Current Pharmaceutical Biotechnology - Volume 1, Issue 4, 2000

The scientific development of immunotherapies and radioimmunotherapies of cancer began more than four decades ago. Over time, it has become apparent that the choice of target antigen, immunogenicity of antibodies, length of antibody half-life, ability of antibodies to recruit immune effector functions, decision on conjugation of antibodies to toxins or radionuclides and antibody manufacturing are critical components of successful development of an immunotherapeutic regimen. Anti-idiotype antibodies were some of the first successful monoclonal antibody treatments developed for non-Hodgkins lymphoma. In 1997, the chimeric antibody, Rituximab, was approved by the United States Food and Drug Administration for treatment of patients with relapsed or refractory low-grade or follicular non-Hodgkins lymphoma. In an effort to enhance the efficacy of immunotherapy, toxins and radionuclides have been conjugated to monoclonal antibodies. Ibritumomab, the parent murine antibody of Rituximab, is conjugated to the radioisotope 90Y to create 90Y Ibritumomab tiuxetan, (90Y Zevalin, IDEC-Y2B8). Promising Phase I/II trials have been completed. Phase III experimental trials of 90Y Ibritumomab tiuxetan as treatment for relapsed or refractory NHL are in progress.

Peptides, proteins, and nucleotides or DNA fragments are the new generation of drugs. They are becoming attractive owing to the fast development of biotechnology. The admnistration of such molecules, however, may be a problem as sensitivity to temperature, instability at some physiological pH values, short plasma half-life, and high molecular dimension, which hinders the diffusive transport, make, at the moment, parenteral route the only possible way of administration of such molecules.Controlled drug delivery that comprises the development of new administration routes could be the answer to the problems for administration of biotechnological molecules.The rational of drug delivery is to change the pharmacokinetic and pharmacodynamic of drugs by controlling their absorption and distribution. Rate and time of drug release at absorption site could be programmed using a so called delivery system. Different technologies, such as chemical (pro-drugs), biological, polymers, lipids (liposomes, LDL), have been proposed to obtain controlled drug release. Also the use of new administration routes is part of controlled drug delivery. In fact, it could increase the drug absorption and reduce the effects of the active ingredient in those districts not interested in the therapy.Drug delivery systems allowing for an effective release in vivo of new biotechnological molecules, such as recombinant antiidiotypic antibodies with antibiotic activity, devoted to the treatment of pulmonary (tuberculosis and pneumocystosis) and mucosal (candidiasis) diseases are discussed under that perspective.

The number of diseases found to be associated with defects of the mitochondrial genome has grown significantly over the last decade. Despite major advances in understanding mtDNA defects at the genetic and biochemical level, there is no satisfactory treatment for the vast majority of patients available. This is largely due to the fact that almost all mitochondrial DNA defects involve the final common pathway of oxidative metabolism making it impossible to bypass the defect by giving alternative metabolic carriers of energy. These seemingly objective limitations of conventional biochemical treatment for patients with defects of mtDNA warrant the exploration of gene therapeutic approaches. However, mitochondrial gene therapy still appears only theoretical and speculative. Any possibility for gene replacement is dependent on the use of a yet unavailable mitochondria-specific transfection vector.Based upon an analysis of the self-assembly behavior of dequalinium, a cationic single-chain bolaamphiphile which is known to selectively accumulate in mitochondria, we have developed a whole new strategy for mitochondria-specific DNA delivery. We have succeeded in preparing vesicles made of dequalinium, which we termed DQAsomes (U.S. Patent 6,090,619). We have shown that DQAsomes efficiently bind and protect DNA and we could demonstrate that DQAsome DNA complexes selectively release DNA at cardiolipin-rich liposomes mimicking both, the inner and the outer mitochondrial membrane. Based on the intrinsic property of dequalinium to preferentially accumulate in mitochondria in response to the electrochemical gradient at the mitochondrial membrane and based on the selective DNA release at mitochondria-like membranes we propose DQAsomes as the first mitochondria-specific vector to deliver DNA to mitochondria in living cells.

The number of therapeutic proteins successfully produced in plants is steadily increasing and is expected to grow even more rapidly in the future. Most therapeutic proteins are glycoproteins and N-glycosylation is often essential for their stability, folding and biological activity. Recombinant glycoproteins of mammalian origin expressed in transgenic plants largely retain their biological activity. However, plants are not ideal for production of pharmaceutical proteins because they produce molecules with glycans that are not compatible with therapeutic applications in humans. As a consequence, strategies to humanise plant N-glycans are now developed. Some of these strategies involve the retention of the recombinant glycoprotein in the endoplasmic reticulum while others are related to the inhibition of endogenous Golgi glycosyltransferases or addition of new glycosyltransferases. Data on both the N-glycosylation of therapeutic glycoproteins produced in transgenic plants and current strategies to humanise their N-glycosylation will be discussed in this review.

Actinomycetes are gram-positive bacteria and commercially important microorganisms. They are producers of approximately two thirds of all bioactive compounds known and they produce a great variety of compounds which have clinical application on the basis of their activity against different kinds of organisms and cells as antibacterial (macrolides, avermectins), antitumor (anthracyclines, angucyclines, aureolic acid group) and also compounds showing immunosuppresant activity (rapamycin, FK506). Most of these clinically useful pharmaceuticals produced by actinomycetes belong to the polyketide family. Polyketides comprise a wide family of chemically diverse compounds, many of which have shown bioactivity. The development of recombinant DNA technology has opened a new and exciting field of research for the generation of new bioactive compounds through genetic manipulation of the biosynthetic pathways. Researchers in this area are trying to take advantage of the enormous capability of actinomycetes to produce pharmaceutically useful compounds in order to manipulate the different biosynthetic pathways and subsequently generate novel drugs. Combinatorial biosynthesis is now emerging as a powerful tool to generate novel families of compounds by interchanging secondary metabolism genes between bioactive producing actinomycetes. Novel compounds will be the consequence of the concerted action of enzymes from different, but related, biosynthetic pathways. Insertional inactivation of selected genes and tailoring modification may also produce novel compounds that can be useful pharmaceuticals or lead compounds for further chemical modification. This minireview will present the state of the art in this field showing the different polyketides biosynthetic pathways so far characterized and how the identified genes are being used to generate structural biodiversity. Emphasis will be made on the polyketide family including type I and type II polyketides.