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Thymosin alpha 1 peptide/polymer conjugates

Thymosin alpha 1 peptide/polymer conjugates description/claims

This application is a continuation of U.S. patent application Ser. No. 10/493,690, filed Jul. 9, 2004, which is a §371 of International Application No. PCT/US02/35094, filed Nov. 1, 2002, which claims the benefit of U.S. Provisional Application No. 60/330,870, filed Nov. 1, 2001, the contents of which are incorporated herein.

1. Field of the Invention

The present invention relates to Thymosin alpha 1 peptides.

2. Description of the Background Art

Thymosin alpha 1 (sometimes referred to as TA1) is a 28-amino acid thymic peptide with immunomodulatory properties, homologous to a natural product originally isolated from thymosin fraction 5 of calf thymus. Its biological effects include augmentation of T lymphocyte functions and include modulation of interleukin-2 (IL-2), stimulation of interferon-γ production, induction of T lymphocytes and NK cell activity, and stimulation of thymopoiesis. Thymosin alpha 1 also has been shown to up-regulate MHC Class I expression.

There remains a need in the art for improved compositions containing TA1 and related peptides.

A pharmaceutical composition in accordance with the present invention comprises a physiologically active conjugate comprising a Thymosin alpha 1 (TA1) peptide conjugated to a material which increases half-life of the TA1 peptide in serum of a patient when said conjugate is administered to a patient. The material may be a substantially non-antigenic polymer. According to a method of the invention, a substantially non-antigenic polymer is conjugated to a TA1 peptide. Compositions in accordance with the present invention are administered to patients in need of immune stimulation.

The present invention is applicable to TA1 peptides including naturally occurring TA1 as well as synthetic TA1 and recombinant TA1 having the amino acid sequence of naturally occurring TA1, amino acid sequences substantially similar thereto, or an abbreviated sequence form thereof, and their biologically active analogs having substituted, deleted, elongated, replaced, or otherwise modified sequences which possess bioactivity substantially similar to that of TA1, e.g., a TA1 peptide having sufficient amino acid homology with TA1 such that it functions in substantially the same way with substantially the same activity as TA1.

A pharmaceutical composition in accordance with the present invention comprises a physiologically active conjugate comprising a TA1 peptide conjugated to a material which increases half-life of the TA1 peptide in serum of a patient when said conjugate is administered to a patient. The material may be a substantially non-antigenic polymer. Suitable polymers will have a molecular weight within a range of about 200-300,000, preferably within a range of about 1,000-100,000, more preferably within a range of about 5,000-35,000, and most preferably within a range of about 10,000-30,000, with a molecular weight of about 20,000 being particularly preferred.

The polymeric substances included are also preferably water-soluble at room temperature. A non-limiting list of such polymers include polyalkylene oxide homopolymers such as polyethylene glycol (PEG) or polypropylene glycols, polyoxyethylenated polyols, copolymers thereof and block copolymers thereof, provided that the water solubility of the block copolymers is maintained. Among the substantially non-antigenic polymers, mono-activated, alkyl-terminated polyalkylene oxides (PAO's), such as monomethyl-terminated polyethylene glycols (mPEG's) are contemplated. In addition to mPEG, C1-4 alkyl-terminated polymers may also be useful.

As an alternative to PAO-based polymers, effectively non-antigenic materials such as dextran, polyvinyl pyrrolidones, polyacrylamides, polyvinyl alcohols, carbohydrate-based polymers and the like can be used. Those of ordinary skill in the art will realize that the foregoing list is merely illustrative and that all polymer materials having the qualities described herein are contemplated. For purposes of the present invention, “effectively non-antigenic” means all materials understood in the art as being nontoxic and not eliciting an appreciable immunogenic response in mammals.

The polymer may be straight-chain or branched. Polyethylene glycol (PEG) is a particularly preferred polymer.

The polymer can be conjugated to the TA1 peptide by any suitable method. Exemplary methods for conjugating polymers to peptides are disclosed in U.S. Pat. Nos. 4,179,337, 4,766,106, 4,917,888, 5,122,614 and 6,177,074, as well as PCT International Publication No. WO 95/13090, all of which are incorporated herein by reference. Thymosin alpha 1 has five separate possible sites for amino group conjugation of a polymer, and polymer(s) can be conjugated at one or a plurality of sites. According to one embodiment, 20,000 molecular weight PEG is conjugated to the N-terminal end of TA1 to form a PEG-TA1. This can be formed by solid phase peptide synthesis of TA1 on insoluble polymeric support beads, as is known in the art, with appropriate side chain protective groups. After complete synthesis of the TA1 peptide on the beads, the protected TA1 is cleaved from the beads leaving the N-terminus with a free amino group, which is reacted with 20,000 molecular weight PEG. The side chain protective groups then are removed to form a conjugate in accordance with this embodiment of the invention.

Compositions in accordance with the present invention may be utilized to treat patients in need of immune stimulation. Such patients may include cancer patients, hepatitis patients including patients infected with Hepatitis B or Hepatitis C virus, HIV patients, etc. The method involves administering to a patient an immune stimulated-effective amount of a physiologically active conjugate in accordance with the present invention.

The isolation, characterization and use of TA1 peptides is described, for example, in U.S. Pat. No. 4,079,127, U.S. Pat. No. 4,353,821, U.S. Pat. No. 4,148,788 and U.S. Pat. No. 4,116,951. Immune stimulating-effective amounts of TA1 peptide can be determined by routine dose-titration experiments. TA1 has been found to be safe for humans when administered in doses as high as 16 mg/kg body weight/day. Preferred dosages of TA1 peptide are within the range of 0.001 mg/kg body weight/day to 10 mg/kg body weight/day, with an exemplary dose being about 0.02 mg/kg body weight/day. According to one embodiment, immune stimulating-effective amounts are at dosages which include the TA1 peptide in an amount within a range of about 0.1-10 mg. Preferred dosages include the TA1 peptide in an amount within the range of about 1-5 mg. The above dosages reflect only the TA1 peptide present in the composition, and not the weight of the polymer conjugated thereto.

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