DB05829 PREOTACT C845H1343N223O243S9 18.8 kDa

DESCRIPTION Preotact is a pharmaceutical form of parathyroid hormone (PTH). PTH is a single-chain polypeptide composed of 84 amino acids. Preotact contains recombinant human parathyroid hormone which is identical to the full-length native 84-amino acid polypeptide. It is produced as a fusion protein. Post-translational processing involves the cleavage of the OmpA leader sequence, leaving the mature protein as a single-chain 84 amino-acids polypeptide (9.4 kDa) whose sequence is identical to that of the full-length native endogenous human PTH. It has no disulfide bonds and no glycosylation sites. Preotact is used in the treatment of osteoporosis in postmenopausal women at high risk of osteoporotic fractures. Preotact is marketed in Europe by Nycomed. Preos is a registered trade mark owned by NPS Pharmaceuticals, Inc. The name Preos and the New Drug Application is pending approval by the U.S. Food and Drug Administration (FDA). INDICATION For use/treatment in osteoporosis.

PHARMACODYNAMICS Parathyroid hormone is responsible for the fine regulation of serum calcium concentration on a minute-to-minute basis. This is achieved by the acute effects of the hormone on calcium resorption in bone and calcium reabsorption in the kidney. The phosphate mobilized from bone is excreted into the urine by means of the hormone's influence on renal phosphate handling. Parathyroid hormone also stimulates calcium absorption in the intestine, this being mediated indirectly by 1,25-dihydroxyvitamin D. Thus, a hypocalcemic stimulus of parathyroid hormone secretion results in an increased influx of calcium from three sources (bone, kidney, and intestine), resulting in a normalization of the serum calcium concentration without change in the serum phosphate concentration. MECHANISM OF ACTION The biological actions of rhPTH are mediated through binding to at least two distinct high- affinity cell-surface receptors specific for the N-terminal and C-terminal regions of the molecule, both of which are required for normal bone metabolism. The N-terminal portion of the molecule is primarily responsible for the bone building effects of parathyroid hormone. The C-terminal portion of the molecule has antiresorptive activity and is necessary for normal regulation of N-terminal fragment activity.

METABOLISM PTH is metabolised in the liver and to a lesser extent in the kidney. Parathyroid hormone is efficiently removed from the blood by a receptor-mediated process in the liver and is broken down into smaller peptide fragments. The fragments derived from the amino-terminus are further degraded within the cell while the fragments derived from the carboxy-terminus are released back into the blood and cleared by the kidney. These carboxy-terminal fragments are thought to play a role in the regulation of PTH activity. Under normal physiological conditions full-length PTH constitutes only 5-30% of the circulating forms of the molecule, while 70-95% is present as carboxy-terminal fragments. Following administration of Preotact, carboxy-terminal fragments make up about 60-90% of the circulating forms of the molecule. Intersubject variability in systemic clearance is about 15%. HALF-LIFE The mean half-life is approximately 1.5 hours. ABSORPTION The absolute bioavailability of 100 micrograms of Preotact after subcutaneous administration in the abdomen is 55%.

ROUTE OF ELIMINATION Not excreted from the body in its intact form. Circulating carboxy-terminal fragments are filtered by the kidney, but are subsequently broken down into even smaller fragments during tubular reuptake. VOLUME OF DISTRIBUTION The volume of distribution at steady-state following intravenous administration is approximately 5.4 liters. Intersubject variability is about 40%. CLEARANCE PTH is rapidly cleared from plasma, primarily by Kupffer cells in the liver. To a lesser extent, PTH is cleared by filtration and reabsorption by the kidney. TARGETS Parathyroid hormone/parathyroid hormone-related peptide receptor,Parathyroid hormone 2 receptor

Preotact (Subcutaneous) European Medicines Agency for the treatment of osteoporosis in postmenopausal women at high risk of fractures. US approval is pending with the FDA DOSAGE 100 micrograms of Preotact administered once-daily as a subcutaneous injection into the abdomen, during 18 months (data support treatment up to 24 months) PLATFORM ORG E. Coli

FORMULATION Preotact is delivered in a two chamber, glass ampoule. One chamber contains the active substance in the form of a white powder (with excipients: mannitol, citric acid monohydrate, NaCl, NaOH, HCl). And the other contains the solvent; water for injection. The powder is mixed with the solvent when the ampoule is insterted into the injection device. HALF-LIFE: 1.5 h ADVERSE REACTION: Hypercalcemia and/or hypercalciuria reflect the known pharmacodynamic actions of PTH in the gastrointestinal tract, the kidney and the skeleton, and is therefore an expected undesirable effect. Nausea is another commonly reported adverse reaction to the use of PTH. PROTEIN SEQUENCE hormoneSVSEIQLMHNLGKHLNSMERVEWLRKKLQDVHNFVALGAPLAPRDAGSQRPRKKEDNVLVESHEKSLGEADKADVNVLTKAKSQ

REFERENCES http://www.ema.europa.eu/docs/en_GB/document_library/EPAR_-_Summary_for_the_public/human/000659/WC500041338.pdf http://www.ncbi.nlm.nih.gov/pubmed/21524248 http://www.ncbi.nlm.nih.gov/pubmed/21524246 http://www.ncbi.nlm.nih.gov/pubmed/21155613 http://www.ncbi.nlm.nih.gov/pubmed/20739387 http://www.ncbi.nlm.nih.gov/pubmed/19189037