Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Advanced Drug Delivery Reviews (v.57, #5)
Pharmacokinetics in gene delivery
by Yoshinobu Takakura Theme Editor; Mitsuru Hashida Theme Editor (pp. 667-668).
Gene medicines: The end of the beginning? by Alain Rolland (pp. 669-673).
First-generation gene medicines and genetic vaccines represent a promising new class of therapeutics that have the potential to prevent, correct, or modulate genetic or acquired diseases. The rational design of synthetic gene delivery and expression systems continues to be essential to enable the precise temporal and spatial control of transgene expression in vivo. With the tantalizing efficacy results and outstanding safety profile observed with nonviral, plasmid-based product candidates in early clinical trials, a multidisciplinary approach remains critical to further improve the effectiveness, reduce the manufacturing costs, and maintain the safety of gene therapeutics and vaccines for their successful development. This commentary provides an historical perspective on somatic gene therapy and briefly addresses the rate-limiting steps in effective gene transfer and expression. The importance of understanding plasmid pharmacokinetics after administration by conventional routes in animal models and in humans is emphasized. Pharmaceutical scientists have a pivotal role to play in deciphering the key biological parameters to effective gene transfer and designing gene delivery systems that will enable plasmid-based products to become an integral part of the future medical armamentarium.
Keywords: Somatic gene therapy; Gene medicines; Genetic vaccines; Plasmid expression systems; Gene delivery systems; Plasmid pharmacokinetics
Theoretical considerations involving the pharmacokinetics of plasmid DNA by Makiya Nishikawa; Yoshinobu Takakura; Mitsuru Hashida (pp. 675-688).
Success of in vivo gene therapy relies on the development of gene delivery technologies, by which a well-controlled transgene expression is achieved as far as the spatial and temporal profile of the expression is concerned. Because transgene expression only occurs in cells that are transduced with the gene administered, the tissue distribution of genes is an important factor determining the efficacy of in vivo gene transfer. Plasmid DNA is the simplest vector and its administration in naked or complexed form results in significant transgene expression in various organs. The route of administration, the use of cationic vectors and the administration technique greatly affects the tissue distribution of plasmid DNA and the subsequent transgene expression. Therefore, a clear understanding of the tissue distribution of naked and complexed plasmid DNA is a prerequisite for strategies for developing effective in vivo gene transfer methods. Pharmacokinetics translates the tissue distribution properties of plasmid DNA into quantitative parameters, which can be compared with parameters obtained under different conditions, or with physiological parameters such as blood flow rate. Here we discuss the pharmacokinetic evaluation of the tissue distribution characteristics of plasmid DNA, in the free and complexed forms.
Keywords: Gene transfer; Tissue distribution; Clearance; Receptor-mediated endocytosis
Implications of pharmacokinetic behavior of lipoplex for its inflammatory toxicity by Jing-Shi Zhang; Feng Liu; Leaf Huang (pp. 689-698).
Inflammatory toxicity represents a typical toxicity associated with systemic administration of cationic liposome/DNA complex (lipoplex). Collected information indicates that the lipoplex gene delivery system mediates an uptake of plasmid DNA by the liver, mainly by Kupffer cells, in which a large amount of cytokine is produced. Therefore, many efforts have been made to overcome this problem. Previous reports by our laboratory demonstrated that sequential injection of cationic liposome and DNA could dramatically decrease the toxicity. In comparison with lipoplex injection, this method significantly suppresses the uptake of DNA by the liver. Opsonization effect in the stimulation of Kupffer cell uptake is proposed as an explanation for the differences in the pharmacokinetic properties of plasmid DNA after lipoplex injection and sequential injection. In this review, we cover the current understanding of the mechanisms underlying inflammatory toxicity and the several attempts to overcome this toxicity. The mechanism related to the pharmacokinetic properties of the lipoplex is focused on here for discussion.
Keywords: Cationic liposomes; Cytokine induction; Plasmid DNA; Nonviral vectors; Immune response; Liver uptake; Kupffer cells; Opsonization
Water insoluble and soluble lipids for gene delivery by Ram I. Mahato (pp. 699-712).
Among various synthetic gene carriers currently in use, liposomes composed of cationic lipids and co-lipids remain the most efficient transfection reagents. Physicochemical properties of lipid/plasmid complexes, such as cationic lipid structure, cationic lipid to co-lipid ratio, charge ratio, particle size and zeta potential have significant influence on gene expression and biodistribution. However, most cationic lipids are toxic and cationic liposomes/plasmid complexes do not disperse well inside the target tissues because of their large particle size. To overcome the problems associated with cationic lipids, we designed water soluble lipopolymers for gene delivery to various cells and tissues. This review provides a critical discussion on how the components of water insoluble and soluble lipids affect their transfection efficiency and biodistribution of lipid/plasmid complexes.
Keywords: Cationic liposomes; Water soluble lipopolymers; Biodistribution; Gene delivery
The hydrodynamics-based procedure for controlling the pharmacokinetics of gene medicines at whole body, organ and cellular levels by Naoki Kobayashi; Makiya Nishikawa; Yoshinobu Takakura (pp. 713-731).
Hydrodynamics-based gene delivery, involving a large-volume and high-speed intravenous injection of naked plasmid DNA (pDNA), gives a significantly high level of transgene expression in vivo. This has attracted a lot of attention and has been used very frequently as an efficient, simple and convenient transfection method for laboratory animals. Until recently, however, little information has been published on the pharmacokinetics of the injected DNA molecules and of the detailed mechanisms underlying the efficient gene transfer. We and other groups have very recently demonstrated that the mechanism for the hydrodynamics-based gene transfer would involve, in part, the direct cytosolic delivery of pDNA through the cell membrane due to transiently enhanced permeability. Along with the findings in our series of studies, this article reviews the cumulative reports and other intriguing information on the controlled pharmacokinetics of naked pDNA in the hydrodynamics-based gene delivery. In addition, we describe various applications reported so far, as well as the current attempts and proposals to develop novel gene medicines for future gene therapy using the concept of the hydrodynamics-based procedure. Furthermore, the issues associated with the clinical feasibility of its seemingly invasive nature, which is probably the most common concern about this hydrodynamics-based procedure, are discussed along with its future prospects and challenges.
Keywords: Naked plasmid DNA; Hydrodynamics-based procedure; Intravenous injection; Pharmacokinetics; Nonviral gene delivery; Gene therapy
Physical methods for gene transfer: Improving the kinetics of gene delivery into cells by Sophie Mehier-Humbert; Richard H. Guy (pp. 733-753).
One factor critical to successful gene therapy is the development of efficient delivery systems. Although advances in gene transfer technology, including viral and non-viral vectors, have been made, an ideal vector system has not yet been constructed. This review describes the basic principles behind various physical methods for gene transfer and assesses the advantages and performance of such approaches, compared to other transfection systems. In particular, the kinetics and efficiency of gene delivery, the toxicity, in vivo feasibility, and targeting ability of different physical methodologies are discussed and evaluated.
Keywords: Gene transfer; Electroporation; Sonoporation; Gene gun; Magnetofection; Ultrasound
Intracellular routing of plasmid DNA during non-viral gene transfer by Delphine Lechardeur; A.S. Verkman; Gergely L. Lukacs (pp. 755-767).
Gene transfer using non-viral vectors is a promising approach for the safe delivery of therapeutic DNA in genetic and acquired human diseases. Whereas the lack of specific immune response favors the use of plasmid–cationic polymer complexes, the limited efficacy and short duration of transgene expression impose major hurdles in the application of non-viral gene delivery techniques. Here, we review the major cellular, metabolic and physico-chemical impediments that non-viral vectors encounter before plasmid DNA enters the nucleus. Following endocytosis of DNA–polycation complexes, a large fraction of the DNA is targeted to the lysosomes. Since the cytosolic release of heterologous DNA is a prerequisite for nuclear translocation, entrapment and degradation of plasmid DNA in endo-lysosomes constitute one of the major impediments to efficient gene transfer. Plasmid DNA that escapes the endo-lysosomal compartment encounters the diffusional and metabolic barriers of the cytoplasm, reducing greatly the number of intact plasmids that reach the nucleosol. Nuclear translocation of DNA requires either the disassembly of the nuclear envelope or active nuclear transport via the nuclear pore complex. A better understanding of the cellular and molecular basis of non-viral vector trafficking from the extracellular compartment into the nucleus may provide strategies to overcome those obstacles that limit the efficiency of gene delivery.
Keywords: Abbreviations; DOPE; dioleoylphosphatidylethanolamine; MT; microtubule; MTOC; microtubule-organizing center; NPC; nuclear pore complex; NLS; nuclear localization sequence; PEI; polyethylenimine; POL; polylysine; PAM; poliamidoamine; WGA; wheat germ agglutinin; NPC; nuclear pore complexLipoplex; Plasmid DNA degradation; Endocytosis; Endo-lysosome; Cytoplasm; Nuclear targeting; Diffusional mobility
Controlling the kinetics of transgene expression by plasmid design by Nelson S. Yew (pp. 769-780).
While a vast array of liposomes, peptides, and molecular conjugates have been evaluated for nonviral gene transfer, the entity containing the actual gene itself is almost always a plasmid. The layout of most plasmid DNA (pDNA) vectors is usually quite simple, consisting of a promoter, transgene, polyadenylation signal, and a backbone that permits propagation of the plasmid in bacteria. Additional sequence elements and modifications can be incorporated to influence the stability of gene expression and retention of the pDNA molecule in a given tissue. This review describes the different choices that can be made when designing a pDNA vector for transient, sustained, or regulated expression. The choice of promoter is a major determinant governing the kinetics of expression, but other factors, such as CpG content and the topological form of the pDNA are also influential. Vectors can also be designed to respond to the local environment of a given cell or tissue, or engineered to respond to a small molecule drug.
Keywords: Plasmid DNA; Promoter; Gene expression; Synthetic vectors; CpG motifs; Gene regulation; Small molecule drugs
Approaches to improving the kinetics of adenovirus-delivered genes and gene products by Zhi-Li Xu; Hiroyuki Mizuguchi; Fuminori Sakurai; Naoya Koizumi; Tetsuji Hosono; Kenji Kawabata; Yoshiteru Watanabe; Teruhide Yamaguchi; Takao Hayakawa (pp. 781-802).
Adenovirus (Ad) vectors have been expected to play a great role in gene therapy because of their extremely high transduction efficiency and wide tropism. However, due to the intrinsic deficiency of their immunogenic toxicities, Ad vectors are rapidly cleared from the host, transgene expression is transient, and readministration of the same serotype Ad vectors is problematic. As a result, Ad vectors are continually undergoing refinement to realize their potential for gene therapy application. Even after 1999, when a patient fatally succumbed to the toxicity associated with Ad vector administration at a University of Pennsylvania (U.S.) experimental clinic, enthusiasm of gene therapists for Ad vectors has not waned. With great efforts from various research groups, significant advances have been achieved through comprehensive approaches to improving the kinetics of Ad vector-delivered genes and gene products.
Keywords: Immunogenic toxicities; Biodistribution; Cationic liposome; PEGylation; Helper-dependent; Targeting; In-cis acting element; Integration; Regulatable expression