Jindřich Kopeček

HPMA copolymer-anticancer drug conjugates: design, activity, and mechanism of action

The design, synthesis and properties of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers as carriers of anticancer drugs are reviewed. Macromolecular therapeutics based on HPMA copolymers are biocompatible, preferentially accumulate in tumors, and possess a higher anticancer efficacy than low molecular weight drugs. Novel designs of HPMA copolymer carriers resulted in long-circulating conjugates and gene and oligonucleotide delivery systems. HPMA copolymer based macromolecular therapeutics were active against numerous cancer models and are in clinical trials. The data obtained indicated that macromolecular therapeutics activated different signaling pathways and possessed a different mechanism of action than free drugs. This bodes well for the success of future research aimed at identification of new intracellular molecular targets as a basis for the design of the second generation of macromolecular therapeutics.

Polymer conjugates with anticancer activity

Polymer conjugates may possess anticancer activity through a variety of mechanisms. The macro-molecules themselves may have anticancer activities, or, more typically, inert biocompatible polymers serve as carriers for low molecular weight anticancer agents. Polymer conjugates may also be targeted to increase the concentration of conjugate in the vicinity of a specific subset of cells. This article reviews the recent literature that pertains to polymer conjugates with anticancer activity. The types of polymers chosen as drug carriers and the biodistribution of polymers in the body are discussed. Also, the synthesis, biological properties, and the means used to evaluate the anticancer activities of polymer conjugates are detailed.

Soluble synthetic polymers as potential drug carriers

Soluble synthetic polymers provide a potential targetable drug delivery system. In this article we discuss the consequences of the attachment of pharmaceuticals to macromolecular carriers with special reference to endocytosis and lysosomotropic drug delivery. The types of polymers which may be used as carriers are reviewed with particular regard to the methodology currently available in polymer chemistry for the synthesis of polymers bearing cell-specific targeting residues and incorporating effective polymer drug linkages. In order to be successful in drug delivery, the polymeric drug carrier must behave in a predictable and favourable manner in the biological environment. Studies concerned with the biological properties of synthetic polymers are also reviewed. The idea of using drug carriers to improve the therapeutic efficacy of pharmacological agents is receiving increasing attention, and the relationship between soluble synthetic polymers and other proposed carriers is discussed together with possible clinical applications.

Smart and genetically engineered biomaterials and drug delivery systems.

The design, synthesis, and properties of novel stimuli-sensitive and genetically engineered biomaterials and drug delivery systems are reviewed. Two approaches to their engineering are presented. One approach is to improve the traditional methods of synthesis, as demonstrated by the example of controlled copolymerization of alpha-amino acid N-carboxyanhydrides. The other approach, discussed in more detail, uses genetic engineering methods. The design of hybrid hydrogel systems whose components derive from at least two distinct classes of molecules, e.g., synthetic macromolecules and protein domains, is assessed. The design of self-assembling block copolymers is discussed in detail. Finally, the pharmaceutics related applications of these materials are presented.

HPMA copolymer bound adriamycin overcomes MDR1 gene encoded resistance in a human ovarian carcinoma cell line

N-(2-Hydroxypropyl)methacrylamide (HPMA) copolymer-adriamycin (ADR) conjugate containing lysosomally degradable oligopeptide (GFLG) side chains terminated in ADR was synthesized. The effect of free and HPMA copolymer-bound ADR on the viability of A2780 sensitive and A2780/AD multidrug resistant human ovarian carcinoma cells was studied in vitro. As expected, the IC50 dose for the HPMA copolymer-ADR conjugate was higher than for free ADR reflecting the difference in the mechanism of cell entry. The resistant A2780/AD cells demonstrated about 40-times higher resistance to free ADR than the sensitive A2780 cells. On the contrary, there was only a small difference in cytotoxicity of the HPMA copolymer-ADR conjugate toward sensitive A2780 or MDR resistant A2780/AD cells. The IC50 value for A2780/AD was only about 20% higher than the value for sensitive A2780 cells. These data seem to indicate that the HPMA copolymer-ADR conjugate may, at least partially, avoid the ATP driven P-glycoprotein (Pgp) efflux pump. The analysis of the expression of the MDR1 gene which encodes the Pgp, has shown that free ADR in high doses stimulated MDR1 gene expression in sensitive A2780 cells. At the same time both free and HPMA copolymer-ADR conjugate partially inhibited the expression of the MDR1 and beta 2 m genes in multidrug resistant A2780/AD cells.

Poly[N-(2-hydroxypropyl)methacrylamide]—I. Radical polymerization and copolymerization

The radical polymerization of N-(2-hydroxypropyl)methacrylamide was investigated kinetically. The hydrophilic character of the polymerization medium was found to affect the rate of decomposition of the initiator [2,2′-azobis(methyl isobutyrate)] and the course of primary radical termination. The presence of the -OH group in the alkyl group attached to the nitrogen atom leads to an increase in the molecular weight of the polymer in comparison with polymers of N-alkyl methacrylamides. This phenomenon was interpreted in terms of the possibility of a polymeranalogous transesteramidation and of an increased possibility of transfer to monomer and polymer. The copolymerization parameters of N-(2-hydroxypropyl)methacrylamide (M1) with methyl methacrylate and styrene were determined; in the first case, r1 = 0·84 ± 0·05, r2 = 0·66 ± 0·07; in the second case, r1 = 0·53 ± 0·08, r2 = 1·72 ± 0·19.

Polymer–drug conjugates: Origins, progress to date and future directions

This overview focuses on bioconjugates of water-soluble polymers with low molecular weight drugs and proteins. After a short discussion of the origins of the field, the state-of-the-art is reviewed. Then research directions needed for the acceleration of the translation of nanomedicines into the clinic are outlined. Two most important directions, synthesis of backbone degradable polymer carriers and drug-free macromolecular therapeutics, a new paradigm in drug delivery, are discussed in detail. Finally, the future perspectives of the field are briefly discussed.

Water soluble polymers in tumor targeted delivery

The rationales for the use of water soluble polymers for anticancer drug delivery include: the potential to overcome some forms of multidrug resistance, preferential accumulation in solid tumors due to enhanced permeability and retention (EPR) effect, biorecognizability, and targetability. The utility of a novel paradigm for the treatment of ovarian carcinoma in an experimental animal model, which combines chemotherapy and photodynamic therapy with polymer-bound anticancer drugs is explained. Research and clinical applications as well as directions for the future development of macromolecular therapeutics are discussed.

Targetable HPMA copolymer-adriamycin conjugates. Recognition, internalization, and subcellular fate

Recognition, internalization, and subcellular trafficking of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer conjugates containing N-acylated galactosamine (GalN) or monoclonal OV-TL16 antibodies (Ab) have been investigated in human hepatocarcinoma HepG2 and ovarian carcinoma OVCAR-3 cells, respectively. The intrinsic fluorescence of fluorescein or adriamycin (ADR) attached to HPMA copolymers permitted us to follow the subcellular fate of HPMA copolymer conjugates by confocal fluorescence microscopy and fluorescence spectroscopy. The pattern of fluorescence during incubation of HPMA copolymer-ADR-GalN conjugate containing lysosomally degradable tetrapeptide (GFLG) side-chains with HepG2 cells was consistent with conjugate recognition, internalization, localization in lysosomes, followed by the release of ADR from the polymer chains and ultimately diffusion via the cytoplasm into the cell nuclei. A similar pattern was observed in OVCAR-3 cells for Ab targeted HPMA copolymer conjugates. To test our hypothesis that HPMA-copolymer-bound anticancer drugs will be inaccessible to the energy-driven P-glycoprotein efflux pump in multidrug resistant (MDR) cells, we have compared the internalization of the HPMA copolymer-ADR conjugates by sensitive (A2780) and ADR-resistant (A2780/AD) ovarian carcinoma cell lines. Preliminary data on relative retention of ADR in MDR (A2780/AD) cells indicate a higher intracellular ADR concentration after incubation with HPMA copolymer-ADR conjugate when compared to incubation with free (unbound) ADR.

Smart Self‐Assembled Hybrid Hydrogel Biomaterials

Hybrid biomaterials are systems created from components of at least two distinct classes of molecules, for example, synthetic macromolecules and proteins or peptide domains. The synergistic combination of two types of structures may produce new materials that possess unprecedented levels of structural organization and novel properties. This Review focuses on biorecognition-driven self-assembly of hybrid macromolecules into functional hydrogel biomaterials. First, basic rules that govern the secondary structure of peptides are discussed, and then approaches to the specific design of hybrid systems with tailor-made properties are evaluated, followed by a discussion on the similarity of design principles of biomaterials and macromolecular therapeutics. Finally, the future of the field is briefly outlined.