United States Patent:  5,994,314

Assignee:  Inhale Therapeutic Systems, Inc. (San Carlos, CA)

Filed:  April 14, 1995

A dry powder composition comprises insoluble nucleic acid constructs dispersed within with a hydrophilic excipient material, where the powder particles have an average size in the range from 0.5 .mu.m to 50 .mu.m. Nucleic acid constructs may comprise bare nucleic acid molecules, viral vectors, or vesicle structures. The hydrophilic excipient material will be selected to stabilize the nucleic acid molecules in the constructs, enhance dispersion of the nucleic acid in dry powder aerosols, and enhance wetting of the nucleic acid constructs as they are delivered to moist target locations within the body.

SUMMARY OF THE INVENTION

According to the present invention, dry powder nucleic acid compositions comprise insoluble nucleic acid constructs (typically small particles) dispersed within a matrix of hydrophilic excipient material to form large aerosol particles. Usually, the nucleic acid particles will be present in excess powdered excipient material, usually being the same excipient which forms the matrix. The powdered aerosol particles will have an average particle size in the range from 0.5 .mu.m to 200 .mu.m, usually being in the range from 0.5 .mu.m to 5 .mu.m for lung delivery with larger sizes being useful for delivery to other moist target locations. The nucleic acid constructs may comprise bare nucleic acid molecules, viral vectors, associated viral particle vectors, nucleic acids present in a vesicle, or the like.

The dry powder nucleic acid compositions may be prepared by suspending the insoluble nucleic acid constructs in an aqueous solution of the hydrophilic excipient and drying the solution to produce a powder comprising particles of the nucleic acid construct dispersed within the dried excipient material, usually in the presence of excess powdered excipient. The weight ratio of nucleic acid construct to hydrophilic excipient in the initial solution is in range from 2:1 to 1:100, preferably from 1:1 to 1:10, and the solution may be dried by spraying droplets into a flowing gas stream (spray drying) or by vacuum drying to produce a crude powder followed by grinding to produce a final powder.

In the case of particles intended for lung delivery, having a particle size from 0.5 .mu.m to 5 .mu.m, each particle may contain from 10 to 10⁷ nucleic acid constructs, usually from 10² to 10⁵ nucleic acid constructs, and preferably from 10³ to 10⁴ nucleic acid constructs. The constructs may be uniformly or non-uniformly dispersed in each particle, and the particles in turn will often be present in excess powdered excipient, usually at a weight ratio (nucleic acid construct:excipient powder free from nucleic acids) in the range from 1:1, to 1:10³ usually from 1:10 to 1:500.

In a preferred aspect of the present invention, aqueous solutions containing the liposome vesicles as nucleic acid constructs will be substantially free from buffering agents and salts. It has been found that drying, particularly spray drying, of such neutrally charged solutions results in powders having enhanced transfection activity compared to powders formed by drying the same liposome vesicles in buffered solutions. In contrast, aqueous solutions containing viral vectors as the nucleic acid constructs usually will be buffered to enhance stability of the viral vectors.

In a second preferred aspect of the present invention, the dry powder nucleic acid compositions will be prepared by spraying droplets of the liquid solution into a heated gas stream over a short time period, typically 50^oC. to 150^oC. over a period from 10 msec to 100 msec, in a spray dryer. The resulting powder comprising particles containing nucleic acid constructs (and usually containing powdered excipient free from nucleic acids) will then be collected in a partially cooled environment, typically maintained at 5^oC. to 50^oC., and thereafter stored at a temperature from 5^oC. to 25^oC. at a low humidity, typically below 5% RH. It has been found that such collection and storage conditions help to preserve and stabilize the compositions and to enhance transfection efficiency.

Methods for delivering nucleic acid constructs according to the present invention comprise directing the dry powder containing the nucleic acid constructs to a moist target location in a host, where the hydrophilic excipient matrix material of the particles will dissolve when exposed to the moist target location, leaving the much smaller nucleic acid construct particles to freely interact with cells. In a preferred aspect of the present invention, the target location is the lung and the particles are directed to the lung by inhalation.

Compositions of the present invention are particularly advantageous since the hydrophilic excipient will stabilize the nucleic acid constructs for storage. Excess powdered hydrophilic excipient can also enhance dispersion of the dry powders into aerosols and, because of its high water solubility, facilitate dissolution of the composition to deposit the nucleic acid constructs into intimate contact with the target membranes, such as the lung surface membrane of the host.

Claim 1 of 27 Claims

1. A dry powder nucleic acid composition comprising a cationic lipid-DNA complex dispersed in a hydrophilic excipient.

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