Modified Human Growth Hormone

Abstract

Modified growth hormone polypeptide and uses thereof are provided.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. provisional patent application 60 / 638,616 filed Dec. 22, 2004 and U.S. provisional patent application 60 / 727,996 filed Oct. 17, 2005, the specifications of which are incorporated herein in their entirety.FIELD OF THE INVENTION [0002] This invention relates to growth hormone polypeptides modified with at least one non-naturally-encoded amino acid. BACKGROUND OF THE INVENTION [0003] The growth hormone (GH) supergene family (Bazan, F. Immunology Today 11: 350-354 (1990); Mott, H. R. and Campbell, I. D. Current Opinion in Structural Biology 5: 114-121 (1995); Silvennoinen, O. and Ihle, J. N. (1996) SIGNALING BY THE HEMATOPOIETIC CYTOKINE RECEPTORS) represents a set of proteins with similar structural characteristics. Each member of this family of proteins comprises a four helical bundle, the general structure of which is shown in FIG. 1. While there are still more members of the family yet to be iden...

AI Technical Summary

Benefits of technology

This patent describes a method for creating new proteins by adding non-naturally encoded amino acids to the end of a naturally occurring protein. These added amino acids can be linked to other amino acids or a water soluble polymer, such as poly(ethylene glycol). The non-naturally encoded amino acids can be incorporated at various positions in the protein, and can be linked to other amino acids or a polymer using a linker or a bifunctional polymer. The added amino acids can have a variety of functions, such as improving the solubility or stability of the protein. The patent also provides a list of specific positions in the protein where non-naturally encoded amino acids can be added. Overall, this patent provides a way to create new proteins with improved properties by adding non-naturally encoded amino acids to the end of a naturally occurring protein.

Problems solved by technology

A significant challenge to using growth hormone as a therapeutic, however, is that the protein has a short in vivo half-life and, therefore, it must be administered by daily subcutaneous injection for maximum effectiveness (MacGillivray, et al., J. Clin. Endocrinol. Metab.

While the depot permits less frequent administration (once every 2-3 weeks rather than once daily), it is also associated with undesirable side effects, such as decreased bioavailability and pain at the injection site and was withdrawn from the market in 2004.

Although several of the amino acid side chain residues in Pegvisomant™ are derivatized with polyethylene glycol (PEG) polymers, the product is still administered once-daily, indicating that the pharmaceutical properties are not optimal.

In addition to PEGylation and depot formulations, other administration routes, including inhaled and oral dosage forms of hGH, are under early-stage pre-clinical and clinical development and none have yet received approval from the FDA.

Proteins and other molecules often have a limited number of reactive sites available for polymer attachment.

To form conjugates having sufficient polymer molecular weight for imparting the desired advantages to a target molecule, prior art approaches have typically involved random attachment of numerous polymer arms to the molecule, thereby increasing the risk of a reduction or even total loss in bioactivity of the parent molecule.

These PEG derivatives all have the common limitation, however, that they cannot be installed selectively among the often numerous lysine residues present on the surfaces of proteins.

This can be a significant limitation in instances where a lysine residue is important to protein activity, existing in an enzyme active site for example, or in cases where a lysine residue plays a role in mediating the interaction of the protein with other biological molecules, as in the case of receptor binding sites.

A second and equally important complication of existing methods for protein PEGylation is that the PEG derivatives can undergo undesired side reactions with residues other than those desired.

This can create complex, heterogeneous mixtures of PEG-derivatized bioactive molecules and risks destroying the activity of the bioactive molecule being targeted.

This approach is complicated, however, in that the introduction of a free sulfhydryl group can complicate the expression, folding and stability of the resulting protein.

As can be seen from a sampling of the art, many of these derivatives that have been developed for attachment to the side chains of proteins, in particular, the —NH2 moiety on the lysine amino acid side chain and the —SH moiety on the cysteine side chain, have proven problematic in their synthesis and use.

Some form unstable linkages with the protein that are subject to hydrolysis and therefore decompose, degrade, or are otherwise unstable in aqueous environments, such as in the bloodstream.

Some are somewhat toxic and are therefore less suitable for use in vivo.

Some are too slow to react to be practically useful.

Some result in a loss of protein activity by attaching to sites responsible for the protein's activity.

Some are not specific in the sites to which they will attach, which can also result in a loss of desirable activity and in a lack of reproducibility of results.

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