Abbott Laboratories announced that the US Food and Drug Administration (FDA) has approved Zemplar (paricalcitol injection) for use in children and adolescent haemodialysis patients, ages 5 to 19, with secondary hyperparathyroidism (SHPT). Zemplar initially was introduced in 1998 and currently is used to treat SHPT in the majority of adult dialysis patients in the United States.

Patients with kidney failure are unable to produce the active form of vitamin D. As a result, many dialysis patients have vitamin D deficiency and develop SHPT, a disorder that causes bone disease and can affect many organs and tissues, including the bones, red blood cells, heart, nerves and muscles.

"Because of the unique characteristics of the growing skeleton, children are particularly vulnerable to the complications of kidney failure and secondary hyperparathyroidism that can lead to bone deformities and growth retardation," said Isidro B. Salusky, M.D., a paediatric nephrologist and professor of paediatrics at the David Geffen School of Medicine at the University of California at Los Angeles, and the lead investigator for the clinical research and data collection used to support Abbott's application to the FDA seeking expanded use of Zemplar. "We need to know that the therapies available for adults are also safe for children - and now we do. This new information allows us to feel comfortable giving children the same therapy prescribed for adult patients."

Approximately 1,400 American children between the ages of 5 and 19 undergo haemodialysis, a time-consuming treatment in which blood is filtered through an artificial kidney machine to remove wastes and extra fluid from the blood.

Kidneys help keep bones healthy by metabolizing vitamin D, converting it into the active D compound that helps regulate parathyroid hormone (PTH) secretion and bone metabolism, as well as calcium and phosphorus levels. In the absence of active vitamin D, many patients with kidney failure develop SHPT, where the parathyroid glands produce excess amounts of PTH. Without proper management, SHPT can lead to weak and brittle bones, anemia, and cardiac and neurological problems. Because bones and other organs are still developing in children, and because they are typically patients for longer periods of time, complications related to SHPT can be more difficult to treat than in adults. Left untreated, SHPT can be a factor in growth retardation and lead to severe disability.

"I have witnessed the toll of kidney disease and dialysis on younger patients and their families," said Joel Melnick, M.D., global medical director, Abbott Laboratories, and a paediatric nephrologist. "One of the reasons that controlling secondary hyperparathyroidism in children is especially challenging is that their diets frequently may be high in phosphorous, the control of which is critical in dialysis patients. A third-generation D compound like Zemplar that did not cause hyperphosphatemia and hypercalcemia in clinical studies is an incredibly important asset for younger patients and can help them lead more normal lives."

"Approval of Zemplar for use in paediatric patients demonstrates Abbott's commitment to addressing the needs of the wide range of patients with kidney disease," said William Dempsey, senior vice president, Pharmaceutical Operations, Abbott Laboratories. "Abbott recently launched a worldwide research program to further study D-Receptor activation in chronic kidney disease and for a variety of related disorders."

The safety and effectiveness of Zemplar were examined in a 12-week randomized, double-blind, placebo-controlled study of 29 paediatric patients, ages 5 to 19 years, with chronic renal failure on haemodialysis. Nearly all had received some form of vitamin D therapy prior to the study.

Sixty per cent of patients in the Zemplar group had two consecutive 30 per cent decreases in parathyroid hormone levels compared with only 21 per cent of patients in the placebo group. Fewer Zemplar patients than placebo patients (23 per cent compared to 31 per cent) experienced elevated serum calcium levels. The overall percentage of serum calcium measurements (defined as 10.3 mg/dL or greater) was 7 percent in the Zemplar group and 7 per cent in the placebo group. No subjects in either the Zemplar group or placebo group developed hypercalcemia (defined as at least one calcium value >11.2 mg/dL) during the study.

Another side effect measurement used in the study was the product of serum calcium and phosphorus levels (Ca x P), measured in terms of mg2/dL2. In this study, 40 per cent of Zemplar patients, compared to 14 per cent of placebo patients, had at least one Ca x P > 72. The overall percentage of patients with Ca x P > 72, however, was 8 per cent in the Zemplar group and 7 per cent in the placebo group.