Chemistry: molecular biology and microbiology – Measuring or testing process involving enzymes or... – Involving antigen-antibody binding – specific binding protein...
Reexamination Certificate
2000-08-21
2002-07-16
Stucker, Jeffrey (Department: 1648)
Chemistry: molecular biology and microbiology
Measuring or testing process involving enzymes or...
Involving antigen-antibody binding, specific binding protein...
C435S975000, C530S328000, C530S330000, C530S388100
Reexamination Certificate
active
06420125
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the assaying of collagen or other protein degradation products and materials useful therefor.
BACKGROUND
Collagens and Disorders of Collagen Metabolism
Osteoporosis is the most common bone disease in humans. Primary osteoporosis, accompanied by increased susceptibility to fractures, results from a progressive reduction in skeletal bone mass. It is estimated to affect 15-20 million individuals in the USA alone. Its basis is an age-dependant imbalance in bone remodelling, i.e. in the rates of formation and resorption of bone tissue.
In the USA about 1.2 million osteoporosis-related fractures occur in the elderly each year including about 538,000 compression fractures of the spine, about 227,000 hip fractures and a substantial number of early fractured peripheral bones. Between 12 and 20% of the hip fractures are fatal because they cause severe trauma and bleeding, and half of the surviving patients require nursing home care. Total costs from osteoporosis-related injuries now amount to at least $10 billion annually in the USA (Riggs, New England Journal of Medicine, 327:620-627 (1992)).
Osteoporosis is most common in postmenopausal women who, on average, lose 15% of their bone mass in the 10 years after menopause. This disease also occurs in men as they get older and in young amenorrheic women athletes. Despite the major, and growing, social and economic consequences of osteoporosis, the availability of reliable assays for measuring bone resorption rates in patients or in healthy subjects is very limited. Other disorders entailing (and correlated with) abnormalities in collagen metabolism include Paget's disease, Marfan's syndrome, osteogenesis imperfecta, neoplastic growth in collagenous tissue, dwarfism, rheumatoid arthritis, osteoarthritis and vasculitis syndrome.
Three known classes of human collagen have been described to date. The Class I collagens, subdivided into types I, II, III, V and XI, are known to form fibrils. The amino-acid sequence of type I-III (to the extent it has been elucidated) is given in Appendix A of WO 95/08115.
Collagen type I accounts for more than 90% of the organic matrix of bone. Therefore, in principle, it is possible to estimate the rate of bone resorption by monitoring the degradation of collagen type I. Likewise, a number of other disease states involving connective tissue can be monitored by determining the degradation of collagen. Examples are collagen type II degradation associated with rheumatoid arthritis and osteoarthritis and collagen type III degradation in vasculitis syndrome.
Amino acid sequences of human type III collagen, human pro &agr;1(II) collagen, and the entire prepro &agr;1(III) chain of human type III collagen and corresponding cDNA clones have been investigated and determined by several groups of researchers; see Loil et al., Nucleic Acid Research 12:9383-9394 (1984): Sangiorgi et al., Nucleic Acids Research, 13:2207-2225 (1985); Baldwin et al., Biochem J., 262:521-528 (1989); and Ala-Kokko et al., Biochem. J. , 260:509-516 (1989).
Type I, II, and III collagens are all formed in the organism as procollagen molecules, comprising N-terminal and C-terminal propeptide sequences, which are attached to the core collagen molecules. After removal of the propeptides, which occurs naturally in vivo during collagen synthesis, the remaining core of the collagen molecules consists largely of a triple-helical domain having terminal telopeptide sequences which are non-triple-helical. These telopeptide sequences have an important function as sites of intermolecular crosslinking of collagen fibrils extracellularly. The alphaheical region also includes crosslinkable sites.
Intermolecular cross-links provide collagen fibrils with biomechanical stability. The formation of these cross-links is initiated by modification of lysine and hydroxylysine residues to the corresponding aldehydes. Several of these residues located on adjacent chains of collagen will spontaneously form different intermolecular cross-links. The exact position of the sites for cross-linking on collagen telopeptides and from the helical region has been previously described. See, for example, Kühn, K., in Immunochemistry of the extracellular matrix, 1:1-29, CRC Press, Inc., Boca Raton, Fla. (1982), Eyre, D. R., Ann.Rev. Biochem., 53:77-48 (1984) or U.S. Pat. No. 5,140,103 and 5,455,179. Furthermore, the amino acid sequences of some potential sites for cross-linking in type I, II, and III collagen are given in Table 1 below.
The fibrous proteins, collagen and elastin, are cross-linked by a unique mechanism based on aldehyde formation from lysine or hydroxylysine side chains. Four homologous loci of cross-linking are evident in molecules of type I, II and III collagens (for review see Kühn, K., in Immunochemistry of the extracellular matrix, 1:1-29 (1982)). Two are aldehyde sites, one in each telopeptide region. The other two sites are hydroxylysine symmetrically placed at about 90 residues from each end of the molecule. When collagen molecules pack into fibrils, these latter sites in the helical region align and react with telopeptide aldehydes in adjacent molecules. There is now strong evidence that 3-hydroxypyridinium residues are the mature cross-link coming from hydroxylysine-derived aldehydes. The mature cross-linking residues of the other pathway, i.e. from aldehyde formation of lysine residues, are however, still unknown.
As illustrated by formula in EP-0394296 discussed below, the two 3-hydroxypyridinium cross-links have been found to be hydroxylysyl pyridinoline (also known simply as “pyridinoline”) and lysyl pyridinoline (also known as “deoxypyridinoline”). These cross-linking compounds are naturally fluorescent. Some hydroxylysyl pyridinoline cross-link are found to be glycosylated as discussed for instance in EP-A-0424428.
However, as described in Last et al, Int. J. Biochem. Vol. 22, No. 6, pp 559-564 (1990), other crosslinks occur naturally in collagen.
Prior Art Assays for Collagen Degradation
In the past, assays have been developed for monitoring degradation of collagen in vivo by measuring various biochemical markers, some of which have been degradation products of collagen.
For example, hydroxyproline, an amino acid largely restricted to collagen, and the principal structural protein in bone and all other connective tissues, is excreted in urine. Its excretion rate is known to be increased in certain conditions, notably Paget's disease, a metabolic bone disorder in which bone turnover is greatly increased, as discussed further below.
For this reason, urinary hydroxyproline has been used extensively as an amino acid marker for collagen degradation; Singer, F. R. et al., Metabolic Bone Disease, Vol. II (eds. Avioli, L. V., and Kane, S. M.), 489-575 (1978), Academic Press, New York.
U.S. Pat. No. 3,600,132 discloses a process for the determinetion of hydroxyproline in body fluids such as serum, urine, lumbar fluid and other intercellular fluids in order to monitor deviations in collagen metabolism. The Patent states that hydroxyproline correlates with increased collagen anabolism or catabolism associated with pathological conditions such as Paget's disease, Marfan's syndrome, osteogenesis imperfecta, neoplastic growth in collagen tissues and in various forms of dwarfism.
Bone resorption associated with Paget's disease has also been monitored by measuring small peptides containing hydroxyproline, which are excreted in the urine following degradation of bone collagen; Russell et al., Metab. Bone Dis. and Rel. Res. 4 and 5, U.S. Pat. No. 2,250,262 (1981), and Singer, F. R., et al., supra.
In the case of Paget's disease, the increased urinary hydroxyproline probably comes largely from bone degradation; hydroxyproline, however, generally cannot be used as a specific index for bone degradation. Much of the hydroxyproline in urine may come from new collagen synthesis (considerable amounts of the newly made protein are degraded and excreted without ever becoming incorporated into
Bonde Martin
Fledelius Christian
Qvist Per
Osteometer Biotech A/S
Pennie & Edmonds LLP
Stucker Jeffrey
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