NEUTRALIZING ANTIBODIES AGAINST GDF-8 AND USES THEREFOR
[001] This application claims priority to United States provisional
Ser. No. 60/419,964, filed October 22, 2002, which is incorporated herein by
reference in its entirety.
TECHNICAL FIELD
[0002] The technical field relates to antibodies against growth and
differentiation factor-8 (GDF-8), in particular human antibodies, and antibody
fragments, especially those that inhibit GDF-8 activity in vitro and/or in vivo.
The field further relates to diagnosing, preventing, or treating degenerative
disorders of muscle or bone, or disorders of insulin metabolism.
BACKGROUND
[0003] Growth and differentiation factor-8 (GDF-8), also known as
myostatin, is a secreted protein and is a member of the transforming growth
factor-beta (TGF-B) superfamily of structurally related growth factors, all of
which possess physiologically important growth-regulatory and morphogenetic
properties (Kingsley et al. (1994) Genes Dev., 8: 133-146; Hoodless et al.
(1998) Curr. Topics Microbiol. Immunol., 228: 235-272). Similarly to TGF-B,
human GDF-8 is synthesized as a 375 amino acid long precursor protein.
The precursor GDF-8 protein forms a homodimer. During processing the
amino-terminal propeptide is cleaved off at Arg-266. The cleaved propeptide,
known as the "latency-associated peptide" (LAP), may remain noncovalently
bound to the homodimer, thereby inactivating the complex (Miyazono et al.

(1988) J. Biol. Chem., 263: 6407-6415; Wakefield et al. (1988) J. Biol. Chem.,
263: 7646-7654; Brown et al. (1990) Growth Factors, 3: 35-43; and Thies et
al. (2001) Growth Factors, 18: 251-259). The complex of mature GDF-8 with
propeptide is commonly referred to as the "small latent complex" (Gentry et al.
(1990) Biochemistry, 29: 6851-6857; Derynck et al. (1995) Nature, 316:
701-705; and Massague (1990) Ann. Rev. Cell Biol., 12: 597-641). Other
proteins are also known to bind to mature GDF-8 and inhibit its biological
activity. Such inhibitory proteins include follistatin and follistatin-related
proteins (Gamer et al. (1999) Dev. Biol., 208: 222-232).
[0004] An alignment of deduced amino acid sequences from various
species demonstrates that GDF-8 is highly conserved throughout evolution
(McPherron et al. (1997) Proc. Nat. Acad. Sci. U.S.A., 94:12457-12461). In
fact, the sequences of human, mouse, rat, porcine, and chicken GDF-8 are
100% identical in the C-terminal region, while in baboon, bovine, and ovine
they differ only by 3 amino acids. The zebrafish GDF-8 is the most diverged;
however, it is still 88% identical to human.
[0005] The high degree of conservation suggests that GDF-8 has
an essential function. GDF-8 is highly expressed in the developing and adult
skeletal muscle and was found to be involved in the regulation of critical
biological processes in the muscle and in osteogenesis. For example, GDF-8
knockout transgenic mice are characterized by a marked hypertrophy and
hyperplasia of the skeletal muscle (McPherron et al. (1997) Nature, 387:
83-90) and altered cortical bone structure (Hamrick et al. (2000) Bone, 27 (3):
343-349). Similar increases in skeletal muscle mass are evident in naturally

occurring mutations of GDF-8 in cattle (Ashmore et al. (1974) Growth, 38:
501-507; Swatland et al. (1994) J. Anim. Sci., 38: 752-757; McPherron et al.
(1997) Proc. Nat. Acad. Sci. U.S.A., 94:12457-12461; and Kambadur et al.
(1997) Genome Res., 7: 910-915). Studies have indicated that muscle
wasting associated with HIV-infection is accompanied by an increase in
GDF-8 expression (Gonzalez-Cadavid et al. (1998) Proc. Nat. Acad. Sci.
U.S.A., 95:14938-14943). GDF-8 has also been implicated in the production
of muscle-specific enzymes (e.g., creatine kinase) and proliferation of
myoblast cells (WO 00/43781). In addition to its growth-regulatory and
morphogenetic properties, GDF-8 is thought to be also involved in a number
of other physiological processes, including glucose homeostasis in the
development of type 2 diabetes, impaired glucose tolerance, metabolic
syndromes (e.g., syndrome X), insulin resistance induced by trauma, such as
burns or nitrogen imbalance, and adipose tissue disorders (e.g., obesity)