Novel synthesis of a tetra-acridinyl peptide as a new DNA polyintercalator

Amino acid or peptide conjugates of acridine/acridone and quinoline/quinolone-containing drugs. A critical examination of their clinical effectiveness within a twenty-year timeframe in antitumor chemotherapy and treatment of infectious diseases

Acridines/acridones, quinolines/quinolones (chromophores) and their derivatives constitute extremely important family of compounds in current medicine. Great significance of the compounds is connected with antimicrobial and antitumor activities. Combining these features together in one drug seems to be long-term benefit, especially in oncology therapy. The attractiveness of the chromophore drugs is still enhanced by elimination their toxicity and improvement not only selectivity, specificity but also bioavailability. The best results are reached by conjugation to natural peptides. This paper highlights significant advance in the study of amino acid or peptide chromophore conjugates that provide highly encouraging data for novel drug development. The structures and clinical significance of amino acid or peptide chromophore conjugates are widely discussed.

Metabolically stabilized long-circulating PEGylated polyacridine peptide polyplexes mediate hydrodynamically stimulated gene expression in liver

A novel class of PEGylated polyacridine peptides was developed that mediate potent stimulated gene transfer in the liver of mice. Polyacridine peptides, (Acr-X)_n-Cys-PEG, possessing 2–6 repeats of Lys-acridine (Acr) spaced by either Lys, Arg, Leu or Glu, were Cys derivatized with polyethylene glycol (PEG _{5000 Da}) and evaluated as in vivo gene transfer agents. An optimal peptide of (Acr-Lys)₆-Cys-PEG was able to bind to plasmid DNA (pGL3) with high affinity by polyintercalation, stabilize DNA from metabolism by DNAse and extend the pharmacokinetic half-life of DNA in the circulation for up to 2 hrs. A tail vein dose of PEGylated polyacridine peptide pGL3 polyplexes (1 μg in 50 μl), followed by a stimulatory hydrodynamic dose of normal saline at times ranging from 5–60 min post-DNA administration, led to a high level of luciferase expression in the liver, equivalent to levels mediated by direct hydrodynamic dosing of 1 μg of pGL3. The results establish the unique properties of PEGylated polyacridine peptides as a new and promising class of gene delivery peptides that facilitate reversible binding to plasmid DNA, protecting it from DNase in vivo resulting in an extended circulatory half-life, and release of transfection-competent DNA into the liver to mediate a high-level of gene expression upon hydrodynamic boost.

Discovery of metabolically stabilized electronegative polyacridine-PEG peptide DNA open polyplexes

Cationic condensing peptides and polymers bind electrostatically to DNA to form cationic polyplexes. While many cationic polyplexes are able to achieve in vitro transfection mediated through electrostatic interactions, few have been able to mediate gene transfer in vivo. The present study describes the development and testing of polyacridine PEG-peptides that bind to plasmid DNA by intercalation resulting in electronegative open polyplex DNA. Polyacridine PEG-peptides were prepared by chemically conjugating 6-(9-acridinylamino) hexanoic acid onto side chains of Lys in PEG-Cys-Trp-(Lys)(3, 4, or 5). The resulting PEG-Cys-Trp-(Lys-(Acr))(3, 4, or 5) peptides bound tightly to DNA by polyintercalation, rather than electrostatic binding. Unlike polycationic polyplexes, polyacridine PEG-peptide polyplexes were anionic and open coiled, as revealed by zeta potential and atomic force microscopy. PEG-Cys-Trp-(Lys-(Acr))(5) showed the highest DNA binding affinity and the greatest ability to protect DNA from metabolism by DNase. Polyacridine PEG-peptide DNA open polyplexes were dosed intramuscularly and electroporated in mice to demonstrate their functional activity in gene transfer. These results establish polyacridine PEG-peptide DNA open polyplexes as a novel gene delivery method for in vivo use.