OPKO Health, Inc. has surpassed 50 per cent enrollment in the second phase III trial of Rayaldy to treat patients with secondary hyperparathyroidism (SHPT), stage 3 or 4 chronic kidney disease (CKD) and vitamin D insufficiency. This trial is the second of two identical randomized, double-blind, placebo controlled, multi-site studies intended to establish the safety and efficacy of Rayaldy as a new treatment for SHPT in the targeted population.

The endpoints of both studies, which are being conducted in parallel, include vitamin D status and changes in serum calcium, serum phosphorus and plasma intact parathyroid hormone (PTH).

Each of the two phase III trials will involve 210 patients recruited at approximately 40 sites in the US. These patients are being stratified by CKD stage and randomized in a 2:1 fashion to receive six months of treatment with either Rayaldy or placebo. Dosing with Rayaldy is titrated, as necessary, to achieve the desired blood concentration and the targeted reduction in PTH.

"I am pleased to report that these pivotal trials with Rayaldy Capsules are progressing as planned toward completion in the first half of 2014," stated Phillip Frost, MD, OPKO's chairman and chief executive officer. "Top-line data are expected in mid-2014. We believe Rayaldy will prove to be superior to high monthly doses of prescription vitamin D2, a common therapeutic approach which has been shown unreliable in correcting vitamin D insufficiency in patients with chronic kidney disease and generally ineffective in controlling elevated levels of parathyroid hormone. We look forward to advancing the standard of care for this patient population when Rayaldy is ultimately approved for marketing."

Rayaldy is a first-in-class oral vitamin D prohormone treatment being developed for SHPT in stage 3 and 4 CKD patients with vitamin D insufficiency. It has a proprietary modified-release formulation designed to gradually and reliably raise serum total 25-hydroxyvitamin D (prohormone) concentrations to targeted levels (at least 30 ng/mL) while avoiding upregulation of CYP24, a cytochrome P-450 enzyme that reduces the PTH lowering potency of current vitamin D supplements. Activation of the product by the kidney is tightly regulated, preventing excessive elevation of serum calcium and related side effects which encumber current vitamin D hormone therapies and promote vascular and renal calcification. Once approved, Rayaldy will address the approximately four million CKD stage 3 and 4 patients in the US and many more, elsewhere, with SHPT and vitamin D insufficiency.

CKD is a condition characterized by a progressive decline in kidney function. The kidney is normally responsible for excreting waste and excess water from the body, and for regulating various hormones. CKD is classified in five different stages — mild (stage 1) to severe (stage 5) disease — as measured by the kidney's glomerular filtration rate.

Vitamin D insufficiency is a condition in which the body has low vitamin D stores, characterized by inadequate blood levels of vitamin D prohormones, collectively known as 25-hydroxyvitamin D.

SHPT is a condition commonly associated with CKD in which the parathyroid glands secrete excessive amounts of PTH. SHPT arises as a result of vitamin D insufficiency or impaired kidney function that prevents sufficient production of vitamin D hormones to properly regulate calcium and phosphorus metabolism, and PTH secretion. Prolonged elevation of blood PTH causes excessive calcium and phosphorus to be released from bone, leading to elevated serum calcium and phosphorus, softening of the bones (osteomalacia) and calcification of vascular and renal tissues.

OPKO is a multi-national biopharmaceutical and diagnostics company that seeks to establish industry-leading positions in large and rapidly growing medical markets by leveraging our discovery, development and commercialization expertise and our novel and proprietary technologies.