Design, controlled synthesis, physico-chemical and biological characteristics of novel well-defined biodegradable star-shaped copolymers intended for advanced drug delivery is described. These new biocompatible star copolymers were synthesised by grafting monodispersed semitelechelic linear (sL) N-(2-hydroxypropyl)methacrylamide copolymers onto a 2,2-bis(hydroxymethyl)propionic acid (bisMPA)-based polyester dendritic core of various structures. The hydrodynamic diameter of the star copolymer biomaterials can be tuned from 13 to 31 nm and could be adjusted to a given purpose by proper selection of the bisMPA dendritic core type and generation and by considering the sL copolymer molecular weight and polymer-to-core molar ratio. The hydrolytic degradation was proved for both the star copolymers containing either dendron or dendrimer core, showing the spontaneous hydrolysis in duration of few weeks. Finally, it was shown that the therapy with the biodegradable star conjugate with attached doxorubicin strongly suppresses the tumour growth in mice and is fully curative in most of the treated animals at dose corresponding approximately to one fourth of maximum tolerated dose (MTD) value. Both new biodegradable systems show superior efficacy and tumour accumulation over the first generation of star copolymers containing non-degradable PAMAM core.

• Keywords
• Cancer, Doxorubicin, Drug delivery, HPMA, Star-like polymers, bisMPA,
• MeSH
• Acrylamides MeSH
• Biocompatible Materials * MeSH
• Doxorubicin MeSH
• Pharmaceutical Preparations * MeSH
• Drug Delivery Systems MeSH
• Methacrylates MeSH
• Mice MeSH
• Cell Line, Tumor MeSH
• Drug Carriers MeSH
• Polymers MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Names of Substances
• Acrylamides MeSH
• Biocompatible Materials * MeSH
• Doxorubicin MeSH
• hydroxypropyl methacrylate MeSH Browser
• Pharmaceutical Preparations * MeSH
• Methacrylates MeSH
• N-(2-hydroxypropyl)methacrylamide MeSH Browser
• Drug Carriers MeSH
• Polymers MeSH

Here we describe the synthesis and biological properties of two types of star-shaped polymer-doxorubicin conjugates: non-targeted conjugate prepared as long-circulating high-molecular-weight (HMW) polymer prodrugs with a dendrimer core and a targeted conjugate with the anti-CD20 monoclonal antibody (mAb) rituximab (RTX). The copolymers were linked to the dendrimer core or to the reduced mAb via one-point attachment forming a star-shaped structure with a central antibody or dendrimer surrounded by hydrophilic polymer chains. The anticancer drug doxorubicin (DOX) was attached to the N-(2-hydroxypropyl)methacrylamide (HPMA)-based copolymer chain in star polymer systems via a pH-labile hydrazone linkage. Such polymer-DOX conjugates were fairly stable in aqueous solutions at pH 7.4, and the drug was readily released in mildly acidic environments at pH 5-5.5 by hydrolysis of the hydrazone bonds. The cytotoxicity of the polymer conjugates was tested on several CD20-positive or negative human cell lines. Similar levels of in vitro cytotoxicity were observed for all tested polymer conjugates regardless of type or structure. In vivo experiments using primary cell-based murine xenograft models of human diffuse large B-cell lymphoma confirmed the superior anti-lymphoma efficacy of the polymer-bound DOX conjugate when compared with the original drug. Targeting with RTX did not further enhance the anti-lymphoma efficacy relative to the non-targeted star polymer conjugate. Two mechanisms could play roles in these findings: changes in the binding ability to the CD-20 receptor and a significant loss of the immunological properties of RTX in the polymer conjugates.

• Keywords
• HPMA copolymers, doxorubicin, drug delivery systems, drug targeting, monoclonal antibody,
• MeSH
• Apoptosis drug effects   MeSH
• Doxorubicin chemistry   pharmacology   MeSH
• Drug Delivery Systems MeSH
• Humans MeSH
• Lymphoma drug therapy   mortality   pathology   MeSH
• Disease Models, Animal MeSH
• Mice MeSH
• Cell Line, Tumor MeSH
• Polymers * chemistry   MeSH
• Prodrugs * chemistry   pharmacology   MeSH
• Antineoplastic Agents chemistry   pharmacology   MeSH
• Rituximab chemistry   pharmacology   MeSH
• Drug Liberation MeSH
• Cell Survival drug effects   MeSH
• Xenograft Model Antitumor Assays MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Doxorubicin MeSH
• Polymers * MeSH
• Prodrugs * MeSH
• Antineoplastic Agents MeSH
• Rituximab MeSH

Linkage of doxorubicin (Dox) to a water-soluble synthetic N-(2-hydroxypropyl)methacrylamide copolymer (PHPMA) eliminates most of the systemic toxicity of the free drug. In EL-4 lymphoma-bearing C57BL/6 mice, a complete regression of pre-established tumours has been achieved upon treatment with Dox-PHPMA-HuIg conjugate. The treatment was effective using a range of regimens and dosages, ranging from 62.5 to 100% cured mice treated with a single dose of 10-20 mg of Dox eq./kg, respectively. Fractionated dosages producing lower levels of the conjugate for a prolonged time period had substantial curative capacity as well. The cured mice developed anti-tumour protection as they rejected subsequently re-transplanted original tumour. The proportion of tumour-protected mice inversely reflected the effectiveness of the primary treatment. The treatment protocol leading to 50% of cured mice produced only protected mice, while no mice treated with early treatment regimen (i.e. starting on day 1 after tumour transplantation) rejected the re-transplanted tumour. Exposure of the host to the cancer cells was a prerequisite for developing protection. The anti-tumour memory was long lasting and specific against the original tumour, as the cured mice did not reject another syngeneic tumour, melanoma B16-F10. The immunity was transferable to naïve recipients in in vivo neutralization assay by spleen cells or CD8(+) lymphocytes derived from cured animals. We propose an effective treatment strategy which eradicates tumours without harming the protective immune anti-cancer responses.

• MeSH
• Doxorubicin analogs & derivatives   therapeutic use   MeSH
• Immunoglobulins therapeutic use   MeSH
• Immune Tolerance * MeSH
• Polymethacrylic Acids therapeutic use   MeSH
• Humans MeSH
• Lymphoma, T-Cell drug therapy   immunology   prevention & control   MeSH
• Melanoma, Experimental drug therapy   immunology   metabolism   MeSH
• Survival Rate MeSH
• Mice, Inbred C57BL MeSH
• Mice, Nude MeSH
• Mice MeSH
• Tumor Cells, Cultured transplantation   MeSH
• Skin Neoplasms drug therapy   immunology   metabolism   MeSH
• Drug Carriers MeSH
• Antibiotics, Antineoplastic therapeutic use   MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Male MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• doxorubicin-N-(2-hydroxypropyl)methacrylamide copolymer conjugate MeSH Browser
• Doxorubicin MeSH
• Immunoglobulins MeSH
• Polymethacrylic Acids MeSH
• Drug Carriers MeSH
• Antibiotics, Antineoplastic MeSH