Title:  Vaccine adjuvant and vaccine

United States Patent:  6,149,922

Assignee:  CytRx Corporation (DE)

Filed:  December 28, 1998

The present invention includes novel polyoxyethylene/polyoxypropylene block copolymers as well as methods for making the block copolymers. The block copolymers are high molecular weight molecules and are useful as general surfactants and display enhanced biological efficacy as vaccine adjuvants.

SUMMARY OF THE INVENTION

In accordance with the present invention, a new class of polyoxyethylene/polyoxypropylene copolymers, useful as surfactants and adjuvants and capable of affecting biological systems is provided. The present invention provides a synthetic method and a resulting composition for nonionic block polyoxyethylene polyoxypropylene copolymers with a molecular weight of the hydrophobic region that is much higher than block copolymers currently available. The compositions are particularly useful as surfactants and as adjuvants in vaccines and gene therapy etc. The superior adjuvant properties of the composition facilitate vaccination with lower amounts of antigen.

The biologically-active copolymer of the present invention comprises a block copolymer of polyoxyethylene (POE), which is hydrophilic, and polyoxypropylene (POP) which is hydrophobic. The block copolymer is built on a propylene glycol initiator. In a preferred embodiment of the biologically-active copolymers of the present invention, the block copolymers that comprise the biologically-active copolymers of the present invention have the following general formulas:

HO(C₂ H₄ O)_a (C₃ H₆ O)_b (C₂ H₄ O)_a H

wherein "b" represents a number such that the molecular weight of the polyoxypropylene hydrophobe (C₃ H₆ O) is between approximately 7,000 and 20,000 Daltons and "a" represents a number such that the percentage of polyoxyethylene hydrophile (C₂ H₄ O) is between approximately 1% and 40% by weight.

According to the present invention, the copolymer is synthesized using propylene glycol as the initiating molecule. Cesium hydroxide, monohydrate (CsOH.H₂ O) is the catalyst, usually used in a mole ratio of 1:2 to 1:8 with the initiating molecule. Under reduced pressure and elevated temperatures, the propylene oxide is added by rate limiting vapor phase addition to the reaction mixture until the molecular weight of the added polyoxypropylene is at least 8000 Daltons depending upon the size of the desired final product. Once the desired molecular weight is achieved, the addition of propylene oxide is halted. Ethylene oxide is then introduced by vapor phase addition to the reaction mixture and allowed to add to the polypropylene termini of the molecule until the polyethylene portion of the molecule is grown to approximately 2% to 40% of the total molecular weight of the molecule. The resulting nonionic block copolymer molecule has a high molecular weight hydrophobic region, the polyoxypropylene block, flanked by a low molecular weight hydrophilic region, the polyoxyethylene region.

Although the reaction of propylene oxide with the reactive hydrogen compound is typically carried out by simply heating a mixture of the reactants under pressure at a sufficiently high temperature, this method is not useful as the temperatures and pressure required are excessive, control of the reaction is difficult, and the amount of low molecular weight fraction is significantly high. In addition, the material resulting from such a method is extremely heterogeneous and polydisperse. According to the present invention, by adding the propylene oxide to the reaction vessel at such a rate that it reacts as rapidly as added, excess propylene oxide in the reaction vessel is avoided, which results in increased control of the reaction, and an unexpectedly improved yield of less-unsaturated and relatively homogeneous high molecular weight copolymer product having a high molecular weight hydrophobic region.

The present invention includes a method of delivering therapeutic drugs to a human or animal for treating disease states such as, but not limited to, bacterial infection and infections caused by HIV and other DNA and RNA viruses. The present invention relates particularly to compositions and methods for treating infectious diseases and genetic disorders through gene therapy and intracellular delivery of antisense oligonucleotides or other nucleic acid sequences.

The present invention also comprises use of the new copolymer as a vaccine adjuvant which, when admixed with an antigen or hapten and administered into a human or animal, will induce a more intense immune response to the antigen than when the antigen is administered alone. In many cases, the adjuvant that is described as the present invention will increase overall titer of antibodies specific for the vaccine antigen and induce cellular immune responses specific for the vaccine antigen. The present invention also includes vaccines comprising an antigen or group of antigens and the new class of polyoxyethylene/polyoxypropylene copolymers which are present in the composition as an adjuvant.

Accordingly, it is an object of the present invention to provide a composition and a method for making the composition comprising a polyoxyethylene/polyoxypropylene block copolymer that has an internal polyoxypropylene block with a molecular weight of between approximately 7000 and 20,000 Daltons and the polyoxypropylene block copolymer being substantially free of unsaturation.

Another object of the present invention is to provide compounds that can stimulate the immune system and act as an effective vaccine adjuvant for use in a human or animal.

Still another object of the present invention is to provide a composition with superior adjuvant properties that facilitates vaccination with lower amounts of antigen.

Another object of the present invention is to provide compositions that facilitate delivery of one or more therapeutic nucleic acid sequence function altering agents into the interior of a cell, such as a phagocytic cell, when admixed with a therapeutic agent.

Another object of the present invention is to provide compositions that act synergistically with a delivered agent once inside a cell.

Still another object of the invention is to provide nonionic block copolymers having surfactant properties that facilitate the transmission and introduction across cellular plasma membranes of nucleic acid sequences and compounds capable of altering nucleic acid sequence function.

A further object of the present invention is to provide compositions and a method for treating genetic and physiologic disorders using nucleic acid sequences and antisense oligonucleotides in combination with nonionic block copolymers.

Another object of the present invention is to provide compositions and a method useful for manipulating the expression of genes using triplex DNA compounds.

Yet another object of the invention is to provide DNA vaccines.

Yet another object of the present invention is to provide a method for synthesizing polyoxyethylene/polyoxypropylene block copolymer where the polyoxypropylene block polymer has a molecular weight of at least 7000 Daltons and is substantially free of unsaturation.

Claim 1 of 5 Claims

What is claimed is:

1. A method of synthesizing a composition consisting of a polyoxypropylene/polyoxyethylene block copolymer having the following general formula:

HO(C₂ H₄ O)_a (C₃ H₆ O)_b (C₂ H₄ O)_a H

wherein "b" represents a number such that the molecular weight of the hydrophobe (C₃ H₆ O) is greater than 15,000 Daltons and "a" represents a number such that the percentage of hydrophile (C₂ H₄ O) is between approximately 3% and 30% by weight, said method comprising:

(a) adding propylene glycol to an oxygen free reactor vessel containing cesium hydroxide (CsOH.H₂ O) and maintaining a temperature of between approximately 90^oC. and 120^oC., wherein the mole ratio of the cesium hydroxide to the propylene glycol is between approximately 12 to 1:8;

(b) adding propylene oxide to the reactor vessel under conditions allowing the formation of a polyoxypropylene molecule, the propylene oxide being added by rate limiting vapor phase addition, minimizing excess propylene oxide, and the propylene oxide being added until the molecular weight of the polyoxypropylene molecule is greater than 15,000 Daltons;

(c) adding ethylene oxide to the reactor vessel under conditions allowing the formation of polyoxyethylene blocks on each end of the polyoxypropylene molecule, thereby forming polyoxypropylene/polyoxyethylene block copolymer in the reactor vessel, the ethylene oxide being added until the percentage of polyoxyethylene is between approximately 3% to 30% by weight of the block copolymer, the block copolymer having significantly reduced level of unsaturation.

(d) removing any remaining cesium hydroxide in the block copolymer.

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