Microspheres containing condensed polyanionic bioactive agents and methods for their production

Abstract

The present invention relates to novel compositions comprising microspheres and / or nanospheres containing condensed polyanionic bioactive agents, such as DNA. The polyanionic bioactive agent in the microspheres and / or nanospheres is preferably condensed using a polycationic condensing agent, such as poly-L-lysine. The present invention further relates to methods for producing the microspheres and / or nanospheres containing condensed polyanionic bioactive agents.

Description

1. FIELD OF THE INVENTION[0001] The subject invention is in the field of sustained drug delivery using micro-encapsulation of bioactive agents. In particular, the invention describes improved methods for incorporating polyanionic bioactive agents into polymeric microspheres and / or nanospheres through the use of a condensing agent, as well as microspheres and / or nanospheres prepared by the method.2. BACKGROUND OF THE INVENTION[0002] 2.1. Gene Therapy[0003] Gene therapy was originally conceived as a specific gene replacement therapy for correcting heritable defects by delivering functionally active therapeutic genes into targeted cells. Initial efforts toward somatic gene therapy have largely relied on indirect means of introducing genes into tissues, called ex vivo gene therapy. In ex vivo protocols, target cells are removed from the body, transfected or infected in vitro with vectors carrying recombinant genes, and re-implanted into the body ("autologous cell transfer"). A variety o...

AI Technical Summary

Benefits of technology

[0022] Many advantages are provided by the present invention, which in one aspect is directed to a method of making microspheres containing polyanionic bioactive agents. The efficiency of incorporation of the polyanionic bioactive agents into the microspheres is increased by using a condensing agent to condense the polyanionic bioactive agent during the manufacture of the microsphere.

Problems solved by technology

Perhaps one of the greatest problems associated with currently devised gene therapies, whether ex vivo or in vivo, is the inability to transfer DNA efficiently into a targeted cell population and to achieve high level expression of the gene product in vivo.

While highly efficient at gene transfer, the major disadvantages associated with the use of viral vectors include the inability of many viral vectors to infect non-dividing cells; problems associated with insertional mutagenesis; inflammatory reactions to the virus and potential helper virus production; antibody responses to the viral coats; and the potential for production and transmission of harmful virus to other human patients.

In addition to the general low efficiency with which most cell types take up and express foreign DNA, many targeted cell populations are found in very low numbers in the body, so that the low efficiency of presentation of DNA to the specific targeted cell types further diminished the overall efficiency of gene transfer.

These polyionic molecules often do not pack well into microspheres and thus have reduced incorporation efficiencies.

However, efforts to formulate DNA within microspheres have been hampered by several difficulties.

Moreover, incorporation of DNA into microspheres is plagued by fragmentation of the DNA.

Unfortunately, each of the two emulsifying steps frequently involves sonication, which causes fragmentation of the DNA.

However, liposomes, including polycationic liposomes, do not have the desirable sustained release properties that microspheres exhibit, as they tend to be less stable and to release their contents rapidly.

Thus, for many purposes, lipsomal delivery systems are not as effective as microsphere delivery systems.