Preclinical evaluation of the cardiotoxicity of PK2: a novel HPMA copolymer-doxorubicin-galactosamine conjugate antitumour agent

Doxorubicin conjugates: a practical approach for its cardiotoxicity alleviation

INTRODUCTION

Doxorubicin (DOX) emerges as a cornerstone in the arsenal of potent chemotherapeutic agents. Yet, the clinical deployment of DOX is tarnished by its proclivity to induce severe cardiotoxic effects, culminating in heart failure and other consequential morbidities. In response, a panoply of strategies has undergone rigorous exploration over recent decades, all aimed at attenuating DOX's cardiotoxic impact. The advent of encapsulating DOX within lipidic or polymeric nanocarriers has yielded a dual triumph, augmenting DOX's therapeutic efficacy while mitigating its deleterious side effects.

AREAS COVERED

Recent strides have spotlighted the emergence of DOX conjugates as particularly auspicious avenues for ameliorating DOX-induced cardiotoxicity. These conjugates entail the fusion of DOX through physical or chemical bonds with diminutive natural or synthetic moieties, polymers, biomolecules, and nanoparticles. This spectrum encompasses interventions that impinge upon DOX's cardiotoxic mechanism, modulate cellular uptake and localization, confer antioxidative properties, or refine cellular targeting.

EXPERT OPINION

The endorsement of DOX conjugates as a compelling stratagem to mitigate DOX-induced cardiotoxicity resounds from this exegesis, amplifying safety margins and the therapeutic profile of this venerated chemotherapeutic agent. Within this ambit, DOX conjugates stand as a beacon of promise in the perpetual pursuit of refining chemotherapy-induced cardiac compromise.

Stimuli responsiveness of recent biomacromolecular systems (concept to market): A review

Stimuli responsive delivery systems, also known as smart/intelligent drug delivery systems, are specialized delivery vehicles designed to provide spatiotemporal control over drug release at target sites in various diseased conditions, including tumor, inflammation and many others. Recent advances in the design and development of a wide variety of stimuli-responsive (pH, redox, enzyme, temperature) materials have resulted in their widespread use in drug delivery and tissue engineering. The aim of this review is to provide an insight of recent nanoparticulate drug delivery systems including polymeric nanoparticles, dendrimers, lipid-based nanoparticles and the design of new polymer-drug conjugates (PDCs), with a major emphasis on natural along with synthetic commercial polymers used in their construction. Special focus has been placed on stimuli-responsive polymeric materials, their preparation methods, and the design of novel single and multiple stimuli-responsive materials that can provide controlled drug release in response a specific stimulus. These stimuli-sensitive drug nanoparticulate systems have exhibited varying degrees of substitution with enhanced in vitro/in vivo release. However, in an attempt to further increase drug release, new dual and multi-stimuli based natural polymeric nanocarriers have been investigated which respond to a mixture of two or more signals and are awaiting clinical trials. The translation of biopolymeric directed stimuli-sensitive drug delivery systems in clinic demands a thorough knowledge of its mechanism and drug release pattern in order to produce affordable and patient friendly products.

Glycomimetics for the inhibition and modulation of lectins

Carbohydrates are essential mediators of many processes in health and disease. They regulate self-/non-self- discrimination, are key elements of cellular communication, cancer, infection and inflammation, and determine protein folding, function and life-times. Moreover, they are integral to the cellular envelope for microorganisms and participate in biofilm formation. These diverse functions of carbohydrates are mediated by carbohydrate-binding proteins, lectins, and the more the knowledge about the biology of these proteins is advancing, the more interfering with carbohydrate recognition becomes a viable option for the development of novel therapeutics. In this respect, small molecules mimicking this recognition process become more and more available either as tools for fostering our basic understanding of glycobiology or as therapeutics. In this review, we outline the general design principles of glycomimetic inhibitors (Section 2). This section is then followed by highlighting three approaches to interfere with lectin function, i.e. with carbohydrate-derived glycomimetics (Section 3.1), novel glycomimetic scaffolds (Section 3.2) and allosteric modulators (Section 3.3). We summarize recent advances in design and application of glycomimetics for various classes of lectins of mammalian, viral and bacterial origin. Besides highlighting design principles in general, we showcase defined cases in which glycomimetics have been advanced to clinical trials or marketed. Additionally, emerging applications of glycomimetics for targeted protein degradation and targeted delivery purposes are reviewed in Section 4.

Active-targeting long-acting protein-glycopolymer conjugates for selective cancer therapy

Non-fouling polymers are effective in improving the pharmacokinetics of therapeutic proteins, but short of biological functions for tumor targeting. In contrast, glycopolymers are biologically active, but usually have poor pharmacokinetics. To address this dilemma, herein we report in situ growth of glucose- and oligo(ethylene glycol)-containing copolymers at the C-terminal site of interferon alpha, an antitumor and antivirus biological drug, to generate C-terminal interferon alpha-glycopolymer conjugates with tunable glucose contents. The in vitro activity and in vivo circulatory half-life of these conjugates were found to decrease with the increase of glucose content, which can be ascribed to complement activation by the glycopolymers. Additionally, the cancer cell endocytosis of the conjugates was observed to maximize at a critical glucose content due to the tradeoff between complement activation and glucose transporter recognition by the glycopolymers. As a result, in mice bearing ovarian cancers with overexpressed glucose transporter 1, the conjugates with optimized glucose contents were identified to possess improved cancer-targeting ability, enhanced anticancer immunity and efficacy, and increased animal survival rate. These findings provided a promising strategy for screening protein-glycopolymer conjugates with optimized glucose contents for selective cancer therapy.

Recent Progress of Novel Nanotechnology Challenging the Multidrug Resistance of Cancer

Multidrug resistance (MDR) of tumors is one of the clinical direct reasons for chemotherapy failure. MDR directly leads to tumor recurrence and metastasis, with extremely grievous mortality. Engineering a novel nano-delivery system for the treatment of MDR tumors has become an important part of nanotechnology. Herein, this review will take those different mechanisms of MDR as the classification standards and systematically summarize the advances in nanotechnology targeting different mechanisms of MDR in recent years. However, it still needs to be seriously considered that there are still some thorny problems in the application of the nano-delivery system against MDR tumors, including the excessive utilization of carrier materials, low drug-loading capacity, relatively narrow targeting mechanism, and so on. It is hoped that through the continuous development of nanotechnology, nano-delivery systems with more universal uses and a simpler preparation process can be obtained, for achieving the goal of defeating cancer MDR and accelerating clinical transformation.

Research progress in strategies to improve the efficacy and safety of doxorubicin for cancer chemotherapy

INTRODUCTION

DOX exerts strong anticancer activity and is commonly used to treat different cancers, including bone sarcomas, soft tissues, bladder, ovary, stomach, thyroid, breast, acute lymphoblastic leukemia, Hodgkin lymphoma, lung cancer, and myeloblastic leukemia. However, the cumulative doses of DOX above 550mg/m2 cause irreversible cardiotoxicity and other severe adverse effects. In this context, concerning DOX, several patents have been published in the last two decades. This activity highlights various aspects of DOX, such as registered patent analysis, pharmacological action, toxicityminimization, formulation development such as those approved by FDA, under clinical trials, and newly developed nano-delivery systems.

AREAS COVERED

This review analyzes the different aspects of DOX-based chemotherapeutics and the development of drug delivery systems in theliterature published from 2000 to early 2020.

EXPERT OPINION

DOX-based chemotherapy is still few steps away from being "perfect and safe" therapy. Certain severe systemic side effects are associated with DOX therapy. It is expected that, in the near future, DOX therapy can be much effective by selecting an ideal nanocarrier system, DOX conjugates, proper structural modifications, DOX-immunotherapy, and combination therapy. The advanced formulationsof DOX from the registered patents and recent research articles need clinical trials to bring safe treatment for cancer patients.

Interaction of a Triantennary Quinoline Glycoconjugate with the Asialoglycoprotein Receptor

Targeted intracellular delivery is an efficient strategy for developing therapeutics against cancer and other intracellular infections. Nonspecific drug delivery shows limited clinical applications owing to high dosage, cytotoxicity, nonspecific action, high cost, etc. Therefore, targeted delivery of less cytotoxic drug candidates to hepatocytes through ASGPR-mediated endocytosis could be an efficient strategy to surmount the prevailing shortcomings. In the present work, the gene encoding ASGPR-H1-CRD was amplified from Huh7 cells, cloned into pET 11a vector, and the ASGPR-H1-CRD protein was expressed and purified from E. coli. A novel triantennary galactose-conjugated quinoline derivative 4 was synthesized that demonstrates 17-fold higher binding affinity to isolated ASGPR-H1-CRD protein receptor (K_d ∼54 μM) in comparison to D-galactose (K_d ∼900 μM). Moreover, micro-calorimetric studies for the interaction of glycoconjugate 4 with ASGPR protein on live hepatocytes showed notable thermal response in case of ASGPR-containing Huh7 cells, in comparison to non-ASGPR Chang cells. These results might serve as an approach towards targeted delivery of small glycoconjugates to hepatocytes.

Advanced nanomedicine and cancer: Challenges and opportunities in clinical translation

Cancer has reached pandemic dimensions in the whole world. Although current medicine offers multiple treatment options against cancer, novel therapeutic strategies are needed due to the low specificity of chemotherapeutic drugs, undesired side effects and the presence of different incurable types of cancer. Among these new strategies, nanomedicine arises as an encouraging approach towards personalized medicine with high potential for present and future cancer patients. Therefore, nanomedicine aims to develop novel tools with wide potential in cancer treatment, imaging or even theranostic purposes. Even though numerous preclinical studies have been published with successful preliminary results, promising nanosystems have to face multiple obstacles before adoption in clinical practice as safe options for patients with cancer. In this MiniReview, we provide a short overview on the latest advances in current nanomedicine approaches, challenges and promising strategies towards more accurate cancer treatment.

Dendrimer Conjugation Enhances Tumor Penetration and Efficacy of Doxorubicin in Extracellular Matrix-Expressing 3D Lung Cancer Models

Doxorubicin (DOX) is a chemotherapeutic agent broadly used in the treatment of a range of solid tumors. In spite of its high potency, as is the case for many other chemotherapeutic drugs, there are many challenges associated with the use of DOX in clinical oncology. This is particularly true for DOX in the treatment of lung cancer, where in vitro potency is shown to be very high, but low lung distribution and off-target toxicity (particularly cardiotoxicity) restrict its use. Nanocarrier-based drug delivery systems (nanoDDS) have been shown to help alter biodistribution and alleviate off-target toxicity associated with DOX. While significant understanding exists regarding the design parameters to achieve those clinical benefits, much less is known regarding the design of nanoDDS capable of enhancing tumor penetration of DOX (and other drugs), which is another major factor leading to DOX's reduced efficacy. The purpose of this study was to design a dendrimer-based nanoDDS capable of enhancing the penetration of DOX as measured in an in vitro 3D lung tumor model and to correlate those results with its efficacy. Spheroids formed with the A549 human lung adenocarcinoma cells/murine fibroblast cell line (NIH/3T3 cell line) are shown to produce the essential components of the extracellular matrix (ECM), which is known as a physical barrier that hinders the transport of DOX. DOX was conjugated to generation 4 succinamic acid-terminated poly(amido-amine) (PAMAM) dendrimers (G4SA) through an enzyme-liable tetrapeptide (G4SA-GFLG-DOX), resulting in a nanoDDS with ∼5.5 DOX, -17 mV surface (ζ) potential, and a 10 nm hydrodynamic diameter (HD). The penetration of DOX to the core of the spheroid in terms of DOX fluorescence was determined to be 3.1-fold greater compared to free DOX, which positively correlated with enhanced efficacy as measured by the Caspase 3/7 assay. This improved penetration happens as the interactions between the G4SA-GFLG-DOX and the highly negatively charged ECM are minimized by shielding the protonatable amine of DOX upon conjugation, and the HD of the conjugate is kept smaller than the estimated mesh size of the ECM. Interestingly, the conjugate provided more specificity for DOX to tumor cells compared to fibroblasts, while free DOX is equally distributed in both tumor and fibroblasts as assessed in the coculture spheroids. Growth inhibition studies show that the released DOX maintains its activity and leads to tumor reduction to the same extent as free DOX. The results obtained here are of relevance for the design of dendrimer-based nanoDDS and for the treatment of solid tumors as they provide critical information regarding desirable surface characteristics and sizes for efficient tumor penetration.

Polymeric Nanocarriers of Drug Delivery Systems in Cancer Therapy

Conventional chemotherapy is the most common therapeutic method for treating cancer by the application of small toxic molecules thatinteract with DNA and causecell death. Unfortunately, these chemotherapeutic agents are non-selective and can damage both cancer and healthy tissues,producing diverse side effects, andthey can have a short circulation half-life and limited targeting. Many synthetic polymers have found application as nanocarriers of intelligent drug delivery systems (DDSs). Their unique physicochemical properties allow them to carry drugs with high efficiency,specificallytarget cancer tissue and control drug release. In recent years, considerable efforts have been made to design smart nanoplatforms, including amphiphilic block copolymers, polymer-drug conjugates and in particular pH- and redox-stimuli-responsive nanoparticles (NPs). This review is focused on a new generation of polymer-based DDSs with specific chemical functionalities that improve their hydrophilicity, drug loading and cellular interactions.Recentlydesigned multifunctional DDSs used in cancer therapy are highlighted in this review.

A glance over doxorubicin based-nanotherapeutics: From proof-of-concept studies to solutions in the market

Cancer is one of the leading causes of death worldwide and, as such, efforts are being done to find new chemotherapeutic drugs or, alternatively, novel approaches for the delivery of old ones. In this scope, when used as vehicles for drugs, nanomaterials may potentially maximize the efficacy of the treatment and reduce its side effects, for example by a change in drug's pharmacokinetics, cell targeting and/or specific stimuli-responsiveness. This is the case of doxorubicin (DOX) that presents a broad spectrum of activity and is one of the most widely used chemotherapeutic drugs as first-line treatment. Indeed, DOX is a very interesting example of a drug for which several nanosized delivery systems have been developed over the years. While it is true that some of these systems are already in the market, it is also true that research on this subject remains very active and that there is a continuing search for new solutions. In this sense, this review takes the example of doxorubicin, not so much with the focus on the drug itself, but rather as a case study around which very diverse and imaginative nanotechnology approaches have emerged.

Clinical developments of antitumor polymer therapeutics

Polymer therapeutics encompasses polymer-drug conjugates that are nano-sized, multicomponent constructs already in the clinic as antitumor compounds, either as single agents or in combination with other organic drug scaffolds. Nanoparticle-based polymer-conjugated therapeutics are poised to become a leading delivery strategy for cancer treatments as they exhibit prolonged half-life, higher stability and selectivity, water solubility, longer clearance time, lower immunogenicity and antigenicity and often also specific targeting to tissues or cells. Compared to free drugs, polymer-tethered drugs preferentially accumulate in the tumor sites unlike conventional chemotherapy which does not discriminate between the cancer cells and healthy cells, thereby causing severe side-effects. It is also desirable that the drug reaches its site of action at a particular concentration and the therapeutic dose remains constant over a sufficiently long period of time. This can be achieved by opting for new formulations possessing polymeric systems of drug carriers. However, many challenges still remain unanswered in polymeric drug conjugates which need to be readdressed and therefore, can broaden the scope of this field. This review highlights some of the antitumor polymer therapeutics including polymer-drug conjugates, polymeric micelles, polymeric liposomes and other polymeric nanoparticles that are currently under investigation.

Experimental evidence of good efficacy and reduced toxicity with peptide-doxorubicin to treat gastric cancer

BACKGROUND

To compare the efficacy and toxicity of peptide-doxorubicin (PDOX) and doxorubicin (DOX) on nude mice models of human gastric cancer.

RESULTS

Both PDOX and DOX could significantly inhibit tumor growth compared with Control (P < 0.05) in both subcutaneous and orthotopic models. Animal survival was much better in PDOX group than DOX group. In peripheral blood test, PDOX group had significantly higher levels of platelets than the Control (P < 0.05), and lymphocyte lower than Control (P < 0.05). There were no significant differences on liver, kidney and cardiac function parameters among three groups (P > 0.05). Immunohistochemistry showed that treatment groups had much higher Tunel than Control (P < 0.05), and PDOX had significantly lower Ki-67 than doxorubicin and Control group (P < 0.01). Western blotting showed that PDOX caused much higher expressions of P53, P21, Aparf-1, pro- and cleaved-caspase 3, compared with DOX.

CONCLUSION

Compared with DOX, PDOX has increased effects but much decreased toxicity in treating animal model of gastric cancer.

MATERIALS AND METHODS

Animals in subcutaneous model were randomized into Control, doxorubicin, PDOX-L, PDOX-M, and PDOX-H groups. Animals in surgical orthotopic implantation model were randomized into Control, doxorubicin and, peptide-doxorubicin groups. The animals were treated, monitored and examined following a set protocol.

New molecular targets for functionalized nanosized drug delivery systems in personalized therapy for hepatocellular carcinoma

Hepatocellular carcinoma, the most frequent solid tumor of the liver, has a very poor prognosis, being the second most common cause of death from cancer worldwide. The incidence and mortality of this liver tumor are increasing in most areas of the world as a consequence of aging and the emerging of new risk factors such as the metabolic syndrome, beside the recognized role of hepatitis B and C viral infections and alcohol abuse. Despite the increasing knowledge on the molecular mechanisms underlying hepatic carcinogenesis, effective therapeutic strategies are still an unmet clinical need. Efforts have been made to develop selective drugs as well as effective targeted drug delivery systems. The development of novel drug carriers for therapeutic molecules can indeed offer a valuable strategy to ameliorate the efficacy of HCC treatment. In this review, we discuss recent drug delivery strategies for HCC treatment based on the exploitation of targeted nanoparticles (NPs). Indeed, a few of these platforms have achieved an advanced stage of preclinical development. Here, we review the most promising drug nanovehicles based on both synthetic and natural polymers, including polysaccharides that have emerged for their biocompatibility and biodegradability. To maximize site-selectivity and therapeutic efficacy, drug delivery systems should be functionalized with ligands which can specifically recognize and bind targets expressed by HCC, namely cell membrane associated antigens, receptors or biotransporters. Cell surface and intracellular molecular targets are exploited either to selectively deliver drug-loaded nanovehicles or to design novel selective therapeutics. In conclusion, the combination of novel and safe drug delivery strategies based on site-specific targeted drug nanovehicles with therapeutic molecular targets may significantly improve the pharmacological efficacy for the treatment of HCC.

Angiogenesis regulation by nanocarriers bearing RNA interference

Since the approval of bevacizumab as anti-angiogenic therapy in 2004 by the FDA, an array of angiogenesis inhibitors have been developed and approved. However, results were disappointing with regard to their therapeutic efficacy. RNA interference approaches offer the possibility of rational design with high specificity, lacking in many current drug treatments for various diseases including cancer. However, in vivo delivery issues still represent a significant obstacle for widespread clinical applications. In the current review, we summarize the advances in the last decade in the field of angiogenesis-targeted RNA interference approaches, with special emphasis on oncology applications. We present pro-angiogenic and anti-angiogenic factors as potential targets, experimental evidence and clinical trials data on angiogenesis regulation by RNA interference. Consequent challenges and opportunities are discussed.

Hemodynamic effects of HPMA copolymer based doxorubicin conjugate: A randomized controlled and comparative spectral study in conscious rats

Conjugation of Doxorubicin (DOX) to N-(2-hydroxypropyl) methylacrylamide copolymer (HPMA) has significantly reduced the DOX-associated cardiotoxicity. However, the reports on the impact of HPMA–DOX conjugates on the cardiovascular system such as blood pressure (BP) and heart rate (HR) were in restrained animals using tail cuff and/or other methods that lacked the resolution and sensitivity. Herein, we employed radiotelemetric-spectral-echocardiography approach to further understand the in vivo cardiovascular hemodynamics and variability post administration of free DOX and HPMA–DOX. Rats implanted with radio-telemetry device were administered intravenously with DOX (5 mg/kg), HPMA–DOX (5 mg DOX equivalent/kg) and HPMA copolymer and subjected to continuous cardiovascular monitoring and echocardiography for 140 days. We found that DOX-treated rats had ruffled fur, reduced body weight (BW) and a low survival rate. Although BP and HR were normal, spectral analysis indicated that their BP and HR variabilities were reduced. All rats exhibited typical signs of cardiotoxicity at histopathology. In contrast, HPMA–DOX rats gained weight over time and survived. Although BP, HR and related variabilities were unaffected, the left ventricular end diastolic volume (EDV) of these rats, as well as of the HPMA copolymer-treated rats, was found increased at the end of observation period. Additionally, HPMA copolymer caused microscopic injury of the heart tissue. All of these suggest the necessity of caution when employing HPMA as carrier for prolonged drug delivery. The current study also indicates the potential of radiotelemetric-spectral-echocardiography approach for improved preclinical cardiovascular risk assessment of polymer–drug conjugate and other nano-sized-drug constructs.

In vitro synergistic action of geldanamycin- and docetaxel-containing HPMA copolymer-RGDfK conjugates against ovarian cancer

HPMA copolymer-RGDfK (HPMA-RGDfK) conjugates bearing either aminohexylgeldanamycin (AHGDM) or docetaxel (DOC) were synthesized and characterized. In vitro stability and binding were evaluated. Cytotoxicity toward ovarian cancer cells was evaluated and the ability of the conjugates to induce cell death was assessed by combination index analysis. Conjugates bearing AHGDM were more stable and exhibited slower drug release than those bearing DOC. Both conjugates demonstrated the ability to bind to avb3 integrins. In combination, HPMA-RGDfK conjugates demonstrated marked synergism as compared to their non-targeted counterparts and free drug controls. HPMA-RGDfK conjugates bearing AHGDM and DOC induce synergistic cytotoxicity in vitro, suggesting their potential as a promising combination therapy.

Anticancer activity of starch/poly[N-(2-hydroxypropyl)methacrylamide]: biomaterial film to treat skin cancer

In the present work, films of pHPMA, pHPMAS hybrid, pHPMA-CPT and pHPMAS-CPT hybrid were prepared by solvent casting method and characterized by FT-IR, FT-Raman, XRD and DSC, respectively. The biocompatibility of the prepared pHPMA film and pHPMAS hybrid film were assessed using VERO cell lines and the percentage cell viability was found to be 97.4 and 98.3% for 7.8 μg/ml of the film extracts after 72 h of incubation. The cancer cell viability of the pHPMA-CPT film and pHPMAS-CPT film using MCF7 cell lines at pH 5.5 and 7.4 were found to be 4.9 and 8.6% and 7.7 and 12.3%, respectively. In vitro release of camptothecin from pHPMA-CPT and pHPMAS-CPT films in phosphate-buffered saline solution at pH 5.5 and 7.4 were monitored and analyzed using UV-vis spectrophotometer at λmax of 360 nm.

Multifunctional nanoparticles for targeted delivery of immune activating and cancer therapeutic agents

Nanoparticles (NPs) have been extensively investigated for applications in both experimental and clinical settings to improve delivery efficiency of therapeutic and diagnostic agents. Most recently, novel multifunctional nanoparticles have attracted much attention because of their ability to carry diverse functionalities to achieve effective synergistic therapeutic treatments. Multifunctional NPs have been designed to co-deliver multiple components, target the delivery of drugs by surface functionalization, and realize therapy and diagnosis simultaneously. In this review, various materials of diverse chemistries for fabricating multifunctional NPs with distinctive architectures are discussed and compared. Recent progress involving multifunctional NPs for immune activation, anticancer drug delivery, and synergistic theranostics is the focus of this review. Overall, this comprehensive review demonstrates that multifunctional NPs have distinctive properties that make them highly suitable for targeted therapeutic delivery in these areas.

Cathepsin B-cleavable doxorubicin prodrugs for targeted cancer therapy (Review)

Doxorubicin (DOX) is one of the most effective cytotoxic anticancer drugs used for the treatment of hematological malignancies, as well as a broad range of solid tumors. However, the clinical applications of this drug have long been limited due to its severe dose-dependent toxicities. Therefore, DOX derivatives and analogs have been developed to address this issue. A type of DOX prodrug, cleaved by cathepsin B (Cat B), which is highly upregulated in malignant tumors and premalignant lesions, has been developed to achieve a higher DOX concentration in tumor tissue and a lower concentration in normal tissue, so as to enhance the efficacy and reduce toxicity to normal cells. In this review, we focused on Cat B-cleavable DOX prodrugs and discussed the efficacy of these prodrugs, demonstrated by preclinical and clinical developments.

Protease-activated drug development

In this extensive review, we elucidate the importance of proteases and their role in drug development in various diseases with an emphasis on cancer. First, key proteases are introduced along with their function in disease progression. Next, we link these proteases as targets for the development of prodrugs and provide clinical examples of protease-activatable prodrugs. Finally, we provide significant design considerations needed for the development of the next generation protease-targeted and protease-activatable prodrugs.

Enhanced anti-tumor activity and safety profile of targeted nano-scaled HPMA copolymer-alendronate-TNP-470 conjugate in the treatment of bone malignances

Bone neoplasms, such as osteosarcoma, exhibit a propensity for systemic metastases resulting in adverse clinical outcome. Traditional treatment consisting of aggressive chemotherapy combined with surgical resection, has been the mainstay of these malignances. Therefore, bone-targeted non-toxic therapies are required. We previously conjugated the aminobisphosphonate alendronate (ALN), and the potent anti-angiogenic agent TNP-470 with N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer. HPMA copolymer-ALN-TNP-470 conjugate exhibited improved anti-angiogenic and anti-tumor activity compared with the combination of free ALN and TNP-470 when evaluated in a xenogeneic model of human osteosarcoma. The immune system has major effect on toxicology studies and on tumor progression. Therefore, in this manuscript we examined the safety and efficacy profiles of the conjugate using murine osteosarcoma syngeneic model. Toxicity and efficacy evaluation revealed superior anti-tumor activity and decreased organ-related toxicities of the conjugate compared with the combination of free ALN plus TNP-470. Finally, comparative anti-angiogenic activity and specificity studies, using surrogate biomarkers of circulating endothelial cells (CEC), highlighted the advantage of the conjugate over the free agents. The therapeutic platform described here may have clinical translational relevance for the treatment of bone-related angiogenesis-dependent malignances.

Sustained liver targeting and improved antiproliferative effect of doxorubicin liposomes modified with galactosylated lipid and PEG-lipid

In this study, a cleavable PEG-lipid (methoxypolyethyleneglycol 2000-cholesteryl hemisuccinate, PEG(2000)-CHEMS) linked via ester bond and galactosylated lipid ((5-cholesten-3beta-yl) 4-oxo-4-[2-(lactobionyl amido) ethylamido] butanoate, CHS-ED-LA) were used to modify doxorubicin (DOX) liposome. DOX was encapsulated into conventional liposomes (CL), galactosylated liposomes (modified with CHS-ED-LA, GalL), pegylated liposomes (modified with PEG(2000)-CHEMS, PEG-CL), and pegylated galactosylated liposomes (modified with CHS-ED-LA and PEG(2000)-CHEMS, PEG-GalL) using an ammonium sulfate gradient loading method and then intravenously injected to normal mice. Both PEG-GalL DOX and GalL DOX gave relatively high overall drug targeting efficiencies to liver ((T(e))(liver)) and were mainly taken up by hepatocyte. However, PEG-GalL DOX showed unique "sustained targeting" characterized by slowed transfer of DOX to liver and reduced peak concentrations in the liver. The biodistribution and antitumor efficacy of various DOX preparations were studied in hepatocarcinoma 22 (H22) tumor-bearing mice. The inhibitory rate of PEG-GalL DOX to H22 tumors was up to 94%, significantly higher than that of PEG-CL DOX, GalL DOX, CL DOX, and free DOX, although the tumor distribution of DOX revealed no difference between PEG-GalL DOX and PEG-CL DOX. Meanwhile, the gradual increase in the liver DOX concentration due to the sustained uptake of PEG-GalL DOX formulations resulted in lower damage to liver. In conclusion, the present investigation indicated that double modification of liposomes with PEG(2000)-CHEMS, and CHS-ED-LA represents a potentially advantageous strategy in the therapy of liver cancers or other liver diseases.

Sustained liver targeting and improved antiproliferative effect of doxorubicin liposomes modified with galactosylated lipid and PEG-lipid

In this study, a cleavable PEG-lipid (methoxypolyethyleneglycol 2000-cholesteryl hemisuccinate, PEG(2000)-CHEMS) linked via ester bond and galactosylated lipid ((5-cholesten-3beta-yl) 4-oxo-4-[2-(lactobionyl amido) ethylamido] butanoate, CHS-ED-LA) were used to modify doxorubicin (DOX) liposome. DOX was encapsulated into conventional liposomes (CL), galactosylated liposomes (modified with CHS-ED-LA, GalL), pegylated liposomes (modified with PEG(2000)-CHEMS, PEG-CL), and pegylated galactosylated liposomes (modified with CHS-ED-LA and PEG(2000)-CHEMS, PEG-GalL) using an ammonium sulfate gradient loading method and then intravenously injected to normal mice. Both PEG-GalL DOX and GalL DOX gave relatively high overall drug targeting efficiencies to liver ((T(e))(liver)) and were mainly taken up by hepatocyte. However, PEG-GalL DOX showed unique "sustained targeting" characterized by slowed transfer of DOX to liver and reduced peak concentrations in the liver. The biodistribution and antitumor efficacy of various DOX preparations were studied in hepatocarcinoma 22 (H22) tumor-bearing mice. The inhibitory rate of PEG-GalL DOX to H22 tumors was up to 94%, significantly higher than that of PEG-CL DOX, GalL DOX, CL DOX, and free DOX, although the tumor distribution of DOX revealed no difference between PEG-GalL DOX and PEG-CL DOX. Meanwhile, the gradual increase in the liver DOX concentration due to the sustained uptake of PEG-GalL DOX formulations resulted in lower damage to liver. In conclusion, the present investigation indicated that double modification of liposomes with PEG(2000)-CHEMS, and CHS-ED-LA represents a potentially advantageous strategy in the therapy of liver cancers or other liver diseases.

Doxorubicin attached to HPMA copolymer via amide bond modifies the glycosylation pattern of EL4 cells

To avoid the side effects of the anti-cancer drug doxorubicin (Dox), we conjugated this drug to a N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer backbone. Dox was conjugated via an amide bond (Dox-HPMA(AM), PK1) or a hydrazone pH-sensitive bond (Dox-HPMA(HYD)). In contrast to Dox and Dox-HPMA(HYD), Dox-HPMA(AM) accumulates within the cell's intracellular membranes, including those of the Golgi complex and endoplasmic reticulum, both involved in protein glycosylation. Flow cytometry was used to determine lectin binding and cell death, immunoblot to characterize the presence of CD7, CD43, CD44, and CD45, and high-performance anion exchange chromatography with pulsed amperometric detector analysis for characterization of plasma membrane saccharide composition. Incubation of EL4 cells with Dox-HPMA(AM) conjugate, in contrast to Dox or Dox-HPMA(HYD), increased the amounts of membrane surface-associated glycoproteins, as well as saccharide moieties recognized by peanut agglutinin, Erythrina cristagalli, or galectin-1 lectins. Only Dox-HPMA(AM) increased expression of the highly glycosylated membrane glycoprotein CD43, while expression of others (CD7, CD44, and CD45) was unaffected. The binding sites for galectin-1 are present on CD43 molecule. Furthermore, we present that EL4 treated with Dox-HPMA(AM) possesses increased sensitivity to galectin-1-induced apoptosis. In this study, we demonstrate that Dox-HPMA(AM) treatment changes glycosylation of the EL4 T cell lymphoma surface and sensitizes the cells to galectin-1-induced apoptosis.

Development of HPMA copolymer-anticancer conjugates: clinical experience and lessons learnt

The concept of polymer-drug conjugates was proposed more than 30 years ago, and an N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer conjugate of doxorubicin covalently bound to the polymer backbone by a Gly-Phe-Leu-Gly peptidyl linker (FCE28068) became the first synthetic polymer-based anticancer conjugate to enter clinical trial in 1994. This conjugate arose from rational design attempting to capitalise on passive tumour targeting by the enhanced permeability and retention effect and, at the cellular level, lysosomotropic drug delivery to improve therapeutic index. Early clinical results were promising, confirming activity in chemotherapy refractory patients and the safety of HPMA as a new polymer platform. Subsequent Phase I/II trials have investigated an HPMA copolymer-based conjugate containing a doxorubicin and additionally galactose as a targeting moiety to promote liver targeting (FCE28069), and also HPMA copolymer conjugates of paclitaxel (PNU 166945), camptothecin (PNU 166148) and two platinates (AP5280 and AP5346- ProLindac). The preclinical and clinical observations made in these, and clinical studies with other polymer conjugates, should shape the development of next generation anticancer polymer therapeutics.

Targeting bone metastases with a bispecific anticancer and antiangiogenic polymer-alendronate-taxane conjugate

A polymer therapeutic designed for combination anticancer and antiangiogenic therapy inhibited the proliferation of prostate carcinoma cells and the proliferation, migration, and tube-formation of endothelial cells. The nanoconjugate was formed from an N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer, the bisphosphonate alendronate (for bone targeting), and the chemotherapy agent paclitaxel (PTX), which is cleaved by cathepsin B (see scheme).

Factors affecting the clearance and biodistribution of polymeric nanoparticles

Nanoparticle (NP) drug delivery systems (5−250 nm) have the potential to improve current disease therapies because of their ability to overcome multiple biological barriers and releasing a therapeutic load in the optimal dosage range. Rapid clearance of circulating nanoparticles during systemic delivery is a critical issue for these systems and has made it necessary to understand the factors affecting particle biodistribution and blood circulation half-life. In this review, we discuss the factors which can influence nanoparticle blood residence time and organ specific accumulation. These factors include interactions with biological barriers and tunable nanoparticle parameters, such as composition, size, core properties, surface modifications (pegylation and surface charge), and finally, targeting ligand functionalization. All these factors have been shown to substantially affect the biodistribution and blood circulation half-life of circulating nanoparticles by reducing the level of nonspecific uptake, delaying opsonization, and increasing the extent of tissue specific accumulation.

The 6-maleimidocaproyl hydrazone derivative of doxorubicin (DOXO-EMCH) is superior to free doxorubicin with respect to cardiotoxicity and mitochondrial damage

Doxorubicin causes a chronic cardiomyopathy in which genetic and functional lesions of mitochondria accumulate in the long-term and explain in part the delayed onset of heart dysfunction. DOXO-EMCH a 6-maleimidocaproyl hydrazone derivative of doxorubicin, is an albumin binding prodrug which has entered clinical trials because of its superior antitumor and toxicological profile. In the present work, we examined the chronic cardiotoxicity of DOXO-EMCH in direct comparison with doxorubicin. Rats (11 weeks of age) were treated with intravenous doxorubicin (0.8 mg/kg weekly for 7 weeks), an equimolar dose of DOXO-EMCH (1.1 mg/kg), or with 3.3 mg/kg of DOXO-EMCH. Controls received saline. Animals were euthanized at 48th week. Rats exposed to doxorubicin had a severe clinical, and histopathological cardiomyopathy with depressed myocardial activity of cytochrome c-oxidase (COX, 26% of controls), reduced expression of the mtDNA-encoded COX II subunit, decreased mtDNA copy numbers (46% of controls), and high levels of malondialdehyde and superoxide (787% of controls). All parameters were highly correlated with myocardial damage. Both DOXO-EMCH groups did not differ from controls with regard to clinical symptomatology, mortality and mitochondrial enzymes, although the myocardia of the high-dose group had slightly increased histopathological abnormalities, depressed mtDNA copies (74% of controls) and elevated superoxide levels (347% of controls). Doxorubicin-exposed hearts and to a lesser extent the myocardia of both DOXO-EMCH groups contained mtDNA-deletions. In summary both DOXO-EMCH doses were superior over doxorubicin with respect to clinical and histopathological evidence of cardiomyopathy, myocardial COX-activity, COX II expression, mtDNA-content, mtDNA mutation loads and superoxide production in rats.