Prolonged Pharmacokinetic and Pharmacodynamic Actions of a Pegylated Parathyroid Hormone (1-34) Peptide Fragment

Abstract

Polyethylene glycol (PEG) addition can prolong the pharmacokinetic and pharmacodynamic actions of a bioactive peptide in vivo, in part by impeding rates of glomerular filtration. For parathyroid hormone (PTH) peptides, pegylation could help in exploring the actions of the hormone in the kidney; e.g., in dissecting the relative roles that filtered versus blood-borne PTH play in regulating phosphate transport. It could also lead to potential alternate forms of treatment for hypoparathyroidism. We thus synthesized the fluorescent pegylated PTH derivative [Lys13(tetramethyl rhodamine {TMR}), Cys35(PEG-20,000 Da)]PTH(1-35) (PEG-PTHTMR) and its non-pegylated counterpart [Lys13(TMR), Cys35]PTH(1-35) (PTHTMR) and assessed their properties in cells and in mice. In PTHR1-expressing HEK-293 cells, PEG-PTHTMR and PTHTMR exhibited similar potencies for inducing cAMP signaling, whereas when injected into mice, the pegylated analog persisted for much longer in the circulation (>24 hours versus ~1 hour) and induced markedly more prolonged calcemic and phosphaturic responses than did the non-pegylated control. Fluorescence microscopy analysis of kidney sections obtained from the injected mice revealed much less PEG-PTHTMR than PTHTMR on the luminal brush-border surfaces of renal proximal tubule cells (PTCs), on which PTH regulates phosphate transporter function, whereas immunostained phosphorylated PKA substrate, a marker of cAMP signaling, was increased to similar extents for the two ligands and for each, was localized to the basolateral portion of the PTCs. Pegylation of a bioactive PTH peptide thus led to prolonged pharmacokinetic/pharmacodynamic properties in vivo, as well as to new in vivo data that support a prominent role for PTH action at basolateral surfaces of renal proximal tubule cells.

Knockin mouse with mutant Gα11 mimics human inherited hypocalcemia and is rescued by pharmacologic inhibitors

“…Spot urine was collected and analyzed for calcium, phosphate, and creatinine at baseline and 4 hours after injection (43). The FEICa was calculated by the equation: urine calcium/(urine creatinine × blood calcium) (44).…”

Probing Polymer Chain Conformation and Fibril Formation of Peptide Conjugates

“…Corresponding results have been reported for r H of pegylated a-lactalbumin, b-lactoglobulin [29] and helix bundle proteins. [20] In contrast, pegylation of lysozyme and an underlaying dumbbell model more than doubled r H . [21] A confirmation of the suggested shroud-like structure for the RP-22 and RP-23 conjugates of PTH requires DLS and SANS data, [22] which is future work.…”

“…Both, PTH(1‐34) and the here studied PTH(1‐84) are approved drugs against osteoporosis (Forteo® and Natpara®, respectively). Chimeras of PTH(1‐34) and polyethylene glycol displayed prolonged pharmacokinetic/pharmacodynamic properties in vivo . Before PTH gets released to the blood it is stored in secretory granules, where it forms functional amyloid fibrils .…”

Design and Preclinical Development of TransCon PTH, an Investigational Sustained-Release PTH Replacement Therapy for Hypoparathyroidism

“…An additional compound, a PEGylated PTH(1‐34) fragment, has also demonstrated promising sustained effects on systemic calcium and phosphate levels beyond 24 hours after a single i.v. dose on 50 nmol/kg in intact mice . Although the study in mice demonstrates sustained effect on systemic calcium levels, PK/PD data after repeat‐dosing in a relevant disease model as well as in humans are not publicly available for this compound and thus preclude further comparison to TransCon PTH.…”