Paricalcitol in Reducing Parathyroid Hormone Levels and Ameliorating Markers of Bone Remodelling in Renal Transplant Recipients With Secondary Hyperparathyroidism

Overview

The risk of fracture for kidney transplant recipients is 4 times higher that of the general population. The hyperparathyroidism plays a key role in the maintenance or development of post-transplant alterations of bone remodelling. Renal transplant patients are at high risk of hyperparathyroidism, largely because of long-lasting renal insufficiency before transplant, and of progressive deterioration of kidney function because of chronic allograft nephropathy (a disease of proteinuria and progressive decline of the glomerular filtration rate).In hemodialysis patients, intravenous paricalcitol (19-nor-1,25-dihydroxyvitamin D2), a new vitamin D analogue, achieves a faster and more effective normalization of parathyroid hormone (PTH) levels than calcitriol (1,25-dihydroxyvitamin D3), an effect that is associated with smaller changes in serum calcium and phosphorus levels. Whether oral paricalcitol may help achieving a prompt reduction in serum PTH levels and, secondarily, in urinary protein excretion in renal transplant recipients with secondary hyperparathyroidism is worth investigating.

BACKGROUND The risk of fracture for kidney transplant recipients is 4 times higher that of the general population. The pathogenesis of post-transplant bone disease is multifactorial, but hyperparathyroidism plays a key role in the maintenance or development of post-transplant alterations of bone remodelling. Vitamin D and its analogues are key components of treatment aimed to prevent or ameliorate secondary hyperparathyroidism in patients with chronic kidney disease (CKD). In hemodialysis patients, intravenous paricalcitol (19-nor-1,25-dihydroxyvitamin D2), a new vitamin D analogue, achieves a faster and more effective normalization of parathyroid hormone (PTH) levels than calcitriol (1,25-dihydroxyvitamin D3), an effect that is associated with smaller changes in serum calcium and phosphorus levels. Preliminary evidence is also available that in pre-dialysis patients with CKD and secondary hyperparathyroidism, treatment with oral paricalcitol may also reduce urinary protein excretion, an effect that is independent of concomitant treatment with agents that block the renin-angiotensin system and that in the long-term might translate into slower progression to end stage kidney disease and need for renal replacement therapy. Renal transplant patients are at high risk of hyperparathyroidism, largely because of long-lasting renal insufficiency before transplant, and of progressive deterioration of kidney function because of chronic allograft nephropathy (a disease of proteinuria and progressive decline of the glomerular filtration rate). Whether oral paricalcitol may help achieving a prompt reduction in serum PTH levels and, secondarily, in urinary protein excretion in renal transplant recipients with secondary hyperparathyroidism is worth investigating. AIMS Primary To evaluate whether 6-months treatment with paricalcitol may achieve a prompt and effective reduction in PTH serum levels in stable renal transplant patients with secondary hyperparathyroidism. DESIGN This will be a Prospective, Randomized, Open label, Cross-over study of 6-months with Paricalcitol or standard treatment for hyperparathyroidism. After one month wash-out from any form of Vitamin D therapy, patients satisfying the inclusion/exclusion criteria will be randomized to two treatment arms: 1. Paricalcitol capsules 1- 2 mcg/day/pts for 26 weeks 2. Standard therapy for hyperparathyroidism for 26 weeks At the end of the first treatment period with Paricalcitol or Standard therapy each patient will cross-over to the other treatment. After baseline evaluation eligible patients will enter a 6 months treatment period whit oral paricalcitol (1-2 mcg/day), or standard treatment for hyperparathyroidism, added-on background therapy whit calcium and phosphate supplementation as deemed clinically appropriate.