 and in control mice = 3693 mm3, difference = 2567 mm3, 95% confidence interval [CI] = 2190 to 2943 mm3, P<.001) than free doxorubicin (mean tumor volumes in doxorubicin-treated mice = 3021 mm3 and in control mice = 3693 mm3, difference = 672 mm3, 95% CI = 296 to 1049 mm3, P = .0332, Wilcoxon signed rank test). M-Dox treatment prolonged survival in both mouse models and reduced metastases in the pulmonary model; it also reduced toxicity. We have developed a novel PEG-PE-based nanocarrier of doxorubicin that increased cytotoxicity in vitro and enhanced antitumor activity in vivo with low systemic toxicity. This drug packaging technology may provide a new strategy for design of cancer therapies.

Non-pegylated lyposomal doxorubicin, cyclophosphamide, vincristine, prednisone, and rituximab (R-COMP) as initial treatment for patients with splenic marginal zone lymphoma (SMZL): A GISL study

18502 Background: SMZL is an indolent lymphoma, presenting with massive splenomegaly generally associated with intrasinusoidal bone marrow infiltration. The encapsulation of doxorubicin into non-pegylated liposomes allows targeting of the drug to affected organs including spleen, lymphnodes and bone marrow. Methods: In 2005, the GISL started a phase II study for the treatment of patients with histologically confirmed SMZL, investigating safety and clinical profile of 6 courses of a modified R-CHOP regimen in which standard doxorubicin was substituted with non pegylated lyposomal doxorubicin (NPLD) used at the same doses (50 mg/m2) (R-COMP). Main inclusion criteria were age &gt;18 yrs, normal cardiac function and active disease (at least one of the following; Hb &lt;10 g/dl; plt &lt;100,000/mmc, symptomatic splenomegaly, elevated LDH, B symptoms, extrasplenic disease, LDT &lt;12 months). Splenectomy was allowed prior to treatment start only in case of symptomatic spleen enlargement. The study was planned according to a two-stage Simon design using overall response rate as primary endpoint. We present the results of the analysis performed after the completion of study stage 1. The access to stage 2 is allowed if at least 12 responses are recorded among among the first 19 evaluable cases. Results: As of January 2007, 20 patient were enrolled with the following characteristics; median age 63 years (30–80), Hb &lt;10 g/dl in 20%, Lymphocytes &gt; 5,000/mmc in 65%, elevated LDH in 65%; 2 patients were splenectomized before treatment start. One patient was not available for response assessment. A clinical response was observed in all remaining 19 cases (ORR 100%); 12 (63%) cases obtained a CR. So far only one patient progressed at +1 month from treatment. Treatment was well tolerated with grade III/IV neutropenia in 8 patients (42%), grade 3 pulmonary toxicity in 1 patient and grade 2 peripheral neuropathy in 5 cases. In one case a reversible cardiac failure was reported after 1 month from the end of treatment. Conclusions: In conclusion 6 cycles of R-COMP combination represent a safe and promising treatment option for patients with clinically active SMZL. No significant financial relationships to disclose.

Comparative study of doxorubicin-loaded poly(lactide-co-glycolide) nanoparticles prepared by single and double emulsion methods

This study describes how the control of doxorubicin (DOX) polarity allows to encapsulate it inside poly(lactide-co-glycolide) (PLGA) nanoparticles formulated either by a single oil-in-water (O/W) or a double water-in-oil-in-water (W/O/W) emulsification method (SE and DE, respectively). DOX is commercially available as a water soluble hydrochloride salt, which is useful for DE. The main difficulty related to DE approach is that the low affinity of hydrophilic drugs to the polymer limits entrapment efficiency. Compared to DE method, SE protocol is easier and should provide an additional gain in entrapment efficiency. To be encapsulated by SE technique, DOX should be used in a more lipophilic molecular form. We evaluated the lipophilicity of DOX in terms of apparent partition coefficient ( P) and modulated it by adjusting the pH of the aqueous phase. The highest P values were obtained at pH ranging from 8.6 to 9, i. e. between two DOX p K a values (8.2 and 9.6). The conditions favorable for the drug lipophilicity were then used to formulate DOX-loaded PLGA nanoparticles by SE method. DOX encapsulation efficiency as well as release profiles were evaluated for these nanoparticles and compared to those with nanoparticles formulated by DE. Our results indicate that the encapsulation of DOX in nanoparticles formulated by SE provides an increased drug entrapment efficiency and decreases the burst effect.

Clinical and Pharmacokinetic Characteristics of Intracavitary Administration of Pegylated Liposomal Encapsulated Doxorubicin in Dogs with Splenic Hemangiosarcoma

Canine splenic hemangiosarcoma (HSA) is a fatal malignancy, and most affected dogs die within a few months of diagnosis. Most dogs present with signs from tumor rupture, resulting in hemoabdomen and intra-abdominal dissemination. The abdomen is also the main site of disease recurrence. Intraperitoneal (IP) administration of doxorubicin will delay or prevent intra-abdominal tumor recurrence and prolong survival in dogs with HSA. Fourteen dogs with splenic HSA. A prospective, unmasked, uncontrolled clinical trial. After staging of disease status and splenectomy, pegylated liposomal encapsulated doxorubicin was administered intraperitoneally (1 mg/kg body weight) every 3 weeks for 4 cycles. All dogs were monitored for recurrence of HSA. Samples of plasma and abdominal fluid were collected for measurement of doxorubicin concentration and pharmacokinetic analysis. Nonlinear mixed-effect modeling was used to describe the pharmacokinetics of liposomal doxorubicin administered IP. All 14 dogs died, 12 because of HSA and 2 from other causes. Postmortem examination was performed on 12 dogs. All 12 dogs died because of HSA-related causes and had hepatic metastases and hemoabdomen. The IP-treated dogs had fewer serosal, mesenteric, and omental metastases than historical controls treated with systemic doxorubicin. Results of the postmortem examination and pharmacokinetic analysis confirmed that IP delivery of doxorubicin resulted in an effective drug concentration with a clearance comparable with that after i.v. delivery. IP pegylated liposomal encapsulated doxorubicin administration did not prevent intraabdominal recurrence of HSA in dogs.

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Doxorubicin (DOX) has been shown to be one of the most effective agents against glioma cells in vitro but is not used in clinical practice because of its poor blood-brain barrier penetration. The latter can be improved by liposomal encapsulation. We studied the potential radiopotentiation of Myocet® (myo: not pegylated liposomal doxorubicin encapsulation) and/or DOX on 2 glioblastomas and 1 rhabdomyosarcoma (RMS) xenografts. The U87 and TCG4 high grade gliomas and RMS Nan2 were used. Six treatment groups were designed: control, doxorubicin, Myo, radiotherapy (RT), dox + RT, myo + RT. Dox and myo were injected IP at the dose of 2 mg/kg, 3 times a week for 2 consecutive weeks. RT consisted on 2 Gy/d, 5 days a week for 2 consecutive weeks, initiated at the same time as DOX or myo. A biodistribution study was performed to compare free DOX levels in brain, heart, spleen, liver and xenografted tumors in mice which received DOX or myo. The biodistribution study showed a higher concentration of DOX in brain and spleen and a lower concentration in heart for Myo compared with DOX. Only mice treated with DOX died of toxicity. Tumor growth delay was not statistically different for DOX and myo while it was 42 and 55 days respectively for DOX and myo for the RMS xenograft . Radiopotentiation could not be assessed in the DOX + RT group due to high mortality, while no mortality occurred in the myo + RT group. Enhancement ratios of 1.22 and 1.12 were observed in the myo + RT group for the U87 and TCG4 xenografts; all the tumors from the myo + RT group are controlled at day 60 post treatment. Given at the same dose as doxorubicin, Myocet® is markedly less toxic than doxorubicin and appears as a radiosensitizer. An orthotopic glioma xenograft model using Myo + RT is under study.

Accelerated blood clearance of PEGylated liposomes upon repeated injections: Effect of doxorubicin-encapsulation and high-dose first injection

The “accelerated blood clearance (ABC) phenomenon”, causing PEGylated liposomes to be cleared very rapidly from the circulation upon repeated injection, has been reported to occur in rodents and rhesus monkeys. This rapid clearance was reported to be caused by the binding of PEG-specific IgM, which was generated by the first dose of injected liposomes, to the second dose of liposomes and the subsequent activation of complement, serving in turn as an opsonin. Although there are several PEGylated liposomal formulations, such as Doxil/Caelyx loaded with doxorubicin (DXR), in clinical use, the rapid clearance phenomenon has never been reported for such formulations. In the present article, we report that a first injection of PEGylated liposomes containing encapsulated DXR failed to induce the ABC phenomenon. Likewise, no rapid clearance of the test dose was observed when the first dose of “empty” PEGylated liposomes (without DXR) exceeded 5 μmol phospholipids/kg. By contrast, “empty” PEGylated liposomes at a low dose (1 μmol phospholipids/kg) induced the phenomenon as before. Western blot analysis revealed abundant binding of IgM to PEGylated liposomes when these were incubated in serum from rats that had received “empty” PEGylated liposomes. Substantially less binding of IgM was found when the liposomes were incubated in serum from rats treated with DXR-loaded PEGylated liposomes. For both the empty and the DXR-containing liposomes the amounts of IgM binding to the liposomes decreased with an increasing dose of injected liposomes. Serum obtained from rats following injection of empty PEGylated liposomes caused complement activation by addition of PEGylated liposomes in an inversely dose-dependent manner: the lower the dose, the higher the complement activation. By contrast, no complement activation was detected with serum from rats that had been treated with DXR-loaded PEGylated liposomes. These findings suggest that encapsulation of DXR as well as a relatively high lipid dose abrogate the immune response against PEGylated liposomes which is observed with the same liposomes but without DXR and at low doses. Our observations may thus have important implications for the development, evaluation and therapeutic use of liposomal cytotoxic drug formulations requiring multiple injection schemes.

Doxorubicin encapsulation and diffusional release from stable, polymeric, hydrogel nanoparticles

We have recently described the preparation of stable, polymeric nanoparticles, composed of poly(ethylene glycol) and poloxamer 407 (Pluronic ® F127), prepared via inverse emulsion photopolymerization. In the present study we report on the performance of this novel colloidal system as a controlled delivery system for small hydrophobic drugs. Successful encapsulation of doxorubicin occurred through hydrophobic interactions, taking advantage of particle nanoarchitecture. Loadings of up to 8.7 wt.% were achieved with a reproducible, fast, solvent evaporation procedure. In vitro drug release, monitored by fluorescence spectrometry and HPLC, revealed a minor burst (approximately 10% at 37 °C) and sustained, diffusional release for over 1 week; furthermore, drug encapsulation significantly delayed doxorubicin degradation kinetics.

Cytotoxicity of doxorubicin‐loaded Con A‐liposomes

AbstractThe present study investigated the potential of Concanavalin A lectin (Con A) conjugated to liposomes (Con A‐liposomes) for targeting doxorubicin (DOX) to cells. The physicochemical properties and the cytotoxicity of DOX‐loaded Con A‐liposomes were evaluated. DOX‐loaded Con A‐liposomes were prepared by incubation of DOX‐loaded liposomes with a Con A‐SATA derivative. Lectin biological activity was monitored before and after conjugation by a hemagglutinating assay. The cytotoxicity of DOX‐loaded Con A‐liposomes was evaluated in terms of the inhibition of NCI‐H299 and HEp‐2 cell proliferation using the MTT method. The affinity of lectinized liposomes with these cells was thus assessed by evaluating the cytotoxic effect of the DOX released into cells. Stable DOX‐loaded Con A‐liposomes were obtained and their high affinity for cells was corroborated. The encapsulation of DOX into Con A‐liposomes produced an inhibition of roughly 70% of Hep‐2 cell proliferation and 50% of cell inhibition was verified on HCI‐H292. DOX in solution was able to inhibit only 20% of cell proliferation for both cell lines. Unloaded Con A‐liposomes were not cytotoxic. The encapsulation of DOX into Con A‐liposomes improves drug penetration into cells, thereby enhancing its cytotoxicity, especially in Hep‐2 cells. Drug Dev. Res. 67:430–437, 2006. © 2006 Wiley‐Liss, Inc.

Tissue affinity of the infusate affects the distribution volume during convection-enhanced delivery into rodent brains: Implications for local drug delivery

Convection-enhanced delivery (CED) is a recently developed technique for local delivery of agents to a large volume of tissue in the central nervous system (CNS). We have previously reported that this technique can be applied to CNS delivery of nanoparticles including viruses and liposomes. In this paper, we describe the impact of key physical and chemical properties of infused molecules on the extent of CED-mediated delivery. For simple infusates, CED distribution was significantly increased if the infusate was more hydrophilic or had less tissue affinity. Encapsulation of tissue-affinitive molecules by neutral liposomes significantly increased their tissue distribution. The poorer brain distribution observed with cationic liposomes, due to their greater tissue affinity, was completely overcome by PEGylation, which provides steric stabilization and reduced surface charge. Finally, liposomal encapsulation of doxorubicin reduced its tissue affinity and substantially increased its distribution within brain tumor tissue. Taken together, the physical and chemical properties of drugs, small molecules and macromolecular carriers determine the tissue affinity of the infusate and strongly affect the distribution of locally applied agents. Thus, an increased and more predictable tissue distribution can be achieved by reducing the tissue affinity of the infusate using appropriately engineered liposomes or other nanoparticles.

Encapsulation of doxorubicin in liposomes containing phosphatidylethanol. Part 2: Physicochemical characterization and antitumor activity of “solid” liposomes

Encapsulation of doxorubicin in liposomes containing phosphatidylethanol. Part 2: Physicochemical characterization and antitumor activity of “solid” liposomes

Encapsulation of doxorubicin in liposomes containing phosphatidylethanol. Part I: Physicochemical characterization and antitumor activity of liquid crystal liposomes

The effect of phosphatidylethanol (PE) anions on the incorporation of doxorubicin into liquid crystal liposomes consisting of soybean phosphatidylcholine (PC) was studied. Over 90% of the antibiotic are encapsulated in liposomes in the case of a PC/PE = 3: 2 molar ratio, with a doxorubicin content reaching 130 μg/(mg phospholipids). The Stokes radius of the antibiotic-containing liposomes is estimated at about 160 A. In terms of the ability to inhibit solid Ehrlich carcinoma in mice, the obtained liposomal doxorubicin preparations are much less effective in comparison to the usual antibiotic.

Liposomal encapsulated doxorubicin (Caelyx) in the treatment of relapsed aggressive non-Hodgkin's lymphoma: A phase II study

Aggressive non-Hodgkin's lymphoma (NHL), such as diffuse large B-cell lymphoma, can be cured in approximately 50% of cases, but those cases that recur and are not amenable to high-dose chemotherapy rely on palliative chemotherapy to improve symptoms and prolong life. Anthracyclines are associated with a high response rate in aggressive NHL but extended treatment results in cardiotoxicity. Liposomal encapsulated doxorubicin has been shown in other tumor types to allow for extended treatment with doxorubicin, but is associated with a low cardiac risk. The present study aimed to assess the response rate, survival and cardiac risk of patients with relapsed aggressive NHL treated with liposomal encapsulated doxorubicin. Eighteen patients with relapsed aggressive NHL were treated with liposomal encapsulated doxorubicin (40 – 50 mg/m2) for a planned six cycles. Some 83% of patients had diffuse large B-cell or mantle cell NHL. Four patients had a partial response (23%), whereas five patients had stable disease. None had a complete response. Eight patients progressed when receiving the liposomal encapsulated doxorubicin therapy. The median survival time was 34 weeks, and the median progression-free survival was 15.7 weeks. Overall survival was 50% at 6 months and 39% at 12 months. Progression-free survival was 33% at 6 months and was 28% at 12 months. The mean ejection fraction pre- and post-liposomal encapsulated doxorubicin treatment remained the same. Only one patient had a drop in ejection fraction to <50%. Liposomal encapsulated doxorubicin offers another choice to patients seeking palliation from their lymphoma recurrence with a response rate of 23% that was well tolerated and had a minimal cardiotoxic risk.

Multidrug resistance in AIDS-related lymphoma

AIDS-related lymphoma has a decreased response rate and poorer prognosis to standard chemotherapy when compared with lymphoma in the non-HIV population. In addition to the known HIV-related and lymphoma-related poor prognostic factors, this review discusses another factor, MDR-1 expression and its impact on response to therapy in patients with AIDS-related lymphoma. There is an increased incidence of de-novo MDR-1 expression in AIDS-related lymphoma compared with lymphoma in the non-HIV settings. MDR-1 expression in AIDS-related lymphoma is associated with poor response to conventional combination chemotherapy. Liposomal encapsulation of doxorubicin when substituted for doxorubicin in the CHOP regimen (cyclophosphamide, doxorubicin, vincristine, prednisone) seems to overcome P-glycoprotein-mediated drug resistance in AIDS-related lymphoma. The overexpression of MDR-1 gene product P-glycoprotein is an adverse prognostic factor in AIDS-related lymphoma. Treatment with liposomal encapsulated doxorubicin seems to overcome the P-glycoprotein-related drug resistance. This and other strategies to modulate MDR-1 should be further explored in order to improve success rates in the treatment of AIDS-related lymphoma.

Comparison of doxorubicin and its non-pegylated liposomal form as radiosensitizer in high grade glioma xenografts

1542 Background: Doxorubicin (dox) has been shown to be one of the most effective agents against glioma cells in vitro but is not used in clinical practice because of its poor blood-brain barrier penetration. The latter can be improved by liposomal encapsulation. We studied the potential radiopotentiation of Myocet (myo: not pegylated liposomal doxorubicin encapsulation) versus doxorubicin on a human glioblastoma xenografted in nude mice. Methods: The U87 high grade glioma was used. 6 treatment groups were designed: control (10 mice), doxorubicin (9), Myocet (9), radiotherapy (RT 9), dox + RT (8), myo + RT (8). Dox and myo were injected IP at the dose of 2 mg/kg, 3 times a week for 2 consecutive weeks. RT consisted on 2 Gy/d, 5 days a week for 2 consecutive weeks, initiated at the same time as dox or myo. Results: Only mice treated with dox died of toxicity (dox alone: 4, dox + RT: 7). Tumor growth delay was not statistically different for dox and myo (p = .14). Radiopotentiation could not be assessed in the dox + RT group due to high mortality, while no mortality occurred in the myo + RT group. An enhancement ratio of 1.22 was observed in the myo + RT group. Conclusions: Given at the same dose as doxorubicin, Myocet is markedly less toxic than doxorubicin and appears as a radiosensitizer. An orthotopic xenograft model using Myocet + RT is under study. No significant financial relationships to disclose.

Encapsulation of doxorubicin into thermosensitive liposomes via complexation with the transition metal manganese

In the present study, doxorubicin was encapsulated into two thermosensitive liposome formulations which were composed of DPPC / MSPC / DSPE-PEG 2000 (90 / 10 / 4 mole ratio) or DPPC/DSPE-PEG 2000 (95/5 mole ratio). Doxorubicin loading was achieved through the use of a pH gradient or a novel procedure that involved doxorubicin complexation with manganese. Regardless of the initial drug-to-lipid ratios (D : L), the final D : L reached a maximum of 0.05 (w / w) when doxorubicin was encapsulated via a pH gradient for both thermosensitive liposome formulations. In contrast, the final maximum D : L achieved through manganese complexation was 0.2 (w / w), and this loading method did not affect temperature-induced drug release, with 85% of drug released from MSPC-containing liposomes within 10 min at 42 °C but < 5% released over 60 min at 37 °C. When the thermosensitive liposomes prepared via the two different loading methods were injected into mice, similar plasma elimination profiles were observed. Cryo-transmission electron microscopy analysis indicated the presence of doxorubicin fiber bundles in liposomes loaded via pH gradient, compared to a stippled and diffuse morphology in those loaded via manganese complexation. To investigate the effect of intraliposomal pH on drug precipitate morphology, the A23187 ionophore (mediates Mn 2+/H + exchange) was added to liposomes loaded with doxorubicin–manganese complex, and the stippled and diffuse appearance could be converted to one exhibiting fiber bundles after acidification of the liposome core. This suggests that the formation of doxorubicin–manganese complex is favored when the intraliposomal pH is > 6.5. During the conversion to the fiber bundle morphology, no doxorubicin release was observed when A23187 was added to liposomes exhibiting a 0.05 (w / w), whereas a significant release was noted when the initial D : L was 0.2 (w / w). Following acidification of the liposomal interior and establishment of an apparent new D : L equilibrium, the measured D : L ratio was 0.05 (w / w). In conclusion, the manganese complexation loading method increased the encapsulation efficiency of doxorubicin in thermosensitive liposomes with no major impact on temperature-triggered drug release or pharmacokinetics.

Pegylated liposomal doxorubicin: Proof of principle using preclinical animal models and pharmacokinetic studies

Encapsulation of doxorubicin in polyethylene glycol-coated liposomes (Doxil/Caelyx [PLD]), was developed to enhance the safety and efficacy of conventional doxorubicin. The liposomes alter pharmacologic and pharmacokinetic parameters of conventional doxorubicin so that drug delivery to the tumor is enhanced while toxicity normally associated with conventional doxorubicin is decreased. In animals and humans, pharmacokinetic advantages of PLD include an increased area under the plasma concentration-time curve, longer distribution half-life, smaller volume of distribution, and reduced clearance. In preclinical models, PLD produced remission and cure against many cancers including tumors of the breast, lung, ovaries, prostate, colon, bladder, and pancreas, as well as lymphoma, sarcoma, and myeloma. It was also found to be effective as adjuvant therapy. In addition, it was found to cross the blood-brain barrier and induce remission in tumors of the central nervous system. Increased potency over conventional doxorubicin was observed and, in contrast to conventional doxorubicin, PLD was equally effective against low- and high-growth fraction tumors. The combination of PLD with vincristine or trastuzumab resulted in additive effects and possible synergy. PLD appeared to overcome multidrug resistance, possibly as the result of increased intracellular concentrations and an interaction between the liposome and P-glycoprotein function. On the basis of pharmacokinetic and preclinical studies, PLD, either alone or as part of combination therapy, has potential applications to treat a variety of cancers.